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

Pulsed laser irradiation at 355 nm 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 alpha-W, WO2, and WO3 in the deposited W films at 1.78-6.67 W and at a scan rate of 4 mu m/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 -80 mu Omega -cm was obtained at a power of from 3.56 to 4.0 W, at which the effect of the laser -induced grain growth on resistivity is maximized, accompanied by the laser enhanced oxidation of W. (C) 2017 Elsevier B.V. All rights reserved.