A. Zeng

Cyclic Voltammetry Studies of Sputtered Nitrogen Doped Diamond-Like Carbon Film Electrodes

The conductive nitrogen-doped diamond-like carbon film (N-DLC) of about 0.14 m in thickness was deposited on highly conductive silicon wafer (111) with DC magnetron sputtering system. The electrochemical characteristics of the film have been studied with cyclic voltammetry (CV). The N-DLC film electrodes compare very favorably with conventional carbon based electrodes such as glassy carbon. The N-DLC film electrode exhibits a low double-layer capacitance, a large electrochemical potential window, and a relatively high electrochemical activity toward ferricyanide reduction. In addition, the electrode exhibits catalytic activity for Cl2/Cl as well as durability to high anodic potential, and a high signal for the trace analysis of Pb 2 . These characteristics demonstrate great promise of the N-DLC film as a novel electrode material for electrochemical analysis.

Stripping Voltammetric Analysis of Heavy Metals at Nitrogen Doped Diamond-Like Carbon Film Electrodes

Conductive nitrogen doped diamond-like carbon (N-DLC) film electrodes were used to investigate the possibility of detecting heavy metals such as lead, copper and cadmium by differential pulse anodic stripping voltammetry (DPASV) in the absence of mercury film. The preconcentration conditions (deposition potential, deposition time) and solution pH were optimized for the determination of lead in aqueous solution. A linear dependence of lead stripping current peak within the concentration (5 10 7 to 2 10 6 MP b 2 ) and deposition time (30 to 300 s at 1.00 V vs. SCE) was obtained. A multi-elemental analysis (Pb 2 ,C d 2 and Cu 2 ) illustrated that the N-DLC film electrode provided a significant stripping response for determination of multi-metals simultaneously. The present novel electrode showed great promise for the analysis of heavy metals.

Impedance study on electrochemical characteristics of sputtered DLC films

Diamond-like carbon (DLC) films with different structure were deposited on highly electrically conductive silicon substrates (SiO ySi), using d.c. magnetron sputtering deposition process. Their structure and electrochemical behavior in a 0.5 M H SO 2 24 solution were studied with micro-Raman spectroscopy, electrochemical impedance spectroscopic analysis and film impedance spectroscopy. The combined polarization resistance of silicon coated with DLC film increased to approximately 10 –10 V cm , 68 2

Compositional depth profile analysis of coatings on hard disks by X-ray photoelectron spectroscopy and imaging

A hard disk medium is typically composed of several layers including the magnetic recording layer, a buffer layer, as well as a wear protective layer. In the work presented here, the hard disks analysed have a total of five layers with the uppermost layer being the lubricant. The second layer is diamond like coating and this is followed by the magnetic layer consisting of an alloy of cobalt and other elements. The fourth layer is a buffer composed of an alloy of chromium, vanadium and molybdenum with the final layer being a nickel transition layer doped with phosphorus. These multilayers were subjected to numerous etchings by argon ions. The chemical structures of these layers were analysed with an X-ray photoelectron spectroscope (XPS) after each etching. Combining the XPS spectra with XPS imaging it is possible to determine the depth distribution of elements in the hard disk coating. In addition, it is also shown that XPS imaging can be employed to monitor the thickness of all multilayers.

MICROSTRUCTURE AND ELECTROCHEMICAL BEHAVIOR OF SPUTTERED DIAMOND-LIKE CARBON FILMS

Diamond-like carbon (DLC) films with different structure were deposited on highly electrically conductive silicon substrates (SiO2/Si), using dc magnetron sputtering deposition process. Their structure and electrochemical behavior in 0.5 MH2SO4 solution were studied with micro-Raman spectroscopy, electrochemical impedance spectroscopic (EIS) analysis and film impedance. The double layer capacitance on the DLC films was about 0.571 - 3.91 μF-cm-2. The capacitance increased with the increased Raman spectrum intensity ratio ID/IG and accelerated at around 2.25 of the ratio. The results suggest that the potential of DLC films as electrode materials for electrochemical analysis.

Structure of post-annealed ferroelectric PbZrxTi1-xO3 and SrBi2Ta2O9 thin films

In order to fabricate good quality ferroelectric thin films, PbZrxTi(1-x)O3 (PZT) and SrBi2Ta2O9 (SBT) films were fabricated on SiO2/Si(100) substrates and on Pt/Ti/SiO2/Si(100) substrates by pulsed laser excimer deposition (PLD). X-ray diffraction, Rutherford backscattering analysis, and atomic force microscopy were used to characterize the structural properties of the samples, which were post-annealed at different temperatures. The results showed that the PZT and SBT films fabricated on Pt/Ti/SiO2/Si(100) substrates and annealed at 700 degreesC exhibited optimum properties

TRIBOLOGICAL AND MECHANICAL PROPERTIES OF ALUMINUM CONTAINING TETRAHEDRAL AMORPHOUS CARBON FILMS

Tetrahedral amorphous carbon (ta-C) films which contained aluminum element were fabricated by filtered cathodic vacuum arc (FCVA) method. The tribological characteristics of the ta-C films were investigated with ball-on-disk tribometer. The increment of aluminum in the ta-C film leads to an increase of sp2 carbon bonding and a decrease of sp3 fraction in the film. The roughness of the films was measured with atomic force microscope, and the hardness and Youngs modulus of the films were measured with nanoindentation. The results showed that the film hardness and Youngs modulus dropped with the increase of Al content in the films. The results have been interpreted with respect to the change of sp3 and sp2 fractions in the ta-C:Al films.

Tribological Behavior of Nanocomposite Diamondlike Carbon-Aluminum Films

Tetrahedral amorphous carbon (ta-C) contains a large percentage of sp carbon bonding. However, high internal stresses develop in ta-C films with a high sp content, which limits their applications for wear protection. In this study, Al containing ta-C films were produced using Filtered cathodic vacuum arc (FCVA) technique. The structure of films was studied using MicroRaman spectroscopy in terms of aluminum content. The pure carbon ta-C films generally contained a relatively high residual compressive stress, which was related to its sp content, amorphous structure and preparation conditions. For the Al containing ta-C films, the stress reduction is significant with increase of aluminum content in the film. A decrease of the mechanical properties of the ta-C:Al nanocomposite films was noticed with the decrease of the internal stress in the films. The tribological behavior of the films was measured using ball-ondisk tribometer. The wear rate and friction coefficient were determined correspondingly. In the ball-on-disk testing, different loads are applied to the sapphire counterbody. All the tests were performed in ambient air (RH50%) and at room temperature (22 °C). It was noted that the friction coefficient of ta-C:Al films increased at the beginning of the testing before reaching a peak value of about 0.25. After the peak, the friction coefficient dropped until reaching a steady state value. The original surface roughness of the counterfaces, surface smoothening due to successive wear, and wear debris produced during the testing are all responsible for the tribological behavior of ta-C:Al films.