Optical Investigation of Hydrogen Intercalation-Deinteracalation Processes in Layered Semiconductorγ-InSe Crystals

Abstract

Processes of hydrogen electrochemical intercalation into layered InSe crystals were investigated. It was ascertained that for concentrations x<2 hydrogen forms the state of ``quasi-liquid monolayer'' from H-2 molecules in the van-der-Waals gap, which results in the increasing interlayer lattice parameter, while for x>2 atomic hydrogen being built into interstices due to quantum-size effects for the gap and H-2 molecules. It was found that the observed at T=80K non-monotonic shift of the exciton absorption peak n=1 with growing x stems from the increasing dielectric permeability of the crystal epsilon(0) due to presence of hydrogen in the van-der-Waals gap. A linear growth of epsilon(0)(x) at x<0.5 results in 30% decrease of the exciton binding energy. At x>0.5 2D localization of exciton motion in the crystal layer plane takes place, which causes reduction and then at x>1 stabilization of sizes both for the exciton and quantum well. As to HxInSe samples, their deintercalation degree increases linearly from 60% at x–>0 up to 80% at x–>2.