Metal and Ceramic Thin Film Growth by Reaction of Alkali Metals with Metal Halides: A New Route for Low-Temperature Chemical Vapor Deposition

Abstract

A new low-temperature chemical vapor deposition (CVD) method for the growth of metal and ceramic thin films has been demonstrated. This method involves the use of a low-pressure coflow diffusion reactor to react alkali metal vapor with metal halide vapor. The reaction chemistry is described by the following general equation: mnNa + nMXm Mn + nmNaX. Here, Na is an alkali metal (e.g. Na, K, Cs, or Rb), M is a metal (e.g. Ti, Ta, Pt, W, ...) or nonmetal (e.g. B, C, Si, ...), X is a halogen (e.g. F, Cl, Br, or I), Ar is an inert gas (e.g. Ar or He), and m and n are integers. In this reaction, the alkali metal strips halogen from the metal halide. The metal is then free to grow into a thin film on a substrate placed in the reaction zone. Metal nitride or metal oxide ceramic films are easily formed by the introduction of nitrogen or oxygen gases into the reactor. Previously, this technique has been successfully employed for the production of nanoparticles and as an industrial synthesis route for the reduction ...