Effect of Titanium and Molybdenum Cover on the Surface Restructuration of Diamond Single Crystal during Annealing

Diamond is an important material for electrical and electronic devices. Because the diamond is in contact with the metal in these applications, it becomes necessary to study the metal-diamond interaction and the structure of the interface, in particular, at elevated temperatures. In this work, we study the interaction of the (100) and (111) surfaces of a synthetic diamond single crystal with spattered titanium and molybdenum films. Atomic force microscopy reveals a uniform coating of titanium and the formation of flattened molybdenum nanoparticles. A thin titanium film is completely oxidized upon contact with air and passes from the oxidized state to the carbide state upon annealing in an ultrahigh vacuum at 800 degrees C. Molybdenum interacts with the (111) diamond surface already at 500 degrees C, which leads to the carbidization of its nanoparticles and catalytic graphitization of the diamond surface. This process is much slower on the (100) diamond surface; sp(2)-hybridized carbon is formed on the diamond and the top of molybdenum carbide nanoparticles, only when the annealing temperature is raised to 800 degrees C. The conductivity of the resulting sample is improved when compared to the Ti-coated diamond substrates and the Mo-coated (111) substrate annealed at 800 degrees C. The presented results could be useful for the development of graphene-on-diamond electronics.

Automated summary

This study investigates the interaction between diamond and metals as well as the interface structure, especially at elevated temperatures. The experiments reveal uniform coating of titanium on the diamond surface and the formation of flattened molybdenum nanoparticles. Titanium is completely oxidized and transforms into a carbide state upon annealing, while molybdenum interacts with the diamond surface, leading to the carbidization of nanoparticles and catalytic graphitization. The conductivity of the resulting sample is improved compared to Ti-coated diamond substrates and Mo-coated (111) substrates annealed at 800 degrees C. These findings are valuable for the development of graphene-on-diamond electronics.