Tian Zhao-Wu

INVESTIGATIONS OF COADSORPTION OF CARBON-MONOXIDE WITH S OR BI ADATOMS AT A PLATINUM-ELECTRODE BY IN-SITU FTIR SPECTROSCOPY AND QUANTUM-CHEMISTRY ANALYSIS

Abstract The adsorption of CO on a Pt electrode was used as a molecular probe, and the surface properties with respect to the electronic structure of the Pt electrocatalyst during modification by S or Bi adatoms were investigated by a combination of cyclic voltammetry, in-situ Fourier transform IR (FTIR) spectroscopy and cluster model analysis using self-consistent charge discrete variational X α (SCC-DV-X α ) calculations. It is found that the S adatom decreases the ability of the Pt surface to donate electrons, resulting in weakened CO adsorption and increasing vibrational frequency of the CO band of adsorbed CO molecules. However, the opposite effects were observed in the case of Bi adatoms. The electronic and vibrational properties of the potential dependence of CO adsorbed on a Pt electrode were also studied carefully. The results of quantum chemistry calculations are in good agreement with the experimental results of in-situ FTIR spectroscopy and also reveal the deeper significance of the IR spectroscopy data.

Research advances of electrochemical micro/nanofabrication based on confined etchant layer technique

Compared with mechanical machining, ECM has several advantages, such as avoiding tool wear, none thermal or mechanical stress on machining surfaces, as well as high removal rate. Moreover, ECM is capable of making complex three-dimensional structures and is appropriate for flexible, fragile, or fissile materials even materials harder than the machining tool. Thus, ECM has been widely used for various industrial applications in the fields of aerospace, automobiles, electronics, etc. ECM methods can be classified usually as electrolytic machining based on anodic dissolution and electroforming based on cathodic deposition of metallic materials. Recently, high technology industry, such as ultralarge scale integration (ULSI) circuits, microelectromechanical systems (MEMS), miniaturized total analysis systems (μ-TAS) and precision optics, has developed more and more rapidly, where miniaturization and integration of functional components are becoming significant. Nowadays, the feature size of interconnectors in ULSI circuits has been down to 20 nanometers, predicted by Moore’s law. Confined etchant layer technique (CELT) was proposed in 1992 to fabricate three-dimensional micro- and nanostructures (3D-MNS) on different metals and semiconductors, which has been developed an effective machining method with independent intellectual property rights. Generally, there are three procedures in CELT: (1) generating the etchant on the surface of the tool electrode by electrochemical or photoelectrochemical reactions; (2) confining the etchant in a depleted layer with a thickness of micro- or nanometer scale; (3) etching process when the tool electrode is fed to the workpiece, which applicable for 1D milling, 2D polishing, and 3D microfabrication with an accuracy at micro or nanometer scale. External physical-field modulations have recently been introduced into CELT to improve its machining precision. In this review, the advances of CELT in principles, instruments and applications will be addressed as well as the prospects.

Factors Influencing Hydroxyl Radical Formation in a Photo-Induced Confined Etching System

In this paper, we studied the formation of free OH on a TiO2nanotube array electrode in a photo-induced confined etching system. We used fluorescence spectroscopy, transient photocurrent response, electrochemical impedance spectroscopy(EIS), and Mott- Schottky analysis to investigate the influence of several key factors, including the applied potential, the illumination time, and the pH value. The highest efficiency for the photoelectrocatalytic formation of free OH on the TiO2nanotube array electrode was achieved at an applied potential of 1.0 V(vs a saturated calomel electrode(SCE)); the photoelectrocatalytic generation and consumption of free OH quickly approached a steady state in this system, as the confined etching layer formed by OH remained stable during illumination. This may allow good control of the etching precision during continuous etching processes. The highest efficiency for the photoelectrocatalytic formation of free OH on the TiO2nanotube array electrode was observed at pH 10. The results have an important significance for regulating and optimizing photo-induced confined etching system, which can be used to improve the etching speed or the leveling precision during the planarization of copper.