An investigation of the role of plasma conditions on the deposition rate of electrochromic vanadium oxide thin films

Plasma-enhanced chemical vapor deposition (PECVD) has been used to form amorphous vanadium oxide thin films from mixtures Of VOCl3, O-2, and H-2. The deposition rate was examined as a function of PECVD operating conditions. Growth rates were found to be first order in VOCl3, and independent of both 0, and H,. High quality vanadium oxide films were also deposited without the use of hydrogen. Rates were observed to increase with rf power, and decrease with operating pressure. Maximum rates were an order of magnitude greater than typically observed with physical vapor deposition techniques. Optical transmission and electrochemical analysis were used to quantify the electrochromic response. After initial cycling films demonstrated high transparency across the visible, and the optical band gap increased with lithium intercalation. Lithium ion diffusion coefficients approached 10(-11) cm(2)/s, approximately an order of magnitude higher than literature values. (c) 2005 Elsevier B.V. All rights reserved.