The role of samarium incorporated structural defects in ZnO thin films prepared by femtosecond pulsed laser deposition

Samarium, a rare-earth element is used as an impurity in ZnO to study the effects it causes in structure thereby changing the optical and electrical characteristics of ZnO thin films. Samarium zinc oxide (SmxZn1-xO, SZO) films are deposited on glass substrates employing femtosecond pulsed laser deposition (fs-PLD). XRD results show that all films are crystalline and prefer c-axis growth. 1 wt% Sm is plausible for doping in ZnO and 2 wt% samarium addition results in reaction among impurity and host atoms forming a compound ZnSm2O4. Higher concentrations lead to defect generation and decline of crystalline quality. AFM results show that surface roughness is increased with samarium incorporation in addition to affecting particle size and shape. These microstructural variations significantly affect the optical transmittance, reflectance and band gap energies of thin films which are calculated using spectroscopic ellipsometry data. Presence of intrinsic defects and extrinsic defects caused by samarium is revealed by Photoluminescence Spectroscopy. Electrical resistivity of SZO films is significantly affected with Sm concentration in nanocrystalline ZnO. These types of films are suitable for use in optical devices for UV and blue emission.