Determination of the polarity of ZnO thin films by electron energy-loss spectroscopy

Exciton and core-level electron confinement effects in transparent ZnO thin films

“…Not only the stress may affect the peak position but the presence of absorbed species. As it is well known, ZnO is a polar compound that can produce polar films404142, which easily adsorb radical species. When the annealing at 170°C was performed, these species have been released promoting the contraction of the unit cell and shift of the peak position to 34.4°.…”

Defect characteristics of ZnO film grown on sapphire with an ultrathin gallium wetting layer

“…Zn polarity) [11]. This probably indicates that the Ga wetting layer is relatively well covered over the sapphire substrate.…”

“…In order to reduce the defect density, an GaN or MgO interlayer has been used [9,10] to decrease the lattice mismatch. Very recently, a surface modification technique of sapphire substrate using an ultrathin Ga wetting layer has been developed to obtain high-quality ZnO film, and a dramatic defect reduction is achieved [11,12]. In this study, the defect nature in the ZnO film prepared by this method is investigated by transmission electron microscopy (TEM) and X-ray diffractometry (XRD) compared to the ZnO film without the Ga wetting layer, aims to characterize the role of the Ga layer in the defect reduction and inversion domain suppression.…”

Effect of MgO in ZnO films grown on nitrided sapphires

“…As a wide-band-gap (3.37 eV) semiconductor with unique promising electronic and optoelectronic properties, ZnO has been investigated extensively in the last decade [1][2][3][4][5][6]. The current challenge is to fabricate device-quality ZnO films for their practical use [3].…”