[3Ia01-06] Two-Dimensional (2D) Materials

[3Ia04] Growth mechanism and vibrational properties of germanene fabricated through Ge segregation

*Hiroki Hibino¹, Akio Ohta², Hiroyuki Kageshima³, Junji Yuhara⁴ (1. Kwansei Gakuin University, 2. Fukuoka University, 3. Shimane University, 4. Nagoya University)

We fabricate various Ge-induced surface structures by annealing Ag(111) thin films grown on Ge(111) and identify their vibrational properties using ultrahigh vacuum Raman spectroscopy. After annealing the Ar-sputtered sample, the √3×6√3 striped phase appeared at lower temperatures and was followed by the so-called disordered hexagonal or quasi-freestanding phases. The (7√7×7√7)R19.1° structure was formed after annealing at the highest temperatures before the formation of the three-dimensional Ge islands. Raman spectra of the striped phase are featureless in the range of 100-300 cm^-1, indicating that the striped phase is Ag-Ge surface alloy. The disordered hexagonal or quasi-freestanding phases showed Raman peaks assignable to germanene. The germanene Raman peaks intensified and shifted to higher wavenumbers as the annealing temperature increased, and the spectral shape continuously changed into that of the (7√7×7√7)R19.1° structure along with the emergence of new peaks.