Substrate-mediated Umklapp scattering at the incommensurate interfaces of monatomic layers

Santosh Chiniwar^1*, Angus Huang¹, Ting-Yu. Chen¹, Chung-Huang Lin¹, Cheng-Rong Hsing², Wei-Chuang Chen¹, Cheng-Maw Cheng³, H. –T. Jeng^1,4, C. M. Wei², Woei Wu Pai5^5,6, S. –J. Tang^1,3,4

¹Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
²Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
³National Synchrotron Radiation Research Center, Hsinchu, Taiwan
⁴Institute of Physics, Academia Sinica, Taipei, Taiwan
⁵Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁶Department of Physics, National Taiwan University, Taipei, Taiwan

* Presenter:Santosh Chiniwar, email:chiniwarsp@gmail.com

Electronic band structure of Ge/Ag(111) was studied using Angle resolved photoemission spectroscopy (ARPES) and compared with Pb/Ag(111). Both films form the surface alloy at 1/3 deposition and forming root(3) R30 structure on Ag (111). However surface electronic structures exhibit vivid difference at the Ag(111) surface zone boundary (SZB) M, where Ag2Ge exhibit split band but Pb2Ag doesn’t. In this article we present our finding and theoretical model to explain the above mentioned. We also reported that larger (smaller) atomic size of Pb (Ge) atom with respect to Ag atom cause the commensurate (incommensurate) interface. Further demonstrate the splitting bands of Ag2Ge/Ag(111) and 1-ML Pb film/Ag(111) originate from the commonly incommensurate interface with Ag(111), that mediate umklapp scattering to induce the mirror image of the pristine Ag2Ge and Pb(111) bands relative to Ag(111) M.

Keywords: ARPES, Surface alloy, Ag2Ge, Umklapp scattering