Structure of tetracene films on
Structure of tetracene?lms on hydrogen-passivated Si(001)studied
via STM,AFM,and NEXAFS
A.Tersigni,J.Shi,D.T.Jiang,and X.R.Qin*
Department of Physics and Guelph-Waterloo Physics Institute,University of Guelph,Guelph,Ontario N1G2W1,Canada ?Received7June2006;revised manuscript received7September2006;published20November2006?
Scanning tunneling microscopy?STM?,atomic force microscopy?AFM?,and near-edge x-ray absorption
?ne structure?NEXAFS?have been used to study the structure of tetracene?lms on hydrogen-passivated
Si?001?.STM imaging of the?lms with nominal thickness of three monolayers?3ML?exhibits the charac-
teristic“herringbone”molecular packing known from the bulk crystalline tetracene,showing standing mol-
ecules on the ab plane.The dimensions and orientation of the herringbone lattice indicate a commensurate
structural relationship between the lattice and the crystalline substrate.The corresponding AFM images illus-
trate that at and above the third layer of the?lms,the islands are anisotropic,in contrast with the submonolayer
fractals,with two preferred growth directions appearing orthogonal to each other.The polarization dependent
NEXAFS measurements indicate that the average molecular tilting angle with respect to the surface?rst
increases with the?lm thickness up to3ML,then stabilizes at a value close to the bulk tetracene case
afterwards.The combined results indicate a distinct growth morphological change that occurs around a few
monolayers of thickness.
DOI:10.1103/PhysRevB.74.205326PACS number?s?:68.55.Jk,68.37.?d,81.15.Hi,61.10.Ht
I.INTRODUCTION
Driven by their potential applications in future organic electronics,small aromatic molecules are attracting increas-ing attention.1–3They are of interest in fundamental studies of the organic electronics because many of these molecules could form high purity and well-ordered crystalline struc-tures by sublimation techniques.3Tetracene is a planar aro-matic molecule?C18H12?consisting of four fused-benzene rings?Fig.1?a??.The bulk crystalline structure of tetracene is layered herringbone molecular packing on the?001?plane
?Fig.1?b??.4Tetracene thin?lms prepared with vacuum sub-limation have already been used to fabricate?eld-effect tran-sistors?FETs?,5and tetracene?lms have also displayed im-pressive properties in organic light-emitting FETs.6In order to achieve optimal material properties for these devices,the control of the?lm growth based on a good understanding is required.However,research on tetracene thin?lms is far from extensive.Theoretical studies on another polyacene, pentacene,7indicate that the bulk crystalline?001?facet has the lowest surface energy,and if the interaction between the molecules within a layer is much stronger than that between the molecule and substrate,as the typical case for the?lm growth on inert substrates,the?lm deposited is expected to exhibit the?001?orientation.7,8Given the similarities in pen-tacene and tetracene crystal structures,the above conclusions are likely applicable to tetracene.Studies aimed on increas-ing the mobility in tetracene thin?lms on silicon dioxide reported that the?lm growth is in favor of forming three-dimensional?3D?islands with a granular structure,and that the mobility limitation is primarily caused by the?lm growth properties.9Similar structural results were indicated by graz-ing incidence x-ray diffraction study that polycrystalline structures with polymorphs of different upright orientations of the molecules were found.10Until recently the layered morphology,similar to those in the pentacene?lm growth,11–13has been realized in tetracene?lm growth on a
solid substrate.14A“layer-by-layer”growth was demon-
strated for the tetracene?lms on hydrogen-passivated
Si?001?-2?1substrates within optimal range of deposition rates,and that good?lm connectivity and signi?cantly im-
proved grain size were obtained.14The Si?001?-2?1surface used in this latter study provides a structurally well-de?ned ?Fig.2?a??substrate template,15while the hydrogen passiva-tion?Fig.2?b??removes surface dangling bonds17resulting
in an inert substrate,leading to a well-suited surface for fun-
damental studies on the organic thin?lm growth.
Previous AFM results indicated that for a tetracene?lm
deposited on H/Si?001?the molecules are in an upright standing con?guration,14similar to that of pentacenes in weak molecule-substrate interaction cases.7,8,18However, more complete structural characterizations of the
tetracene
FIG.1.?a?Schematic side view of a single tetracene molecule ?C18H12?which consists of four fused benzene rings.C atom is shown in shaded black,and H atom in light gray.?b?Schematic top view?along the molecule long axis?of a single ab layer of tetracene in its bulk crystalline structure with two molecules in the unit cell.
PHYSICAL REVIEW B74,205326?2006?
