Layer-dependent and light-tunable surface potential of two-dimensional indium selenide(InSe)flakes

As a fundamental surface property of two-dimensional(2 D)materials,surface potential is critical for their emerging electronic applications and essential for van der Waals heterostructure engineering.Here,we report the surface potential of few-layer InSe.The effect of layer count,light intensity and different deposited substrates is considered.Few-layer InSe flakes were exfoliated from bulk InSe crystals on Si/SiO_(2)with 300-nm-thick thermal oxide and Si/SiO_(2)with 300-nm-thick thermal oxide and prefabricated micro-wells with 3μm in diameter.The samples were measured by Kelvin probe force microscopy and tuned by an integrated 405-nm(3.06 eV)laser.Based on the work function of SiO_(2)(5.00 eV),the work functions of supported and suspended InSe are determined.These results show that the work function of InSe decreases with the increase in the layer count of both supported InSe and suspended InSe.Besides,by introducing a tunable laser light,the influence of light intensity on surface potential of supported InSe was studied.The surface potential(SP)and surface potential shift between light and dark states(ASP=SP_(lignt)-SP_(dark))of supported InSe were measured and determined.These results present that the surface potential of supported InSe decreases with the increase in the light intensity and also decreases with the increase in the layer count.This is evident that light excites electrons,resulting in decreased surface potential,and the amount of electrons excited is correlated with light intensity.Meanwhile,⊿SP between light and dark states decreases with the increase in the layer count,which suggests that the influence of light illumination decreases with the increase in the layer count of few-layer InSe flakes.

Signatures of strong interlayer coupling inγ-InSe revealed by local differential conductivity

Interlayer coupling in layered semiconductors can significantly affect their optoelectronic properties.However,understanding the mechanisms behind the interlayer coupling at the atomic level is not straightforward.Here,we study modulations of the electronic structure induced by the interlayer coupling in theγ-phase of indium selenide(γ-InSe)using scanning probe techniques.We observe a strong dependence of the energy gap on the sample thickness and a small effective mass along the stacking direction,which are attributed to strong interlayer coupling.In addition,the moirépatterns observed inγ-InSe display a small band-gap variation and nearly constant local differential conductivity along the patterns.This suggests that modulation of the electronic structure induced by the moirépotential is smeared out,indicating the presence of a significant interlayer coupling.Our theoretical calculations confirm that the interlayer coupling inγ-InSe is not only of the van der Waals origin,but also exhibits some degree of hybridization between the layers.Strong interlayer coupling might play an important role in the performance ofγ-InSe-based devices.

Molten Salt Synthesis, Crystal Structure and Optical Properties of a Novel Quaternary Metal Selenide, K_2AgIn_3Se_6

K2AgIn3Se6 was synthesized by a molten-salt (alkali-metal polyselenide flux) reaction at 500 ℃. The orange red granular crystal crystallizes in monoclinic space group C2/c with cell parameters, a=1.16411(7) nm, b=1.16348(8) nm, c=2.14179(12) nm, V=2.8740(9) nm3, and Z=8. The crystal has a new two-dimensional structure containing 2∞[AgIn3Se6]2- anionic layers separated by K+ cations and the 2∞[AgIn3Se6]2- layer is constructed with corner-shared [AgSe4] and [InSe4] tetrahedra. The optical band gap of K2AgIn3Se6 was determined to be ca. 2.9 eV by UV/vis/NIR diffuse reflectance spectra.

Recent progress in contact, mobility, and encapsulation engineering of InSe and GaSe

The field of two-dimensional(2D)materials has stimulated considerable interest in the scientific community.Owing to quantum confinement in one direction,intriguing properties have been reported in 2D materials that cannot be observed in their bulk form.The advent of semiconducting 2D materials with a broad range of electronic properties has provided fascinating opportunities to design and configure next-generation electronics.One such emerging class is the family of III-VI monochalcogenides,the two prominent members of which are indium selenide(InSe)and gallium selenide(GaSe).In contrast to transition metal dichalcogenides,their high intrinsic mobility and the availability of a direct bandgap at small thicknesses have attracted researchers to investigate the underlying physical phenomena as well as their technological applications.However,the sensitivity of InSe and GaSe to environmental influences has limited their exploitation in functional devices.The lack of methods for their scalable synthesis further hinders the realization of their devices.This review article outlines recent advancements in the synthesis and understanding of the charge transport properties of InSe and GaSe for their integration into technological applications.A detailed summary of the improvements in the device structure by optimizing extrinsic factors such as bottom substrates,metal contacts,and device fabrication schemes is provided.Furthermore,various encapsulation techniques that have been proven effective in preventing the degradation of InSe and GaSe layers under ambient conditions are thoroughly discussed.Finally,this article presents an outlook on future research ventures with respect to ongoing developments and practical viability of these materials.