Metal Oxide Bilayer Research Articles

Density of States-Based Design of Metal Oxide Thin-Film Transistors for High Mobility and Superior Photostability

A novel method to design metal oxide thin-film transistor (TFT) devices with high performance and high photostability for next-generation flat-panel displays is reported. Here, we developed bilayer metal oxide TFTs, where the front channel consists of indium-zinc-oxide (IZO) and the back channel material on top of it is hafnium-indium-zinc-oxide (HIZO). Density-of-states (DOS)-based modeling and device simulation were performed in order to determine the optimum thickness ratio within the IZO/HIZO stack that results in the best balance between device performance and stability. As a result, respective values of 5 and 40 nm for the IZO and HIZO layers were determined. The TFT devices that were fabricated accordingly exhibited mobility values up to 48 cm(2)/(V s), which is much elevated compared to pure HIZO TFTs (∼13 cm(2)/(V s)) but comparable to pure IZO TFTs (∼59 cm(2)/(V s)). Also, the stability of the bilayer device (-1.18 V) was significantly enhanced compared to the pure IZO device (-9.08 V). Our methodology based on the subgap DOS model and simulation provides an effective way to enhance the device stability while retaining a relatively high mobility, which makes the corresponding devices suitable for ultradefinition, large-area, and high-frame-rate display applications.

Low-Voltage Organic Field-Effect Transistors (OFETs) with Solution-Processed Metal-Oxide as Gate Dielectric

In this study, low-voltage copper phthalocyanine (CuPc)-based organic field-effect transistors (OFETs) are demonstrated utilizing solution-processed bilayer high-k metal-oxide (Al(2)O(y)/TiO(x)) as gate dielectric. The high-k metal-oxide bilayer is fabricated at low temperatures (< 200 °C) by a simple spin-coating technology and can be controlled as thin as 45 nm. The bilayer system exhibits a low leakage current density of less than 10(-5) A/cm(2) under bias voltage of 2 V, a very smooth surface with RMS of about 0.22 nm and an equivalent k value of 13.3. The obtained low-voltage CuPc based OFETs show high electric performance with high hole mobility of 0.06 cm(2)/(V s), threshold voltage of -0.5 V, on/off ration of 2 × 10(3) and a very small subthreshold slope of 160 mV/dec when operated at -1.5 V. Our study demonstrates a simple and robust approach that could be used to achieve low-voltage operation with solution-processed technique.

Ultraviolet-induced erasable photochromism in bilayer metal oxide films

We demonstrate that the optical transmittance of bilayer samples consisting of pyrolytically coated amorphous Mg–Sn–O and metal oxide films such as In 2O 3 and SnO 2 decreases upon ultraviolet illumination, but can be recovered by annealing in air at ∼300 ∘C. Spectral, structural, and compositional studies suggest that this photochromic phenomenon is induced by photoelectronic excitation in the Mg–Sn–O film, electron injection into the metal oxide, which becomes negatively charged, and subsequent formation of metallic particles, which absorb and/or scatter visible light.

Bilayer metal oxide gate insulators for scaled Ge-channel metal-oxide-semiconductor devices

We investigate the electrical properties of germanium-channel metal-oxide-semiconductor capacitors with an amorphous atomic-layer-deposited (ALD)-Al2O3 interlayer (IL) and higher-k ALD-TiO2 gate dielectric. An ALD-Al2O3 IL of ∼1 nm thickness reduces the gate leakage current density at the otherwise low band-offset TiO2/Ge interface by six orders of magnitude at flatband. Devices with the thinnest Al2O3 IL exhibited a low capacitance equivalent thickness of 1.2 nm. The hysteresis of the capacitance-voltage curves was &amp;lt;10 mV for TiO2/Al2O3/Ge capacitors with different Al2O3 thicknesses. We obtained a relatively low minimum density of interface states, Dit ∼3×1011 cm−2 eV−1, suggesting the potential of Al2O3 ILs for higher-k/Ge interface passivation.

