Processing dependence of structural and physical properties of Mg2Ge thin films prepared by pulsed laser deposition

Magnesium germanide (Mg2Ge) thin films were deposited on MgO (001) substrates using pulsed laser deposition technique. The films were deposited at various substrate temperatures, ranging from 300 to 600 degrees C. The effects of substrate temperature on structural, electrical and optical properties were studied. All the films, except the samples prepared at 300 degrees C, were polycrystalline with major diffraction from (200) plane. The highest electrical conductivity of 141.86 Omega(-1) m(-1) measured at room temperature was observed for the sample deposited at the highest temperature, with the corresponding charge carrier mobility and concentration of 2.62 cm(2) V/s and 8.66x10(18) cm(-3), respectively. The carrier concentration dependence of the optical absorption edge energy is accounted for by the Burstein-Moss shift. The variation of strain value may have also contributed to the change in bandgap energy. The reduction in direct bandgap energy was found to vary from 2.20 to 2.00 eV with increasing the deposition temperature. (C) 2012 Elsevier B. V. All rights reserved.