Low pressure chemical vapor deposition of Cu_xS

Abstract
Cu_xS thin films have been prepared on glass substrates by Low-Pressure Chemical Vapor Deposition (LPCVD) in a hot wall reactor from copper(II) bis-tetramethylheptanedionate (Cu(thd)₂) hydrogen sulfide (H²S), and hydrogen. The influence of the temperature, the H²S partial pressure, and the Cu(thd)₂ partial pressure on the crystalline phase composition, the stoichiometry, and the morphology has been examined. It is found that the temperature determines the crystalline phase of the films. Pure CuS thin films form up to 227 °C, whereas films with mixed phases of increased copper content form when the temperature increases up to 505 °C. The reaction kinetics are investigated and discussed by analyzing the axial deposition profile of the deposited films. We propose a mechanism based on the competitive adsorption and reaction of Cu(thd)₂, H₂S, and 2H(thd). Downstream the reactor the surface reaction between Cu(thd)₂ and H₂S is retarded by co-absorption of H(thd)(g) which leads to blocking of the active surface sites.