Understanding the Role of Oxygen Vacancies in the Stability of ZnO(0001)-(1 × 3) Surface Reconstructions

Abstract

The atomic-scale explanation of ZnO surface reconstructions is relevant to strengthen its use in technological applications and to guide experimental efforts in improving the growth techniques. Several surface reconstructions have been observed for both ZnO polar surfaces, the so-called ( 0001) and (0001̅ ), which correspond to the Zn and O terminations. The experimental evidence for the (0001) surface reconstructions brings an insight into the stabilization mechanisms vital for surface processes. This work explores the stability between the previously reported reconstructions (2 × 2), (4 × 4) pit, and (4 × 4) pit + Zn, against the (1 × 3) reconstruction found experimentally by Torbrugge et al. [J. Phys. Chem. C 2009, 113, 4909−4914]. It is found that the original Zn-vacancy model is not favorable in any range of oxygen chemical potential. We report two stable reconstructions for the oxygen-poor limit associated with O vacancies. Models with one and two oxygen vacancies arise as candidates to explain the (1 × 3) reconstruction. We present theoretical Tersoff−Hamann scanning tunneling microscopy images for both reconstructions and compare them with the experimental atomic force microscopy images. The striped pattern composed of single and double Zn rows, obtained from the two oxygen vacancy model, is consistent with the experimental measurements. Density of states of the stable models depicts metallic character, where the typical sp 3 bulk hybridization is preserved in the upper layers. Charge density plots confirm the formation of Zn atomic wires in the [1000] direction.

Spin-Polarized Total-Energy Calculations on Designing Magnetic Single-Atom Catalysts on the ZnO(0001̅) Surface with Pt and Pd

“…On the other hand, the O vacancies induce (1 × 3)-V 2O (double O vacancy) and (1 × 3)-V O (single O vacancy) surface reconstructions; also, in the presence of both Zn and O vacancies, the (4 × 4)-pit+Zn reconstruction appears to be stable. 12,8,13 Similar to the previous case, the (0001̅ ) surface stabilizes in the presence of O vacancies, generating the (1 × 3)-V O O missing row and the (2 × 2)-V O O vacancy reconstruction. In the presence of both Zn and O vacancies, the (2 × 2)-Zn 3 O 2 hexagonal honeycomb hole reconstruction appears.…”

Interaction of an Ultrathin Zinc Surface Passivation Layer with a Room Temperature-Deposited Al-Doped ZnO Film Leading to Highly Improved Electrical Transport Properties

“…Let us now discuss the conduction mechanism of 2AZO5.3 film having K F l = 1.56, which suggests very less disorderinduced localization of the system as compared to the other two. For metal, the well-known Boltzmann transport equation can be expressed as 65 (7) where ρ 0 is the resistivity at T → 0, and K is a constant. The observed MST of 2AZO5.3 can be explained in the framework of quantum corrections to conductivity (QCC) to the classical Boltzmann equation for metal.…”

“…ZnO doped with Al, Ga, B, In, and so forth show very similar electrical and optical properties to conventional ITO. 1,6,7 Al-doped ZnO thin films (AZO), being low-cost, are extensively used in a wide range of photonic devices such as flat panel display, solar cell, LED, and so forth. 8−10 Various vacuum-assisted deposition processes such as sputtering, 11 pulsed laser deposition, 12 electron beam evaporation, 13 and so forth as well as non-vacuum-aided technique such as spray pyrolysis, 14 chemical vapor deposition, 15 sol−gel, 16 and so forth are reported aplenty for the deposition AZO film.…”

“…In the substitute group, doped ZnO is considered to be the utmost promising candidate for its low cost, non-toxicity, high optical bandgap. ZnO doped with Al, Ga, B, In, and so forth show very similar electrical and optical properties to conventional ITO. ,, Al-doped ZnO thin films (AZO), being low-cost, are extensively used in a wide range of photonic devices such as flat panel display, solar cell, LED, and so forth. − Various vacuum-assisted deposition processes such as sputtering, pulsed laser deposition, electron beam evaporation, and so forth as well as non-vacuum-aided technique such as spray pyrolysis, chemical vapor deposition, sol–gel, and so forth are reported aplenty for the deposition AZO film. However, all these techniques require elevated temperature at some stage to have high quality AZO film with a higher figure of merit (FOM) value.…”

Atomic-Scale Understanding of Li Storage Processes in the Ti4C3 and Chemically Ordered Ti2Ta2C3 MXenes: A Theoretical and Experimental Assessment

“…The formation energy formalism used throughout this paper is based on the principles of thermodynamics, and previous reports have demonstrated the effectiveness of the formalism in comparison with experimental results. − Formation energy depends on chemical potentials, rather than number of atoms, allowing us to compare the relative stability of models with different stoichiometries . Our goal with this formalism is to compare the formation energy of our structures and find the most stable ones.…”