Dissertation > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics

Template and Superhardness Effects in Two-phase Nanostructured Films

Author KongMing
Tutor LiGeYang
School Shanghai Jiaotong University
Course Materials Science
Keywords Two-phase nanostructure films Nano-multilayers Nanocomposite films Template effect Superhardness effect Crystallization of the amorphous layer Coherent interface
CLC O484
Type PhD thesis
Year 2009
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Hard film surface coating materials with a wide range of applications. In recent years, the study found that the ceramic nano-multilayers and nanocomposite films have a hardness of superhard abnormally elevated effect. The performance of two-phase nanostructure films due to the diversity of material combinations can be cut, demonstrating the broad application prospects, and their micro-structure of the nano-scale, rather than high hardness can be obtained through the tradition of the strong bonds between atoms strengthening mechanisms, more theoretical research value. Nano-multilayers and nanocomposite films has become in recent years superhard material and research focus of the film material. Nano-composite membrane research papers from the two-dimensional structure of nano-multilayers and the three-dimensional structure of the two-phase nanostructure film to produce the effect of micro-structure of superhard nature and strengthen reason. In nano-multilayer film, paper design, preparation of TiN and amorphous SiC of AlON and AlN amorphous Si 3 N 4 nano-multilayers composed, study cubic structure TiN and AlN crystals of hexagonal structure of the amorphous layer crystal template effect, as well as changes in the pattern of growth of the amorphous layer on the microstructure and mechanical properties of nano-multilayers. Nanocomposite film, the essays reveal TiN / Si 3 N 4 nanocomposite film microstructure features, and further using a two-dimensional structure of TiN / Si N 4 nano-multilayers experimental simulation method to study the amorphous Si 3 N 4 the TiN crystal template layer on crystallization phenomena and structural changes in the film microstructure and mechanical properties. Paper the main conclusions are as follows: 1. Cubic structure of nanocrystalline TiN and amorphous SiC multilayers promoted by effects of a crystal growth: due to the template effect of the B1-NaCl structure TiN crystal layer, SiC layer in a thickness of less than 0.6 nm crystallized into crystals of the same structure and epitaxial growth and TiN; SiC crystallization after the TiN layer, the crystal growth also promoting effect, so that the TiN layer integrity of the crystal growth to significantly improve, TiN / SiC multilayers resulting in a strong (111) preferred orientation of columnar crystals, and a hardness of superhard abnormally elevated effect, the highest hardness values ??of up to 60.6 GPa. The SiC slice thickness increases to 0.8 nm after gradually becomes amorphous structure hindered by the crystal structure, the epitaxial growth NANOMULTILAYERS multilayer film hardness decreases. SiC crystallization and the TiN formation of epitaxial growth structure nanomultilayers the TiN thickness change the mechanical properties of the multilayer film is not so obvious. Using sputtered metal Ti target and compound in a mixed atmosphere of Ar, N2 Al2O3 target reactive sputtering method can be prepared by the multilayer film of TiN / AlON nano. Multilayers of TiN / AlON nano the TiN crystal layer template role, the original amorphous AlON layer thickness of less than about 0.6 nm mandatory crystallization and formed TiN layer epitaxial growth structure, The multilayers get the hardness significantly the the superhard effect, increased the maximum hardness of 40.8 GPa. AlON layer changes with increasing thickness of the amorphous growth, multilayer film epitaxial growth structure was destroyed, its hardness reduced accordingly. Due to high deposition rate reactive sputtering TiN reactive sputtering high hardness NANOMULTILAYERS method provides a new way of thinking for the industrial production of superhard multilayer films. AlN / Si 3 N 4 nano-multilayers amorphous the Si 3 N 4 When its thickness is less than 0.8 nm when crystallized into a hexagonal structure in the hexagonal structure of the template effect of the AlN crystal layer pseudospin crystal and the AlN (0001) preferred orientation, epitaxial growth structure, the multilayer film is formed produce the effect of superhard abnormally elevated hardness, maximum hardness of 32.8 GPa. Si 3 N 4 with increasing layer thickness into amorphous growth, multilayer film epitaxial growth structure was destroyed, its hardness also will reduced. This hexagonal structure of AlN also has so that the phenomena of crystallization of the amorphous material and provides a new example is the universality of the template effect of nano-multilayered film crystal growth. High hardness of TiN / Si 3 N 4 nanocomposite film microstructure analysis found that the composite film of TiN was a diameter of about 10 nm and a height of about several hundred nanometers a columnar crystal, Si 3 N 4 the thickness of the boundary phase is about 0.5-0.7 nm, and render the crystal state, and epitaxial growth is formed and adjacent to the TiN grains structure, composite film has a number of TiN nano columnar grain by Si 3 N 4 interface relative to total grid connected and form a cluster of columnar grain microstructure features. Two-dimensional structure of TiN / Si 3 N 4 NANOMULTILAYERS experimental simulations show that due to the template effect of TiN crystal layer of amorphous Si 3 N 4 is crystallized in a thickness of less than 0.7 nm, and is formed adjacent to the TiN crystal of epitaxial growth structure, a multilayer film obtained 38.5 GPa of the high hardness, Si < sub> 3 N 4 with the further increase of the thickness of the transition to the amorphous state, the multilayer film of the total cell growth structure destruction, also will quickly reduce its hardness. TiN / Si 3 N 4 nanocomposite films and multilayers micro-structural characteristics and mechanical properties of the contrast can be found, the two-phase nanostructures superhard films in high hardness obtained with the amorphous phase crystallization template form a coherent interface structure, and their hardness rapidly decreases with the attendant increase in the thickness of the amorphous interface for Amorphous result from changes in the crystal state coherent relevant structural destroyed. Based on the above research papers reveal key role and universality of the template effect of special micro-structure of the two-phase nano-structured film formation and produce superhard effect; TiN / Si 3 N nano composite film microstructure and strengthening mechanism new perspective; using nanomultilayers template effect of crystal growth, expand the high hardness of the two-phase nano-structured ceramic thin film material combinations range through the crystallization of amorphous design route .

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