Transparent conducting oxides (TCOs) are increasingly critical components in photovoltaic cells, low‐e windows, flat panel displays, electrochromic devices, and flexible electronics. The conventional TCOs, such as Sn‐doped In2O3, are crystalline single phase materials. Here, we report on In‐Zn‐O (IZO), a compositionally tunable amorphous TCO with some significantly improved properties. Compositionally graded thin film samples were deposited by co‐sputtering from separate In2O3 and ZnO targets onto glass substrates at 100 °C. For the metals composition range of 55–84 cation% indium, the as‐deposited IZO thin films are amorphous, smooth (RRMS < 0.4 nm), conductive (σ ∼ 3000 Ω−1 · cm−1), and transparent in the visible (TVis > 90%). Furthermore, the amorphous IZO thin films demonstrate remarkable functional and structural stability with respect to heating up to 600 °C in either air or argon. Hence, though not completely understood at present, these amorphous materials constitute a new class of fundamentally interesting and technologically important high performance transparent conductors.

We have studied optical surface second harmonic generation and have determined the magnitude and relative phase of the second-order susceptibility tensor elements for thermally evaporated gold, and sputtered silver, copper, aluminum, and tantalum. The second harmonic data are understood using an isotropic model of the surfaces. The measurements of the parameters from this nonlinear optical characterization, in conjunction with linear optical characterization of the samples, allow us to extract the elements of the tensors. The typical size of χ⊥(2), the tensor element that produces the surface current perpendicular to the surface and is the largest surface element, ranges from 3(±1)×10−12cm2∕statvolt for an aluminum sample with 24(±4)Årms surface roughness to 1.1(±0.1)×10−13cm2∕statvolt for a copper sample with 5(±1)Årms surface roughness. Film preparation and associated surface roughness can reproducibly change the values of χ(2); increasing sample roughness increases the magnitudes of the tensor elements. In agreement with previous aluminum measurements, we again find that the tensor elements associated with creating the second harmonic currents normal to the surface are of roughly the theoretically predicted magnitude, but that the elements associated with creating the second harmonic currents parallel to the surface and in the bulk are an order of magnitude smaller than expected.

High near-infrared transparency and carrier mobility of Mo doped In 2 O 3 thin films for optoelectronics applications

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