Microstructures of GaN buffer layers grown on Si(111)substrates using rapid thermal process low-pressure metalorganic chemical vapor deposition are investigated by an atomic force microscope(AFM)and a high-resolution ...Microstructures of GaN buffer layers grown on Si(111)substrates using rapid thermal process low-pressure metalorganic chemical vapor deposition are investigated by an atomic force microscope(AFM)and a high-resolution transmission electron microscope(HBTEM).AFM images show that the islands appear in the GaN buffer layer after annealing at high temperature.Cross-sectional HBTEM micrographs of the buffer region of these samples indicate that there are bunched steps on the surface of the Si substrate and a lot of domains in GaN misorienting each other with small angles.The boundaries of those domains locate near the bunched steps,and the regions of the Him on a terrace between steps have the same crystal orientation.An amorphous-like layer,about 3nm thick,can also be observed between the GaN buffer layer and the Si substrate.展开更多
C_(60)-benzene solutions are used as a new type of nonlinear Medium for observing cw self-focusing of laser beams.Self-phase modulation of much low power laser beam has been observed.The response time of C_(60)-benzen...C_(60)-benzene solutions are used as a new type of nonlinear Medium for observing cw self-focusing of laser beams.Self-phase modulation of much low power laser beam has been observed.The response time of C_(60)-benzene solution has been measured.展开更多
An experimental study of the optical diffraction on SierpiAski carpet is performed.The theoretical formula for diffraction intensity is derived and computer Simulation is carried out in order to compare with experimen...An experimental study of the optical diffraction on SierpiAski carpet is performed.The theoretical formula for diffraction intensity is derived and computer Simulation is carried out in order to compare with experimentally observed diffraction pattern.The results show that the pattern of the Fourier transform of a fractai grating is also selfsimilar and the fractal dimension may be determined with optical measurement.展开更多
An nc-Si floating gate MOS structure is fabricated by thermal annealing of SiN_(x)/a-Si/SiO_(2).There are nc-Si dots isolated by a-Si due to partial crystallization.Conductance-voltage(G–V)measurements are performed ...An nc-Si floating gate MOS structure is fabricated by thermal annealing of SiN_(x)/a-Si/SiO_(2).There are nc-Si dots isolated by a-Si due to partial crystallization.Conductance-voltage(G–V)measurements are performed to investigate the effect of multiple interface states including Si-sub/SiO_(2),a-Si related(as-deposited sample)and nc-Si(annealed sample)in a charge trapping/releasing process.Double conductance peaks located in the depletion and weak inversion regions are found in our study.For the as-deposited sample,the Si-sub/SiO_(2) related G–V peak with weak intensity shifts to the negative as test frequency increases.The a-Si related G–V peak with strong intensity shifts slightly with the increasing frequency.For the annealed sample,little change appears in the intensity and shift of Si-sub/SiO_(2) related G–V peaks.The position of a-Si/nc-Si related peak is independent of frequency,and its intensity is weaker compared to that of the as-deposited sample.It is also found that as the size of nc-Si becomes larger,the a-Si/nc-Si related peak shifts to the depletion region due to the size effect of nc-Si.展开更多
Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders,not in single crystals,of C_(60) from which solvents and impuri...Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders,not in single crystals,of C_(60) from which solvents and impurities had been carefully excluded.This is attributed to phase transformation facilitated by nucleation around stacking faults.This proposal is supported by internal friction measurements on films,which confirmed the presence of this secondary transition,and by x-ray diffraction,which detected an hcp structure within the fcc lattice of C_(60) at room temperature.展开更多
