Article ID Journal Published Year Pages File Type
5370203 Applied Surface Science 2006 8 Pages PDF
Abstract

Thin films of Ti-B-N with different N contents were deposited on Si(1 0 0) at room temperature by reactive unbalanced close-field dc-magnetron sputtering using three Ti targets and one TiB2 target in an Ar-N2 gas mixture. The effect of N content on bonding structure, microstructure, phase configuration, surface roughness and mechanical properties have been investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), cross-sectional scanning electron microscopy (SEM), plan-view and cross-sectional high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and microindentation measurements. It was found that the N content significantly affected phase segregation and microstructure. The nitrogen-free TiB0.65 films showed an amorphous compound consisting of Ti and TiB2 (Ti-TiB2). After adding about 28 at.% N, Ti was preferentially bonded to N to form TiN, accompanying with formation of small amounts of TiB and BN bonds. At this stage they combined TiB2 to form a two-phase nanocomposite with microstructures comprising of nanocrystalline (nc-) TiN phase in nitrogen-containing amorphous (a-) TiB2 matrix. Addition of more N promoted formation of BN bonding at cost of TiB2, which resulted in formation of nanocomposite nc-TiN/a-(TiB2, BN) thin films. A small grain less than 8 nm in size was found at low N content, and the grain size increased with increasing N content. A low microhardness value of about 20 GPa was obtained in the amorphous Ti-TiB2 compound, and a maximum microhardness value of about 50 GPa was achieved in nc-TiN/a-TiB2. A decrease of microhardness took place after formation of BN (i.e. amorphous matrix composed by both TiB2 and BN) with further increasing N content, and a hardness value of about 35 GPa was followed at high N contents. The surface roughness strongly depended on the phase configuration. The higher the mole fraction of nanocrystalline TiN phase, the rougher the surface became.

Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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