Pulsed laser chemical vapor deposition of a mixture of W, WO2, and WO3 from W(CO)6 at atmospheric pressure

Publication date: 31 March 2017
Source:Thin Solid Films, Volume 626
Author(s): Kyunghoon Jeong, Jiwon Lee, Injae Byun, Myung-jun Seong, Jongsoo Park, Ho-seok Nam, Jaegab Lee
Pulsed laser irradiation at 355nm was used to deposit tungsten (W) films from tungsten hexacarbonyls (W(CO)6) on transparent glass substrates in air. The time dependence of W deposition revealed that the reaction proceeded via nucleation and growth; photolytic decomposition initiated W nuclei, which acted as laser absorbers and grew by direct deposition on the nuclei, driven mainly by a pyrolytic process. In addition, the laser power dependence showed that the thickness of W films linearly increases with power; however, the thickness decreased significantly at a sufficiently high power to allow the evaporation of tungsten oxide. Various analyses (X-ray diffraction (XRD), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS)) identified α-W, WO2, and WO3 in the deposited W films at 1.78–6.67W and at a scan rate of 4μm/s, and their compositional and microstructural changes according to laser power. The loss of carbon (C) is attributable to the background oxygen. An increase in laser power increased the oxygen content, the WO3 to WO2 ratio, and the size of W grains. The resistivity of W films was closely related to the oxygen concentration and microstructure of W. The minimum resistivity of ~80μΩ-cm was obtained at a power of from 3.56 to 4.0W, at which the effect of the laser-induced grain growth on resistivity is maximized, accompanied by the laser-enhanced oxidation of W.