MAPLE deposition and characterization of SnO2 colloidal nanoparticle thin films

In this paper we report on the deposition and characterization of tin oxide (SnO2) nanoparticle thin films. The films were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. SnO2 colloidal nanoparticles with a trioctylphosphine capping layer were diluted in toluene with a concentration of 0.2 wt% and frozen at liquid nitrogen temperature. The frozen target was irradiated with a KrF (248 nm, tau = 20 ns) excimer laser (6000 pulses at 10 Hz). The nanoparticles were deposited on silica (SiO2) and < 100 > Si substrates and submitted to morphological (high resolution scanning electron microscopy (SEM)), structural Fourier transform infrared spectroscopy (FTIR) and optical (UV-Vis transmission) characterizations. SEM and FTIR analyses showed that trioctylphosphine was the main component in the as-deposited films. The trioctylphosphine was removed after an annealing in vacuum at 400 degrees C, thus allowing to get uniform SnO2 nanoparticle films in which the starting nanoparticle dimensions were preserved. The energy gap value, determined by optical characterizations, was 4.2 eV, higher than the bulk SnO2 energy gap (3.6 eV), due to quantum confinement effects.