Structural and photoluminescence properties of Zn 0.8Mg 0.2O thin films grown on Si substrate by pulsed laser deposition

Abstract

Ternary Zn 1− x Mg x O (0< x<0.42) alloy thin films with complete c-axis orientation have been deposited on p-type Si(100) substrate by pulsed laser deposition. X-Ray diffraction measurements indicate that the hexagonal wurtzite type structure of Zn 1− x Mg x O can be stabilized up to Mg content x∼0.37. The deposition temperature was found to exert evident influence on the crystalline grain size and c-axis orientation of the film. Zn 0.8Mg 0.2O film grown at 650 °C displays the narrowest full width of half maximum value of ∼0.19° for (002) reflection peak and the largest grain size (∼150 nm in diameter). An apparent blueshift (∼40 nm ∼0.40 eV) in near band edge (NBE) emission peak has been observed in the room temperature photoluminescence (PL) spectra of Zn 0.8Mg 0.2O compared with that of ZnO. The ratio ( R= I NBE/ I DL) of NBE intensity to defect level (DL) peak intensity was found to be as large as 159, indicating that the film is of high crystalline quality and is nearly defect free. High resolution transmission electron microscopy photograph indicates that the c-axis oriented Zn 0.8Mg 0.2O film was grown on an amorphous SiO 2 intermediate layer with ∼8 nm thickness.