Effect of nitrogenized Si(1 1 1) substrates on the quality of ZnO films grown by pulsed laser deposition

ZnO thin films were grown on Si(1 1 1) substrates by the pulsed laser deposition (PLD) technique, where the Si(1 1 1) surface was nitrogenized via nitrogen plasma prior to growth. N–Si bonds were formed on the Si(1 1 1) surface due to nitrogenation. In general, an imbalance in the interface charge is one of the serious problems associated with the growth of a polar semiconductor (ZnO) on a nonpolar one (Si). However, the N–Si bonds formed at the Si(1 1 1) surface play an important role at the initial stage of growth to balance the interface charge between ZnO and Si(1 1 1). In terms of x-ray photoelectron spectroscopy results, a nitrogenized layer and a stable bonding configuration in the sequence of O–Zn–N–Si at the interface of ZnO/Si(1 1 1) could be deduced. The theoretical results of natural bond orbital also supplied a positive support to the existence of a stable bonding configuration. The bad effects of imbalance charge related to the crystal growth were decreased and the crystal quality was improved, which were validated by x-ray diffraction (XRD) and photoluminescence spectra.