Yunhao Tong | Searcharxiv

arXiv2026

Composition-Driven Tunable Optical and Electrical Properties in Van der Waals Ferroelectric NbOI2-xClx Alloys

Layered niobium oxide dihalides NbOX2 (X = I, Cl), as a new family of Van der Waals (vdW) ferroelectrics, have attracted extensive attention, while achieving non-volatile modulation of their optical and electrical properties remains challenging, thereby limiting their integration into next-generation nanoelectronics and optoelectronics. Here, we report the controlled fabrication of highly crystalline NbOI2-xClx vdW alloys with composition-driven tunable optical and electrical properties via a chemical vapor transport method. Comprehensive experimental characterization combined with first-principles calculation shows that the crystal lattices, phonon modes, and band structures of NbOI2-xClx can be well tailored, which are distributed between NbOI2 and NbOCl2. Both the amplitude and polarization of second harmonic generation optical signal in NbOI2-xClx exhibit pronounced compositional dependence, offering optical evidence for tunable in-plane ferroelectric characteristic. Moreover, field-effect transistors based on NbOI2-xClx display robust n-type semiconducting behavior, with threshold voltage and carrier mobility precisely modulated through adjustment of I/Cl molar ratio. Furthermore, 2D NbOI2-xClx photodetectors across all compositions exhibit exceptional gate-tunable current on/off ratio and strong polarization-sensitive photo-response. This study thus provides a new vdW ferroelectric material platform with tunable optical and electrical properties, paving the path for its implementation in modern nanophotonics and nanoelectronics.

cond-mat.mtrl-sci↗

arXiv2023

Space-confined solid-phase growth of two-domain 1T'-ReSe2 for tunable optoelectronics

Two-dimensional layered ReX2 (X = Se, S) has attracted researcher's great interest due to its unusual in-plane anisotropic optical and electrical properties and great potential in polarization-sensitive optoelectronic devices, while the clean, energy-saving, and ecological synthesis of highly-crystalline ReSe2 with controlled domains remains challenging yet promising. Here, we develop a novel space-confined solid-phase approach for the growth of high-quality two-domain 1T'-ReSe2 with tunable optoelectronic properties by using pure Re powder film as Re precursor. The results show that ReSe2 can be grown at a temperature as low as 550 oC in a small-tube-assisted space-confined reactor, with its size and shape well-tailored via temperature control. A solid-phase two-domain ReSe2 growth mechanism is proposed, as evidenced by combining in-situ optical monitoring, ex-situ electron microscope and elemental mapping, and polarized optical imaging. Moreover, we have fabricated two-domain ReSe2 transistors, which exhibit switchable transport behavior between n-type and ambipolar character via grain boundary orientation control. This modulation phenomenon is attributed to the different doping levels between the grain boundary and the single domain. Furthermore, the as-fabricated two-domain ReSe2 photodetectors exhibit a highly gate-tunable current on-off ratio (with a maximum value of ~8.2x10^3), a polarization-sensitive photo-response, and a high-speed response time (~300 us), exceeding most of the previously reported ReX2 photodetectors. Our work thus provides a new, low-consumption, energy-saving growth strategy toward high-quality, domain-controlled ReX2 for highly tunable and high-performance optoelectronics.

physics.optics↗