Enhanced photocatalytic activity of TiO2 nano-structured thin film with a silver hierarchical configuration

TiO2 sol-gels with various Ag/TiO2 molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO2 thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO2 nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO2 sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO2 sol-gel, four types of the TiO2 thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO,), TA (bottom layer was pure TiO,, surface layer was Ag modified), TT (pure TiO, thin film) and AA (TiO, thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent (I-ph). LSV confirmed the existence of Ago state in the TiO, thin film. SEM and XRD experiments indicated that the sizes of the TiO,, nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO2 thin film.

RESONANT TUNNELING, EIGENVALUE AND ENERGY-BAND CALCULATION FOR POTENTIAL AND PERIODIC POTENTIAL STRUCTURES

Recursion formulae for the reflection and the transmission probability amplitudes and the eigenvalue equation for multistep potential structures are derived. Using the recursion relations, a dispersion equation for periodic potential structures is presented. Some numerical results for the transmission probability of a double barrier structure with scattering centers, the lifetime of the quasi-bound state in a single quantum well with an applied field, and the miniband of a periodic potential structure are presented.

An asymmetric MOSFET-C band-pass filter with on-chip charge pump auto-tuning

An asymmetric MOSFET-C band-pass filter(BPF)with on chip charge pump auto-tuning is presented.It is implemented in UMC (United Manufacturing Corporation)0.18μm CMOS process technology. The filter system with auto-tuning uses a master-slave technique for continuous tuning in which the charge pump OUtputs 2.663 V, much higher than the power supply voltage, to improve the linearity of the filter. The main filter with third order low-pass and second order high-pass properties is an asymmetric band-pass filter with bandwidth of 2.730-5.340 MHz. The in-band third order harmonic input intercept point(HP3) is 16.621 dBm,wim 50 Ω as the source impedance. The input referred noise iS about 47.455μVrms. The main filter dissipates 3.528 mW while the auto-tuning system dissipates 2.412 mW from a 1.8 V power supply. The filter with the auto-tuning system occupies 0.592 mm~2 and it can be utilized in GPS (global positioning system)and Bluetooth systems.

Fabrication of a Silicon-Based Microprobe for Neural Interface Applications

A two-dimensional (2D) multi-channel silicon-based microelectrode array is developed for recording neural signals. Three photolithographic masks are utilized in the fabrication process. SEM images show that the microprobe is 1. 2mm long,100μm wide,and 30μm thick, with recording sites spaced 200μm apart for good signal isolation. For the individual recording sites, the characteristics of impedance versus frequency are shown by in vitro testing. The impedance declines from 14MΩ to 1.9kv as the frequency changes from 0 to 10MHz. A compatible PCB (print circuit board) aids in the less troublesome implantation and stabilization of the microprobe.

射频能量AC/DC电荷泵的MOS实现研究

在射频能量AC/DC的能源转换实现研究中提出一种采用低阈值MOS管构成的高效电荷泵.新方案消除了现有的肖特基二极管高效电荷泵制作工艺特殊、批次性能不够一致的缺陷.分析表明,通过有机调整MOS管宽长比、器件电容、充电级数等设计参量,可以方便地满足不同的性能要求,实现集成制作方便、性能稳定的高效射频能量AC/DC型电荷泵.

AIN Monolithic Microchannel Cooled Heatsink for High Power Laser Diode Array

A novel AIN monolithic microchannel cooled heatsink for high power laser diode array is introduced.The high power stack laser diode array with an AIN monolithic microchannel heatsink is fabricated and tested.The thermal impedance of a 10 stack laser diode array is 0.121℃/W.The pitch between two adjacent bars is 1.17mm.The power level of 611W is achieved under the 20% duty factor condition at an emission wavelength around 808nm.

Design and fabrication of GaAs OMIST photodetector

We designed and fabricated GaAs OMIST (Optical-controlled Metal-Insulator-Semiconductor Thyristor) device. Using oxidation of A1As layer that is grown by MBE form the Ultra-Thin semi-Insulating layer (UTI) of the GAAS OMIST. The accurate control and formation of high quality semi-insulating layer (AlxOy) are the key processes for fabricating GaAs OMIST. The device exhibits a current-controlled negative resistance region in its I-V characteristics. When illuminated, the major effect of optical excitation is the reduction of the switching voltage. If the GaAs OMIST device is biased at a voltage below its dark switching voltage V-s, sufficient incident light can switch OMIST from high impedance low current"off"state to low impedance high current "on"state. The absorbing material of OMIST is GaAs, so if the wavelength of incident light within 600 similar to 850nm can be detected effectively. It is suitable to be used as photodetector for digital optical data process. The other attractive features of GaAs OMIST device include suitable conducted current, switching voltage and power levels for OEIC, high switch speed and high sensitivity to light or current injection.