Vickers Hardness
Vickers Hardness vs. Melting Point
The UHV Used

Featured PhD Student: Koichi Tanaka

This summer Koichi Tanaka, who works in Kodambaka's lab, presented his work, Ultra-high vacuum dc magnetron sputter-deposition of TaC and Ta2C thin films on MgO(001) and Al2O3(0001), to the 15th International Symposium on Sputtering and Plasma Processes. His work focused on the deposition of tantalum carbide films on single crystal substrates and the role a 2-D hBN (hexagonal boron nitride) layer plays in said growth. These transition metal carbides, the material family of tantalum carbide, are interesting due to them boasting high heat resistance and good electrical conductivity, while still having high hardness.

In order to grow the tantalum carbide films, Koichi used a custom-designed ultra-high vacuum (UHV) deposition system. Within the chamber the TaC was grown on a MgO(001) substrate, in both a high and low pressure ethylene atmosphere. The different pressures from the ethylene lead to different crystal structures of the TaC, only one of which is desired, that being of the higher pressure experiment.

Ta2C was synthesized next on a sapphire substrate, both with and without an hBN buffer layer. By doing this and then characterizing the produced film with XRD (x-ray powder diffraction), Koichi was able to show that the inclusion of an hBN buffer layer helped to increase the crystallinity of the Ta2C film. The hBN accomplishes this by limiting the interaction of the substrate with the Ta2C film thereby reducing strain on the film as it forms.

Koichi demonstrated with these experiments definitive ways to produce TaC and Ta2C with different crystal structures and crystallinity. In the future he plans to work on high resolution STEM (scanning transmission electron microscopy) imaging and EELS (Electron Energy Loss Spectroscopy) characterization to determine hBN layer formation and interfacial structure.

Come back to this page in two weeks to learn about a new professor!