Controlled Crystal Growth of Indium Selenide, In₂Se₃, and the Crystal Structures of α-In₂Se₃

Abstract

InSe has been known for over 100 years and recently attracted interest as a promising candidate for a variety of applications, such as solar cells, photodiodes, and phase-change memories. Despite the broad concern for possible uses, its polymorphism and structure are poorly characterized. By combining X-ray diffraction, transmission electron microscopy, and quantum-chemical calculations, we present here the crystal structures of two layered room-temperature polytypes: 3R and 2H InSe. Both polymorphs are stacking variants of the same Se-In-Se-In-Se layers comprising two coordination environments for the In atoms, one tetrahedral and one octahedral. By using chemical-bonding analysis, we look at the different In positions in α-InSe and compare them to those in the metastable β-phase.

Exploring Chemical Bonding in Phase‐Change Materials with Orbital‐Based Indicators

“…Competition between different crystalline structure types, understood using orbital‐based bonding analyses: a) Interpreting the existence of unconventional, homopolar GeGe bonds for Ge 4 Se 3 Te in two different structures, the experimentally observed hexagonal P 6 3 mc type and a rhombohedral R 3 m type known from α‐GeTe, and b) understanding the coordination polyhedra in different In 2 Se 3 phases . Panel (a) adapted from Ref.…”

“…Panel (b) adapted under the terms of an ACS AuthorChoice License from Ref. ; Copyright 2018, American Chemical Society.…”

“…However, the α‐phases of In 2 Se 3 are also interesting candidates, because they show a remarkable coexistence of tetrahedrally and octahedrally coordinated In atoms in a layered structure. To understand the plethora of possible coordination environments for this seemingly simple binary compound, chemical‐bonding as well as charge analyses were employed (Figure b) . Compared to PCMs on the quasi‐binary GeTe–Sb 2 Te 3 line, all In 2 Se 3 structures show almost no antibonding levels below ϵ F .…”

“…Traditionally used PCMs such as the Ge–Sb–Te phases (Figure ) are not strongly influenced by ionicity because the electronegativity differences between, say, Ge and Te are very small. Still, switching coordination environments as controlled by Coulomb interactions may play an important role to understand the structure of new PCM candidates, such as In 2 Se 3 as discussed in Section 3.3 . Chemical bonding analysis using a local basis set (or projection of plane‐wave output into a local basis) allows the user to calculate accurate atom‐ and orbital‐resolved DOS, but it also enables charge analysis based on Mulliken's and Löwdin's population analysis .…”

Growth of vertical heterostructures based on orthorhombic SnSe/hexagonal In2Se3 for high-performance photodetectors

“…33 They found the degree of anisotropy of ReS 2 on WS 2 largely depends on the domain size, which is a signicant leap forward for the large-scale nanomanufacturing of anisotropic systems. [35][36][37][38][39][40] Recently, the n-type In 2 Se 3 is becoming one of the promising materials for detecting visible light due to its direct and narrow band gap (1.95 eV) and high absorption coefficient in the visible range. [41][42][43][44][45][46] In this study, by combining orthorhombic SnSe and hexagonal In 2 Se 3 , a new vertical heterostructure was prepared via a simple two-step PVD method.…”