Laser induced morphological and optical properties changes in Au doped aluminum oxide and silicon oxide thin films

• Laser processing of composite Au/Al2O3 and Au/SiO2 films is reported.
• The optical and morphological changes induced by the processing are described.
• Ns processing leads to separation of Au and oxide as Au nanoparticles are formed.
• Fs processing may induce optical properties changes without damage of the film.

Results on laser processing of thin oxide films containing gold are presented. The Au doped aluminum oxide and silicon oxide thin films are fabricated by pulsed laser deposition using targets composed by areas of gold and the oxide material. The as fabricates samples are processed by laser pulses with broad range of parameters – pulse duration, wavelength, fluence and pulse number. The changes of the morphology and optical properties after the laser irradiation are studied. It is found that laser irradiation with both nanosecond and femtosecond pulses may induce clear color change of the samples, which is accompanied by modification of the film structure. Nanosecond laser pulse treatment results in disintegration of the film induced by melting and surface tension forces. The process is accompanied by formation of nanoparticles at the edges of the surface modifications. At higher fluences nanosecond pulse irradiation leads to formation of wires composed of oxide material and gold nanoparticles. The femtosecond laser pulses induce a homogeneous decomposition of the film, as melt dynamics is not observed. The decomposition is however accompanied by color change of the irradiated area and clear dip in the transmission spectra. The dynamics of the film decomposition is discussed. The conducted study can be applied in fabrication of optical elements and in plasmonics.