Direct Growth of Germanene at Interfaces between Van der Waals Materials and Ag(111)

Abstract

Germanene, a 2D honeycomb germanium crystal, is grown at graphene/Ag(111) and hexagonal boron nitride (h‐BN)/Ag(111) interfaces by segregating germanium atoms. A simple annealing process in N2 or H2/Ar at ambient pressure leads to the formation of germanene, indicating that an ultrahigh‐vacuum condition is not necessary. The grown germanene is stable in air and uniform over the entire area covered with a van der Waals (vdW) material. As an important finding, it is necessary to use a vdW material as a cap layer for the present germanene growth method since the use of an Al2O3 cap layer results in no germanene formation. The present study also proves that Raman spectroscopy in air is a powerful tool for characterizing germanene at the interfaces, which is concluded by multiple analyses including first‐principles density functional theory calculations. The direct growth of h‐BN‐capped germanene on Ag(111), which is demonstrated in the present study, is considered to be a promising technique for the fabrication of future germanene‐based electronic devices.

Self‐Limiting Synthesis of Ultrathin Ge(110) Single Crystal via Liquid Metal

“…The structure of ultrathin Ge(110) single crystal contains two vibrational modes with Raman activity, which are located at 265.6 and 249.3 cm −1 , exhibiting the red-shifted and entirely different vibrational mode compared with the bulk phonon structure (301 cm −1 ). [12] The relative difference value of two vibration molds are 16.3 cm −1 , greatly in consistence with the DFT calculation results shown in Figure 2i, which has the relative difference value of 16.5 cm −1 . The thickness-dependent Raman spectra are also investigated, as shown in Figure S13 (Supporting Information), which demonstrate that the redshift phenomenon is caused by the decrease of thickness.…”

“…These synthesis methods generally rely on the epitaxial growth, which indicates the substrates should be compatible with the target orientation of Ge-based materials. In these ways, the substrates like Ag(111), [12][13][14] Cu(111), [15,16] Pt(111), [17] Au(111), [18][19][20][21][22][23] Al(111), [24][25][26][27][28][29][30][31] Sb(111), [32] MoS 2 , [33] and graphite [34] are employed to synthesize the Ge flakes, and the (111)-oriented structure is synthesized by the epitaxial growth in these researches. However, the gapless property [35] of ultrathin Ge(111) flakes makes it fail to inherit the semiconductor characteristic of the classical germanium material and greatly hampers the application.…”

Tunable Hollow Nanoreactors for In Situ Synthesis of GeP Electrodes towards High‐Performance Sodium Ion Batteries

“…[2,24] In the spectrum of GeP/CN-3, two peaks corresponding to Ge-P and Ge-Ge stretching modes are observed at 361.0 and 200.4 cm À1 ,respectively. [20,25] Theo ther three peaks located at 135.7, 246.3 and 308.1 cm À1 can be assigned to the plane deformation, rocking and skeleton stretching for Ge-P-Ge modes,r espectively. [26] Furthermore,t wo peaks appear at 1329.5 and 1581.8 cm À1 for both samples,w hich correspond to Da nd Gb ands of nitrogen-doped carbon, respectively.…”

Optical Signatures of Dirac Electrodynamics for hBN-Passivated Silicene on Au(111)

“…29 In this study, silicene was passivated in situ directly after the growth using few-layer hBN, which has already been proven to be a suitable passivation for silicene 30 and germanene. 31 The intrinsic transparency of hBN with a wide band gap of 5.95 eV 32 enables direct access to the optical properties of the subjacent silicene layer over a wide spectral range. Furthermore, the absence of Raman-active modes of hBN in the fingerprint region of silicene facilitates the evaluation of ex situ Raman measurements.…”