Control of Na contents in group IV clathrate and their electrical and optical characterizations

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K03820
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Gifu University
• Principal Investigator: Ohashi Fumitaka 岐阜大学, 工学部, 准教授 (20613087)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 半導体 / クラスレート / 薄膜

Outline of Final Research Achievements

Firstly, controls of Na contents and distributions in group IV clathrate films were conducted by applying electric field. Reductions of Na contents in the entire clathrate films were confirmed, however, local reductions of Na contents at the films were not observed. Secondly, the formations of electrodes on the films were conducted. When Ag were used as the electrode material, ohrmic I-V characteristics were appeared while Al showed higher resistance in several order. This is suggesting that Al and Na formed insulating compound between the clathrate and electrode films. The I-V characteristics of clathrate films with reductions of Na contents using a long vacuum annealing showed an increase of current by photo-irradiation. The photo-absorption spectra were analyzed to understand the fundamental absorption edge.

Free Research Field

半導体

Academic Significance and Societal Importance of the Research Achievements

SiまたはGeがフレームワークを構成するII型クラスレートは、計算結果から直接遷移型半導体であり、その合金化によりバンドギャップを1.2 eVから1.8 eVの間で制御できるとされている。これらの特性により毒性の低いIV元素による、高効率太陽電池や発光素子への応用を期待できる。しかしながら、薄膜化が困難であり、半導体の詳細な物性評価およびデバイス化には至っていない。また、合成時に結晶構造中に内包されるアルカリ金属の除去技術の確立が必要不可欠である。本研究では、クラスレートの物性評価およびデバイス化を目的として、内包Naの除去技術、電極材料の選定、適切な電極材料による半導体物性評価を行った。