Surface and dynamical properties of GeI <sub>2</sub>
Archit Dhingra, Alexey Lipatov, Haidong Lu, Katerina Chagoya, J.C. Dalton, Alexei Gruverman, Alexander Sinitskii, Richard G. Blair, P. A. Dowben
Abstract
Abstract GeI 2 is an interesting two-dimensional wide-band gap semiconductor because of diminished edge scattering due to an absence of dangling bonds. Angle-resolved x-ray photoemission spectroscopy indicates a germanium rich surface, and a surface to bulk core-level shift of 1.8 eV in binding energy, between the surface and bulk components of the Ge 2p 3/2 core-level, making clear that the surface is different from the bulk. Temperature dependent studies indicate an effective Debye temperature ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>D</mml:mi> </mml:msub> </mml:mrow> </mml:math> ) of 186 ± 18 K for the germanium x-ray photoemission spectroscopy feature associated with the surface. These measurements also suggest an unusually high effective Debye temperature for iodine (587 ± 31 K), implying that iodine is present in the bulk of the material, and not the surface. From optical absorbance, GeI 2 is seen to have an indirect (direct) optical band gap of 2.60 (2.8) ± 0.02 (0.1) eV, consistent with the expectations. Temperature dependent magnetometry indicates that GeI 2 is moment paramagnetic at low temperatures (close to 4 K) and shows a diminishing saturation moment at high temperatures (close to 300 K and above).