?lm are still not yet available.The structural properties of interest include the in-plane unit cell dimensions and pos-sible registration with the substrate lattice and the molecule tilting angles,and in addition the evolution of these struc-tural parameters with the ?lm thickness.In this paper,we report a combined multitechnique investigation on these structural characterizations for the tetracene ?lms.We show that the ?lm of a few monolayers coverage possesses appar-ent epitaxial domains on the hydrogen-passivated Si ?001?substrate with a bulk-kind herringbone lattice and a compres-sive in-plane lattice commensurate with the substrate.Also,the average molecular tilting angle with respect to the sur-face ?rst increases with the coverage in forming the expi-
taxial domains and stabilizes around the bulk tetracene value in further growth.We associate the molecular-level structural information to a distinct growth morphological change that occurs around a few mononlayers of thickness.
II.EXPERIMENTAL DETAILS A.Sample preparation and STM
The ?lm growth and in situ scanning tunneling micros-copy ?STM ?studies were conducted in a two-chamber ultra-high vacuum ?UHV ?STM and growth system built in our laboratory.19The two chambers were isolated by a gate valve with base pressure ?1?10?10Torr for the STM chamber and ?3?10?9Torr for the growth chamber,respectively.Samples can be transferred between the two chambers in vacuum with a transfer arm.
In the STM chamber,Si ?001?wafers were cleaned by thermal annealing.The Si substrate was resistively heated and the temperature was monitored by a C -type thermo-couple in contact with the backside of the substrate.The in situ substrate cleaning procedure involves degassing the sili-con wafer at 970K and ?ashing at 1470K for ?1min,dur-ing which time the chamber pressure remained in the 10?10Torr range.
Atomic hydrogen passivation was carried out with the silicon substrate at ?600K.By dissociating molecular hy-drogen ?H 2?gas via a tungsten ?lament heated at ?1800K,we generated atomic hydrogen inside the STM chamber by ?lling H 2gas into the chamber at a pressure of ?1?10?6Torr for 30min in order to form monohydride H/Si ?001?-?2?1?surface.20The substrate was placed ?8cm away from the tungsten ?lament.After the hydrogen passivation,the substrate was radiation cooled and trans-ferred to the ?lm growth chamber.
Tetracene ?98%,Sigma-Aldrich ?was evaporated in the growth chamber with the same setup and procedure de-scribed previously.14The deposition rate used was 1nm/min,which was monitored by a quartz crystal mi-crobalance.All the ?lm growth was done with the substrate at room temperature.After ?lm growth,the sample was then transferred back to the STM chamber for imaging.
The home-made STM ?Ref.19?uses a quadrant tube scanner and two inchworms for the Z and X coarse motion.Swartzentruber 21type of control electronics and data acqui-sition software are adopted for the STM.All the STM images presented here were obtained in a constant-current mode.The sample bias used in imaging tetracene ?lm was +2.4V and tunneling current 20pA.
B.AFM
After substrate preparation and ?lm evaporation inside the UHV system as described above,the sample can be removed from the vacuum for other analysis via a load https://www.wendangku.net/doc/6217082821.html,rge scale topographic images were obtained by an ex situ atomic force microscopy ?Digital Instruments Dimension?3100?in tapping mode with Si tips,and the images were analyzed using software WSxM.
22
FIG.2.Typical STM images ?150??150??of ?a ?a clean Si ?001?surface ??lled state,at a bias of ?2.0V ?and ?b ?monohydride-terminated Si ?001??empty state,+2.0V ?,with a tun-neling current of 0.2nA.For both surfaces,the alternating 2?1and 1?2domains are energetically degenerate,with dimer rows running along the ?110?and ??110?directions,respectively.The image of the monohydride Si ?001?has the tunneling intensity mini-mums at the troughs between the dimer rows,as indicated by the dark lines in ?b ?,clearly different from that for an empty-state im-age of a clean Si ?001?under +2.0V ?see Ref.16?.
TERSIGNI et al.PHYSICAL REVIEW B 74,205326?2006?
C.NEXAFS
Polarization dependent carbon1s near edge x-ray absorp-
tion?ne structure?NEXAFS??Ref.23?characterization was
performed ex situ on the tetracene?lms with three different
thicknesses?1.2ML,3ML,and15ML?that were prepared
using the growth system and procedure described above.
