Thermal Conductivity Comparison of Indium Gallium Zinc Oxide Thin Films: Dependence on Temperature, Crystallinity, and Porosity

Abstract

The cross-plane thermal conductivity of In-GaZnO (IGZO) thin films was measured using the 3ω technique from 18 to 300 K. The studied morphologies include amorphous (a-IGZO), semicrystalline (semi-c-IGZO), and c-axis-aligned single-crystal-like IGZO (c-IGZO) grown by pulsed laser deposition (PLD) as well as a-IGZO deposited by sputtering and by solution combustion processing. The atomic structures of the amorphous and crystalline films were simulated with ab initio molecular dynamics. The film quality and texturing information was assessed by X-ray diffraction and grazing incidence wide-angle X-ray scattering. X-ray reflectivity was also conducted to quantify film densities and porosities. All the high-density films exhibit an empirical powerlaw temperature dependence of the thermal conductivity κ ∼ T 0.6 in the specified temperature range. Among the PLD dense films, semi-c-IGZO exhibits the highest thermal conductivity, remarkably exceeding both films with more order (c-IGZO) and with less order (a-IGZO) by a factor of 4. The less dense combustion-synthesized films, on the other hand, exhibited lower thermal conductivity, quantitatively consistent with a porous film using either an effective medium or percolation model. All samples are consistent with the porosity-adapted Cahill−Pohl (p-CP) model of minimum thermal conductivity.

Wearable 1 V operating thin-film transistors with solution-processed metal-oxide semiconductor and dielectric films fabricated by deep ultra-violet photo annealing at low temperature

“…Over the past few years, amorphous indium-gallium-zinc-oxide (IGZO) has become a promising active channel material for thin-film transistors (TFTs) which have been utilized in different types of electronics, including display backplanes and sensor arrays 1–3 . This is due to its excellent material properties of superb mechanical stability, good electrical conductivity, and optical transparency 4–6 . Compared to silicon-based materials, metal-oxide semiconductors exhibit relatively good electrical characteristics even in an amorphous phase 7–9 .…”

Relationship between electrical properties and crystallization of indium oxide thin films using ex-situ grazing-incidence wide-angle x-ray scattering

“…12 Recent experiments also showed that the thermoelectric conductivity of partially crystalline TCO films is higher compared to amorphous or crystalline films. 13 Commonly used TCOs and AOSs consist of oxides of indium, tin, gallium, cadmium, and zinc. Indium-tin oxide (ITO) is obtained by doping indium oxide (IO) with tin.…”

“…12 The thermal conductivity of semi-crystalline indium-gallium zinc oxide (IGZO) films can also be higher than that of amorphous or fully crystalline samples. 13 A better understanding of the depth and lateral uniformity of the crystalline films is also crucial in understanding specific properties. For example, in materials such as graphene oxide, the in-plane and crossplane thermal conductivities can vary by a factor of 675.…”

Highly conductive low-temperature combustion-derived transparent indium tin oxide thin film

“…al demonstrated that the porosity of spin-coated CS-processed indium gallium zinc oxide (IGZO) film (~50 nm-thick) can be as high as 40 %, which seriously deteriorates its functional properties. 25 In this work, we take CS-derived indium tin oxide (ITO) conductive metal oxide thin films processed at 350 o C as a model system to explore the porosity problem and improve their electrical ARTICLE Materials Advances…”