Humidity-Resistant High-Conductivity Amorphous-InZnO Transparent Conductors

Sputtered, amorphous mixed metal transparent conductive oxides, TCOs, are of increasing interest. The TCOs have excellent opto-electronic properties and smoothness (RRMS < 0.5 nm) obtained for films deposited at 50-150 °C.¹ In the case of amorphous InZnO (a-InZnO) films grown from a ceramic target with 20 atomic % ZnO in In₂O_3, conductivities σ ≥ 2500 S/cm are common.^2-5 This project specifically centers on the combined materials phase space of oxygen stoichiometry and metals composition (In:Zn ratio) and their effect on the environmental stability and water permeability of the resultant transparent films. Amorphous IZO films deposited from a fixed composition target with a range of oxygen concentrations allowed for a comparison of the relative stability of various composition and conductivity. In the initial testing within an 85/85 chamber, the more conductive a-InZnO films with > 1000 S/cm, did not show any change in conductivity or transparency after 1000 hrs. In contrast a-InZnO films of comparable thickness and <0.01 S/cm while remaining transparent would improve in conductivity anywhere from 10% to over 2 orders of magnitude. These results establish the possibility that a-InZnO layers may be a viable replacement to traditional resistive and conductive ZnO layers and may find application as a transparent, non-organic barrier layer.