Multiple samples for each tetracene?lm thickness were used
and consistent results among the different batch of samples
were obtained.The NEXAFS experiment was carried at the
SGM beamline?11ID-2?at the Canadian Light Source?CLS?
in Saskatoon,SK Canada.Total electron yield was used for
the measurements under different beam incidence angles???relative to sample surface.Sample?uorescence yield was
monitored simultaneously using a multichannel plate detec-
tor and mainly used for signal diagnostic purpose in this
experiment.The geometry for manipulating sample orienta-
tion with respect to the direction of the incoming synchrotron
x-ray beam was the same as that in Ref.23and the NEXAFS
measurements were conducted at room temperature.The
SGM solid-state chamber vacuum was between low10?8to
low10?9torr during the measurements.In order to avoid the
effect of beam damage on the sample,each sampling area
was used for one pair of the measurements at two incident
angles?i.e.,?=90°and10°?for about10min each.During the measurements,the CLS storage ring current was between
150mA to200mA,and the monochromator entrance and
exit slits were set to be5?m and25?m,respectively.The monochromator energy scale was calibrated by measuring
CO gas phase C1s→?*resonance energy at287.40eV ?Ref.24?during the same experimental run using a gas cell connected to the solid state chamber on the SGM beam line.
The beam line optical transmission function was measured
using a photodiode at normal incidence and the background
data for the tetracene?lm samples were measured from a
Si?001?wafer.The raw data background correction and nor-
malization were carried out using the same multiple step
procedure as that in Ref.25.
III.RESULTS
A.Real-space imaging(STM and AFM)
Figure3displays the surface morphology of a tetracene submonolayer?lm on H-terminated Si?001?prepared as de-scribed in Sec.II A.As expected from our previous work,14 the?lm islands appear as fractals under the growth condi-tions.The feature dimension is close to100microns?Fig. 3?a??,much larger than the value we obtained previously with a H-terminated substrate prepared using a wet chemistry method.14In Fig.3?b?a close AFM examination reveals de-tails of a fractal and also presents the morphology of the substrate with visible single atomic-layer steps that are ori-ented in random directions on the image scale.There is no clear indication of in?uence from these single-atomic-layer steps in the development of the fractal branches:branch splitting and extending occur on both local hills and valleys of the substrate.The heights of these submonolayer islands are measured using the AFM images,a value around?1nm is typically obtained?Fig.3?c??,which is smaller than the length of the tetracene molecule?Fig.1?.This apparent layer thickness suggests that the molecules are essentially in an upright standing con?guration in the submonolayer?lm but likely tilted away from surface normal direction.
To characterize the resulting structure of the fractal?lms at the molecular scale,efforts have been made to use our STM to image samples with either submonolayer coverage or with a coverage that has the top surface islands being the second molecular layer?i.e.,the nominal thickness is?1.2 ML?Ref.14??.So far no ordered structures have been im-aged from the?lm surface at these coverages.We cannot exclude the possibility that the absence of molecular features in the STM image of the?lms is a result of the weak molecule-substrate interaction such that the soft?lm be-comes susceptible to deformations induced by the STM scanning operations.On the other hand,the STM results could also indicate a possibility that there is a
signi?cant FIG.3.?a?AFM phase image?100?m?100?m?shows sub-monolayer tetracene fractals?dark feature?.?b?A zoom-in topo-graphic image?20?m?20?m?of the area in the white frame of ?a?.?c?A line pro?le taken from the white bar marked by two triangles in?b?shows the height of?1nm for the layer.
STRUCTURE OF TETRACENE FILMS ON HYDROGEN-…PHYSICAL REVIEW B74,205326?2006?
density of different molecular tilting domains that heavily disturbs the imaging of the domain structures.Because the fractal formation is largely based on diffusion-limited aggre-gation ?DLA ??hit and stick ?mechanism,11,14the as-grown ?rst layer could be highly disordered.
Successful STM imaging of the molecular packing has been realized when we deposit three monolayer ?ML ??nomi-nal thickness ?of tetracene onto the surface.Figure 4shows a typical STM image of such ?lms.The characteristic “her-ringbone”molecular packing known from the bulk crystal-line tetracene is clearly visible,with the intensity protrusions indicating molecules in the image.The intensity protrusions form rows,with one row being brighter than its adjacent row in an alternating pattern,and the unit cell appears rect-angular.Based on STM images of multiple independent samples,we calibrate the herringbone lattice ?e.g.,Fig.4?as with a =7.3±0.6?and b =5.5±0.6?,closely resembling the ab unit cell dimensions of bulk crystalline tetracene ?Fig.1?within the uncertainty of the measurements.In other words,the STM image in Fig.4provides direct evidence that the ?lm is crystallized with standing tetracene molecules on the ab plane on the inert substrate used.
Another striking feature of the STM image ?Fig.4?is that the bright rows ?i.e.,along the b axis ?appear matching the substrate lattice orientation.With the same sample and imag-ing orientation settings as that used for the silicon substrate ?Fig.2?a ??,the b -axis orientation imaged for the tetracene ?lm in Fig.4appears precisely along the ?110?direction as marked in Fig.2?a ?and Fig.4.Among many STM images obtained,the orientations of the bright rows ?along b axis in Fig.4?are either as that shown in Fig.4or appearing or-thogonal to it.Such ?lm lattice orientation aligned to the crystalline substrate indicates that the molecules can recog-nize and lock into some speci?c structure sites on the sub-strate at this ?lm coverage.
