Heterogeneous Integration of Diamond

ConspectusThe heterogeneous integration of materials offers new paradigms in many extreme applications, where single materials cannot solve the problem alone. Diamond has a plethora of superlative properties that make it attractive in a diverse array of applications, such as its unique combination of unrivalled thermal conductivity combined with high electrical impedance; single photon emission at room temperature; superlative acoustic wave velocity, and Debye temperature. Most of these properties are directly related to diamond’s atomically dense lattice of light carbon atoms, which has consequences such as difficulty in doping diamond n-type and low thermal coefficient of thermal expansion. This last property presents a significant problem for the growth of diamond on nondiamond materials as the linear coefficients of thermal expansion of other materials are often several times larger than diamond.The integration of diamond with other materials is thus a complex and multifaceted problem, with various solutions with individual pros and cons. Our work focused on the growth of diamond directly on various materials or with enabling interlayers. In particular, we have focused on driving the self-assembly of diamond nanoparticles onto nondiamond surfaces as the precursors to diamond growth. This approach requires knowledge of the zeta potential as a function of pH of the surface to be treated as well as that of the diamond particles, and this Account provides a detailed summary of the most critical materials for diamond integration. The high density of nanodiamond particles as precursors for diamond growth is unfortunately not sufficient, and this Account discusses issues with adhesion and stress which are exacerbated by the aforementioned anomalously low thermal expansion coefficient.In this Account, we review this approach with references to competing approaches, detailing unavoidable issues such as wafer bow, stresses, and the harsh environment of diamond chemical vapor deposition.