Low-operating-voltage polymeric transistor with solution-processed low- k polymer/high- k metal-oxide bilayer insulators

We have successfully demonstrated a polymeric semiconductor-based transistor with low- k polymer/high- k metal-oxide (TiO 2) bilayer as gate dielectric. The TiO 2 layers are readily processable from solution and cured at low temperature, instead of traditionally sputtering or high temperature sintering process, thus may suitable for a low-cost organic field effect transistors (FETs) manufacture. The low- k polymer capped on TiO 2 layer could further smooth the TiO 2 dielectric surface and suppress the leakage current from grain boundary of TiO 2 films. The resulting unpatented P3HT-OFETs could operate with supply voltage less than 10 V and the mobility and threshold voltage were 0.0140 cm 2/V s and 1.14 V, respectively. The on/off ratio was 1.0 × 10 3.

イオンビーム分析による金属・酸化物２層複合材料の水素吸収・放出特性の研究

イオンビーム分析による金属・酸化物２層複合材料の水素吸収・放出特性の研究

Single-mask microfabrication of three-dimensional objects from strained bimorphs

Recently, techniques known as ‘micro-origami’ or ‘strain architecture’ have emerged for the fabrication of out-of-plane micro- and nanostructures by relaxation of a pair of strain-mismatched thin films. Applications of such structures include optical reflectors, actuators and micropositioners. We illustrate how control of the folding order can generate complex three-dimensional objects from metal-oxide bilayers using this approach. By relying on the fact that narrower structures are released from the substrate first, it is possible to create multi-axis loops and interlinked objects with several sequential release steps, using a single photomask. The structures remain planar until released by XeF2 dry silicon etching, making it possible to integrate them with other MEMS and microelectronic devices early in the process.

Self‐Assembled Metal Oxide Bilayer Films with “Single‐Crystalline” Overlayer Mesopore Structure

Mesoporous films with almost “single-crystalline” arrangements of spherical pores are obtained by “evaporation- induced self-assembly”: the films are dip-coated onto a sublayer with sufficiently different surface tension and nanometer-scale periodicity. A film with almost single-crystalline (biaxially oriented) pore structure nucleating on an appropriately mesostructured sublayer is shown in the figure and on the cover.

Synthesis and Structure of the Bilayer Hydrate Na0.3NiO2·1.3D2O

The metal oxide bilayer deuterate (hydrate) Na(0.3)NiO2.1.3D2O (Na(0.3)NiO2.1.3H2O) were prepared from NaxNiO2 by extracting Na+ cations and simultaneously intercalating fully and nondeuterated water. High-resolution neutron powder diffraction, thermogravimetric analysis, and inductively coupled plasma atomic emission spectroscopy were used to show that a Na(0.3)(D2O)(1.3) network separates layers of edge-sharing NiO6 octahedra.

Observation of the First-Order Raman Scattering inSrTiO3Thin Films

We have studied lattice dynamic properties of ${\mathrm{SrTiO}}_{3}$ thin films from 5 to 300 K using metal-oxide bilayer Raman scattering. First-order zone-center optical phonons, symmetry forbidden in single crystals, have been observed in the thin films, indicating strain-induced lowering of symmetry. The asymmetric line shape of the ${\mathrm{TO}}_{2}$ phonon is interpreted as evidence for micropolar regions in the thin films, likely due to oxygen vacancies. The optical phonon lines and the asymmetry persist up to room temperature.

Metal–oxide bilayer Raman scattering in SrTiO3 thin films

We have used a metal–oxide bilayer Raman scattering technique to study lattice dynamics in SrTiO3 thin films. The SrTiO3 thin films were epitaxially grown on a conducting metal–oxide layer which reflects the exciting laser beam so that it does not enter the LaAlO3 substrate. Raman scattering from the SrTiO3 thin films was clearly observed, including the first-order Raman peaks forbidden by the cubic symmetry in single crystals. We suggest that strain exists in the films, which changes the crystal symmetry and will affect the dielectric properties of the SrTiO3 thin films.