Hyo-Young Yeom

High-mobility amorphous In2O3–10wt%ZnO thin film transistors

The authors report on the fabrication and characterization of thin film transistors that use sputter deposited amorphous indium zinc oxide both for the channel and source-drain metallizations in a gate-down configuration. The channel and source-drain layers were deposited from a single In2O3–10wt%ZnO ceramic target using dc magnetron sputtering onto an unheated substrate. The carrier densities in the channel (2.1×1017∕cm3) and source/drain regions (3.3×1020∕cm3) were adjusted by changing the reactive oxygen content in the sputter chamber during deposition. The resulting transistors operate as depletion mode n-channel field effect devices with saturation mobility of 20cm2∕Vs and on/off current ratio of 108.

Crystallization of amorphous In2O3–10 wt % ZnO thin films annealed in air

We report on the crystallization of amorphous indium zinc oxide (a-IZO) with stoichiometry of In2Zn0.38O3.38 (In2O3–10 wt % ZnO) thin films deposited by dc magnetron sputtering. Transmission electron microscopy and glancing incidence x-ray diffraction were used to show that, when annealed in air at 500 °C, the product of a-IZO thin film crystallization is a compositionally modulated crystal of high-pressure corundum In2O3 phase. The composition, microstructure, resistivity, carrier density, and mobility of this new IZO phase are reported and are compared to the bixbyite ITO (In2O3–9.8wt%SnO2) deposited and annealed under identical conditions.

A study of the effect of process oxygen on stress evolution in d.c. magnetron-deposited tin-doped indium oxide

Abstract We report on the effect of oxygen stoichiometry on the amorphous structure and crystallization kinetics of indium tin oxide. DC magnetron sputtering was used to deposit 200-nm-thick films under low, optimum (with respect to conductivity), and high oxygen partial pressures (0, 0.1 and 2 vol.%, respectively). The film stress and electron transport characteristics (hall mobility and carrier density) of these films were measured before, during and after the crystallization of 9.8 wt.% SnO 2 doped In 2 O 3 . We report that the crystallization rate of films grown with oxygen contents above (2 vol.%) and below (0 vol.%) that required for optimum conductivity (0.1 vol.%) is reduced and that the as-deposited stress is, in all three cases, compressive and increases with increasing oxygen content in the sputter gas. In situ stress measurements were used to determine the change in molar volume attending both the crystallization of ITO and the oxidation of oxygen vacancies. Based on these measurements we report a measure of the effective volume of an oxygen vacancy in indium oxide.

A Structural Study of the Amorphous to Crystalline Transformation in In 2 O 3 Thin Films

We have investigated the structure of sputter deposited amorphous and crystalline indium oxide films by electron diffraction. Selected area diffraction patterns were recorded for both states from which radial density functions were derived. The comparison of the crystalline radial density function to the amorphous one shows that the first nearest neighbor distance corresponding to the In-O bond length is 2.2A and is the same for both states. A model density function for crystalline structure was used to explore the difference in higher order peak positions. We report that the In-In separation in amorphous state has a single characteristic distance of 3.6A compared to the crystalline state which has two non-equivalent In sites and consequently different separations as In(1)-In(2) at 3.4A and In(2)-In(2) at 4.3A.

Stress and Microstructure Evolution during the Deposition and Crystallization of DCMagnetron Sputter Deposited Amorphous ITO

The deposition of ITO onto glass substrates at room temperature results in a metastable amorphous phase that undergoes crystallization at remarkably low homologous temperatures (T/T m