Using photon impinging effect to study the disparate anchoring stabilities of polar-organic molecules adsorbed on bulk and thin-film metal surfaces

Kowsalya Arumugam^1*, Hong-Ming Chen¹, Jing-Huan Dai¹, Mau-Fu Gao¹, Abhishake Goyal¹, Meng-Kai Lin¹, Yasuo Nakayama³, Tun-Wen Pi², Sebastian Metz⁷, Theodoros A. Papadopoulos⁸, S-J Tang^1,2

¹Department of Physics and Astronomy, National Tsing Hua University, Hsinchu, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan
³Department of Pure and Applied Chemistry, Tokyo University of Science, Chiba, Japan
⁴Department of Physics, University of Illinois, Illinois, USA
⁵Center for Frontier Science, Chiba University, Inage-ku, Japan
⁶Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Japan
⁷Scientific Computing Department, STFC Daresbury Laboratory, Warrington, UK
⁸Department of Natural Sciences, University of Chester, Chester, UK

* Presenter:Kowsalya Arumugam, email:kowsalya3691@gmail.com

The behaviors of polar organic molecules, chloroaluminum phthalocyanine (ClAlPc), upon photon-irradiation effects were investigated to realize their adsorption stabilities on the Ag(111) thin film and crystal. Angle-resolved photoelectron spectroscopy (ARPES) was mainly employed to measure the photon-flux dependence of molecular energy states (MES) and vacuum level shift (VLS) for 1-ML ClAlPc in Cl-down configurations, indicating a consistent trend that ClAlPc in Cl-down configuration is evidently more stable on the Ag thin-film surface than on the corresponding surface of the Ag bulk crystal. The intermediate adsorption state, tilted configuration, during the photon impinging, is identified by the large positive VL shifts and broad line shapes to infer the flipping mechanism from Cl-down to Cl-up configuration. The strained effect on Ag thin films from the underlying, 30% lattice mismatched, Ge(111) substrate is considered to cause the enlarged vacancy sites of Ag-film surfaces, that help anchor Cl-down configuration more tightly, as confirmed by the first-principles calculations.

Keywords: Chloroaluminium phthalocyanine, photon irradiation effect, ARPES, Flipping Mechanism