Formation Mechanism and Bandgap Reduction of GaN–ZnO Solid‐Solution Thin Films Fabricated by Nanolamination of Atomic Layer Deposition. Issue 9 (1st January 2023)

• Record Type: Journal Article
• Authors: Liao, Ming‐Wei; Jeng, Horng‐Tay; Perng, Tsong‐Pyng
• Is Part Of: Advanced materials. Volume 35:Issue 9(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-01
• Subjects: atomic layer deposition -- density functional theory -- GaN -- hydrogen evolution -- nanolamination -- ZnO; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202207849
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Nanolamination of GaN and ZnO layers by atomic layer deposition (ALD) is employed to fabricate GaN–ZnO homogenous solid‐solution thin films because it offers more precise control of the stoichiometry. By varying the ALD cycle ratios of GaN:ZnO from 5:10 to 10:5, the (GaN)1− x (ZnO) x films with 0.39 ≦ x ≦ 0.79 are obtained. The formation of solid solution is explained based on the atomic stacking and preferred orientation of the layers of GaN and ZnO. However, the growth rates of GaN and ZnO during the lamination process are different from those of pure GaN and ZnO films. It is found that GaN grows faster on ZnO, whereas ZnO grows slower on GaN. The density functional theory (DFT) calculations are performed using a superlattice model for GaN and ZnO laminated layers fabricated by ALD to understand the difference of density of states (DOS) and evaluate the bandgaps for various atomic configurations in the solid‐solution films. The band positions are experimentally defined by ultraviolet photoelectron spectroscopy. Significant bandgap reduction of the solid solutions is observed, which can be explained by the DOS from the DFT calculations. Visible‐light‐driven photocatalytic hydrogen evolution is conducted to confirm the applicability of the solid‐solution films. Abstract : Nanolamination of GaN and ZnO layers by atomic layer deposition is employed to fabricate (GaN)1− x (ZnO) x homogenous solid‐solution films with 0.39 ≦ x ≦ 0.79 by varying the cycle ratios. The density functional theory calculations using a superlattice model are performed to evaluate and validate the reduction of bandgaps that results in enhanced visible‐light‐driven photocatalytic hydrogen evolution.