Workfunction measurements of surface-adsorbed molecule for non-equilibrium dynamics analysis

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K21180
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 32:Physical chemistry, functional solid state chemistry, and related fields
• Research Institution: National Institute for Materials Science
• Principal Investigator: ARAFUNE Ryuichi 国立研究開発法人物質・材料研究機構, 国際ナノアーキテクトニクス研究拠点, 主任研究員 (50360483)
• Project Period (FY): 2020-07-30 – 2022-03-31
• Keywords: 仕事関数 / 時間分解分光 / ダイナミクス

Outline of Final Research Achievements

An ultrafast work function measurement system with time and energy resolutions of 100 fs and 10 meV was constructed. The high time resolution was demonstrated through two-photon photoemission spectroscopy experiments using Graphene/Ir(111) as a sample. The experimental system was then validated using Xe/Au(111) as a model sample. However, unfortunately, although we could observe that the work function changed due to Xe adsorption, we could not induce the work function change by laser irradiation. Whild the work function changed when the laser intensity was increased, this work function change could not be time-resolved. Unfortunately, the system did not behave as a work function change with an appropriate time scale for the current system. It is necessary to explore a wider range of sample systems, such as molecular adsorption systems, and to construct a measurement system with shorter time resolution.

Free Research Field

表面科学

Academic Significance and Societal Importance of the Research Achievements

固体表面における吸着分子の運動を理解する上で、ボルン近似が成立しない非断熱効果の重要性は広く認識されている。高い時間分解能を持つパルスレーザーを用いた分析手法は強力である。時間分解能 を高めようすると、不確定性原理に由来する励起光のスペクトル幅の広がりが無視できないためである。本研究はこの困難を打破するためのもので、原理実証に成功した。今後さらなル時間分解能の向上を測ることによって、吸着分子系、表面光誘起相転移や表面ポテンシャル変調によるスピン軌道相互作用操作など多様な 系に対して表面ダイナミクスを支配する非断熱効果の本質を追求できるユニークな手法となることが期待される。