Structural evidence of secondary phase segregation from the Raman vibrational modes in Zn1−xCoxO (<x<0.6)

Micro-Raman measurements were performed to study the influence of Co doping on the lattice dynamic properties of the host ZnO. The structural evidence of secondary phase segregation was detected from two distinct phonon vibrational modes at around 472 and 678cm−1 in Zn1−xCoxO (0<x<0.6) ternary alloys with x above 0.098. In addition, an intense, broad, and symmetric phonon vibration was apparent at about 530cm−1 for alloys with x not more than 0.155. The authors suggest the shallow donor defects bound on the Co sites rather than the local vibrational mode involving Co motion as the origin.