Photoreflectance was used to study the optical properties of single crystal hexagonal GaN finis on(0001)sapphire substrate grown by metalorganic chemical vapor deposition.The energy gap of GaN was determined as 3.400 ...Photoreflectance was used to study the optical properties of single crystal hexagonal GaN finis on(0001)sapphire substrate grown by metalorganic chemical vapor deposition.The energy gap of GaN was determined as 3.400 eV and the possible origin of the signal was discussed.Optical absorption and reflection were measured.The optical absorption edge of 3.38 eV,and the reilectivity peak at 3.3 eV, confirmed the results of photoreiiectance.展开更多
Raman spectra of LiNbO_(3) crystals with different hydrogen-ion-exchanged time were examined.E(TO)and A1(TO)modes appear gradually in the transverse A1-and E-symmetry spectra respectively with increasing the exchange ...Raman spectra of LiNbO_(3) crystals with different hydrogen-ion-exchanged time were examined.E(TO)and A1(TO)modes appear gradually in the transverse A1-and E-symmetry spectra respectively with increasing the exchange time and the dependence of their intensities on the exchange time is also observed.We attribute these results to both the internal strains resulting from the ordering-disordering distribution of H ions in the sample and the enhanced photorefractive effect.展开更多
We report the successful synthesis of Ge clusters embedded in a-SiNy:H matrix prepared by the plasma enhanced chemical vapor deposition(PECVD)method.Chemical and microstructural characteristics of this granular thin f...We report the successful synthesis of Ge clusters embedded in a-SiNy:H matrix prepared by the plasma enhanced chemical vapor deposition(PECVD)method.Chemical and microstructural characteristics of this granular thin film were analyzed using the infrared absorption,x-ray diffraction,Raman scattering,and transmission electron microscopy.Finally we discuss briefly the synthesis mechanism of this new material.展开更多
By flux method,potassium tantalate niobate crystals with 46%Nb contents were prepared.In this material 90°a-type domains with(011)and(01ī)walls were observed by a transmission electron microscope,and the nature ...By flux method,potassium tantalate niobate crystals with 46%Nb contents were prepared.In this material 90°a-type domains with(011)and(01ī)walls were observed by a transmission electron microscope,and the nature of fringe patterns associated with these domain walls was analysed.According to the extinction rules for the domain walls,the displacement vector R along<01ī>direction can be determined.Finally,using a selected area electron diffraction method,we examined the crystallographic character of these 90°domains and defined the ratio of lattice parameters c to a.展开更多
The a-Ge:H/a-SiNx:H multiquantiim-well structures were prepared by a computercon trolied plasma,enhanced clieinicaJ vapor deposition method and tAeii crystallized by At+laser annealing technique.When the Ge well-layer...The a-Ge:H/a-SiNx:H multiquantiim-well structures were prepared by a computercon trolied plasma,enhanced clieinicaJ vapor deposition method and tAeii crystallized by At+laser annealing technique.When the Ge well-layer thickness was reduced to 30 A,the crystallized sample showed a roojn temperature pLotoluininescence with a peak at about 2.26 eV.Mennwhile some significant characteristics of such a novel Ge na.nostructiire were also revealed by x-ray difEraction.Possible mechanisms of this visible PL phenomenon have been discussed.展开更多
We report the experimental observation of electric field induced Gso redistribution,in benzene solution by thermal blooming change of transmitted light.The pol&riz&tion of C_(60) molecules in external field is...We report the experimental observation of electric field induced Gso redistribution,in benzene solution by thermal blooming change of transmitted light.The pol&riz&tion of C_(60) molecules in external field is analyzed.展开更多
We present nieasureinents of two-pho ton absorption(TPA)coefficient of C_(60) thin Hhn at 633nm.Large values of β〜5cm/W were determined.Nearly~resona.nt TPA transition around 3.76eV absorption region was discussed.
