Microstructure and enhanced exciton-phonon coupling in Fe doped ZnO nanoparticles.

We report the microstructure and exciton-phonon coupling properties of Fe doped ZnO nanoparticles. Particles are prepared through sol-gel method at room temperature. Doping of Fe(3+) induces strain in the host lattice. Microstructural properties are analysed through Williamson-Hall analysis. Optical absorption studies show strong free excitonic absorption band at 369 nm. The photoluminescence (PL) studies reveal that ultraviolet, blue and green emission bands are located at 380, 445 and 500 nm respectively. Fe doped ZnO nanoparticles exhibits only ultraviolet and blue emission bands. Increase of Fe concentration makes green emission gradually disappeared. Gaussian fitted photoluminescence spectra show the emission is composed of free exciton (FX) recombination and its higher orders of longitudinal optical (LO) phonon replicas. Doping induced blue shift in FX peak and also increases the exciton-phonon coupling.