Combined effect of the target composition and deposition temperature on the properties of ZnO:Ga transparent conductive oxide films in pulsed dc magnetron sputtering

Abstract

Composition-dependent changes in the properties of Ga-doped ZnO (GZO) transparent conductive oxide (TCO) films were investigated by preparing a series of GZO films on glass substrates via pulsed dc magnetron sputtering with ZnO ceramic targets having various Ga 2 O 3 concentrations at various temperatures. As the Ga 2 O 3 content in the target increased, crystalline quality was improved as revealed in the intense ZnO (0 0 2) diffraction peaks, which accompanied increased carrier concentrations. When the Ga 2 O 3 content was low, it was deduced from the crystallinity and carrier concentration that Ga or its oxide species functioned primarily as a crystal growth promoter, which was more distinctive at lower deposition temperatures. Meanwhile, formation of the secondary oxide phases, detrimental to the carrier mobility, was rather enhanced up to intermediate temperature and then suppressed by further increasing the deposition temperature. Consequently, improved crystallinity and enhanced doping efficiency and therefore the lowest electrical resistivity could be achieved with the combination of higher Ga 2 O 3 content in the target and higher deposition temperature. Electrical resistivity and optical transmittance of the GZO films prepared by the pulsed dc magnetron sputtering in this study fulfilled requirements for TCO films.

Effects of ZnO Buffer Layer on Characteristics of ZnO:Ga Films Grown on Flexible Substrates: Investigation of Surface Energy, Electrical, Optical, and Structural Properties

“…Such consistency is reasonable because the increased grain size indicates a decreased number of free electrons on grain boundaries, and thus decreased absorption of visible light. [16][17][18][19] Additionally, the GZO grown on rougher ZnO buffer/PES substrates may suffer more light scattering, leading to reduced transmittance. Accordingly, the variation in transmittance with increasing ZnO buffer thickness can also be interpreted in terms of the change of GZO roughness.…”

Ultrafast nonlinear absorption properties of SnO2/Ag/SnO2 composite films based on Z-scan measurement

“…7 Transparent conductive oxide (TCO) thin films have gained widespread application in optoelectronic devices due to their excellent conductivity and high visible light transmittance. [8][9][10][11][12] Importantly, the considerable wide band gap exhibited by these materials renders them highly promising for the era of optoelectronic devices, wherein they are anticipated to assume a significant role. 13 SnO 2 , as a TCO material, exhibits stable physical and chemical properties, a wide direct band gap, and high exciton binding energy at room temperature.…”

Fabrication of Transparent ZnO Thick Film with Unusual Orientation by the Chemical Bath Deposition

“…Zinc oxide (ZnO) is an important material attracting considerable research interest due to its wide-ranging applications such as in photoluminescence, − photocatalysis, , dye-sensitized solar cells, − and sensors. − Moreover, Al- and Ga-doped ZnO are potential candidates for transparent conductive oxide (TCO) materials, − which are used in various electronic devices such as flat-panel displays and solar cells. Indium tin oxide films are representative TCO films used in these electronic devices, − though alternative materials are needed due to the problem of acquiring indium resources.…”

“…High-quality TCO films are generally fabricated by a sputtering process, − which requires a large equipment with a vacuum system and is a high energy-cost process as well as an atomic layer deposition process and chemical vapor deposition process. , In contrast, direct deposition methods such as a chemical bath deposition (CBD) and a liquid phase deposition are attracting attention as low-cost film formation processes. In these processes, nucleation and crystal growth on substrate in solution result in the formation of metal–oxide and metal–chalcogenide films. − Fabrication processes of microstructured ZnO films have been intensively studied by many researchers. − For application to TCO films, it is necessary to prepare ZnO thick films to reduce the resistivity, though the thick films prepared by solution processes tend to cause severe light scattering due to the formation of internal pores or voids.…”