Synthesis of 2D Germanane (GeH): a New, Fast, and Facile Approach

Abstract

Germanane (GeH), ag ermanium analogue of graphane,h as recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices,p hotovoltaics,a nd photocatalysis.U pt on ow,t he synthesis of GeH has been conducted by substituting Ca by H in a b-CaGe 2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6t o1 4days. The new and facile protocol presented here allows to synthesize GeH at room temperature in as ignificantly shorter time (a few minutes), which renders this method highly attractive for technological applications.T he GeH produced with this method is highly pure and has aband gap (E g)close to 1.4 eV,alower value than that reported for germanane synthesized using HCl, whichi s promising for incorporation of GeH in solar cells.

Two-Dimensional Functionalized Germananes as Photoelectrocatalysts

“…36 We evaluated the optical band gap of all germananes by combining the Tauc plot with the Kubelka−Munk function based on the absorbance measurement included in Figure S5 of the Supporting Information. Figure 6A presents the optical band gaps determined using direct allowed transition for germananes, 14,20 where Ge-H presented the smallest band gap of 1.66 eV, followed by Ge-Me with 1.76 eV. These values are close to the experimentally determined values in the literature.…”

“…15−17 These encouraging outcomes have stimulated the possibility to alter the properties of 2D germanenes by rationally designed terminations, succeeding in the functionalization of graphene. In turn, this has elicited the interest to gradually develop other synthetic and functionalization techniques, such as ionexchange, 18 solvothermal reaction, 19 deintercalation by hydrofluoric acid, 20 and deprotonation of germanene by alkali metal arenides such as sodium naphthalenide followed by alkylation for different modifications. 8,21 In particular, the alkylation approach utilizing n-alkyl halides or trifluoromethyl groupcontaining benzyl halides has emerged as a versatile technique that has created rich possibilities for the functionalization of germananes.…”

Transport Properties of Methyl-Terminated Germanane Microcrystallites

“…However, it is interesting to compare the resistance of methyl-terminated germanane microcrystallites with the resistance of H-terminated germanane flakes found in the literature. Although the H-terminated germanane flakes show similar lateral sizes, they were much thinner [ 9 , 18 ]. Hence, we normalized the resistance by multiplying it by the measured thickness of the microcrystallite.…”

“…The data for the H-passivated flakes were deduced from the experimental results published in Refs. [ 9 , 18 ]. ( b – d ) TEM images and SAED patterns of the thin edge of a microcrystallite collected at room temperature (RT), 185 °C and 280 °C, respectively.…”

“…Both silicane and germanane have a reduced theoretical band gap compared to graphane: 2.9 eV and 1.9 eV, respectively [ 8 ]. The experimental value has been found to be even lower, between 1.4 and 1.6 eV for germanane [ 6 , 9 ], with carrier mobilities of tens of cm 2 ·V −1 ·s −1 [ 10 ], raising hope for its use as an active channel in field effect transistors [ 11 ].…”