Intrinsic defects and mid-gap states in quasi-one-dimensional Indium Telluride

TL;DR

This study combines STM/STS measurements and DFT calculations to reveal the atomic-scale structure, electronic properties, and defect-induced states in quasi-one-dimensional Indium Telluride, highlighting its potential for electronic and thermoelectric applications.

Contribution

It provides the first direct imaging of one-dimensional In1+ chains in InTe and links defect states to high p-type doping, advancing understanding of 1D quantum materials.

Findings

InTe exhibits a ~0.40 eV band gap at the M point.

Direct observation of In1+ chains and line defects in InTe.

In1+ vacancies induce localized gap states near the VBM.

Abstract

Recently, intriguing physical properties have been unraveled in anisotropic semiconductors, in which the in-plane electronic band structure anisotropy often originates from the low crystallographic symmetry. The atomic chain is the ultimate limit in material downscaling for electronics, a frontier for establishing an entirely new field of one-dimensional quantum materials. Electronic and structural properties of chain-like InTe are essential for better understanding of device applications such as thermoelectrics. Here, we use scanning tunneling microscopy/spectroscopy (STM/STS) measurements and density functional theory (DFT) calculations to directly image the in-plane structural anisotropy in tetragonal Indium Telluride (InTe). As results, we report the direct observation of one-dimensional In1+ chains in InTe. We demonstrate that InTe exhibits a band gap of about 0.40 +-0.02 eV located at the M point of the Brillouin zone. Additionally, line defects are observed in our sample, were attributed to In1+ chain vacancy along the c-axis, a general feature in many other TlSe-like compounds. Our STS and DFT results prove that the presence of In1+ induces localized gap state, located near the valence band maximum (VBM). This acceptor state is responsible for the high intrinsic p-type doping of InTe that we also confirm using angle-resolved photoemission spectroscopy.