Electrochemical Formation of Germanene: pH 4.5

Abstract

Germanene is a single layer allotrope of Ge, with a honeycomb structure similar to graphene. This report concerns the electrochemical formation of germanene in a pH 4.5 solution. The studies were performed using in situ Electrochemical Scanning Tunneling Microscopy (EC-STM), voltammetry, coulometry, surface X-ray diffraction (SXRD) and Raman spectroscopy to study germanene electrodeposition on Au(111) terraces. The deposition of Ge is kinetically slow and stops after 2–3 monolayers. EC-STM revealed a honeycomb (HC) structure with a rhombic unit cell, 0.44 ± 0.02 nm on a side, very close to that predicted for germanene in the literature. Ideally the HC structure is a continuous sheet, with six Ge atoms around each hole. However, only small domains, surrounded by defects, of this structure were observed in this study. The small coherence length and multiple rotations domains made direct observation with surface X-ray diffraction difficult. Raman spectroscopy was used to investigate the multi-layer Ge deposits. A peak near 290 cm−1, predicted to correspond to germanene, was observed on one particular area of the sample, while the rest resembled amorphous germanium. Electrochemical studies of germanene showed limited stability when exposed to oxygen.

Germanene Nanosheets: Achieving Superior Sodium‐Ion Storage via Pseudointercalation Reactions

“…In addition, the Raman spectra of germanene exhibited a significantly redshifted peak at around 292.8 cm À1 compared with the pristine GeH single crystal, which is in good agreement with the calculated and experimental vibrational results. [37,38] The XRD patterns and the Raman spectra indicate that the hexagonal layered structure of germanene is initially preserved with rich H defects and gradually changed into the cubic structure of Ge with increasing temperature during the annealing treatment. To further clearly confirm the impact of increased temperature on the defect formation and structural change, the germanium element (Ge 3d) XPS spectra for the three different samples are shown in Figure 2c and Figure S3, Supporting Information.…”

Edge-Hydrogenated Germanene by Electrochemical Decalcification-Exfoliation of CaGe2: Germanene-Enabled Vapor Sensor

“…UHV germanene has been grown on various substrates such as Au, 24 Pt, 25 Ag, 26 Al, 27 Si, 28 graphite, 29 , and MoS2. 30 Germanene formation is not limited to bottom-up synthesis as shown by the electrochemical deposition of germanene in aqueous, 1,[31][32][33][34] and nonaqueous medium. [35][36][37] However, electrochemical deposition can be self-limited to approximately several germanene layers filled with the defect domains.…”

“…Germanene is a near-planar hexagonal structure with 0.24 and 0.42 nm distances between Ge-Ge atoms and layers, respectively. 1 Free-standing germanene layer was theoretically predicted for the first time in 2009 2 reporting a narrow bandgap opening (about 0.024 eV) 1 in contrast to the zero bandgap of graphene. This promotes a quantum-spin Hall effect 3 and massless Dirac fermions, 4 that together with the tunable bandgap, 5,6 makes germanene's use realistic for optoelectronics, [7][8][9] sensing, [10][11][12] energy storage, [13][14][15] and catalysis.…”

Role of doping and sheet size in tailoring optoelectronic properties of germanene: A TDDFT study

“…The analogy between Si, C, and Ge, also leads to similarity among their 2D counterparts, silicene, graphene, and germanene, respectively . 2D sheets of Germanium (Ge), that is, germanene and multilayer hydrogenated germanene are relatively new and less studied members in the 2D materials family. Germanene is a zero‐gap semi‐metal, whose low‐buckled structure is more stable than the planar one.…”

“…Germanene is a zero‐gap semi‐metal, whose low‐buckled structure is more stable than the planar one. The limitation of zero gap can be surmounted by attaching hydrogen to each Ge atom in the sheet and/or by introducing defects . Notwithstanding a relative dearth of investigation on germanene compared to other 2D materials, important investigations have been carried out on germanene.…”