Electronic structure, optical and magnetic studies of PLD-grown (Mn, P)-doped ZnO nanocolumns at room temperature

Abstract

We prepared well-aligned Zn1−xMnxO:yP nanocolumns (x = 0–0.02, and y = 0 and 1 mol%) on SiO2/Si(0 0 1) substrates by using pulsed laser deposition (PLD) and then investigated their electronic structure and optical and magnetic properties at room temperature. The analyses of x-ray photoelectron and x-ray absorption fine structure spectra revealed Mn2+ and/or P ions existing in nanocolumns, where Mn2+ ions are situated in the Zn2+ site of the ZnO-wurtzite structure. Although the incorporation of Mn2+ and/or P ions did not form secondary phases, as confirmed by x-ray and electron diffraction patterns, more lattice defects were created, and consequently changed the band-gap energy as well as the electron–phonon interactions in the nanocolumns. Magnetization versus magnetic-field measurements revealed that all the samples exhibited FM order. In particular, the (Mn, P) co-doping with x = 0.02 and y = 1 remarkably enhanced the magnetic moment up to 2.92 µB/Mn. Based on the results obtained from analyzing the electronic structures, UV–Vis absorption and resonant Raman scattering spectra, and theoretical calculations, we believe that the enhancement of the FM order in (Mn, P)-doped ZnO nanocolumns is due to exchange interactions taking place between vacancy-mediated Mn2+ ions.