Toward controlling the Al₂O₃/ZnO interface properties by in situ ALD preparation

Abstract

The electronic band alignment of an alumina/zinc oxide thin-film heterostructure solely grown by atomic layer deposition has been determined by XPS/UPS depth profiling, correlating the electronic properties with the interface chemical composition.

Bottom-Up Design of a Supercycle Recipe for Atomic Layer Deposition of Tunable Indium Gallium Zinc Oxide Thin Films

“…The depth profiles reveal a nearly constant atomic concentration of the metallic elements within the films beyond the topmost surface region, with only slight deviations at the film/substrate interface, similar to previous reports on the interfaces of atomic layer-deposited films. 32,33 A closer look reveals that the Zn-rich PE(1/1/2) and In-rich PE(2/1/1) samples exhibit a very homogeneous distribution of the elements within the bulk of the films, whereas the PE(1/1/1) and Ga-rich PE(1/2/1) samples show a slight increase in the Ga content with increasing sputtering time, especially close to the interface. EDX mapping measurements show excellent spatial composition homogeneity and the absence of any excess of Ga, giving very close In/Ga/Zn ratios to those obtained by XPS after 35 s of sputtering (the EDX spectra and related Tables S1−S5 with raw elemental composition for all PEALD samples are shown in Supporting Information, Figure S5a, while the calculated metal ratios are given in Table 2).…”

Atomic-Layer-Deposited ZnO/Al2O3 Nanolaminates for White-Light-Emitting Diodes

“…The Zn 2p 3/2 XPS profile of the ZANL shows an asymmetrical characteristic, which can be deconvoluted into a pink peak and an orange peak. The pink peak at 1021.2 eV originates from Zn 2+ at normal ZnO lattice sites, which is always observed in pure ZnO films . The yellow peak with an obvious chemical shift of 1.4 eV is hardly seen in the pure ZnO, because Zn-related bulk intrinsic defects such as oxygen vacancies and Zn interstitials always have tiny chemical shifts .…”

“…The pink peak at 1021.2 eV originates from Zn 2+ at normal ZnO lattice sites, which is always observed in pure ZnO films. 22 The yellow peak with an obvious chemical shift of 1.4 eV is hardly seen in the pure ZnO, because Zn-related bulk intrinsic defects such as oxygen vacancies and Zn interstitials always have tiny chemical shifts. 23 It is known that Zn occupies the tetrahedral center of oxygen atoms, whereas Al occupies the octahedral center of oxygen atoms.…”