It is plausible that the herringbone lattice observed ?Fig.4?has a commensurate structural relationship to the substrate lattice.In addition to the orientation alignment between the molecular structure and the crystalline substrate as men-tioned above,the calibrated spacing between the bright rows ?i.e.,the lattice constant measured along a axis ?also matches well with the distance between the substrate monohydride dimer rows ?7.68??within the uncertainty of the measure-ments.Along the b axis ?i.e.,bright row ?direction in Fig.4,the lattice matching is not obvious,as neither substrate dimer spacing ?3.84??nor dimer row spacing ?7.68??match the b value.However,the multiple of b ?e.g.,5times as large ?in principle could lead to a superlattice to match the substrate ?as 5?6.03?=8?3.84?=4?7.68??.Though there is no visible superlattice modulation of image contrast indicated from our STM data,the existence of the superlattice cannot be excluded,as the modulation caused by the interface could be smeared out when imaged from a few molecular layers above.
Figure 5shows an AFM image of a 3ML tetracene ?lm on a H-terminated Si ?001?substrate.The image adds large-scale morphology information to what we learned from the STM data mentioned above.A line pro?le taken at the white bar ?AB ?is shown at the bottom of Fig.5,indicating the height of ?1.4nm for every layer including the buried ?rst layer at the ?lm-substrate interface.In contrast to the height measured on the fractal islands ?Fig.1?,the ?rst layer mol-ecules in the multilayer regions must have had their orienta-tions and packing rearranged to increase the tilt angle and hence the layer height in the growth.The line pro?le in Fig.5also allows a clear de?nition of the layers,we label them on the image with the second layer marked as “2,”and the third layer as “3,”etc.Since we never obtain any well-de?ned surface structure with STM when the ?lms were pre-pared with only the ?rst two monolayers presented,the mo-lecularly resolved STM images ?e.g.,Fig.4?most likely re?ect the structure of the third or higher layer in the sam-pling surface area.Nevertheless,all the molecularly resolved STM images consistently show the surface symmetry as that in Fig.4and orientation registration to the substrate lattice discussed above.
The AFM image shown in Fig.5indicates that the ?lm has a dramatic structure change and is highly crystallized on and after the third layer adsorption.First,the early third layer islands ?Fig.5?present two-dimensional ?2D ?dendrites with preferred branch orientations appearing perpendicular to each other,in clear contrast to the submonolayer fractal mor-phology ?Fig.2?that have randomly orientated branches.Second,there is a signi?cant change on the nucleation den-sity on top of the third layer:the density of the fourth layer islands is much higher than that of the previous layers ?Fig.6?,exhibiting a lower surface diffusivity on the third layer.Third,the step-edge nucleation appears effective once the third layer is formed ?e.g.,as marked by an arrow in Fig.5?that does not occur in the lower layers,indicating a structure change that causes Ehrlich-Schwoebel step barrier formed at the third layer edges.Finally,the formation of highly crys-tallized layers is consistent with our STM results that a well-ordered periodical lattice is presented on the https://www.wendangku.net/doc/6217082821.html,-pared to the ?lm morphology in Fig.6with that in Fig.3,
it
FIG.4.STM image ?85??85??of ?3ML tetracene ?lm on H/Si ?001?surface.A rectangular lattice mimics the tetracene “her-ringbone”crystalline structure on the ab layer.The coordinates in-dicate that of the underlying substrate lattice orientations.The ori-entation of the herringbone lattice appears to follow the substrate lattice.
TERSIGNI et al.PHYSICAL REVIEW B 74,205326?2006?
is concluded that a growth mode change has occurred be-tween these coverage stages.
In most cases,the orthogonal branched dendrites ?i.e.,the crosslike islands in Figs.5and 6?appear to have their two orthogonal branches oriented along the substrate domain di-rections ?Fig.6?,i.e.,along substrate ?110?and ??110?direc-tions,respectively.But,some dendritic islands rotated ap-proximately 45°in azimuth angle away from the substrate lattice directions are also observed,as shown in the middle part of Fig.5.Independent to which way the dendritic is-lands are oriented with respect to the substrate lattice,they always have their two main branch axes appearing mutually orthogonal.This structure character for the dendrites is not only consistent with what we have discussed that these third
layer islands are highly crystallized,but also indicating that their formation is mainly driven by molecular self-assembling.The fact that the majority of these surface is-lands follow the substrate lattice orientations ?Fig.6?sug-gests the existence of a non-negligible in?uence of the substrate lattice in the ?lm nucleation and growth,presum-ably the commensurate registration is more energetically fa-vorable.
