Effects of Annealing on the Optical Absorption Spectrum of Strontium Titanate Implanted with Ag Ions

Ag ions were implanted into strontium titanate (STO) single crystal with the thickness of 0.5mm at largely different energies. The doses are 0.1 - 5 times 10¹⁶ ions/cm² and the implantation energy was 20keV, 128keV and 3MeV. Optical absorption spectrum in the visible range was measured for the samples heated at up to 1000degC. A small absorption peak was observed at 440 nm for an as-implanted sample with the dose of 0.5 times 10¹⁶ ions/cm ². The peak intensity increased and its position gradually shifted to 490nm as increasing the dose. The absorption peak for the sample implanted with the energy of 128keV shifted to more longer wavelength side from 490 to 590nm, when heated at high temperatures. A lot of nano size particles could be observed from the TEM photograph in the layer to the depth of about 60nm for the sample (implanted at 128 keV) heated at 700degC, 6h, in air