Raman spectra of TiN/AlN superlattices

TiN (4.5 nm)/AlN (3, 6, 22 nm) superlattices deposited by DC magnetron sputtering on MgO(001) at a temperature of 850°C exhibit Raman signals. They indicate N and Ti vacancies (as in thick TiN) in TiN1−x layers (x=3±2%). x is higher for the sample with 3-nm thick AlN layers, which is ascribed to N diffusion from AlN (standing close to the TiN interfaces) to TiN. In comparison to Raman peaks of thick AlN, there are split signals of wurzite AlN phase, and a signal from another phase, which might be defective rocksalt AlN standing close to the TiN interfaces. The Raman signals clearly show interactions between AlN and TiN layers.