CHAPTER 13: Low Temperature Diamond Growth

Diamond thin films represent a class of multi-functional materials whose morphological, chemical, optical and electronic properties can be tailored on demand for specific applications. Nevertheless, this material's versatility inherently requires a high degree of control and understanding of the diamond growth technology. Here, especially, processes at low temperatures become important because of physical limitations regarding the intrinsic properties of typical target substrates (i.e., low melting temperature, high expansion coefficient, high thermal diffusion and chemical reactivity) and compatibility with standard semiconductor industrial technologies. However, low temperature diamond growth (LTDG) is still highly challenging, where novel phenomena are encountered that still remain to be understood. The present chapter focuses on low temperature diamond growth from technological and practical points of view. The LTDG process is divided in two strategies, which are based on i) the modification of the deposition systems and ii) the change of gas chemistry. The state of the art of each strategy and the fundamental growth processes that are involved are reviewed. Among the discussed diamond growth processes, microwave surface wave plasma in linear antenna configuration with oxygen-containing gas mixtures is shown as the most promising process for LTDG over large areas with high optical and electronic grade materials. The growth phenomena observed in linear antenna microwave plasma provide a simple way to control nano- and poly-crystalline diamond character. A practical comparison between focused and linear antenna microwave plasma is presented on several key studies, which utilize LTDG on amorphous silicon, glass, germanium and optical elements used for IR spectroscopy.