By a simple one-step H2-assisted thermal evaporation method, high quality CdS nanos- tructures have been successfully fabricated on Au coated Si substrates in large scale. The as-synthesized CdS nanostructures consist...By a simple one-step H2-assisted thermal evaporation method, high quality CdS nanos- tructures have been successfully fabricated on Au coated Si substrates in large scale. The as-synthesized CdS nanostructures consisted of sword-like nanobelts and toothed nanosaws with a single-crystal hexagonal wurtzite structure. The deposition temperature played an important role in determining the size and morphology of the CdS nanostruetures. A combination of vapor-liquid-solid and vapor-solid growth mechanisms were proposed to interpret the formation of CdS nanostructures. Photoluminescence measurement indicated that the nanobelts and nanosaws have a prominent green emission at about 512 nm, which is the band-to-band emission of CdS. The waveguide characteristics of both types of CdS nanos-truetures were observed and discussed.展开更多
Cassava is vulnerable to frost and snow, so it is suitable for planting in tropical and subtropical region. Low temperature is an important environment factor affecting the growth and development and production of cas...Cassava is vulnerable to frost and snow, so it is suitable for planting in tropical and subtropical region. Low temperature is an important environment factor affecting the growth and development and production of cassava, and the region with annual average temperature below 15 ℃ is not conducive to its normal growth and development. The improvement of cold resistance of cassava can increase the planting area and improve the yield and quality of cassava. In this study, morphological,physiological and biochemical and molecular researches on cold resistance of cassava, as well as the latest research progress,were reviewed in this paper. At the same time, some potential difficulties in the research on cold resistance of cassava were put forward, and the future work focus was also discussed.展开更多
With in situ optical emission spectroscopy （OES） diagnosis on VHF-generated H2 ＋ SiH4 plasmas,and with the measurements of deposition rate and structure of μc-Si. H thin films fabricated with VHFPECVD technique at...With in situ optical emission spectroscopy （OES） diagnosis on VHF-generated H2 ＋ SiH4 plasmas,and with the measurements of deposition rate and structure of μc-Si. H thin films fabricated with VHFPECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si.H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature,the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for μc-Si：H thin films deposition under our current growth system is about 210 ℃ ,at which deposition rate O. 8 nm/s of pc-Si;H thin film with Xc-60% and d-9 nm can be obtained.展开更多
The temperature is a key factor for the quality of the SiGe alloy grown by D-UHV/CVD. In conventional conditions,the lowest temperature for SiGe growth is about 550℃. Generally, the pressure of the growth chamber is ...The temperature is a key factor for the quality of the SiGe alloy grown by D-UHV/CVD. In conventional conditions,the lowest temperature for SiGe growth is about 550℃. Generally, the pressure of the growth chamber is about 10 ^-5 Pa when liquid nitrogen is introduced into the wall of the growth chamber with the flux of 6sccm of the disilane gas. We have succeeded in depositing SiGe films at much lower temperature using a novel method. It is about 10.2 Pa without liquid nitrogen, about 3 magnitudes higher than the traditional method,leading to much faster deposition rate. Without liquid nitrogen,the SiGe film and SiGe/Si superlattice are grown at 485℃. The DCXRD curves and TEM image show that the quality of the film is good. The experiments show that this method is efficient to deposit SiGe at low temperature.展开更多
Cu(In,Ga)Se2(CIGS) films are deposited on the Na-free glass substrate using three-stage co-evaporation process,and the effects of thickness and growth temperature on the orientation of CIGS film are investigated by X-...Cu(In,Ga)Se2(CIGS) films are deposited on the Na-free glass substrate using three-stage co-evaporation process,and the effects of thickness and growth temperature on the orientation of CIGS film are investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM).When the growth of CIGS film does not experience the Cu-rich process,the increase of the growth temperature at the second stage(Ts2) promotes the(112) orientation of CIGS film,and weakens the(220) orientation.Nevertheless,when the growth of CIGS film experiences Cu-rich process,the increase of Ts2 significantly promotes the(220) orientation.In addition,with the thickness of CIGS film decreasing,the extent of(In,Ga)2Se3(IGS) precursor orientation does not change except for the intensity of Bragg peak,yet the(220) orientation of following CIGS film is hindered,which suggests that(112) plane preferentially grows at the initial growth of CIGS film.展开更多
