3.11 - Single Crystal Diamond Growth on Iridium

Abstract

As for many other materials, the synthesis of diamond single crystals with a low defect density in wafer size is the ultimate goal and a prerequisite for the development of novel devices. The development of chemical vapor deposition (CVD) methods eradicated the inherent size limitations of the classical high-pressure high-temperature technique. Combining CVD with heteroepitaxial nucleation and growth on an appropriate substrate represents a very promising concept for the synthesis of single crystal diamond wafers. Many years of research were necessary before iridium was identified as a unique template for diamond heteroepitaxy. It exceeds by far all other competing substrate materials in terms of the achievable diamond crystal quality. Bias-enhanced nucleation (BEN) is the crucial step to obtain epitaxial diamond nucleation on Ir. Its mechanism cannot be described by classical nucleation theory. A broad range of characterization tools was applied to study the BEN process. Combining all the results into a big puzzle allowed the development of a consistent model that explains the nucleation on iridium and the characteristic pattern formation. The initial mosaic structure of thin heteroepitaxial diamond films on Ir transforms into a real single crystal by a mosaic spread reduction process that is based on the merging of grains by the formation of disclinations. The texture development was successfully modeled numerically. Diamond/Ir/SrTiO3/Si and diamond/Ir/yttria-stabilized zirconia/Si are powerful multilayer structures for the upscaling of (100)- and (111)-oriented diamond films. The growth of single crystal metal films on biaxially textured oxide layers offers an attractive concept for single crystal diamond deposition on arbitrary substrates. Off-axis growth and epitaxial lateral overgrowth are strategies for further improvement of the film quality. Among potential applications, diamond mosaic crystals as neutron monochromators and detectors for tracking and timing in high-energy particle physics are described.