Effect of nitrogen-argon flow ratio on the microstructural and mechanical properties of AlSiN thin films prepared by high power impulse magnetron sputtering

Abstract

High power impulse magnetron sputtering (HiPIMS) technique was used to deposit AlSiN coatings on silicon Si (100) substrates using metallurgical Al0.8Si0.2 alloy target and under varying nitrogen-argon flow ratios from 5% to 50%. The current-voltage characteristics of the Al0.8Si0.2 alloy target was first investigated, and then the microstructure evolution and mechanical properties of AlSiN coatings grown with increasing nitrogen-argon flow ratios were analyzed by an x-ray photoelectron spectroscopy, grazing incident X-ray diffractometry, scanning electron microscope, transmission electron microscopy, and a nanoindenter. We found that the target was fully poisoned when the nitrogen-argon flow ratio was higher than 50%. The nitrogen-argon flow ratio plays a crucial role in the phase evolution. The phase changed from a metal-rich AlSi crystalline structure (nitrogen-argon flow ratio<10%) to a nanocomposites structure consisting of nanocrystalline c-AlN surrounded in the amorphous Si3N4 phase, which becomes more amorphous phase and smaller nanocrystalline as nitrogen-argon flow ratio increases. As a result, the hardness of AlSiN coating increased with increasing nitrogen-argon flow ratio, and reached a maximum value of 20.6GPa in this study.