TiO2 nanofilms on surface of fused silica were fabricated by Ti ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by 20 k V Ti ions to 1.5 × 1017ions/cm2 on a...TiO2 nanofilms on surface of fused silica were fabricated by Ti ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by 20 k V Ti ions to 1.5 × 1017ions/cm2 on an implanter of metal vapor vacuum arc(MEVVA) ion source. Effects of annealing parameters on formation,growth and phase transformation of the TiO2 nanofilms were studied in detail. Optical absorption spectroscopy,Raman scattering spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy measurements were done to figure out formation mechanism of the TiO2 nanofilms.The formation of TiO2 nanofilms was due to out-diffusion of the implanted Ti ions to the substrate surface,where they were oxidized into TiO2 nanoparticles. Formation, phase, and thickness of the TiO2 nanofilms can be well tailored by controlling annealing parameters.展开更多
Narrow-gap Hg_(1-x)Cd_x Te material with a composition x of about 0.3 plays an extremely important role in mid-infrared detection applications. In this work, the optical properties of doped HgCdTe with x ≈ 0.3 are re...Narrow-gap Hg_(1-x)Cd_x Te material with a composition x of about 0.3 plays an extremely important role in mid-infrared detection applications. In this work, the optical properties of doped HgCdTe with x ≈ 0.3 are reviewed, including the defects and defect levels of intrinsic V_(Hg) and the extrinsic amphoteric arsenic(As) dopants, which can act as shallow/deep donors and acceptors. The influence of the defects on the determination of band-edge electronic structure is discussed when absorption or photoluminescence spectra are considered. The inconsistency between these two optical techniques is demonstrated and analyzed by taking into account the Fermi level position as a function of composition, doping level,conductivity type, and temperature. The defect level and its evolution, especially in As-doped HgCdTe, are presented. Our results provide a systematic understanding of the mechanisms and help for optimizing annealing conditions towards p-type As-activation, and eventually for fabricating high performance mid-infrared detectors.展开更多
Using transmission electron microscopy （TEM） and x-ray diffraction analysis, we have studied the structural and morphological evolution of highly Er/Yb co-doped A1203 films in the temperature range from 600℃-900℃....Using transmission electron microscopy （TEM） and x-ray diffraction analysis, we have studied the structural and morphological evolution of highly Er/Yb co-doped A1203 films in the temperature range from 600℃-900℃. By comparison with TEM observation, the annealing behaviours of photoluminescence （PL） emission and optical loss were found to have relation to the structure and morphology. The increase of PL intensity and optical loss above 800℃ might result from the crystallization of amorphous Al2O3 films. Based on the study on the structure and morphology, a rate equation propagation model of a multilevel system was used to calculate the optical gains of Er-doped Al2O3 planar waveguide amplifiers involving the variation of PL efficiency and optical loss with annealing temperature. It was found that the amplifiers had an optimized optical gain at the temperature corresponding to the minimum of optical loss, rather than at the temperature corresponding to the maximum of PL efficiency, suggesting that the optical loss is a key factor for determining the optical gain of an Er-doped Al2O3 planar waveguide amplifier.展开更多
Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematical...Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction （XRD）, pressure-com- position isotherm （PCI）, and electrochemical measure- ments. The results show that all samples contain LaNi5 and LaMg2Ni9 phases. LaCo5 phase appears at 1,000 ℃. The enthalpy change of all hydrides is close to -30.6 kJ.mo1-1 H2 of LaNi5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 ℃. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 ℃, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g-1 after 140 charge-discharge cycles.展开更多
ZnO nanorods in the form of thin films were synthesized by a facile chemical route and the effect of annealing temperature on the structure and sensitivity of such ZnO-based sensors was studied in detail towards metha...ZnO nanorods in the form of thin films were synthesized by a facile chemical route and the effect of annealing temperature on the structure and sensitivity of such ZnO-based sensors was studied in detail towards methane sensing.Morphological analyses of such films were carried out by scanning electron microscopy,whereas,the crystalline structure and phase purity of the films were analysed by X-ray diffraction technique.The films were observed to display a gradual change in their morphology from granular to dense nanorods and each of them was used to fabricate methane sensor prototype.They were also tested for temperature-dependent methane-sensing capability with varying methane concentrations.The optimized sensor exhibited highest gas response of ＊80% at 250 °C with significantly low response and recovery time.展开更多
SiO_2/TiO_2/methylcellulose composite materials processed by the sol-gel technique were studied for optical waveguide applications. With the help of methylcellulose, an organic binder, SiO2/TiO2/methylcellulose hybrid...SiO_2/TiO_2/methylcellulose composite materials processed by the sol-gel technique were studied for optical waveguide applications. With the help of methylcellulose, an organic binder, SiO2/TiO2/methylcellulose hybrid thick films were prepared by a single spin-coating processes. After annealing at 70 °C for an hour, 2.5-μm crack-free and dense organic-inorganic hybrid optical films with a refractive index of 1.537 were achieved. Optical losses of plane waveguide made up of those films and ordinary slide glass substrate are around 0.3 dB/cm at 650 nm. Scanning electronmicroscopy (SEM) and UV-visible spectroscopy (UV-VIS), have been used to characterize the thick films.展开更多
基金Supported by National Natural Science Foundation of China(No.11405280)Foundation from Education Department of Henan Province(No.14B140021)the Startup Foundation for Doctors of Zhoukou Normal University(No.zksybscx201210)
文摘TiO2 nanofilms on surface of fused silica were fabricated by Ti ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by 20 k V Ti ions to 1.5 × 1017ions/cm2 on an implanter of metal vapor vacuum arc(MEVVA) ion source. Effects of annealing parameters on formation,growth and phase transformation of the TiO2 nanofilms were studied in detail. Optical absorption spectroscopy,Raman scattering spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy measurements were done to figure out formation mechanism of the TiO2 nanofilms.The formation of TiO2 nanofilms was due to out-diffusion of the implanted Ti ions to the substrate surface,where they were oxidized into TiO2 nanoparticles. Formation, phase, and thickness of the TiO2 nanofilms can be well tailored by controlling annealing parameters.