Hydrogenated amorphous silicon carbide(a-Sic_(x):H)films were prepared by glow discharge technique with gas mixture of silane(SiH_(4))and methan(CH_(4)).The room-temperature optical bistability was demonstrated in unc...Hydrogenated amorphous silicon carbide(a-Sic_(x):H)films were prepared by glow discharge technique with gas mixture of silane(SiH_(4))and methan(CH_(4)).The room-temperature optical bistability was demonstrated in uncoated a-SiC_(x):H films at the excitation wavelength about 532nm.The switch-on intensity of device is about 0.8 MW/cm^(2) and the switching time is in the nanosecond scale.The physical origin of the optical nonlin5arity in these materials is also discussed.展开更多
Two types of the ordered structures associated with the ordering of Sc and Nb cations in the perovskite-type compound Pb_(2)ScNbO_(6) were revealed by electron diffraction,and the 111-type ordering was further confirm...Two types of the ordered structures associated with the ordering of Sc and Nb cations in the perovskite-type compound Pb_(2)ScNbO_(6) were revealed by electron diffraction,and the 111-type ordering was further confirmed by a special high resolution electron microscopy.The 111-type ordered domains,from a few unit cells to 3nm in size,distribute in the matrix with a disordered structure,and exhibit a characteristic of local ordering.展开更多
The degradation of C_(60) in organic solution by light has been reported by Taylor et al.[Nature,351(1991)277].The powders of the mixture of C_(60) and C_(70) prepared by arc heating ofgraphite electrodes in the envir...The degradation of C_(60) in organic solution by light has been reported by Taylor et al.[Nature,351(1991)277].The powders of the mixture of C_(60) and C_(70) prepared by arc heating ofgraphite electrodes in the environment of He gas was not to be stable with respect to intense irradiation of argon laser(488.0nm),as monitored by Raman spectrascopy,C_(70) is found to be first decomposed into fragmentary graphite,then C_(60) followed suit.It is interesting to note that besides graphite,some traces of diamond-like structure are shown confirming some speculations of Mackay[Nature,352(1991)762].展开更多
1-D quasiperiodic(Fibonacci)Cu/Ti metallic superlattices have been pared tn a dual magnetron sputter deposition system.X-ray scattering measurements of these samples are presented・The X-ray diffraction peaks at low an...1-D quasiperiodic(Fibonacci)Cu/Ti metallic superlattices have been pared tn a dual magnetron sputter deposition system.X-ray scattering measurements of these samples are presented・The X-ray diffraction peaks at low angles can be indexed by the projection method from the high-dimensional periodic structure.In the high angle region,there is one broad peak,which indicates that the samples are amorphous.展开更多
The kinesics of the early stages of the decomposition reaction in a Cu-1.75at.%Co solid solution aged at 853K were investigated with APFIM(Atom Probe Field Ior Microscopy)and TEM(Transmission Electron Microscopy).The ...The kinesics of the early stages of the decomposition reaction in a Cu-1.75at.%Co solid solution aged at 853K were investigated with APFIM(Atom Probe Field Ior Microscopy)and TEM(Transmission Electron Microscopy).The radius of the critical nucleus ofα-phase was revealed to be about 0.8nm.The Co-concentration in the fine precipitates was determined to be(95±2)at.%.The results were interpreted in terms of Kampmann-Wagner numerical model for the kinetics of nucleation and growth decomposition in solids.展开更多
K_(o)-image of the Brazil twin boundary in quartz crystal by X-ray section topography and the same contrasts of the first fringes for entrance and exit surface are shown in this paper.
A radio-frequency heating Czochralski technique to obtain LiTaO3 crystals with modulated structure(periodic lamina of ferroelectric domains)is first presented.The alternation of the ferroelectric domains whose half-pe...A radio-frequency heating Czochralski technique to obtain LiTaO3 crystals with modulated structure(periodic lamina of ferroelectric domains)is first presented.The alternation of the ferroelectric domains whose half-period nearly corresponds to the coherence length LC has been achieved.Quasi-phase-matching for the nonlinear coefficient d_(33) has been first realized using 1.06μm Nd:YAG laser in crystals LiTnO_(3).展开更多
Raman spectra during the transformation from fullerite to amorphous carbon are analyzed.The transformation temperature is obtained from intensity ratio of Stokes and anti-Stokes lines by using Placzek’s formula.The t...Raman spectra during the transformation from fullerite to amorphous carbon are analyzed.The transformation temperature is obtained from intensity ratio of Stokes and anti-Stokes lines by using Placzek’s formula.The temperature,less than 2.0 x103K,is in consistence with previous work.展开更多
基金Supported by Project of High Technology Research&Development of China(863-715-011-0030),Project of Fundamental Research of China,the National Natural Science Foundation of China under Grant Nos.69636010 and 69636040,and MOTOROLA(China Inc.)Semiconductor Scholarship.
文摘Microstructures of GaN buffer layers grown on Si(111)substrates using rapid thermal process low-pressure metalorganic chemical vapor deposition are investigated by an atomic force microscope(AFM)and a high-resolution transmission electron microscope(HBTEM).AFM images show that the islands appear in the GaN buffer layer after annealing at high temperature.Cross-sectional HBTEM micrographs of the buffer region of these samples indicate that there are bunched steps on the surface of the Si substrate and a lot of domains in GaN misorienting each other with small angles.The boundaries of those domains locate near the bunched steps,and the regions of the Him on a terrace between steps have the same crystal orientation.An amorphous-like layer,about 3nm thick,can also be observed between the GaN buffer layer and the Si substrate.
