THIN-FILM TI/6H-SIC INTERFACIAL REACTION - HIGH-SPATIAL-RESOLUTION ELECTRON-MICROSCOPY STUDY

The structure and chemistry of thin Ti films on Si-terminated vicinal (0001) alpha-SiC substrates was investigated by high-resolution imaging and high-spatial-resolution nanospectroscopy. The Ti was deposited on in-situ cleaned SiC substrates under UHV conditions by evaporation; subsequent post-deposition heat treatments were also performed under UHV conditions. Examination of as-deposited interfaces showed that Ti deposited epitaxially with basal plane/close-packed direction alignment on the substrate. No reaction zone was visible and the interface was chemically sharp. Lattice misfit was accommodated by interface dislocations. Post-deposition heat treatment at 700 degrees C caused formation of Ti5Si3 and TiC reaction products at the Ti/SiC interface. The reaction product morphology was complex and dependent on reaction time. For short times (similar to 20 min) parabolic rate kinetics were obeyed, but for longer times (similar to 60 min) formation of Ti5Si3 dominated and the rate decreased. HREM image contrast of SiC, Ti5Si3 and TiC varied with position near the interfaces. Preliminary theoretical calculations indicated these apparent changes in structure resulted from local changes in orientation and thickness.