[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above.

Metal oxide gas sensors: Sensitivity and influencing factors

Transparent conductors as solar energy materials: A panoramic review

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion Besides, doping is also an effective method to decrease particle size and improve gas sensing properties Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given

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Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review

Aligned Single‐Crystalline Si Nanowire Arrays for Photovoltaic Applications

Influence of Bi concentration on the electrical and ac conduction properties of amorphous Sb-Bi-Te thin films

In this study, p-channel polycrystalline silicon (poly-Si) thin-film transistors (TFTs) using an active layer of ultralarge-grain (ULG) silicon and multistack gate insulators of SiNx/SiO2 were fabricated and investigated. The ULG silicon thin films were formed by nickel (Ni)-induced crystallization and the average grain area of ULG silicon is 118 µm2. The field-effect mobility of p-channel ULG poly-Si TFTs was 111 cm2/(Vs), which can be sufficiently applied to high driving parts of display systems. The p-channel ULG poly-Si TFT has a low threshold voltage of -1.06 V, a high ON/OFF current ratio of 9.2×107, and a subthreshold swing of 0.27 V/decade. Moreover, the fabricated TFTs have stable characteristics under temperature and gate bias stress owing to the large grains and smooth surface. These results show that the ULG poly-Si TFTs are remarkably suitable for the application to a low power and high speed pixel-driving device in flat panel displays.

https://iopscience.iop.org/article/10.1143/JJAP.51.09MF01/pdf

High Mobility P-Channel Thin-Film Transistors with Ultralarge-Grain Polycrystalline Silicon Formed Using Nickel-Induced Crystallization

Anodic Aluminum Oxide (AAO) template prepared in acid electrolyte possess regular and highly anisotropic porous structure with pore diameter range from five to several hundred nanometers, and with a density of pores ranging from 10(9) to 10(11) cm(-2). AAO can be used as microfilters and templates for the growth of CNTs and metal or semiconductor nanowires. Varying anodizing conditions such as temperature, electrolyte, applied voltage, anodizing and widening time, one can control the diameter, the length, and the density of pores. In this work, we deposited Al thin film by radio frequency magnetron sputtering method to fabricate AAO nano template and synthesized multi-well carbon nanotubes on a glass substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). AAO nano-porous templates with various pore sizes and depths were introduced to control the dimension and density of CNT arrays. The AAO nano template was synthesize on glass by two-step anodization technique. The average diameter and interpore distance of AAO nano template are about 65 nm and 82 nm. The pore density and AAO nano template thickness are about 2.1 x 10(10) pores/cm2 and 1 microm, respectively. Aligned CNTs on the AAO nano template were synthesized by MPECVD at 650 degrees C with the Ni catalyst layer. The length and diameter of CNTs were grown 2 microm and 50 nm, respectively.

Growth control of carbon nanotubes using by anodic aluminum oxide nano templates.

Polycrystalline silicon (poly-Si) is an widely studied material, for use in high quality thin film transistor active layer. High temperature process is not used for glass substrate because of its low softening temperature below 450°C. However, high temperature crystallization has an advantage to get high crystalline volume fraction (Xc). In this paper, the a-Si deposited by hot-wire CVD was crystallized at a temperature between 750°C to 1050°C within 2 min as to induce high current over 48A between electrodes. The film grown at a condition of crystallization temperature of 850°C for 2 min exhibits the crystalline volume fraction of 80.9%, the preferential growth of (220) orientation, and the activation energy of 0.22eV. Moreover, high temperature poly-Si using a Mo substrate has special advantage of crystallization such as high crystallinity, simple, low cost and high temperature endurance.

Junsin Yi

Papers

Influence of Bi concentration on the electrical and ac conduction properties of amorphous Sb-Bi-Te thin films

High Mobility P-Channel Thin-Film Transistors with Ultralarge-Grain Polycrystalline Silicon Formed Using Nickel-Induced Crystallization

Growth control of carbon nanotubes using by anodic aluminum oxide nano templates.

High-Temperature Crystallization of Amorphous Silicon on a Molybdenum Substrate

A Study on the Selective Hole Carrier Extraction Layer for Application of Amorphous/crystalline Silicon Heterojunction Solar Cell