Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used...Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.展开更多
The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth condi...The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 （TO）, E1 （TO） and A1 （LO） phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 （TO） modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 （TO） mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 （longitudinal optical plasma coupling （LOPC）） mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 （LOPC） mode in 4H-SiC.展开更多
This paper investigates the effect of growth temperature on morphology, structure and photoluminescence （PL） of Tb-doped boron nitride （BN） films grown by magnetron sputtering, and the relationships of growth-temp...This paper investigates the effect of growth temperature on morphology, structure and photoluminescence （PL） of Tb-doped boron nitride （BN） films grown by magnetron sputtering, and the relationships of growth-temperature- structure-PL by scanning electron microscopy, transmission electron microscopy and PL. The characteristic emission lines of the Tb^3＋ were observed in the PL spectra at room temperature. The 473-K-grown film is mainly consisted of amorphous BN particles. With the growth temperature increasing up to 1273 K, the amount of amorphous BN decreases, while the amount of turbostratic BN increases. Correspondingly, the PL intensities from the Tb^3＋ ions increase with the increase of temperature in the range of 473 1273 K.展开更多
The initial growth and microstructure feature of Ag films formation were investigated, which were prepared by using the very-high-frequency（VHF）（60 MHz） magnetron sputtering. Because of the moderate energy and ver...The initial growth and microstructure feature of Ag films formation were investigated, which were prepared by using the very-high-frequency（VHF）（60 MHz） magnetron sputtering. Because of the moderate energy and very low flux density of ions impinging on the substrate, the evolutions of initial growth for Ag films formation were well controlled by varying the sputtering power. It was found that the initial growth of Ag films followed the island（Volmer—Weber, VW） growth mode, but before the island nucleation, the adsorption of Ag nanoparticles and the formation of Ag clusters dominated the growth. Therefore, the whole initial stages of Ag films formation included the adsorption of nanoparticles, the formation of clusters, the nucleation by the nanoparticles and clusters simultaneously, the islands formation, and the coalescence of islands.展开更多
We report the successful growth of the tetragonal FeS film with one or two unit-cell （UC） thickness on SrTiO33（001） substrates by molecular beam epitaxy. Large lattice constant mismatch with the substrate leads to...We report the successful growth of the tetragonal FeS film with one or two unit-cell （UC） thickness on SrTiO33（001） substrates by molecular beam epitaxy. Large lattice constant mismatch with the substrate leads to high density of defects in single-UC FeS, while it has been significantly reduced in the double-UC thick film due to the lattice relaxation. The scanning tunneling spectra on the surface of the FeS thin film reveal the electronic doping effect of single-UC FeS from the substrate. In addition, at the Fermi level, the energy gaps of approximately 1.5？meV are observed in the films of both thicknesses at 4.6？K and below. The absence of coherence peaks of gap spectra may be related to the preformed Cooper-pairs without phase coherence.展开更多
We report the growth of InSb layers directly on GaAs （001） substrates without any buffer layers by molecular beam epitaxy （MBE）. Influences of growth temperature and V/Ⅲ flux ratios on the crystal quality, the su...We report the growth of InSb layers directly on GaAs （001） substrates without any buffer layers by molecular beam epitaxy （MBE）. Influences of growth temperature and V/Ⅲ flux ratios on the crystal quality, the surface morphology and the electrical properties of InSb thin films are investigated. The InSb samples with room- temperature mobility of 44600cm2/Vs are grown under optimized growth conditions. The effect of defects in InSb epitaxial on the electrical properties is researched, and we infer that the formation of In vacancy （VIn） and Sb anti-site （SbIn） defects is the main reason for concentrations changing with growth temperature and Sb2/In flux ratios. The mobility of the InSb sample as a function of temperature ranging from 90 K to 360K is demonstrated and the dislocation scattering mechanism and phonon scattering mechanism are discussed.展开更多
Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of...Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of the samples are characterized by atomic force microscopy. The full width at half maximum （FWHM） of the HVPE sample shows a W-shape and that of the MOVPE sample shows an M-shape plane with the degree of 0 in the high-resolution x-ray diffraction （HRXRD） results. The surface morphology attributes to this significant anisotropic. HRXRD reveals that there is a significant reduction in the FWHM, both on-axis and off-axis for HVPE GaN are compared with the MOVPE template. The decrease of the FWHM of E2 （high） Raman scat tering spectra further indicates the improvement of crystal quality after HVPE. By comparing the results of secondary- ion-mass spectroscope and photoluminescence spectrum of the samples grown by HVPE and MOVPE, we propose that C-involved defects are originally responsible for the yellow luminescence.展开更多
Visible photoluminescence （PL） has been observed from rare earth （Tm, Sm and Dy）-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-orient...Visible photoluminescence （PL） has been observed from rare earth （Tm, Sm and Dy）-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-oriented hexagonal wurtzite type structure with an average crystal size of about 80-110 nm. Room-temperature PL spectra indicate that the blue emission is due to the transition of ^1D2 to ^3F4 and ^1G4 to ^3H6 intra 4f electron of Tm^3＋, the yellow emissions of AlN：Sm are due to ^4G5/2 to the ^6HJ （J=5/2, 7/2, 9/2, 11/2） and the reddish emissions of AlN：Dy correspond to the ^4F9/2 to ^6HJ （J=5/2, 13/2, 11/2 and 9/2） and ^6Fll/2 transitions.展开更多
TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition （PCVD） system and the morphologies of ZiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial t...TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition （PCVD） system and the morphologies of ZiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial titanium tetra-isopropoxide （TTIP） concentration increases in PCVD reactor, the shapes of TiO2 particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm. The TiO2 particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO2 thin film. We observed the TiO2 thin film with smooth morphology at low initial TTIP concentration, granular morphology at medium initial TTIP concentration, and columnar morphology at high initial TTIP concentration. It is proposed that we can prepare the TiO2 thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD .展开更多
基金This work was supported by Doctor Foundation of Hebei Education Committee Hebei Natural Science Foundation(599091 ) of China
文摘Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61176085,11474365 and 61377055the Department of Education of Guangdong Province under Grant No gjhz1103the Open-Project Program of the State Key laboratory of Opto-Electronic Material and Technologies of Sun Yatsen University
文摘The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 （TO）, E1 （TO） and A1 （LO） phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 （TO） modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 （TO） mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 （longitudinal optical plasma coupling （LOPC）） mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 （LOPC） mode in 4H-SiC.
基金supported by the National Natural Science Foundation of China (Grant No 50672007)the NCET-06-0082the MOST 973 Program of China (Grant No 2007CB936202)
文摘This paper investigates the effect of growth temperature on morphology, structure and photoluminescence （PL） of Tb-doped boron nitride （BN） films grown by magnetron sputtering, and the relationships of growth-temperature- structure-PL by scanning electron microscopy, transmission electron microscopy and PL. The characteristic emission lines of the Tb^3＋ were observed in the PL spectra at room temperature. The 473-K-grown film is mainly consisted of amorphous BN particles. With the growth temperature increasing up to 1273 K, the amount of amorphous BN decreases, while the amount of turbostratic BN increases. Correspondingly, the PL intensities from the Tb^3＋ ions increase with the increase of temperature in the range of 473 1273 K.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11675118 and 11275136)
文摘The initial growth and microstructure feature of Ag films formation were investigated, which were prepared by using the very-high-frequency（VHF）（60 MHz） magnetron sputtering. Because of the moderate energy and very low flux density of ions impinging on the substrate, the evolutions of initial growth for Ag films formation were well controlled by varying the sputtering power. It was found that the initial growth of Ag films followed the island（Volmer—Weber, VW） growth mode, but before the island nucleation, the adsorption of Ag nanoparticles and the formation of Ag clusters dominated the growth. Therefore, the whole initial stages of Ag films formation included the adsorption of nanoparticles, the formation of clusters, the nucleation by the nanoparticles and clusters simultaneously, the islands formation, and the coalescence of islands.