The two apparently orthogonal orientations of the 2D den-drites shown on the third layer of the ?lm are believed to be the herringbone lattice ?010?and ?100?directions ?i.e.,along the directions of b axis and a axis,respectively,in Fig.1?.Theoretical results on pentacene crystal show that the mo-lecular binding energies ?E b ?at the in-plane facets are in the following relation:7E b ?010??E b ?100??E b ?other facets ?.The corresponding growth velocities of the ?010?and ?100?steps are thus relatively higher than the other facet steps,7i.e.,the growth probability along the b axis is the highest and the a axis the second highest ?see Fig.1?b ??.If a similar binding energy relation is applicable to the case of tetracene due to the structural similarity between the two polyacenes,then the preferred island branch developments observed ?Fig.5?can be explained by the relatively higher growth probabil-ity along the b axis and a axis ?which are close to orthogonal to each other ?,with the longer dimension being along the b axis.
B.X-ray absorption spectroscopy (NEXAFS)
To examine the interior structure of the ?lm and how it evolves with the ?lm morphology change discussed above,polarization dependent carbon 1s near edge x-ray absorption ?ne structure ?NEXAFS ??Ref.23?technique was applied.In this application the C 1s →?*photoionization resonance in-tensity ?I ?*?of the carbon atoms in the sample is measured,which varies with the relative orientation between the polar-ization of the incoming x-ray photon ?and the transition dipole moment ?P ?of the molecules following the relation-ship I ?*???·P ?2.The orientation of transition dipole
moment
FIG.5.AFM image ?25?m ?45?m ?of a 3ML tetracene ?lm on H/Si ?001?with anisotropic tetracene islands on the third and higher layer.A line pro?le taken at the white bar ?AB ?is shown at the bottom,indicating the height of ?1.4nm for each layer and suggesting the second,third,and fourth layers as marked by 2,3,and 4in the upper image,respectively.The coordinates indicate that of the underlying substrate lattice.An arrow marks a step-edge nucleation occurring on a third layer
island.
https://www.wendangku.net/doc/6217082821.html,rge scale AFM image ?50?m ?45?m ?of a 3ML tetracene ?lm on H/Si ?001?.Most of the anisotropic islands with their longer axes along substrate lattice orientations.The second and the third layers are marked by 2and 3in the image,respec-tively.The coordinates at the lower left corner indicate that of the substrate lattice.
STRUCTURE OF TETRACENE FILMS ON HYDROGEN-…PHYSICAL REVIEW B 74,205326?2006?
P for the ?*states of the aromatic rings is along the normal of the molecular plane.Therefore by measuring I ?*at differ-ent x-ray polarizations ?varying ??the orientation of P and hence that of the molecule with respect to the substrate can be deduced.In the current case the molecular orientation obtained represents an average over all the tetracene mol-ecule layers.
The angular relationships among the various quantities involved in the NEXAFS experiment are illustrated in Fig.7.For x-rays incident along the surface normal ??=90°?,an upright standing molecule such as the one schematically shown in Fig.7would yield strong ?*resonances,while for grazing-incidence x rays ??=10°?the ?*resonance intensity would be minimized.Note that the angle ?in Fig.7is the polar angle of P relative to the surface normal but there are two ways the molecular plane can be oriented to produce it:when the molecules are standing,e.g.,as the case illustrated in Fig.7;or when the molecule long axis lies in the plane and the molecule is rotated around its long axis.We exclude the latter case because the STM results shown in Fig.4and the AFM thickness estimates ?Figs.3and 5?clearly indicate that through all the growth stages the molecules are in a standing orientation.Therefore,the bigger tilting angle ?resulted from NEXAFS measurements indicates more up-right standing orientation.
In general,the resonance intensity I ?*may also depend on the azimuth orientation of the dipole transition moment relative to that of the x-ray polarization.However when the substrate lattice possesses a threefold or higher order of sym-metry,the azimuth dependence of I ?*vanishes.23Con-sidering that the H/Si ?100?-2?1substrate possesses two de-generate reconstruction domains ?2?1and 1?2?orthogonal to each other,under the macroscopic sampling area covered by x-ray beam,the substrate surface would behave as if there is a 2?2?fourfold ?symmetry.Therefore in our case the NEXAFS of the tetracene ?lms should be independent to
the ?lm azimuth orientation.This was con?rmed by our NEXAFS measurements.26In this simpli?ed high symmetry case,only two NEXAFS measurements at different x-ray incident angles ???are needed 22for determining the average molecule tilting angle ??in Fig.7?.The resonance intensity can now be described by the following expression:
I ?*??,???
p
3?1+12?3cos 2??1??3cos 2??1?
?
