TABLE OF CONTENTS In chemical vapor deposition (CVD), the vaporized precursors are introduced into a CVD reactor, where the precursor molecules adsorb onto a substrate held at an elevated temperature. These adsorbed molecules will be either thermally decomposed or reacted with other gases/vapors to form a solid film on the substrate. Such a gas-solid chemical reaction at the surface of a substrate is called the heterogeneous reaction. Because a number of chemical reactions may occur in the CVD process, CVD is considered to be a process of potentially great complexity as well as one of great versatility and flexibility. It can be used to grow a variety of materials including metals, semiconductors, and ceramics. The solid films can be made as amorphous, polycrystalline, or single crystalline materials with the desired properties, depending on the growth conditions. In general, particle formation in the gas phase in a CVD process should be avoided because this will not only considerably deplete the reactants, leading to a non-uniform film thickness, but also incorporate the undesirable particles in the growing film. However, under certain experimental conditions, particle formation in the gas phase can be used to synthesize nanosize powders or particles. Gas-phase nucleation and controlled growth of the particles are of prime concern in the growth processes. The particle-size range is controlled by the number of nuclei formed in the reactor and the concentration of the condensing species.
This chapter is intended to give some description of the developments of the CVD synthesis of...
