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The electronic states of oxygen vacancies (V O s) in amorphous oxide semiconductors are shallow donors, deep donors or electron traps; these are determined by the local atomic structure. Because the amorphous phase is metastable compared with the crystalline phase, the degree of structural disorder is likely to decrease, which is referred to as structural relaxation (SR). Thus SR can affect the V O electronic state by changing the local atomic conditions. In this study, we demonstrated that electron doping is possible through the SR of amorphous oxides without redox reactions using a novel device structure that prevents extrinsic reactions with electrodes and ambient atmosphere during annealing. The concentration of V O s in the shallow-donor state in amorphous In-Ga-Zn-O (a-IGZO) increases from~10 16 to~10 19 cm − 3 with increasing annealing temperatures between 300 and 450°C. The SR-driven doping effect is strongly dependent on the annealing temperature but not on the annealing time. The Arrhenius activation energy of the SR-driven doping effect is 1.76 eV, which is similar to the bonding energies in a-IGZO. Our findings suggest that the free volume in a-IGZO decreases during SR, and the V O s in either deep-donor or electrontrap states are consequently transformed into shallow-donor states. NPG Asia Materials (2016) 8, e250; doi:10.1038/am.2016.11; published online 25 March 2016 INTRODUCTION Amorphous metal oxides, such as amorphous indium gallium zinc oxide (a-IGZO), have become mainstream materials for large-area and flexible electronics because the long-range structural disorder enhances the uniformity of the electrical properties and mechanical flexibility compared with crystalline metal oxides. 1-5 A notable characteristic of amorphous oxides, relative to their crystalline counterparts, is that these materials contain structural disorder-related defects (for example, free volume) in addition to non-stoichiometric defects (for example, oxygen vacancies), which significantly affect the corresponding electrical properties. 3,[6][7][8] Moreover, the degree of structural disorder in amorphous metal oxides is always likely to decrease to form more stable structures because internal atomic rearrangement occurs even below the glass transition temperature (T g ). This process is known as structural relaxation (SR) 9-11 and results in continuous changes in the electrical properties. Thus understanding the effects of SR on the electrical properties of amorphous oxides is important for applications in future electronics.In addition to uniformity and flexibility, amorphous metal oxides exhibit tunable electrical conductivity through redox reaction control

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Ge 2 Sb 2 Te 5 (GST) films with a thickness of 300 nm, in which the nitrogen (N) implant dose was 0, 10 13 , or 10 15 ions/cm 2 , were prepared by RF magnetron sputtering on Si and glass substrates. The thermomechanical properties of the GST films, viz., the biaxial modulus and coefficient of thermal expansion (CTE), were determined using the substrate curvature method for the two different substrates. The biaxial modulus of the GST films decreased with increasing N dose, whereas the CTE varied only slightly. The dependence of the microstructure on the N implantation dose was examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FE-SEM). The lattice parameter of the crystalline structure increased with increasing N dose, which indicated the distortion of the lattice by the implanted N atoms. Because the crystallite size increased with increasing N dose, grain growth refinement caused by the formation of nitrides did not occur. Also, the presence of nitrides in the N-implanted GST film was not observed in the binding energy spectra of 1s for the N element.