Evolution of the Electronic Band Structure and Efficient Photo-Detection in Atomic Layers of InSe

Abstract

Atomic layers of two-dimensional (2D) materials have recently been the focus of extensive research. This follows from the footsteps of graphene, which has shown great potential for ultrathin optoelectronic devices. In this paper, we present a comprehensive study on the synthesis, characterization, and thin film photodetector application of atomic layers of InSe. Correlation between resonance Raman spectroscopy and photoconductivity measurements allows us to systematically track the evolution of the electronic band structure of 2D InSe as its thickness approaches few atomic layers. Analysis of photoconductivity spectra suggests that few-layered InSe has an indirect band gap of 1.4 eV, which is 200 meV higher than bulk InSe due to the suppressed interlayer electron orbital coupling. Temperature-dependent photocurrent measurements reveal that the suppressed interlayer interaction also results in more localized pz-like orbitals, and these orbitals couple strongly with the in-plane E' and E″ phonons. Finally, we measured a strong photoresponse of 34.7 mA/W and fast response time of 488 μs for a few layered InSe, suggesting that it is a good material for thin film optoelectronic applications.

Electronic and thermoelectric properties of van der Waals materials with ring-shaped valence bands

“…The height of the step function using Eq. (15) and k 0 is either underestimated or equivalent to the numerical density of modes. For all four materials GaS, GaSe, InS and InSe, decreasing the film thickness increases k 0 and the height of the step-function of the band-edge density of modes.…”

“…Experimental studies have demonstrated synthesis of monolayers and or few layers of GaS, GaSe and InSe thin films. 10,[14][15][16][17][18][19][20] .…”

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

“…23 Very recently, samples of few-layer hexagonal InSe have been produced and their optical properties have been studied. 24,25 Indium sulfide (InS) and indium telluride (InTe) exhibit orthorhombic and tetragonal structures, respectively, but this does not exclude the possibility of growing metastable hexagonal structures (structural changes induced by annealing have been reported in transmission electron microscopy of indium chalcogenide thin films 26 ). We have investigated whether monolayers of the hexagonal phase are stable in any of these three materials.…”

Vibrational spectrum renormalization by enforced coupling across the van der Waals gap betweenMoS2andWS2Fan1, Zhu2, Ke3 et al. 2015Phys. Rev. B311221View full textAdd to dashboardCite

“…[4][5][6][7] A few other layered semiconductors (e.g., InSe) exhibit the opposite trend, i.e., switching from direct bandgap in the bulk to indirect bandgap toward the monolayer limit. 8,9 The normalization of band structure by the interlayer coupling signifies a crossover from two-dimensional (2D) electronic system in the monolayer to three-dimensional (3D) electronic system in the bulk. Therefore, the degree of twodimensionality, or, the "2Dness", of the system is defined by the strength of interlayer coupling.…”