基金Supported by the National Natural Science Foundation of Chinathe Ministry of Science and Technology of Chinathe Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20130002120033
文摘We report the successful growth of the tetragonal FeS film with one or two unit-cell （UC） thickness on SrTiO33（001） substrates by molecular beam epitaxy. Large lattice constant mismatch with the substrate leads to high density of defects in single-UC FeS, while it has been significantly reduced in the double-UC thick film due to the lattice relaxation. The scanning tunneling spectra on the surface of the FeS thin film reveal the electronic doping effect of single-UC FeS from the substrate. In addition, at the Fermi level, the energy gaps of approximately 1.5？meV are observed in the films of both thicknesses at 4.6？K and below. The absence of coherence peaks of gap spectra may be related to the preformed Cooper-pairs without phase coherence.
基金Supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2015094the National Natural Science Foundation of China under Grant Nos 61204012,61274049 and 61376058+1 种基金the Beijing Natural Science Foundation under Grant Nos 4142053 and 4132070the Beijing Nova Program under Grant Nos 2010B056 and xxhz201503
文摘We report the growth of InSb layers directly on GaAs （001） substrates without any buffer layers by molecular beam epitaxy （MBE）. Influences of growth temperature and V/Ⅲ flux ratios on the crystal quality, the surface morphology and the electrical properties of InSb thin films are investigated. The InSb samples with room- temperature mobility of 44600cm2/Vs are grown under optimized growth conditions. The effect of defects in InSb epitaxial on the electrical properties is researched, and we infer that the formation of In vacancy （VIn） and Sb anti-site （SbIn） defects is the main reason for concentrations changing with growth temperature and Sb2/In flux ratios. The mobility of the InSb sample as a function of temperature ranging from 90 K to 360K is demonstrated and the dislocation scattering mechanism and phonon scattering mechanism are discussed.
基金Supported by the National Natural Science Foundation of China under Grant No 61204006the Fundamental Research Funds for the Central Universities under Grant No 7214570101the National Key Science and Technology Special Project under Grant No 2008ZX01002-002
文摘Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of the samples are characterized by atomic force microscopy. The full width at half maximum （FWHM） of the HVPE sample shows a W-shape and that of the MOVPE sample shows an M-shape plane with the degree of 0 in the high-resolution x-ray diffraction （HRXRD） results. The surface morphology attributes to this significant anisotropic. HRXRD reveals that there is a significant reduction in the FWHM, both on-axis and off-axis for HVPE GaN are compared with the MOVPE template. The decrease of the FWHM of E2 （high） Raman scat tering spectra further indicates the improvement of crystal quality after HVPE. By comparing the results of secondary- ion-mass spectroscope and photoluminescence spectrum of the samples grown by HVPE and MOVPE, we propose that C-involved defects are originally responsible for the yellow luminescence.
基金Project supported by the National Natural Science Foundation of China （Grant No 50372082）.
文摘Visible photoluminescence （PL） has been observed from rare earth （Tm, Sm and Dy）-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-oriented hexagonal wurtzite type structure with an average crystal size of about 80-110 nm. Room-temperature PL spectra indicate that the blue emission is due to the transition of ^1D2 to ^3F4 and ^1G4 to ^3H6 intra 4f electron of Tm^3＋, the yellow emissions of AlN：Sm are due to ^4G5/2 to the ^6HJ （J=5/2, 7/2, 9/2, 11/2） and the reddish emissions of AlN：Dy correspond to the ^4F9/2 to ^6HJ （J=5/2, 13/2, 11/2 and 9/2） and ^6Fll/2 transitions.
基金supported by the Regional Innovation Center for Environmental Technology of Thermal Plasma(ETTP) at Inha University, designated by MKE(2009)supported from the Central Laboratory of Kangwon National University
文摘TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition （PCVD） system and the morphologies of ZiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial titanium tetra-isopropoxide （TTIP） concentration increases in PCVD reactor, the shapes of TiO2 particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm. The TiO2 particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO2 thin film. We observed the TiO2 thin film with smooth morphology at low initial TTIP concentration, granular morphology at medium initial TTIP concentration, and columnar morphology at high initial TTIP concentration. It is proposed that we can prepare the TiO2 thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD .
