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成果報告書詳細
管理番号20170000000714
タイトル*平成28年度中間年報 エネルギー・環境新技術先導プログラム α型酸化ガリウム高品質自立基板の研究開発
公開日2017/8/3
報告書年度2016 - 2016
委託先名国立研究開発法人物質・材料研究機構 国立大学法人京都大学 国立大学法人佐賀大学 株式会社FLOSFIA
プロジェクト番号P14004
部署名イノベーション推進部
和文要約
英文要約Title: Advanced Research Program for Energy and Environmental Technologies / Development of high-quality freestanding α-Ga2O3 substrates(FY2016-FY2017) FY2016 Annual Report

The quartz template for thermoelectric nanowire element has been prepared by applying the technique for optical fiber. The fabrication technique for the quartz template with a 20nm-diameter pore has been achieved. Moreover, although we have been challenging the fabrication of quartz template with multi-pores, some issues were found out to achieve multi-pore template.
Based on the fabrication of quartz template with a nanometer-pore, the thermoelectric nanowire elements with the diameter in the range from 20 nm to 500 nm have been developed. As a result, we have obtained the 50nm-diameter Bi nanowire by utilizing the above-mentioned quartz template. However, in order to specify the accurate wire diameter and to obtain the electrical contact, the mechanical polishing technique for the edges of element is a very important issue, and we are investigating the optimum condition of mechanical polishing by using automatic mechanical polishing system.
On the other hand, we attempt to fabricate new nanowire materials such as Si and PbTe, which have higher melting point than that of Bi. In order to realize such nanowires, the temperature for pressing into the quartz template and the control of melting point are very important. Thus, the temperature for pressing into the quartz template with nano-pores was arranged up to 450℃ and the melting points of these materials were lowered by flux method. By using these techniques, we have been developing new nanowire materials.
In order to obtain electrical contact at nanowire edges with low contact resistance, the conditions of plasma etching and mechanical polishing were investigated. The low resistance contact has been obtained by using the optimum etching conditions and Cr/Cu bilayer electrodes. Moreover, the precise electrodes for nano-trench structure have been obtained by using the long-throw sputtering system.
In order to measure the electrical resistance and the Seebeck coefficient for nanowires, the measurement system for high impedance elements is necessary. Thus, we develop the measurement systems for high impedance elements and fabricate the element for four-wire measurement by FIB. By controlling the FIB conditions, we obtained the technique for fabricating four-wire elements. Moreover, in order to measure Seebeck coefficient of high impedance elements, we developed the quasi-AC method by using 5mHz frequency of heating current, and introduced the electrometer for high impedance element.
The fabrication of thermoelectric semiconductor Si and insulator nanocomposite is attempted. It has been found that the combination of the high energy ball milling and the spark plasma sintering processes results in the cell structure where Al2O3 particles surrounded by the Si semiconductor phase but with a micrometer scale. Finer structures will be pursued by longer time or higher energy ball milling.
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