Shinya Ohno | Searcharxiv

arXiv2026

Optical Signature of Bias-Induced Carrier Injection in a WSe2/MoS2 Heterostructure Diode

We investigate the bias-dependent photoluminescence (PL) response of a WSe$_2$/MoS$_2$ heterostructure diode. Under forward bias, trion-related emission in WSe$_2$ is markedly enhanced, whereas reverse bias produces minimal spectral changes. This asymmetric response cannot be explained by electric-field effects alone and instead reflects carrier injection at the functional interface. These results demonstrate that PL provides a direct optical probe of carrier injection in an operating van der Waals heterostructure. More broadly, this approach establishes spatially resolved PL spectroscopy as a versatile tool for pinpointing the interfaces governing device operation in van der Waals heterostructures.

cond-mat.mtrl-sci↗

arXiv2023

Emergence of metallic surface states and negative differential conductance in thin $β$-FeSi$_2$ films on Si(001)

The electronic properties of the surface of $β$-FeSi$_2$ have been debated for a long while. We studied the surface states of $β$-FeSi$_2$ films grown on Si(001) substrates using scanning tunnelling microscopy (STM) and spectroscopy (STS), with the aid of density functional theory (DFT) calculations. STM simulations using the surface model proposed by Romanyuk et al. [Phys. Rev. B 90, 155305 (2014)] reproduce the detailed features of experimental STM images. The result of STS showed metallic surface states in accordance with theoretical predictions. The Fermi level was pinned by a surface state that appeared in the bulk band gap of the $β$-FeSi$_2$ film, irrespective of the polarity of the substrate. We also observed negative differential conductance at $\sim$0.45 eV above the Fermi level in STS measurements performed at 4.5 K, reflecting the presence of an energy gap in the unoccupied surface states of $β$-FeSi$_2$.

cond-mat.mtrl-sci↗