Resonant raman scattering in ZnO : Mn and ZnO: Mn : Al thin films grown by RF sputtering

• Autor(a) principal: Cerqueira, M. F.
• Data de Publicação: 2011
• Outros Autores: Vasilevskiy, Mikhail, Oliveira, Fernando, Rolo, Anabela G., Viseu, T. M. R., Campos, J. Ayres de, Alves, E., Correia, Rosário
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/1822/13429
• topic: ZnO; Raman spectroscopy; Mn and Al doping; Phonons; Science & Technology

Raman spectroscopy results obtained under visible (non-resonant) and UV (resonant) excitation for nanocrystalline ZnO, ZnO:Mn and ZnO:Mn:Al thin films grown by radio frequency magnetron sputtering are presented and compared. The origin of the multiple longitudinal optical (LO) phonon Raman peaks, strongly enhanced under resonance conditions, and the effects of the dopants on them are discussed in the framework of the ‘cascade’ model. It is suggested that the observed suppression of the higher-order LO phonon lines for ZnO:Mn:Al is caused by the dissociation of excitons in the heavily n-type doped material. On the basis of the cascade model interpretation of the higher-order Raman peaks in the resonant spectra, the LO phonon frequencies for wavevectors away from the gamma point are evaluated and compared topreviously published phonon dispersion curves.