Properties, Synthesis, and Device Applications of 2D Layered InSe

Abstract

Since monolayer graphitic film was successfully exfoliated by using scotch tape in 2004, [3] 2D materials like carbon group, transition metal dichalcogenides (TMDs), and layered metal oxides have received considerable attention and provided brand-new potential in nano-scale electronic devices. [4][5][6][7] Differ from 3D materials, 2D materials possess strong chemical bonds in each layer and weak van der Waals (vdW) forces between the adjacent layers. [8] The monolayer and fewlayer sheets of 2D layered materials can be obtained via various synthesis methods such as micromechanical exfoliation, [9] liquid exfoliation, [10] and chemical vapor deposition (CVD). [7] Due to the weak vdW force, the thermal and lattice mismatches between different materials become insignificant, which is conducive to construct heterostructure. [11][12][13] Additionally, there are no dangling bands on the 2D material surface owing to the sheet structure, thus such an excellent feature allows carrier scattering to be largely eliminated compared to bulk semiconductors. Besides, the inherent ultrathin properties enable the enhanced gate modulation effect, mitigating SCEs. All these remarkable merits of 2D materials render them promising candidates for sub-10 nm FETs. [14][15][16] Furthermore, 2D layered structure materials with high surface area, flexibility, unique optical and electronic properties are also potentially feasible for application in micro-electromechanical systems (MEMS), optoelectronics, biosensors, super capacitors, and solar cells. [7,[17][18][19][20][21] Van der Waals layered indium selenide (InSe) is an emerging star of the 2D semiconducting materials because of its excellent fundamental properties, such as ultrahigh carrier mobility, layer-tunable bandgap, large elastic deformability, and rich polytypes. In addition, 2D layered indium selenide has demonstrated outstanding device performance including photodetector, fieldeffect transistor, memory and synapse, mechanical and gas sensor, which has offered a new chance to next-generation electrical and optoelectronic devices. This review presents a comprehensive summary of recent progress in 2D layered indium selenide. The novel fundamental properties and synthetic methods are summarized. Also, the indium selenide-based stateof-the-art electronic/optoelectronic devices, such as a functional field-effect transistor, photodetector, and mechanical and gas sensors are systematically summarized. The techniques to enhance the performances of devices are also discussed. Finally, a brief discussion on the challenges and future opportunities as a guideline for this field is provided.

Formation of 2D-Structured InSe Ceramics from Amorphous Phase Deposited on a Kapton Foil

“…The amorphous spectrum shows a typical broad band at ∼103 cm –1 . The majority of the InSe films deposited on the Kapton foil and crystallized in the DSC cell exhibit bands characteristic of the γ-InSe crystalline phase: A 1 1g at 114 cm –1 , E 1 2g at 177 cm –1 , A 1 1g (LO) at 200 cm –1 , E 1 2g (LO) at 210 cm –1 , and A 2 1g at 225 cm –1 . ,,, The Raman spectra obtained for samples with slow crystallization rates are recognizably better evolved, which suggests a higher structural uniformity of the crystalline phase. All the spectra of the DSC-crystallized InSe films displayed in Figure A also do not show signals suggestive of the amorphous phase being present.…”

“…are of paramount importance. The synthesis of ideally 2D-layered InSe material may be challenging, considering the complicated In–Se phase diagram, the number of InSe polymorphic phases (β, γ, and ε), , and the sensitivity of InSe to ambient conditions. , Despite the 2D-functional InSe films being formed almost exclusively by the crystallization of the amorphous phase, there are only few, rather qualitative, reports on the actual crystal growth kinetics during the heat-induced amorphous-to-crystalline transformation. , This may be due to the inability to accurately measure/record the in situ crystallization process for the as-deposited thin films. Note that the most common way to study the crystallization kinetic measurements is to employ differential scanning calorimetry (DSC) for films scraped off of a substrate.…”

“…Indium selenide (InSe) has recently become a major focus of research on 2D semiconducting materials. 1 The structure of 2D materials is characterized by strong chemical bonds within the layer and weak van der Waals bonds between neighboring layers. This type of atomic arrangement leads to a reduction in the importance of thermal processes and interface lattice mismatch in the growth of heterostructures in the absence of dangling bands, leading to the reduced scattering of carriers.…”

Uniaxial Strain Dependence on Angle-Resolved Optical Second Harmonic Generation from a Few Layers of Indium Selenide

“…Since van der Waals materials can be mechanically exfoliated and transferred to arbitrary substrates, including bendable polymeric or plastic substrates, studies of the strain-dependent properties of 2D materials are therefore beneficial for the development of flexible devices [ 4 , 5 ]. Indium selenide (InSe) is an emerging star in van der Waals semiconductors [ 6 ] due to its superior properties such as ultrahigh mobility [ 7 , 8 ] and large elastic deformability [ 9 , 10 ]. It has been applied to bendable photodetectors with a good performance and a broad spectral response [ 11 ].…”

Ultrafast carrier dynamics and layer-dependent carrier recombination rate in InSe

“…6,7 In recent years, InSe has attracted renewed attention and the layer dependence of electrical, optical, and mechanical properties has been investigated. 8 2D layered InSe has demonstrated excellent performance for nanoscale devices such as field-effect transistors with high mobility 9 and photodetectors with high gains and broad-band spectral responses. [10][11][12][13] The carrier mobility of atomically thick InSe was demonstrated to exceed 10 3 cm 2 V −1 s −1 at room temperature 9,14 and could be even higher than 10 4 cm 2 V −1 s −1 at liquid helium temperature.…”