Characterizaton of pulsed laser deposited SmFeO3 morphology: effect of fluence, substrate temperature and oxygen pressure

Abstract

The morphology of SmFeO3 thin films grown on quartz substrate by pulsed laser ablation (PLD) is studied by ex situ spectroscopic ellipsometry (SE), as a function of oxygen pressure (PO2) and substrate temperature (TS). Analysis of the films is performed with commercial Sentech software using simplex algorithm and roughness is determined using standard Bruggemann model. Results compare well with those obtained on some samples by transmission electronic microscope (TEM) for roughness and thickness, on the one hand and atomic force microscope (AFM) for roughness, on the other. They show that relative roughness varies with PO2, linearly below 100 mTorr and non linearly above, but not with TS. Comparison with results obtained for YIG (Y3Fe5O12) samples shows similar linear relation with PO2 but with a smaller slope. In terms of fluence, it has been determined that roughness increases linearly for low values. TS effect is observed namely on the structure and Faraday magneto-optic response of the films. Structure is amorphous for TS below 755 °C and crystalline above with two types of structures, cubic and orthorhombic as shown by TEM. Similarly, for TS below 755 °C, no magneto-optic response is observed. SE analysis in terms of Cauchy model shows optical constants of thin films to be lower than for bulk crystal at all PO2 and TS .