Control of Microstructure and Texture in Nanocrystalline Transition -Metal Nitride Coatings by Ion Beam Assisted Deposition Method
Ma, Cheng-Hsin
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https://hdl.handle.net/2142/82722
Description
Title
Control of Microstructure and Texture in Nanocrystalline Transition -Metal Nitride Coatings by Ion Beam Assisted Deposition Method
Author(s)
Ma, Cheng-Hsin
Issue Date
2002
Doctoral Committee Chair(s)
Chen, Haydn
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
In this study, titanium nitride (TiN), chromium nitride (CrN) and vanadium nitride (VN) were prepared by ion-beam-assisted deposition method (IBAD). The film microstructure was observed using scanning electron microscopy (SEM). The results showed that the microstructure was controlled by homologous temperature (TS/TM), and mostly followed by the structure zone diagram summarized by Thornton and Messier. The ion beam assistance could accelerate the transition from Zone 1 to Zone T, and Zone T to Zone 2. In addition, the ion beam increased the packing density and the reactivity of Cr and N. The grain sizes, determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), were in nano-scale (∼15nm) when ion to atom ratio (J I/JM) = 2. Results of XRD pole figures showed that the films were highly textured. By the control of ion beam energy, JI/J M ratio, incident angle, and the deposition temperature, seven kinds of textures were observed. Four parameters, (1) surface energy, (2) strain energy, (3) adatom mobility, (4) preferential sputtering and differential damage, were identified and used to explain the texture evolution of the films. Results of nanohardness, measured by nanoindentation, indicated that the hardness of the films is not related to the film texture, which suggested that the dislocation theory is not applicable for the nano-sized grains. The minimum grain size required for the activation of slip systems in grains, was estimated to be ∼100nm. The grain rotational deformation and grain boundary sliding followed by mass transfer could be two possible mechanisms of deformation in the nanocrystalline films.
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