Faster and Safer "In situ" Synthesis of Germanane and Silicane

Abstract

Germanane (GeH) and silicane (SiH), members of the Xanes family, have garnered significant attention as 2D materials due to their diverse properties, which hold promise for applications in electronics, optoelectronics, energy storage, and sensing. Typically, highly concentrated hydrochloric acid (HCl) or hydrofluoric acid (HF) is employed in the synthesis of these Xanes, but both routes are problematic due to slow kinetics and safety concerns, respectively. Here for the first time, a faster and safer method is demonstrated for Xanes synthesis that harnesses the generation of HF "in situ" using a solution of HCl and lithium fluoride (LiF) salt, overcoming the key challenges of the conventional methods. A variety of characterization techniques to establish a baseline is utilized for both Xanes and to provide a holistic knowledge regarding this method, the possible consequences of this approach, and the possibility of applying it to other layered Zintl phases. The novel synthesis protocol results in high-quality GeH and SiH with bandgaps (E_g) of 1.75 and 2.47 eV respectively, highlighting their potential suitability for integration into semiconductor applications.

Keywords: 2D materials; Xanes; germanane; silicane; synthesis; “in situ” HF.

Figure 1

XRD patterns of Zintl phase precursors a) CaGe₂ and b) CaSi₂ before (black line) and after (blue line) treatment with NaOH solution to remove impurities.

Figure 2

Powder XRD patterns of synthesized Xanes a) GeH (inset: schematic illustration crystal structure of GeH), b) SiH (inset: schematic illustration crystal structure of SiH) and SEM images of c) multilayered GeH, d) multilayered SiH, e) few layered GeH and f) few layered SiH.

Figure 3

a,d) TEM images, b, d) SAED patterns, and c,f) EDS spectra of flakes from GeH, SiH samples, respectively. Position of SAED aperture used to acquire patterns in b,e) are show by brown and purple circles in a,d), respectively. GeH and SiH STEM EDS spectra acquired from regions shown by insets in Figures S12 and S13 (Supporting Information), respectively.

Figure 4

Raman spectrum of synthesized Xanes a) GeH (deconvoluted E _2g band, inset), b) SiH (deconvoluted E _2g band, inset), and FT‐IR spectra of c) GeH and d) SiH.

Figure 5

XPS of GeH and SiH. a) GeH survey scan with high‐resolutions scans of b) Ge 3d, c) O 1 s, and d) SiH survey scan with high‐resolutions scans of e) Si 2p and f) O 1 s.

Figure 6

TGA and DSC of synthesized Xanes a) GeH (black line DSC & brown line TGA) and b) SiH (black line DSC & purple line TGA). Diffuse reflectance absorbance (DRA) spectrum plotted as Kubelka‐Munk function versus wavelength; inset: Tauc‐plot analysis of the Kubelka‐Munk function of c) GeH in propanol and d) SiH in ethanol.