Intrinsic Dual-Phase Regulated GeSe₂ Nanoparticles Triggered by Ball-Milling Treatment for Photonic Multi-Valued...

Germanium diselenide (GeSe₂), a binary IV-VI chalcogenide material, holds immense potential for ultra-violet (UV) optoelectronics due to its exceptional light-absorption efficiency and chemical stability. Among the existing polymorphs, including α-, β-, and γ-GeSe₂, the β phase with layered features standing to the relatively thermodynamic stable configuration has been investigated, whereas the photodetection feasibility is limited within the UV spectral regions. We affirm the phase engineering to transform the single-crystallite β-GeSe₂ bulk crystals into the air-stable β/α GeSe_2-x nanoparticles, where the formation of the α-GeSe₂ phase triggered by the solid-state ball milling has never been experimentally revealed. From investigating the conduction mechanism, characterizing the photophysical origin, and uneviling the band features, the mediations of dual trap states are validated to access the β to α phase transformation and morphological change. The hybrid photodetector design, by means of incorporating PMMA coating with GeSe_2-x nanoparticles, features the light-power-resolved characteristics and exceptional photodetection performance upon detecting the visible 525 nm light, with a flicker noise amplitude of 4.5 × 10^-12 A Hz^-1/2 and response time/decay time of 9.6/6.7 µs. We further showcase the photonic multi-valued logic circuits triggered by the light-power modulation, enabling the optical ternary NOT gate to perform the logic inversions for ternary levels.