We have recently demonstrated that GaAs nanosheets can be grown by metal-organic chemical vapor deposition （MOCVD）. Here, we investigate these nanosheets by secondary electron scanning electron microscopy （SE-SEM）...We have recently demonstrated that GaAs nanosheets can be grown by metal-organic chemical vapor deposition （MOCVD）. Here, we investigate these nanosheets by secondary electron scanning electron microscopy （SE-SEM） and electron beam induced current （EBIC） imaging. An abrupt boundary is observed between an initial growth region and an overgrowth region in the nanosheets. The SE-SEM contrast between these two regions is attributed to the inversion of doping at the boundary. EBIC mapping reveals a p-n junction formed along the boundary between these two regions. Rectifying I-V behavior is observed across the boundary further indicating the formation of a p-n junction. The electron concentration （ND） of the initial growth region is around 1 × 10^18 cm^-3, as determined by both Hall effect measurements and low temperature photoluminescence （PL） spectroscopy. Based on the EBIC data, the minority carrier diffusion length of the nanosheets is 177 nm, which is substantially longer than the corresponding length in unpassivated GaAs nanowires measured previously.展开更多
A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K0.09MnO3 （LCKMO）/zinc oxide （ZnO） heterojunction bilayers grown on ITO substrate by pulsed laser deposition ...A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K0.09MnO3 （LCKMO）/zinc oxide （ZnO） heterojunction bilayers grown on ITO substrate by pulsed laser deposition （PLD） at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/A1 exhibits reproducible rectifying characteristics and light cur- rent under continuous laser irradiation of 2 = 325 nm. We report here the influence of LCKMO/ZnO bilayers＇ thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency （PCE） is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.展开更多
Single-walled carbon nanotubes （SWNTs） have been grown on a silica-supported monometallic nickel （Ni） catalyst at temperatures ranging from as low as 450℃to 800℃. Different spectroscopic techniques, such as Rama...Single-walled carbon nanotubes （SWNTs） have been grown on a silica-supported monometallic nickel （Ni） catalyst at temperatures ranging from as low as 450℃to 800℃. Different spectroscopic techniques, such as Raman, photoluminescence emission （PLE）, and ultra violet-visible-near infrared （UV-vis-NIR） absorption spectroscopy were used to evaluate file diameter and quality of the SWNTs grown over the Ni catalyst at different temperatures. The analysis revealed that high quality SWNTs with a very narrow diameter distribution were obtained at a growth temperature of 500 ℃. In the PLE and absorption spectra, differences were observed between the SWNTs grown oil Ni and those grown on cobalt （Co）. This result expands the potential of growing a specific （n, m） tube species with relatively high abundance by tuning the catalyst composition. Furthermore, the prerequisites for the low temperature growth of SWNTs over a monometallic transition metal catalyst have been elucidated.展开更多
文摘By a simple one-step H2-assisted thermal evaporation method, high quality CdS nanos- tructures have been successfully fabricated on Au coated Si substrates in large scale. The as-synthesized CdS nanostructures consisted of sword-like nanobelts and toothed nanosaws with a single-crystal hexagonal wurtzite structure. The deposition temperature played an important role in determining the size and morphology of the CdS nanostruetures. A combination of vapor-liquid-solid and vapor-solid growth mechanisms were proposed to interpret the formation of CdS nanostructures. Photoluminescence measurement indicated that the nanobelts and nanosaws have a prominent green emission at about 512 nm, which is the band-to-band emission of CdS. The waveguide characteristics of both types of CdS nanos-truetures were observed and discussed.
基金Supported by Earmarked Fund for China Agriculture Research System(CARS-11-cssy)
文摘Cassava is vulnerable to frost and snow, so it is suitable for planting in tropical and subtropical region. Low temperature is an important environment factor affecting the growth and development and production of cassava, and the region with annual average temperature below 15 ℃ is not conducive to its normal growth and development. The improvement of cold resistance of cassava can increase the planting area and improve the yield and quality of cassava. In this study, morphological,physiological and biochemical and molecular researches on cold resistance of cassava, as well as the latest research progress,were reviewed in this paper. At the same time, some potential difficulties in the research on cold resistance of cassava were put forward, and the future work focus was also discussed.
