Improved Nanoscale Al-Doped ZnO with a ZnO Buffer Layer Fabricated by Nitrogen-Mediated Crystallization for Flexible Optoelectronic Devices

Abstract

To achieve excellent semiconductor device performance, especially for low-temperature processing of semiconductors, the need to devise strategies to engineer the surface and interface and to develop characterization techniques to understand the cause−effect relationship of surface and interface of semiconductor devices remains to be a key issue. Here, we present a nucleation control method, termed nitrogen-mediated crystallization (NMC), to engineer the surface morphology of a ZnO buffer layer and analyze firstand seconddegree statistical surfaces to reveal the morphological relationship between the buffer layer and the buffered AZO film. The surface parameter is generally understood as the surface roughness (roughness average or RMS roughness) or the surface height profile, and our experimental results suggest that the physical properties of the buffered AZO films are strongly influenced by the fractal geometry of the buffer layers and are insensitive to their surface roughness. We demonstrate that the NMC method promotes enhanced surface migration and effectively prevents the development of nonuniform fractal geometry in the ZnO buffer layer, enabling the stress relaxation in the buffered AZO films and mitigating the threedimensional columnar growth. At a low thermally induced kinetic energy, a 90 nm thick AZO film with an ultralow resistivity of 4.4 × 10 −4 Ω•cm can be achieved, indicating its potential for the realization of high-efficiency flexible optoelectronic devices.

Growth of Single-Crystalline ZnO Films on 18%-Lattice-Mismatched Sapphire Substrates Using Buffer Layers with Three-Dimensional Islands

“…ZnO has attracted much attention as a remarkable multi-functional material with a wide range of existing and emerging applications, such as varistors, , transparent conducting electrodes, − surface-acoustic-wave (SAW) devices, , gas sensors, , X-ray imaging systems, and thin-film transistors. − Several studies have reported that high-quality single-crystalline ZnO films grow on lattice-matched epitaxial substrates, such as bulk ZnO substrates and ScAlMgO 4 substrates. − However, these substrates are expensive and thus make ZnO films of potentially limited use for large-scale devices. Cost-effective c -plane sapphire is a promising candidate as a substrate for the epitaxial growth of ZnO films because of its cost efficiency if single-crystalline ZnO films grew by overcoming the obstacle of the large lattice mismatch of 18%, which causes a number of crystal defects including 30°-rotated domains and threshold dislocations. , …”

In Situ Growth and Interlayer Modulation of Layered Double Hydroxide Thin Films from a Transparent Conducting Oxide Precursor

“…In this work, we developed a new synthetic method to rapidly (<5 min) produce thin films of interconnected Zn–Cr LDH particles with uniform morphology and thickness, and without cracks, pinholes, or other physical defects, from aluminum-doped zinc oxide (AZO) precursor films at room temperature. AZO was chosen as a precursor because of its transparent and conducting properties and its use in optoelectronic applications. − Zn–Cr LDH was found to be the only LDH that could be grown from this particular method for mechanistic reasons detailed in the discussion section. This synthetic approach allows Zn–Cr LDH thin films to be grown on any substrate and in any patternable dimension to which AZO can first be deposited (Scheme ).…”

Tunable physical properties of Al-doped ZnO thin films by O2 and Ar plasma treatments

“…Currently, indium tin oxide (ITO) is the most widely used material in the transparent electrode industry. However, its high price and brittle characteristics limit its application in transparent electrodes [9][10][11]. Al-doped ZnO (AZO) can be used as a flexible transparent electrode owing to its high conductivity, good flexibility, low cost, and eco-friendly characteristics [12][13][14][15].…”