+
1?p
2
sin 2?,?1?
where p =?E ??2/??E ??2+?E ??2?is the degree of linear polariza-tion in the plane of the synchrotron storage ring electron beam orbit and E ?and E ?are the projections of the synchro-tron x-ray in and out of electron orbit plane,respectively.For radiation from a planar undulator as the case in this study,the polarization is always linear if observed in the same horizon-tal plane of the insertion device center.27When considering various factors,the estimated uncertainty of ?using the cur-rent CLS SGM beam line setup is ±3°,26so the degree of linear polarization p is estimated to be in the range of 97%to 100%.The results on using either 100%or 97%for p differ less than 2°and this uncertainty will be included in the ?nal ?angle error bar to be reported below.
Figure 8shows the typical NEXAFS data for the three tetracene ?lm thicknesses,with beam at normal incidence and grazing incidence with respect to sample surface.The strong contrast in the ?*resonance intensity from the two beam polarizations indicates that all the ?lms of different thicknesses possess a high degree of molecular orientation order.The overall spectral features in Fig.8are consistent with the results previously reported by Yokoyama et al.28for thick tetracene ?lm measured at the magic angle,but with more detail resolved below the ionization potential ?IP ?around ?291eV.The strongest resonance peak at 285.7eV,which has been generally assigned as a C 1s to ?*-orbitals resonance in polyacenes,29,30has its energy location and in-tensity unchanged through the ?lm thicknesses measured.This is actually the case for the other resolved features below IP as well.31Therefore chemically the molecules in all the ?lms are similar to each other,which is consistent with the expected chemically weak in?uence of the ?lm-substrate in-terface interaction.
Quantitative assessments on the molecular orientation re-quire molecular orbital identi?cations of observed resonance features in Fig.8.Theoretical study by ?gren et al.29has shown that the discrete resonance features in tetracene NEXAFS below the ionization potential consist predomi-nantly in the split single ?*states of the excited carbon at-oms.The spreading of the ?*resonance has been mainly attributed to energy and intensity variation of the resonance caused by the core-hole interaction effect ??nal state effect ?,and in addition to the site-dependent core ionization energy ?initial state effect ?.29,30Similar conclusion as that of ?gren et al.was reached in a recent NEXAFS study of epitaxial growth pentacene ?lms on Cu ?110?surface by S?hnchen et al.,32where the discrete resonance features below the ioniza-tion potential were found to have an almost pure ?*
charac-
FIG.7.Schematic view of the set-up geometry for the NEXAFS measurements.Tetracene molecule is represented by the rectangular grid sheet.The angle between the molecular transition dipole mo-ment ?P ??oriented normal to the plane of aromatic rings ?and the substrate surface normal ?Z ?is the tilting angle ?measured by NEXAFS.X-ray incidence angle ???with respect to the substrate surface is adjusted by rotating around R ?x-ray direction is station-ary in experiment ?.The linear polarization direction of the x ray is indicated by the vector ?.
TERSIGNI et al.PHYSICAL REVIEW B 74,205326?2006?
ter.Based on these results,we treat all the resonance features below IP in Fig.8as due to ?*contributions ?I ?*?,and the insigni?cant intensity with ?*character from the tetracene end atoms 29in this spectral region is neglected.26With these spectral assignments,the clear polarization dependence of the ?*states in Fig.8indicates that the molecules in these ?lms are all in an upwards standing state.The area under-neath the ?*resonances was integrated from 284.2eV to 291.0eV to obtain the measured resonance in-tensities at the two polarization angles and hence the experi-mental I ?*??=10°?/I ?*??=90°?ratios ?Table I ?.Using the expression ?1?,the theoretical I ?*??=10°?/I ?*??=90°?ratio as a function of molecular orientation angle ?is plotted,and
on this curve with an experimentally measured resonance intensity ratio the corresponding angle ?is read out.Quan-titative analysis of the data in Fig.8leads to the results of ?varying as the ?lm thickness,which is summarized in Table I and plotted in Fig.9.
IV .DISCUSSIONS
Some insights about the structural evolution in the tet-racene ?lm growth on H/Si ?100?-2?1bore out by compar-ing the results from the three techniques applied,i.e.,the lateral lattice orientation and dimensions given by STM,the interlayer separation or monolayer height and the morphol-ogy measured by AFM,and the molecular tilting angles as a function of the ?lm thickness by NEXAFS.
For bulk tetracene crystal,the unit cell of the herringbone lattice on the ab plane consists of two molecules.With re-spect to the ab plane normal,these two molecules have their molecular plane normal oriented at angles of 81.9°and 70.1°,respectively.4Therefore,the average tilting angle of the two molecular-plane normals is 76°for the bulk tetracene crystal.33In other words,if measured by NEXAFS,the av-erage tilting angle ???for the bulk case would be 76°.
