Polarity of pulsed laser deposited ZnO nanostructures

Abstract

ZnO nanostructures were grown by pulsed laser deposition on planar ZnO with different surface polarities. While for planar layers of pulsed laser deposited ZnO polarity control is feasible, the polarity relation of ZnO nanostructures to their substrate layers is not yet investigated. Depending on the polarity of the nucleation layer, two distinct morphologies were found, namely, nanorods on O-polar and nanowalls on Zn-polar ZnO. Convergent beam electron diffraction was performed to reveal the polarity of the ZnO nanostructures. The evolution of ZnO nanostructures is described in terms of a growth rate and a surface diffusion model.

Epitaxial Growth of Vertically Aligned Antimony Selenide Nanorod Arrays for Heterostructure Based Self‐Powered Photodetector

“…[43] Sb 2 Se 3 prepared on an undoped ZnO substrate with a large exposure of the (002) polar surface exhibited dominant (hk0) orientation peaks. [2,44] Only one type of dative bond of ZnSe or SbO could be constructed between Sb 3+ , Se 2ions in (Sb 4 Se 6 ) n , and Zn 2+ and O 2ions in ZnO. [2] Hence, dangling bonds could easily form at the terminals of the (Sb 4 Se 6 ) n ribbons, preventing the (Sb 4 Se 6 ) n ribbons from bonding to the substrate in the form of covalent bonds.…”

Polarity Control in Growing Highly Ga-Doped ZnO Nanowires with the Vapor–Liquid–Solid Process

“…Therefore, the formation of Zn-polar ZnO NWs under the Zn-rich conditions is consistent with our results and can be well explained with our model. Third, based on the VS process, pulsed laser deposition of ZnO on c-plane sapphire substrate under the O-rich conditions first forms O-polar ZnO pyramids . However, further growth of ZnO led to the formation of a Zn-polar ZnO nanorod on a pyramid due to defect-caused domain inversion.…”

“…Third, based on the VS process, pulsed laser deposition of ZnO on c-plane sapphire substrate under the O-rich conditions first forms Opolar ZnO pyramids. 29 However, further growth of ZnO led to the formation of a Zn-polar ZnO nanorod on a pyramid due to defect-caused domain inversion. Under the O-rich conditions, the Zn-polar ZnO structure has the higher c-axis growth rate based on VS growth, as demonstrated in Figure 10(b1).…”

“…In this situation, when the laterally grown GaZnO portions of different lattice constants from different nucleation islands meet, planar defects of a high density can be formed. The existence of planar defects can lead to domain inversion, i.e., the change from Zn polarity into O polarity or vice versa. , Hence, in the early stage of NW growth, the polarity is unstable. As illustrated in Figure (b), in the upper portion of the NW, the cross-sectional area becomes smaller.…”

“…In other words, a ZnO thin film or NW grown on Ga- (N-) face GaN through the VS mode is expected to be Zn (O) polar. However, in vapor–liquid–solid (VLS) growth for forming a NW, the growth mechanisms are more complicated, − and the observed NW polarities and their interpretations are still controversial. ,, In the VLS growth mode using extrinsic metal catalyst, the constituent atoms of the NW are absorbed by the melted metal droplet. When the supersaturation condition is reached, the NW crystal precipitates at the bottom of the metal droplet and pushes the droplet upward to form a NW.…”