新規な２次元ホウ素ナノシステムの創製とその熱電変換応用

2014 Fiscal Year Annual Research Report

• Project/Area Number: 14F04332
• Research Institution: National Institute for Materials Science
• Principal Investigator: 森 孝雄 独立行政法人物質・材料研究機構, 無機ナノ構造ユニット, グループリーダー (90354430)
• Co-Investigator(Kenkyū-buntansha): PAKDEL Amir 独立行政法人物質・材料研究機構, 無機ナノ構造ユニット, 外国人特別研究員
• Project Period (FY): 2014-04-25 – 2016-03-31
• Keywords: ２次元ナノ構造 / 熱電

Outline of Annual Research Achievements

The JSPS project commenced from Nov. 30, 2014. In this relatively short period of 4 months, the following was achieved.
First of all, milligram-level chemical vapor deposition synthesis of boron-based nanomaterials (based on BN) was achieved by using precursor materials. This scale-up is necessary to consider it for thermoelectric applications. This material itself does not have good thermoelectric properties, but we have started doping experiments to try to control the electronic band structure and also modify the thickness of films to achieve possible phonon confinement effects in order to enhance the thermoelectric properties.
While the boron-based nanomaterial research was proceeding, at the same time, one of the large goals of this research is to achieve dramatic breakthroughs of high thermoelectric performance in 2 dimensional materials. As a good template material, we also moved forward the solid-state synthesis of 2 dimensional bismuth telluride, which is the champion material at room temperature, achieving preliminary results of very high thermoelectric efficiency of ZT (a patent is now being prepared).

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

Regarding the progress of the research, considering that the time period was 4 months in this fiscal year, we think that the progress has been satisfactory.
We have achieved a start in synthesizing the necessary amounts of a target boron-based nanomaterial by achieving milligram-level chemical vapor deposition synthesis. Doping of this material has been commenced as has been starting investigation into possible phonon confinement effects.
Synthesis has been carried out on a high performance 2 dimensional thermoelectric material (bismuth telluride-based material as a model material) with aim to achieve a fundamental breakthrough jump-up in thermoelectric performance, and high ZT which is patent-worthy has already been achieved. With the 4 months, this is just the start, but promising outlook has been achieved.

Strategy for Future Research Activity

Regarding the future research plan, first, we will try for improvement in the purity and crystallinity of boron-based nanomaterials for thermoelectric applications, now that the necessary scale-up has been achieved. Doping experiments on the boron-based nanomaterial will be continued to try to control the electronic band structure and also modification of the thickness of film will be carried out to achieve possible phonon confinement effects in order to enhance the thermoelectric properties. Thermoreflectance measurements of the films will be carried out to accurately evaluate the thermal conductivity of thin films.
Second, with aim to achieve a fundamental breakthrough jump-up in thermoelectric performance, the investigation into a model system 2 dimensional thermoelectric system, will continue by nanostructuring of the Bi-Sb-Te system that we have obtained, to enhance the thermoelectric properties.