Chun-Chi Chang

Photoluminescence and Raman studies of porous silicon under various temperatures and light illuminations

Abstract The detailed photoluminescence (PL), Raman and infrared absorption spectra of porous silicon (PS) prepared at different anodization current densities, annealing conditions and light illumination durations are studied. The intricate spectra imply diverse mechanisms to address the origin. We suggest that the quantum confinement effect of PS determines the blue-shift of the spectra, and that the breaking of Si-H x bonds on the porous walls degrades the PL intensity.

Improvement of the Ar/N2 binary plasma-treated carbon passivation layer deposited on Li4Ti5O12 electrodes for stable high-rate lithium ion batteries

In this study, nanoscale carbon overlayers, with and without nitrogen doping, have been investigated as surface passivation layers to enhance the rate capability and cycling stability of Li4Ti5O12 (LTO). As indicated by optical emission spectroscopy, Raman spectra and high resolution X-ray photoelectron spectroscopy analysis, nitrogen successfully dopes into the carbon overlayer by Ar/N2 binary plasma irradiation, owing to the interaction between the carbon overlayer and chemically reactive plasma species such as N2+ and N. In addition, the results of SEM and XPS depth profiles also prove that the N-doped carbon overlayer can effectively suppress the formation of a resistive solid–electrolyte-interface (SEI) film. The electrochemical test results demonstrate that the LTO coated with N-doped carbon overlayer (NC-overlayer/LTO) exhibits superior capacity (133 mA h g−1) and excellent stability with 91% capacity retention over 300 cycles at a high C rate (10C). The excellent electrochemical performance of NC-overlayer/LTO can be attributed to the N-doped carbon passivation layer that effectively facilitates Li+ ion diffusion and reduces internal resistance.

The bistable switching property of a porous-silicon Schottky barrier diode during the charging period

Abstract A bistable switching property is displayed by a gold-plated porous silicon (PS) Schottky barrier diode. Charging the molecules attached on the walls of the PS underneath some depth during forward bias forming a p–p heterojunction within the PS ensuing a four-layer diode is the plausible mechanism.