基金Supported by the National Natural Science Foundation of China.
文摘C_(60)-benzene solutions are used as a new type of nonlinear Medium for observing cw self-focusing of laser beams.Self-phase modulation of much low power laser beam has been observed.The response time of C_(60)-benzene solution has been measured.
文摘An experimental study of the optical diffraction on SierpiAski carpet is performed.The theoretical formula for diffraction intensity is derived and computer Simulation is carried out in order to compare with experimentally observed diffraction pattern.The results show that the pattern of the Fourier transform of a fractai grating is also selfsimilar and the fractal dimension may be determined with optical measurement.
基金Supported by the National Basic Research Program of China under Grant No 2010CB934402the National Natural Science Foundation of China under Grant Nos 61071008,10974091,and 60976001the Fundamental Research Funds for the Central Universities under Grant Nos 1095021030,1116021004,and 1114021005.
文摘An nc-Si floating gate MOS structure is fabricated by thermal annealing of SiN_(x)/a-Si/SiO_(2).There are nc-Si dots isolated by a-Si due to partial crystallization.Conductance-voltage(G–V)measurements are performed to investigate the effect of multiple interface states including Si-sub/SiO_(2),a-Si related(as-deposited sample)and nc-Si(annealed sample)in a charge trapping/releasing process.Double conductance peaks located in the depletion and weak inversion regions are found in our study.For the as-deposited sample,the Si-sub/SiO_(2) related G–V peak with weak intensity shifts to the negative as test frequency increases.The a-Si related G–V peak with strong intensity shifts slightly with the increasing frequency.For the annealed sample,little change appears in the intensity and shift of Si-sub/SiO_(2) related G–V peaks.The position of a-Si/nc-Si related peak is independent of frequency,and its intensity is weaker compared to that of the as-deposited sample.It is also found that as the size of nc-Si becomes larger,the a-Si/nc-Si related peak shifts to the depletion region due to the size effect of nc-Si.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grand No.BK97224Hong Kong Baptist University.
文摘Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders,not in single crystals,of C_(60) from which solvents and impurities had been carefully excluded.This is attributed to phase transformation facilitated by nucleation around stacking faults.This proposal is supported by internal friction measurements on films,which confirmed the presence of this secondary transition,and by x-ray diffraction,which detected an hcp structure within the fcc lattice of C_(60) at room temperature.
文摘Photoreflectance was used to study the optical properties of single crystal hexagonal GaN finis on(0001)sapphire substrate grown by metalorganic chemical vapor deposition.The energy gap of GaN was determined as 3.400 eV and the possible origin of the signal was discussed.Optical absorption and reflection were measured.The optical absorption edge of 3.38 eV,and the reilectivity peak at 3.3 eV, confirmed the results of photoreiiectance.
文摘Raman spectra of LiNbO_(3) crystals with different hydrogen-ion-exchanged time were examined.E(TO)and A1(TO)modes appear gradually in the transverse A1-and E-symmetry spectra respectively with increasing the exchange time and the dependence of their intensities on the exchange time is also observed.We attribute these results to both the internal strains resulting from the ordering-disordering distribution of H ions in the sample and the enhanced photorefractive effect.
基金the National Natural Science Foundation of China.
文摘We report the successful synthesis of Ge clusters embedded in a-SiNy:H matrix prepared by the plasma enhanced chemical vapor deposition(PECVD)method.Chemical and microstructural characteristics of this granular thin film were analyzed using the infrared absorption,x-ray diffraction,Raman scattering,and transmission electron microscopy.Finally we discuss briefly the synthesis mechanism of this new material.
基金Supported by the National Natural Science Foundation of China。
文摘By flux method,potassium tantalate niobate crystals with 46%Nb contents were prepared.In this material 90°a-type domains with(011)and(01ī)walls were observed by a transmission electron microscope,and the nature of fringe patterns associated with these domain walls was analysed.According to the extinction rules for the domain walls,the displacement vector R along<01ī>direction can be determined.Finally,using a selected area electron diffraction method,we examined the crystallographic character of these 90°domains and defined the ratio of lattice parameters c to a.
