Creation and comprehensive exploration of high performance thermoelectric semiconductor utilizing natural quantum structure of layered transition metal compound

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H02425
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Katase Takayoshi 東京工業大学, 科学技術創成研究院, 准教授 (90648388)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 熱電変換材料 / 層状半導体 / 量子構造 / 材料設計 / 低環境負荷

Outline of Final Research Achievements

Design, synthesis, and electronic property characterization of high purity layered transition metal nitride semiconductors, AETMN2 (AE=Ca,Sr,Ba and TM=Ti,Zr,Hf) were performed to search new high performance thermoelectric materials with two dimensional electron gas (2DEG) structure. Density functional theory defect calculations clarified that nitrogen vacancy and oxygen impurity substitution, as shallow donor, are easily formed in SrTiN2, while the defect formation is largely suppressed by Ca substitution at Sr site and Zr,Hf substitution at Ti site. The electronic, optical, and magnetic properties were clarified by using high phase purity (>94 mol%) AETMN2 bulks synthesized by a solid-state reaction between AENH and TMN precursors with NaN3. The easiness of impurity incorporation is designed to produce a more intrinsic semiconductor in wider chemical conditions, opening a way to cultivating novel functional materials that are sensitive to atmospheric impurities and defects.

Free Research Field

材料科学

Academic Significance and Societal Importance of the Research Achievements

第一原理計算による電子構造・欠陥計算と化学結合解析を併用して合成プロセスを設計し、大気中で不安定な物質でも不純物や欠陥の生成を抑制して新しい半導体材料を実現する材料探索手法になると期待される。本提案を発展させ、関連層状化合物の探索と電子構造・半導体物性評価を更に進めていくことにより、優れた環境調和型熱電材料の実現に繋がると考える。