Two phases at the incommensurate interface of an monoatomic alloy layer Ag2Ge on Ag(111).

Santosh Chiniwar^1*, Angus Huang¹, Ting-Yu Chen¹, Chung-Huang Lin¹, Cheng-Rong Hsing², Wei-Chuan Chen¹, Cheng-Maw Cheng³, H-T. Jeng^1,4, C.M. Wei², Woei Wu Pai^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, NSRRC, 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

In this article, bright and dim regions of two alloy phases of Ge/Ag(111) and ratio of bright to dim region vary with coverage are studied. The aforementioned ratio has profound effect on electronic band structure observed on ARPES. An Ag2Ge, Root3 R30° structure forms on Ag(111) at 1/3ML and electronic structure exhibits splitting at surface zone boundary (SZB) Mbar. In Comparison, the alloy phase of Pb2Ag on Ag(111) does not exhibit splitting at Mbar SZB. However, at 1-ML Pb on Ag(111) forms incommensurate at interface with the substrate, thus observing splitting at Mbar SZB. Aforementioned phenomenon was explained with help of theoretical model. As the atomic size of Pb (Ge) atoms are larger (smaller) relative to substrate atoms cause commensurate (incommensurate) at interface. Here incommensurate interface on Ag(111) exhibits splitting at Mbar SZB caused by mediate umklapp scattering to induce the mirror image of the pristine Ag2Ge and Pb(111) bands relative to Ag(111) Mbar SZB. Furthermore, bright and dim region of Ag2Ge has distinct Local density of state observed using scanning tunneling spectroscopy (STS). Due to variation in the relaxation of Alloy phase on Ag(111), at dim region, Pz band of Ag2Ge is quenched causing to suppress the intensity in the empty state of LDOS thus appearing as dim region on LT-STM scan, later favors the interaction between Pz orbitals of Ag2Ge surface alloy and Ag(111) more than the former phase does.

Keywords: Surface Alloy , Incommensurate , STS, ARPES, STM