Room-Temperature Preparation of Large-Area Transparent Two-Dimensional ZnO-Doped Ga₂O₃ Nanostructure-Based Layers: Implications for Optoelectronic Nanodevices

Abstract

Herein, we demonstrated the controllable synthesis of a centimeter-scale two-dimensional (2D) ZnO-doped Ga 2 O 3 nanostructure layer by a liquid Ga−Zn alloy printing strategy at near room temperature. Different from the liquid Ga−In and Ga− In−Sn alloys, the surface oxidation behavior of a liquid Ga−Zn alloy follows an obvious competition and cooxidation characteristics instead of the dominant oxidation characteristic of Ga, which could be effectively used to precisely tailor the Zn content of 2D Ga 2 O 3 films. With an increase of the nominal Zn content in the Ga−Zn alloy from 0 to 8 atom %, the real Zn content of 2D ZnOdoped Ga 2 O 3 films gradually increases and finally reaches a maximum saturated value of 16−18 atom % at the eutectic component of 3.87 atom %. Correspondingly, the transmittance and band gap of 2D ZnO-doped Ga 2 O 3 films could also be tuned by changes of the Zn content and crystallinity. The method proposed in this work provides a general route toward the doping synthesis of a diverse nonlayered 2D structure, which will shed light on the applications of various displays and deep-ultraviolet optoelectronic devices.

Large Area, Ultrathin, and Transparent InGaZnO Films from Printing of Liquid Ga–In–Zn Alloys for Thin Film Transistors

“…It indicates that the Δ G f is the key governing factor for forming metal oxides on the liquid alloy surface. The elements Ga and Zn have approximate Δ G f values of metal oxide formation, so Zn atoms in liquid Ga 1 In 95 Zn 4 alloy were oxidized and formed ZnO nanosheets, this corresponds to the results in the former report about liquid Ga–Zn alloys . The Ga and Zn contents of printed IGZO films increase with increasing Ga and Zn concentrations in liquid alloys, while the In contents of printed IGZO films gradually decrease.…”

“…The observed O 1s spectrum (Figure d) can be fitted and split into two characteristic peaks, which were located at ∼531.0 and ∼532.7 eV, respectively. The O 1s peak of 531.0 eV is ascribed to the O 2– state of Ga–O, In–O, and Zn–O, which is almost the same as the observed O 1s peak of 530.8 eV for printed ZnO-doped Ga 2 O 3 layers . The O 1s peak of 532.7 eV is the lattice O of SiO 2 substrate, because the characteristic spectra of SiO 2 substrates were also shown in the XPS results.…”

“…33 The characteristic peaks of ∼444.4 eV and ∼452.1 eV are corresponding to the In 3d 5/2 and In 3d 3/2 for In 2 O 3. 33 Though the ΔG f of formation ZnO is 32 The O 1s peak of 532.7 eV is the lattice O of SiO 2 substrate, 34 because the characteristic spectra of SiO 2 substrates were also shown in the XPS results. The observed chemical states of Ga 3+ , In 3+ , Zn 2+ , and O 2− on the oxide film's surface can confirm that the printed oxide skins are IGZO films.…”

“…Additionally, some amorphous structures are observed between the In 2 O 3 and ZnO crystal planes. The amorphous structures are ascribed to Ga 2 O 3 , which correspond to the results of former reports. , The observed amorphous Ga 2 O 3 , polycrystal In 2 O 3 , and polycrystal ZnO can be further confirmed from the selected area electron diffraction (SAED) patterns. We can see the polycrystalline diffraction spots of In 2 O 3 and ZnO from Figure d.…”

“…Jannat and co-workers found that Zn-doped In 2 O 3 (IZO) can form on the surface of molten In–Zn alloy, when the Zn concentrations in the liquid In–Zn alloys are 0.5 and 5 wt %. Liu et al discovered that 2D ZnO-doped Ga 2 O 3 can be prepared by printing liquid Ga–Zn alloys, because the approximate Δ G f of Ga 2 O 3 and ZnO cause Ga–Zn alloys to not completely obey the thermodynamics rule. The co-oxidation of elements Ga and Zn occurs on the surfaces of liquid Ga–Zn alloys.…”