文摘The a-Ge:H/a-SiNx:H multiquantiim-well structures were prepared by a computercon trolied plasma,enhanced clieinicaJ vapor deposition method and tAeii crystallized by At+laser annealing technique.When the Ge well-layer thickness was reduced to 30 A,the crystallized sample showed a roojn temperature pLotoluininescence with a peak at about 2.26 eV.Mennwhile some significant characteristics of such a novel Ge na.nostructiire were also revealed by x-ray difEraction.Possible mechanisms of this visible PL phenomenon have been discussed.
基金Supported by the National Natural Science Foundation of China.
文摘We report the experimental observation of electric field induced Gso redistribution,in benzene solution by thermal blooming change of transmitted light.The pol&riz&tion of C_(60) molecules in external field is analyzed.
基金Supported by the National Natural Science Foundation of China。
文摘We present nieasureinents of two-pho ton absorption(TPA)coefficient of C_(60) thin Hhn at 633nm.Large values of β〜5cm/W were determined.Nearly~resona.nt TPA transition around 3.76eV absorption region was discussed.
基金Supported by the National Natural Science Foundation of China.
文摘Hydrogenated amorphous silicon carbide(a-Sic_(x):H)films were prepared by glow discharge technique with gas mixture of silane(SiH_(4))and methan(CH_(4)).The room-temperature optical bistability was demonstrated in uncoated a-SiC_(x):H films at the excitation wavelength about 532nm.The switch-on intensity of device is about 0.8 MW/cm^(2) and the switching time is in the nanosecond scale.The physical origin of the optical nonlin5arity in these materials is also discussed.
文摘Two types of the ordered structures associated with the ordering of Sc and Nb cations in the perovskite-type compound Pb_(2)ScNbO_(6) were revealed by electron diffraction,and the 111-type ordering was further confirmed by a special high resolution electron microscopy.The 111-type ordered domains,from a few unit cells to 3nm in size,distribute in the matrix with a disordered structure,and exhibit a characteristic of local ordering.
基金Supported by the National Ph.D.Foundation of Chinathe Center of Materials Analysis,No.1991-1992.
文摘The degradation of C_(60) in organic solution by light has been reported by Taylor et al.[Nature,351(1991)277].The powders of the mixture of C_(60) and C_(70) prepared by arc heating ofgraphite electrodes in the environment of He gas was not to be stable with respect to intense irradiation of argon laser(488.0nm),as monitored by Raman spectrascopy,C_(70) is found to be first decomposed into fragmentary graphite,then C_(60) followed suit.It is interesting to note that besides graphite,some traces of diamond-like structure are shown confirming some speculations of Mackay[Nature,352(1991)762].
基金supported by National Natural Science Foundation of China.
文摘1-D quasiperiodic(Fibonacci)Cu/Ti metallic superlattices have been pared tn a dual magnetron sputter deposition system.X-ray scattering measurements of these samples are presented・The X-ray diffraction peaks at low angles can be indexed by the projection method from the high-dimensional periodic structure.In the high angle region,there is one broad peak,which indicates that the samples are amorphous.
基金Project supported by the National Science Foundation of China。
文摘The kinesics of the early stages of the decomposition reaction in a Cu-1.75at.%Co solid solution aged at 853K were investigated with APFIM(Atom Probe Field Ior Microscopy)and TEM(Transmission Electron Microscopy).The radius of the critical nucleus ofα-phase was revealed to be about 0.8nm.The Co-concentration in the fine precipitates was determined to be(95±2)at.%.The results were interpreted in terms of Kampmann-Wagner numerical model for the kinetics of nucleation and growth decomposition in solids.
文摘K_(o)-image of the Brazil twin boundary in quartz crystal by X-ray section topography and the same contrasts of the first fringes for entrance and exit surface are shown in this paper.
文摘A radio-frequency heating Czochralski technique to obtain LiTaO3 crystals with modulated structure(periodic lamina of ferroelectric domains)is first presented.The alternation of the ferroelectric domains whose half-period nearly corresponds to the coherence length LC has been achieved.Quasi-phase-matching for the nonlinear coefficient d_(33) has been first realized using 1.06μm Nd:YAG laser in crystals LiTnO_(3).
文摘Raman spectra during the transformation from fullerite to amorphous carbon are analyzed.The transformation temperature is obtained from intensity ratio of Stokes and anti-Stokes lines by using Placzek’s formula.The temperature,less than 2.0 x103K,is in consistence with previous work.
