Applied Surface Science, Vol.426, 856-863, 2017
Improving crystallization and electron mobility of indium tin oxide by carbon dioxide and hydrogen dual-step plasma treatment
Obtaining high conductivity indium tin oxide (ITO) films simultaneously with a "soft-deposited" (low temperature, low ions bombardment) and cost-efficient deposition process are critical aspect for versa tile photo-electronic devices application. Usually, the low-cost "soft-deposited" process could be achieved via evaporation technique, but with scarifying the conductivity of the films. Here, we show a CO(2 )and H-2 two-step plasma (TSP) post-treatment applied to ITO films prepared by reactive thermal evaporation (RTE), allows to meet the special trade-off between the deposition techniques and the electrical properties. Upon treatment, an increase in electron concentration and electron mobility is observed, which subsequently resulting a low sheet resistivity. The mobility reaches high values of 80.9 cm(2)/Vs for the TSP treated similar to 100nm thickness samples. From a combination of X-ray photoelectron spectroscopy and opto-electronic measurements, it demonstrated that: during the TSP process, the first-step CO2 plasma treatment could promote the crystallinity of the RTE ITO films. While the electron traps density at grain boundaries of polycrystalline RTE ITO films could be passivated by hydrogen atom during the second-step H-2 plasma treatment. These results inspired that the TSP treatment process has significant application prospects owing to the outstanding electrical properties enhancement for "soft-deposited" RTE ITO films. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:Photo-electronic devices;Indium tin oxide films;Plasma treatment;Electron mobility;Reactive thermal evaporation