Photothermal laser processing of thin silicon nanoparticle films: on the impact of oxide formation on film morphology

Photothermal laser processing of thin films of H-terminated silicon nanoparticles (Si NPs) is investigated. Ethanolic dispersions of Si NPs with an average diameter of 45 nm are spin-coated on silicon substrates yielding films with thicknesses ≤500 nm. Small-area laser processing is carried out using a microfocused scanning cw-laser setup operating at a wavelength of 532 nm and a 1/e laser spot size of 1.4 μm. In conjunction with microscopic techniques, this provides a highly reproducible and convenient approach in order to study the dependence of the resulting film morphology and composition on the experimental parameters. Processing in air results in strongly oxidized granular structures with sizes between 100 and 200 nm. The formation of these structures is dominated by surface oxidation. In particular, changing the processing parameters (i.e., laser power, writing speed, and/or the background air pressure) has little effect on the morphology. Only in vacuum at pressures