By developing a low-temperature (≤300 °C) fabrication process for the gate-stack structure on Ge(111), we study electrical properties of thin film transistors (TFTs) consisting of (111)-oriented pseudo-single-crystalline-germanium (PSC-Ge) channels on glass. Although the Hall mobility (μHall) of p-type PSC-Ge layers reaches 210 cm2/V s and the gate-stack/Ge interface has low trap density, we observe field-effect-mobility (μFE) fluctuation in the p-channel TFTs from 8.2 to 71 cm2/V s, depending on the thickness of the PSC-Ge layer. Considering the μFE fluctuation and low Ion/Ioff ratio in the p-TFTs, we infer the presence of defective Ge layers near the surface of the glass substrate. This study reveals that it is quite important for the high-performance p-Ge TFTs to improve the quality of the Ge layer near the surface of the glass substrate or to choose other materials with better Ge/substrate interface qualities.

We experimentally demonstrate a flexible thin-film transistor (TFT) with (111)-oriented crystalline germanium (Ge) layers grown by a gold-induced crystallization method. Accumulation-mode metal source/drain p-channel Ge TFTs are fabricated on a polyimide film at ≤400 °C. A field-effect mobility (μFE) of 10.7 cm2/Vs is obtained, meaning the highest μFE in the p-TFTs fabricated at ≤400 °C on flexible plastic substrates. This study will lead to high-performance flexible electronics based on an inorganic-semiconductor channel.

Abstract:Micrometer order magnetophotonic crystals with periodic arranged metallic glass and oxide glass composite materials were fabricated by stereolithographic method to reflect electromagnetic waves in terahertz frequency ranges through Bragg diffraction. In the fabrication process, the photo sensitive acrylic resin paste mixed with micrometer sized metallic glass of Fe 72 B 14.4 Si 9.6 Nb 4 and oxide glass of B 2 O 3 ·Bi 2 O 3 particles was spread on a metal substrate, and cross sectional images of ultra violet ray were exposed. Through the layer by layer stacking, micro lattice structures with a diamond type periodic arrangement were successfully formed. The composite structures could be obtained through the dewaxing and sintering process with the lower temperature under the transition point of metallic glass. Transmission spectra of the terahertz waves through the magnetophotonic crystals were measured by using a terahertz time domain spectroscopy.

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Magnetophotonic crystals with periodic arranged of permeability can reflect terahertz waves through Bragg diffraction. The micrometer order photonic crystals were fabricated by stereolithographic method. In this process, acrylic resin including metallic and oxide glass particles was spread on a polyethylene substrate with 10 μm in layer thickness. Then a two dimensional pattern was formed by illuminating visible laser with 405 nm in wavelength. Through stacking layer process, a micrometer order three dimensional structure was constructed. Metallic and oxide glass composite material was obtained through heat treatment. The amorphous structure of the metallic glass was kept by low temperature heating process. The transmission spectrum of terahertz wave for the fabricated crystals was measured by terahertz time domain spectroscopy.