Boron-doped hydrogenated silicon films with different gaseous doping ratios（B2H6/SiH4） were deposited in a plasma-enhanced chemical vapor deposition（PECVD） system.The microstructure of the films was investigated b...Boron-doped hydrogenated silicon films with different gaseous doping ratios（B2H6/SiH4） were deposited in a plasma-enhanced chemical vapor deposition（PECVD） system.The microstructure of the films was investigated by atomic force microscopy（AFM） and Raman scattering spectroscopy.The electrical properties of the films were characterized by their room temperature electrical conductivity（σ） and the activation energy（Ea）.The results show that with an increasing gaseous doping ratio,the silicon films transfer from a microcrystalline to an amorphous phase,and corresponding changes in the electrical properties were observed.The thin boron-doped silicon layers were fabricated as recombination layers in tunnel junctions.The measurements of the I-V characteristics and the transparency spectra of the junctions indicate that the best gaseous doping ratio of the recombination layer is 0.04,and the film deposited under that condition is amorphous silicon with a small amount of crystallites embedded in it.The junction with such a recombination layer has a small resistance,a nearly ohmic contact,and a negligible optical absorption.展开更多
Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases.Establishing biological retinal models and simulating how the biological retina convert incoming light...Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases.Establishing biological retinal models and simulating how the biological retina convert incoming light signal into spike trains that can be properly decoded by the brain is a key issue.Some retinal models have been presented,ranking from structural models inspired by the layered architecture to functional models originated from a set of specific physiological phenomena.However,Most of these focus on stimulus image compression,edge detection and reconstruction,but do not generate spike trains corresponding to visual image.In this study,based on stateof-the-art retinal physiological mechanism,including effective visual information extraction,static nonlinear rectification of biological systems and neurons Poisson coding,a cascade model of the retina including the out plexiform layer for information processing and the inner plexiform layer for information encoding was brought forward,which integrates both anatomic connections and functional computations of retina.Using MATLAB software,spike trains corresponding to stimulus image were numerically computed by four steps：linear spatiotemporal filtering,static nonlinear rectification,radial sampling and then Poisson spike generation.The simulated results suggested that such a cascade model could recreate visual information processing and encoding functionalities of the retina,which is helpful in developing artificial retina for the retinally blind.展开更多
基金supported by the State Key Development Program for Basic Research of China(No.2006CB202604)the National Natural Science Foundation of China (No. 60576036)the National High Technology Research and Development Program of China (No. 2006AA05Z405)
文摘Boron-doped hydrogenated silicon films with different gaseous doping ratios（B2H6/SiH4） were deposited in a plasma-enhanced chemical vapor deposition（PECVD） system.The microstructure of the films was investigated by atomic force microscopy（AFM） and Raman scattering spectroscopy.The electrical properties of the films were characterized by their room temperature electrical conductivity（σ） and the activation energy（Ea）.The results show that with an increasing gaseous doping ratio,the silicon films transfer from a microcrystalline to an amorphous phase,and corresponding changes in the electrical properties were observed.The thin boron-doped silicon layers were fabricated as recombination layers in tunnel junctions.The measurements of the I-V characteristics and the transparency spectra of the junctions indicate that the best gaseous doping ratio of the recombination layer is 0.04,and the film deposited under that condition is amorphous silicon with a small amount of crystallites embedded in it.The junction with such a recombination layer has a small resistance,a nearly ohmic contact,and a negligible optical absorption.
基金supported by the National Natural Science Foundation of China,No.30870649the National Program on Key Basic Research Project of China (973 Program),No.2005CB724302
文摘Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases.Establishing biological retinal models and simulating how the biological retina convert incoming light signal into spike trains that can be properly decoded by the brain is a key issue.Some retinal models have been presented,ranking from structural models inspired by the layered architecture to functional models originated from a set of specific physiological phenomena.However,Most of these focus on stimulus image compression,edge detection and reconstruction,but do not generate spike trains corresponding to visual image.In this study,based on stateof-the-art retinal physiological mechanism,including effective visual information extraction,static nonlinear rectification of biological systems and neurons Poisson coding,a cascade model of the retina including the out plexiform layer for information processing and the inner plexiform layer for information encoding was brought forward,which integrates both anatomic connections and functional computations of retina.Using MATLAB software,spike trains corresponding to stimulus image were numerically computed by four steps：linear spatiotemporal filtering,static nonlinear rectification,radial sampling and then Poisson spike generation.The simulated results suggested that such a cascade model could recreate visual information processing and encoding functionalities of the retina,which is helpful in developing artificial retina for the retinally blind.
