Crystallographic properties of 3d transition metal (Ti, V, and Cr) doped AlN films

The crystallographic properties of AlN films doped with 3d transition metal (3d-TM: Ti, V, and Cr, concentration x: 0-12 %) showing distinctive optical absorption structures in visible light region were investigated. The films were prepared on SiO2 glass substrates by rf sputtering. X-ray diffraction (XRD), transmission electron microscopy (TEM), and 3d-TM K-edge X-ray absorption fine structure (XAFS) measurements have been made at room temperature on the films. Both out-of-plane and in-plane XRD profiles revealed that all the films had wurtzite structure with a high degree of c-axis preferred orientation. TEM results showed that the films consisted of columnar crystals with random rotation of a-axis. The 3d-TM K-edge XAFS spectrum indicated that TM ions are substituted for Al in wurtzite AlN. These results suggest that the distinctive absorption structures in visible light region derive from crystals described as wurtzite (Al1-x, TMx)N.