The NEXAFS data clearly indicate that the measured ?of the tetracene ?lm changes with increasing thickness ?Table I and Fig.9?.For the 1.2ML ?lm,the average tilting angle is 65°±3°,well below the bulk case ?76°?.Considering the smaller height ??1nm ?obtained from AFM for the uncov-ered ?rst monolayer and the corresponding result of nonor-dered structures imaged from STM,it is no surprise that the ?lm exhibits a different molecular tilting angle from that of the bulk at this thickness.The obtained lower tilting angle in conjunction with the AFM and STM data suggests that the ?lm is signi?cantly disordered with an average molecular density lower than that in the bulk crystal.
At 3ML nominal coverage,NEXAFS results indicate that the average tilting angle has increased signi?cantly to 74°±4°,close to the bulk case value.STM and AFM also indicate signi?cant structural changes at this ?lm thickness:the molecularly resolved STM images exhibit ordered sur-face structures with commensurate relations to the
substrate
FIG.8.Carbon K -edge NEXAFS data for tetracene ?lms on H/Si ?001?.The ?lm thicknesses are as marked in the ?gure.The data with x ray at normal incidence ??=90°?and grazing-incidence ??=10°?are shown by the solid lines and dotted lines,respectively.Data for 3ML and 15ML are shifted vertically for clarity.
TABLE I.Determination of the average molecule tilting angle ???between the molecular transition dipole moment and the sub-strate normal.
Thickness ?ML ?
Experimental I ??=10°?/I ??=90°?
?15ML 13.9%78°±4°3ML 20.6%74°±4°1.2ML
46.7%
65°±3°
FIG.9.The measured average molecule tilting angle ???as a function of the ?lm thickness.The line segments linking the points are only for visual aid purpose.
STRUCTURE OF TETRACENE FILMS ON HYDROGEN-…PHYSICAL REVIEW B 74,205326?2006?
lattice;and the AFM images illustrate drastic changes in the ?lm morphology and a uni?ed length for the monolayer height of each layer in the multilayer regions.We believe that these results from different techniques must be origi-nated from a common structural evolution event.We at-tribute the signi?cant increase of molecule tilting angle at3 ML as due to the formation of the extended epitaxial do-mains?Fig.4and the anisotropic islands on and above the third layer in Fig.5?.Even though the STM imaging mostly shows the lattice symmetry of the top layer of the?lm,judg-ing from the absence of any additional contrast modulation in the STM imaging,the difference in lattice symmetry be-tween the top layer and the layer underneath is unlikely.In addition,the essentially same layer height for each layer in the multilayer islands shown by AFM?Fig.5?indicates a vertical crystalline uniformity among the layers,including the?rst monolayer at the interface,which is consistent with our conjecture that the herringbonelike crystalline symmetry in Fig.4has been con?gured through all the layers forming the epitaxial https://www.wendangku.net/doc/6217082821.html,paring the lattice constants be-tween a bulk tetracene crystal?a=7.90??and the silicon substrate?dimer row spacing=7.68??,a laterally compres-sive?lm lattice is expected for the epitaxial domains.Appar-ently,in a laterally compressed epitaxial domain the mol-ecules would stand more upright than in the bulk to accommodate the higher lateral packing density.The fact that the average titling angle for the whole?lm from NEXAFS is about the bulk value would require some mol-ecules in the?lm having lower tilting angles.Two aspects may be accountable:?1?The areas where only two monolay-ers present in Fig.5are likely the modest tilting angle re-gions,as the ordered structures were not obtained from our STM measurements on top of a second layer;?2?from the ?lm morphology shown in Figs.5and6there are terraced islands up to seven layers above the interface where the tilt-ing angle for the upper layer molecules are expected,lower, as the?lm lattice is anticipated to be gradually relaxed along the distance away from the interface.
It appears that there is a structural phase transition asso-ciated with the?lm thickness.In addition to the presented data,we notice that the highly crystallized islands?i.e.,the apparent epitaxial domains?emerge with the third layer for-mation on the surface from our AFM measurements.34The detail mechanism behind the phase transition is not clear.We speculate that with the increasing coverage more molecules may squeeze into the less densely packed?rst and second layers;the densi?cation of the layers would enhance the in-tralayer molecular interaction and lead to a rearrangement on the packing and orientation towards the bulk con?guration, and the in?uence of the substrate lattice remains somewhat effective,therefore resulting in the apparent epitaxial do-mains observed.Similar?lm coverage-dependent rearrange-ment of molecules was reported for physisorbed benzene on Ru?001?surface,3,35where the initially parallel oriented?rst physisorbed layer?above the parallel oriented?rst chemi-sorbed layer on the clean Ru surface?was found to rearrange into a more crowded layer with a high molecular tilt angle at higher coverages??1ML?.35In the growth of tetracene on H/Si?001?in this work,the effect of the proposed molecule rearrangement and reorientation is signi?cant at about3ML, and we believe that the apparent epitaxial domains?Fig.4?are not formed initially at a lower coverage.The kinetics and the driving force of the structure transition require further investigations
After the drastic tilting angle change at3ML?Fig.9?,a new type of growth template appears on the?lm surface. Comparing to the fast increase of the molecule tilting angle from1.2ML to3ML,the further growth up to15ML introduces an insigni?cant increase in the molecule tilting angle?Fig.9?.The small average tilting angle increase,if meaningful,is likely related to the existence of nonepitaxial regions at3ML which are transformed to the epitaxial do-mains in the further growth.In fact at both3ML and15ML the average tilting angles?Table I?are basically in agreement with that of the average bulk value of76°.
