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.Comment: n