Hydrogenated nanocrystalline silicon thin films were fabricated from Sill4 with H2 dilution at a low substrate temperature of 200℃ by the conventional plasma enhanced chemical vapor deposition technique. A high depos...Hydrogenated nanocrystalline silicon thin films were fabricated from Sill4 with H2 dilution at a low substrate temperature of 200℃ by the conventional plasma enhanced chemical vapor deposition technique. A high deposition rate over 0.75 nm/s can be achieved. Raman scattering spectral measurements revealed that the crystalline fraction and grain size increased with the increase in hydrogen dilution ratio. Fourier transform infrared spectrum measurements showed that the hydrogen content decreased and the Si-H bonding configuration changed mainly from Sill to Sill2 with the increase in hydrogen dilution ratio. This suggested that the hydrogen dilution played an important role in the low-temperature growth of nanocrystalline silicon thin film. The growth mechanism is discussed in terms of a surface diffusion model and hydrogen etching effects.展开更多
Densification behavior of nanocrystalline Mg2Si （n-Mg2Si） with grain size about 30-50 nm was investigated by hot-pressing at 400℃. The results indicated that the densification process of n-Mg2Si exhibited three lin...Densification behavior of nanocrystalline Mg2Si （n-Mg2Si） with grain size about 30-50 nm was investigated by hot-pressing at 400℃. The results indicated that the densification process of n-Mg2Si exhibited three linear segments： p〈0.3 GPa, 0.3 GPa〈p〈1.2 GPa, and p〉1.2 GPa determined by Heckel formula, among which the third fast increasing segment in high pressure range p〉1.2 GPa has seldom been reported in conventional coarse-grained polycrystalline materials. Nevertheless, in the whole pressure range （0.125-1.500 GPa） investigated the densification behavior of n-Mg2Si can be well described by a Kawakita formula p/C=（1/a）p＋ 1/（ab） with constant α=0.452 being in good agreement with the initial porosity of the compact.展开更多
Using p~＋-type crystalline Si with n~＋-type nanocrystalline Si（nc-Si） and n~＋-type crystalline Si with p~＋-type nc-Si mosaic structures as electrodes,a type of power diode was prepared with epitaxial technique a...Using p~＋-type crystalline Si with n~＋-type nanocrystalline Si（nc-Si） and n~＋-type crystalline Si with p~＋-type nc-Si mosaic structures as electrodes,a type of power diode was prepared with epitaxial technique and plasmaenhanced chemical vapor deposition（PECVD） method.Firstly,the basic p~＋-n^--n~＋-type Si diode was fabricated by epitaxially growing p~＋- and n~＋-type layers on two sides of a lightly doped n^--type Si wafer respectively.Secondly,heavily phosphorus-doped Si film was deposited with PECVD on the lithography mask etched p~＋-type Si side of the basic device to form a component with mosaic anode.Thirdly,heavily boron-doped Si film was deposited on the etched n~＋-type Si side of the second device to form a diode with mosaic anode and mosaic cathode.The images of high resolution transmission electronic microscope and patterns of X-ray diffraction reveal nanocrystallization in the phosphorus- and boron-deposited films.Electrical measurements such as capacitancevoltage relation,current-voltage feature and reverse recovery waveform were carried out to clarify the performance of prepared devices.The important roles of（n^-）Si/（p~＋）nc-Si and（n^-）Si/（n~＋）nc-Si junctions in the static and dynamic conduction processes in operating diodes were investigated.The performance of mosaic devices was compared to that of a basic one.展开更多
基金supported by the Major State Basic Research and Development Program of China,Ministry of Science and Technology of China (No.G2000028208)
文摘Hydrogenated nanocrystalline silicon thin films were fabricated from Sill4 with H2 dilution at a low substrate temperature of 200℃ by the conventional plasma enhanced chemical vapor deposition technique. A high deposition rate over 0.75 nm/s can be achieved. Raman scattering spectral measurements revealed that the crystalline fraction and grain size increased with the increase in hydrogen dilution ratio. Fourier transform infrared spectrum measurements showed that the hydrogen content decreased and the Si-H bonding configuration changed mainly from Sill to Sill2 with the increase in hydrogen dilution ratio. This suggested that the hydrogen dilution played an important role in the low-temperature growth of nanocrystalline silicon thin film. The growth mechanism is discussed in terms of a surface diffusion model and hydrogen etching effects.
基金the National Natural Science Foundation of China under grant No. 50371081.
文摘Densification behavior of nanocrystalline Mg2Si （n-Mg2Si） with grain size about 30-50 nm was investigated by hot-pressing at 400℃. The results indicated that the densification process of n-Mg2Si exhibited three linear segments： p〈0.3 GPa, 0.3 GPa〈p〈1.2 GPa, and p〉1.2 GPa determined by Heckel formula, among which the third fast increasing segment in high pressure range p〉1.2 GPa has seldom been reported in conventional coarse-grained polycrystalline materials. Nevertheless, in the whole pressure range （0.125-1.500 GPa） investigated the densification behavior of n-Mg2Si can be well described by a Kawakita formula p/C=（1/a）p＋ 1/（ab） with constant α=0.452 being in good agreement with the initial porosity of the compact.
基金supported by the National Natural Science Foundation of China(No.61274006)
文摘Using p~＋-type crystalline Si with n~＋-type nanocrystalline Si（nc-Si） and n~＋-type crystalline Si with p~＋-type nc-Si mosaic structures as electrodes,a type of power diode was prepared with epitaxial technique and plasmaenhanced chemical vapor deposition（PECVD） method.Firstly,the basic p~＋-n^--n~＋-type Si diode was fabricated by epitaxially growing p~＋- and n~＋-type layers on two sides of a lightly doped n^--type Si wafer respectively.Secondly,heavily phosphorus-doped Si film was deposited with PECVD on the lithography mask etched p~＋-type Si side of the basic device to form a component with mosaic anode.Thirdly,heavily boron-doped Si film was deposited on the etched n~＋-type Si side of the second device to form a diode with mosaic anode and mosaic cathode.The images of high resolution transmission electronic microscope and patterns of X-ray diffraction reveal nanocrystallization in the phosphorus- and boron-deposited films.Electrical measurements such as capacitancevoltage relation,current-voltage feature and reverse recovery waveform were carried out to clarify the performance of prepared devices.The important roles of（n^-）Si/（p~＋）nc-Si and（n^-）Si/（n~＋）nc-Si junctions in the static and dynamic conduction processes in operating diodes were investigated.The performance of mosaic devices was compared to that of a basic one.
