Influence of substrates and e-beam evaporation parameters on the microstructure of nanocrystalline and epitaxially grown Ti thin films

Abstract

Titanium thin films were deposited on silicon nitride (SiNx) coated Si, NaCl, and sapphire substrates varying the deposition conditions using e-beam evaporation to investigate thin film growth modes. The microstructure and texture evolution in dependence of substrate, deposition rate, film thickness, and substrate temperature were studied using X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Thin films obtained on SiNx and NaCl substrates were nanocrystalline, while the films deposited on sapphire transformed from nanocrystalline to single crystalline at deposition temperatures above 200 °C. Predominantly, a surface plane orientation of (0002) was observed for the single crystalline films due to the minimization of surface energy. The orientation relationship of epitaxial single crystalline films grown on C-plane sapphire substrate is found to be (0002)Ti‖(0006)Sapphire,〈112¯0〉Ti‖〈033¯0〉Sapphire. In this orientation relationship, both the total surface and strain energy of the film are minimized. The results were complemented by resistivity measurements using the four-point probe method reporting an increase from ~60 μΩ cm to ~95 μΩ cm for single crystalline and nanocrystalline films, respectively.