Basal-plane thermal conductivity of nanocrystalline and amorphized thin germanane

Abstract

Germanane (GeH), a hydrogen-terminated layered germanium structure, has recently been synthesized. Here, we employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. The obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53±0.03 W m-1 K-1, which is close to the value calculated for 3.3 nm grain size, to 0.29±0.02 W m-1 K-1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.