V.CONCLUSIONS
The structure of tetracene?lms on H-terminated Si?001?, obtained under the optimized layer-by-layer growth process,14has been investigated by different structural probes?STM,AFM,NEXAFS?.All the?lms investigated exhibit tetracene molecules in upright standing geometry on the ab plane.Under the?lm growth condition,the lateral packing for the molecules in the initial?lm is largely disor-dered.With increasing the?lm coverage to around3ML,a structural phase transition occurs which leads to the forma-tion of apparent epitaxial domains with a commensurate structural relationship with the substrate lattice.From an abrupt increase in the molecular tilting angle in the?lm when approaching3ML coverage?NEXAFS?and from the compressive nature of the lateral?lm lattice?STM?,it is suggested that the molecules in the epitaxial domains could be tilting more upright than in the corresponding bulk case. For the growth beyond3ML,the average molecule tilting angle levels around the bulk value.
ACKNOWLEDGMENTS
We gratefully acknowledge Brian S.Swartzentruber for valuable discussions and help in setting up our STM control system and John R.Dutcher for permitting our access to his AFM instrument for this study.D.T.J.would like to thank Tom Regier and Tom Koztzer for assistance in NEXAFS measurements at Canadian Light Source.This work was sup-ported by the Natural Science and Engineering Research Council of Canada?NSERC?,and by the Canada Foundation for Innovation?CFI?and the Ontario Innovation Trust?OIT?. The operation of the CLS is supported by an NSERC MFA grant.
TERSIGNI et al.PHYSICAL REVIEW B74,205326?2006?
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31Note:For the1.2ML grazing angle data in Fig.8,the peak feature near the onset of the resonances??283.5eV?is likely due to the imperfection of the background correction scheme, not a real spectral feature.
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STRUCTURE OF TETRACENE FILMS ON HYDROGEN-…PHYSICAL REVIEW B74,205326?2006?
on the contrary的解析
On the contrary Onthecontrary, I have not yet begun. 正好相反，我还没有开始。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, the instructions have been damaged. 反之，则说明已经损坏。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, I understand all too well. 恰恰相反，我很清楚 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, I think this is good. ⑴我反而觉得这是好事。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, I have tons of things to do 正相反，我有一大堆事要做 Provided by jukuu Is likely onthecontrary I in works for you 反倒像是我在为你们工作 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, or to buy the first good. 反之还是先买的好。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, it is typically american. 相反，这正是典型的美国风格。 222.35.143.196 Onthecontrary, very exciting.
恰恰相反，非常刺激。 https://www.wendangku.net/doc/6217082821.html, But onthecontrary, lazy. 却恰恰相反，懒洋洋的。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, I hate it! 恰恰相反，我不喜欢！ https://www.wendangku.net/doc/6217082821.html, Onthecontrary, the club gathers every month. 相反，俱乐部每个月都聚会。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, I'm going to work harder. 我反而将更努力工作。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, his demeanor is easy and nonchalant. 相反，他的举止轻松而无动于衷。 https://www.wendangku.net/doc/6217082821.html, Too much nutrition onthecontrary can not be absorbed through skin. 太过营养了反而皮肤吸收不了. https://www.wendangku.net/doc/6217082821.html, Onthecontrary, I would wish for it no other way. 正相反，我正希望这样 Provided by jukuu Onthecontrary most likely pathological. 反之很有可能是病理性的。 https://www.wendangku.net/doc/6217082821.html, Onthecontrary, it will appear clumsy. 反之，就会显得粗笨。 https://www.wendangku.net/doc/6217082821.html,
英语造句
一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
学生造句--Unit 1
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
英语句子结构和造句
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
六级单词解析造句记忆MNO
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
base on的例句
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
(完整版)主谓造句
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
初中英语造句
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
The Kite Runner-美句摘抄及造句
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high
翻译加造句
一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。 二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时 助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房
改写句子练习2标准答案
The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.
用以下短语造句
M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of
英语造句
English sentence 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能 句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的 句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character.（2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品