文摘With in situ optical emission spectroscopy （OES） diagnosis on VHF-generated H2 ＋ SiH4 plasmas,and with the measurements of deposition rate and structure of μc-Si. H thin films fabricated with VHFPECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si.H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature,the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for μc-Si：H thin films deposition under our current growth system is about 210 ℃ ,at which deposition rate O. 8 nm/s of pc-Si;H thin film with Xc-60% and d-9 nm can be obtained.
文摘The temperature is a key factor for the quality of the SiGe alloy grown by D-UHV/CVD. In conventional conditions,the lowest temperature for SiGe growth is about 550℃. Generally, the pressure of the growth chamber is about 10 ^-5 Pa when liquid nitrogen is introduced into the wall of the growth chamber with the flux of 6sccm of the disilane gas. We have succeeded in depositing SiGe films at much lower temperature using a novel method. It is about 10.2 Pa without liquid nitrogen, about 3 magnitudes higher than the traditional method,leading to much faster deposition rate. Without liquid nitrogen,the SiGe film and SiGe/Si superlattice are grown at 485℃. The DCXRD curves and TEM image show that the quality of the film is good. The experiments show that this method is efficient to deposit SiGe at low temperature.
基金supported by the National Natural Science Foundation of China (Nos.60906033,50902074,90922037,61076061)the Natural Science Foundation of Tianjin City (No.11JCYBJC01200)the National "863" Key Project of China (No.2004AA513020)
文摘Cu(In,Ga)Se2(CIGS) films are deposited on the Na-free glass substrate using three-stage co-evaporation process,and the effects of thickness and growth temperature on the orientation of CIGS film are investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM).When the growth of CIGS film does not experience the Cu-rich process,the increase of the growth temperature at the second stage(Ts2) promotes the(112) orientation of CIGS film,and weakens the(220) orientation.Nevertheless,when the growth of CIGS film experiences Cu-rich process,the increase of Ts2 significantly promotes the(220) orientation.In addition,with the thickness of CIGS film decreasing,the extent of(In,Ga)2Se3(IGS) precursor orientation does not change except for the intensity of Bragg peak,yet the(220) orientation of following CIGS film is hindered,which suggests that(112) plane preferentially grows at the initial growth of CIGS film.
文摘We have recently demonstrated that GaAs nanosheets can be grown by metal-organic chemical vapor deposition （MOCVD）. Here, we investigate these nanosheets by secondary electron scanning electron microscopy （SE-SEM） and electron beam induced current （EBIC） imaging. An abrupt boundary is observed between an initial growth region and an overgrowth region in the nanosheets. The SE-SEM contrast between these two regions is attributed to the inversion of doping at the boundary. EBIC mapping reveals a p-n junction formed along the boundary between these two regions. Rectifying I-V behavior is observed across the boundary further indicating the formation of a p-n junction. The electron concentration （ND） of the initial growth region is around 1 × 10^18 cm^-3, as determined by both Hall effect measurements and low temperature photoluminescence （PL） spectroscopy. Based on the EBIC data, the minority carrier diffusion length of the nanosheets is 177 nm, which is substantially longer than the corresponding length in unpassivated GaAs nanowires measured previously.
基金supported by the National Natural Science Foundation of China (No. 90922034 and No. 21131002)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20110061130005)
文摘A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K0.09MnO3 （LCKMO）/zinc oxide （ZnO） heterojunction bilayers grown on ITO substrate by pulsed laser deposition （PLD） at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/A1 exhibits reproducible rectifying characteristics and light cur- rent under continuous laser irradiation of 2 = 325 nm. We report here the influence of LCKMO/ZnO bilayers＇ thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency （PCE） is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.
文摘Single-walled carbon nanotubes （SWNTs） have been grown on a silica-supported monometallic nickel （Ni） catalyst at temperatures ranging from as low as 450℃to 800℃. Different spectroscopic techniques, such as Raman, photoluminescence emission （PLE）, and ultra violet-visible-near infrared （UV-vis-NIR） absorption spectroscopy were used to evaluate file diameter and quality of the SWNTs grown over the Ni catalyst at different temperatures. The analysis revealed that high quality SWNTs with a very narrow diameter distribution were obtained at a growth temperature of 500 ℃. In the PLE and absorption spectra, differences were observed between the SWNTs grown oil Ni and those grown on cobalt （Co）. This result expands the potential of growing a specific （n, m） tube species with relatively high abundance by tuning the catalyst composition. Furthermore, the prerequisites for the low temperature growth of SWNTs over a monometallic transition metal catalyst have been elucidated.
