Growth and Characterization of Hard Nitrides Films Prepared by Pulsed Laser Deposition
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R. B. INTURI*, ASHOK KUMAR**, U. EKANAYAKE**, N. SHU**, AND J. A. BARNARD*, "**Department of Electrical Engineering, University of South Alabama, Mobile, AL 36688 *Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487-0202 ABSTRACT
Transition metal of nitrides have many desirable properties for application at elevated temperatures because of extremely high melting point, hardness, high temperature strength, good thermal shock resistance, and high thermal conductivity. We have investigated the thin film coatings of nitrides (titanium nitride, and composite carbon nitride) on various commercial useful substrates by the pulsed laser deposition (PLD) method. The PLD method is unique process for depositing high quality thin films with novel microstructure and properties. The laser parameters: energy density, pulse rate, target/substrate distance and substrate temperature have been optimized to improve the quality of thin films. The mechanical properties of the films have been evaluated at different processed conditions by nanoindentation technique. The films were characterized by X-ray diffraction, scanning electron microscope and FTIR techniques. Optimization of laser deposition parameters to obtain high quality thin films will be discussed in detail. INTRODUCTION
Thin films of metal nitrides have a large field of applications in mechanics and microelectronics due to their hardness, good conductivity, and chemical stability. Titanium nitride (TiN) possess many interesting properties such as high thermal and electrical conductivity, high melting point, good thermodynamic stability, and low mass diffusivity. Due to its unique properties, TiN thin films have wide range of applications; such as wear-resistant coating for tools and wear parts, diffusion barrier layer for semiconducting parts, and surface decoration for commercial goods [1]. The current interest in carbon nitride (CNx) stems from the recent theoretical work by Liu and Cohen [2] predicting the extreme hardness of the material, comparable to or greater than diamond. It has been recently reported that crystalline carbon nitride/TiN composite coatings deposited by dual-cathode magnetron sputtering system have remarkably enhanced the hardness value of the films, [3]. It has been shown that TiN provides a lattice-matched structural template to seed the growth of carbon nitride crystallites. The pulsed laser deposition (PLD) technique has proven to be the best technique to deposit excellent quality of TiN thin films on Si (100) and metal substrates [4, 5]. This first paper describes the same approach to grow carbon nitride composite coatings with varying thicknesses of buffer layers TiN and CN, films at different processing conditions by PLD process. Mechanical properties of thin films, such as film cohesiveness and bonding to the substrate, are influenced by film stresses which are characteristic to the deposition condition. This paper presents the detailed evaluation of mechanical properties by nanoindentation 28
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