基金Project supported by the Major Program of the National Natural Science Foundation of China(Grant Nos.61790583,61874043,61874045,and 61775060)the National Key Research and Development Program,China(Grant No.2016YFB0501604)
文摘Narrow-gap Hg_(1-x)Cd_x Te material with a composition x of about 0.3 plays an extremely important role in mid-infrared detection applications. In this work, the optical properties of doped HgCdTe with x ≈ 0.3 are reviewed, including the defects and defect levels of intrinsic V_(Hg) and the extrinsic amphoteric arsenic(As) dopants, which can act as shallow/deep donors and acceptors. The influence of the defects on the determination of band-edge electronic structure is discussed when absorption or photoluminescence spectra are considered. The inconsistency between these two optical techniques is demonstrated and analyzed by taking into account the Fermi level position as a function of composition, doping level,conductivity type, and temperature. The defect level and its evolution, especially in As-doped HgCdTe, are presented. Our results provide a systematic understanding of the mechanisms and help for optimizing annealing conditions towards p-type As-activation, and eventually for fabricating high performance mid-infrared detectors.
基金Project supported by the National Natural Science Foundation of China （Grant No 50240420656）.
文摘Using transmission electron microscopy （TEM） and x-ray diffraction analysis, we have studied the structural and morphological evolution of highly Er/Yb co-doped A1203 films in the temperature range from 600℃-900℃. By comparison with TEM observation, the annealing behaviours of photoluminescence （PL） emission and optical loss were found to have relation to the structure and morphology. The increase of PL intensity and optical loss above 800℃ might result from the crystallization of amorphous Al2O3 films. Based on the study on the structure and morphology, a rate equation propagation model of a multilevel system was used to calculate the optical gains of Er-doped Al2O3 planar waveguide amplifiers involving the variation of PL efficiency and optical loss with annealing temperature. It was found that the amplifiers had an optimized optical gain at the temperature corresponding to the minimum of optical loss, rather than at the temperature corresponding to the maximum of PL efficiency, suggesting that the optical loss is a key factor for determining the optical gain of an Er-doped Al2O3 planar waveguide amplifier.
基金financially supported by the National Natural Science Foundation of China(Nos.51071054 and51271061)the Natural Science Foundation of Guangxi(Nos.2010GXNSFD013004 and 2012GXNSFBA053149)
文摘Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction （XRD）, pressure-com- position isotherm （PCI）, and electrochemical measure- ments. The results show that all samples contain LaNi5 and LaMg2Ni9 phases. LaCo5 phase appears at 1,000 ℃. The enthalpy change of all hydrides is close to -30.6 kJ.mo1-1 H2 of LaNi5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 ℃. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 ℃, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g-1 after 140 charge-discharge cycles.
文摘ZnO nanorods in the form of thin films were synthesized by a facile chemical route and the effect of annealing temperature on the structure and sensitivity of such ZnO-based sensors was studied in detail towards methane sensing.Morphological analyses of such films were carried out by scanning electron microscopy,whereas,the crystalline structure and phase purity of the films were analysed by X-ray diffraction technique.The films were observed to display a gradual change in their morphology from granular to dense nanorods and each of them was used to fabricate methane sensor prototype.They were also tested for temperature-dependent methane-sensing capability with varying methane concentrations.The optimized sensor exhibited highest gas response of ＊80% at 250 °C with significantly low response and recovery time.
基金This work was supported by the National Natu- ral Science Foundation of China (No. 90206002 and 90201013)the National "863" Project of China (No. 2002AA313030).
文摘SiO_2/TiO_2/methylcellulose composite materials processed by the sol-gel technique were studied for optical waveguide applications. With the help of methylcellulose, an organic binder, SiO2/TiO2/methylcellulose hybrid thick films were prepared by a single spin-coating processes. After annealing at 70 °C for an hour, 2.5-μm crack-free and dense organic-inorganic hybrid optical films with a refractive index of 1.537 were achieved. Optical losses of plane waveguide made up of those films and ordinary slide glass substrate are around 0.3 dB/cm at 650 nm. Scanning electronmicroscopy (SEM) and UV-visible spectroscopy (UV-VIS), have been used to characterize the thick films.
