Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl4/O-2/N-2 Gas Mixtures

National Natural Science Foundation of China [10875025, 20803007]; Fundamental Research Funds for Central Universities of China [DC12010116, DC13010106]; Program for Liaoning Excellent Talents in University [LJQ20l3128]Low-pressure dielectric barrier discharge (DBD) TiCl4/O-2 and N-2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A home-made large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15 degrees. Compared to titanium oxide films deposited in TiCl4/O-2 gas mixtures, those in TiCl4/O-2/N-2 gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O-2/N-2 gas mixtures with the addition of 50% N-2 and 20% TiCl4 is still smaller than 20 degrees, while that of undoped titanium oxide films is larger than 640 when they are measured after one week. The low-pressure TiCl4/O-2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film's fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl4/O-2 DBD plasmas at various power supply driving frequencies are presented

Plasma-assisted chemical vapor deposition of titanium oxide films by dielectric barrier discharge in TiCl4/O2/N2 gas mixtures

Low-pressure dielectric barrier discharge (DBD) TiCl4/O2 and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15°. Compared to titanium oxide films deposited in TiCl4/O2 gas mixtures, those in TiCl4/O2/N2 gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2 gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20°, while that of undoped titanium oxide films is larger than 64° when they are measured after one week. The low-pressure TiCl4/O2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film's fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl4/O2 DBD plasmas at various power supply driving frequencies are presented

Approach for Multiattribute Decision-Making with an Interval Grey Number Based on Bonferroni Mean

Aiming at the multiattribute decision-making problem in the form of interval grey number, considering the interrelationship between the scheme attributes, this study defines the grey number weighted geometric Bonferroni mean GNWGBM operator for aggregating information. The feasibility of the proposed method is verified through a comparison of the example analysis and methods

Optical emission characteristics of medium- to high-pressure N-2 dielectric barrier discharge plasmas during surface modification of polymers

National Science Foundation [NSF-20803007, NSF-10875025]The authors measured the band spectra (first and second positive systems) of the nitrogen molecule by optical emission spectroscopy with an aim to understand the mechanism of surface processing by medium- to high-pressure dielectric barrier discharge (DBD) plasmas. The experimentally measured and calculated spectra were compared to determine the vibrational and rotational temperatures of the N-2 (C-3 Pi(u)) state in the generated plasmas. The authors generated the N-2 DBD plasmas at a driving frequency of 1-7 kHz and a discharge pressure of 20-10(5) Pa for the surface modification of a polyethylene terephthalate (PET) sample. It was found that the vibrational temperature was greatly affected by the N-2 pressure while the rotational temperature remained constant in the N2 pressure range of 20-10(5) Pa. The emission intensity of N-2 first positive system (B-3 Pi -> A(3)Sigma) rapidly decreased at an increasing N-2 pressure due to the collisional relaxation process of the B-3 Pi state with N-2 molecules. The N-2(+)(B-2 Sigma(+)(u) -> X-2 Sigma(+)(g)) radiative transition was observed in the low-pressure DBD plasmas, which was attributed to the direct electron impact ionization of N-2 molecules. The surface characterizations of treated PET samples by contact angle measurement and atomic force microscopy indicate that the low-pressure N-2 DBD plasma is an effective method for the surface modification of polymers. Analysis indicates the plasma characteristics such as electron temperature and ion energy are mainly dependent on the N-2 pressure, which turn to determine the surface properties of treated PET samples. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3635372

The density and velocity of plasma bullets propagating along one dielectric tube

This study shows that the propagation of plasma bullets along one dielectric tube is strongly affected by many discharge parameters, such as the waveform of applied voltage (AC or pulsed DC), peak voltage, He flow rate, and the frequency of AC voltage. Analysis indicates that the density and velocity of plasma bullets are mainly determined by the electric field at the front of plasma bullets. These discharge parameters may significantly influence the distribution of plasma potential along the tube, thus control the electric field at the front of plasma bullets and their propagation. An increase in the pulsed DC voltage with its rise time of <40-50 ns can lead to an obvious improvement in the electric field at the front of plasma bullets, resulting in generation of a plasma in the high density gas and a fast propagation of plasma bullets. He flowing through the tube can contribute to the surface diffusion of charged species, and greatly increase the electric field at the front of plasma bullets. During the propagation of plasma bullets, their density is decreased due to the surface recombination of charged species, such as electrons and ions

Surface modification of PET polymers by using atmospheric-pressure air brush-shape plasma for biomedical applications

In this study, we report a method to generate a reliable and homogeneous brush-shape air plasma plume at atmospheric pressure for surface modification of PET polymers and biomedical applications. The room-temperature air plasma plume consists of well-aligned and stable microplasma jets formed in the vicinity of the ends of hollow optical fibers at atmospheric pressure. This plasma plume may lead to the uniform and large-area surface modification of PET polymers. The plasma plume may efficiently prevent the heat-sensitive polymers from being damaged and significantly affect the surface properties of treated polymers, such as surface chemical compositions, hydrophobicity and biocompatibility. Compared to a high density of blood platelets adhering onto the untreated PET sample, no adhesion of blood platelets is observed on the plasma-activated PET sample due to the surface functionalization. The reaction processes of plasma-activated species at the surface of treated polymers are discussed based on the obtained experimental results

Large-area and uniform surface modification of polymers by barrier discharge plasmas

National Natural Science Foundation of China [10875025, 20803007]A barrier discharge experimental setup for low-pressure and large-area (400 mm x 600 mm) surface modification of polymers is reported. The low-pressure barrier discharge plasma consists of pulsed and glow-like breakdowns with peak widths of several microseconds and leads to the uniform surface modification of polymers. In contrast, the filamentary discharges produced at atmospheric pressure cause surface damage and nonuniform treatment of polymers. This study indicates that barrier discharge plasmas generated in the small gas spacing at low discharge pressure result in efficient collisions between polymer surface and activated species, and an extremely low consumption of feed gas and discharge power. (C) 2010 Elsevier B.V. All rights reserved

Deposition of Large-Area and Protective Diamond-like Carbon Coatings on Glass Substrates by Low-Pressure Dielectric Barrier Discharges

Large-area (370mm x 500mm) diamond-like carbon (DLC) films were deposited on the glass substrate by low-pressure dielectric barrier discharges. The deposited DLC films were hard, homogeneous and extremely smooth. The DLC film deposited on the large-area glass can be potentially used as a scratch resistant and corrosion barrier layer.National Natural Science Foundation of China [10875025, 20803007