Recently, two-dimensional materials were widely studied as candidates for new generation of photodetectors. In this paper, we reported on the fabrication and the optoelectronic characterizations of p-type gallium selenide (GaSe) back-gated field effect transistor based photodetector. The phototransistor showed excellent gate control capability with an ${\text{I}}_{ON}/{\text{I}}_{OFF}$ value exceeding 10³. The photoresponsivity can be easily tunable to maximum value of 1.4 AW^–1 by changing the gate voltage, however, the photodetector showed the best performance at gate voltage of −18V, with photoresponsivity, external quantum efficiency and detectivity of 0.9 AW^–1, 210% and 8.08 × 10¹¹ cmHz^0.5W^–1, respectively.

Unidimensional photonic crystal-based biosensors have gained much attention in the area of blood glucose measurement. In this paper, we propose two novel designs based on two-dimensional (2D) Van der Waals materials. The first 1D photonic crystal design consists of multilayers of 2D gallium sulfide and 2D muscovite mica [GaS/Mica]^ND[GaS/Mica]^N, and the second design consists of multilayers of 2D gallium sulfide [GaS/G]^ND[GaS/G]^N. We conducted a numerical analysis using the transfer matrix method to investigate the properties of photonic crystals, both with and without defect layers, in order to assess their suitability for biosensing applications. The biosensors’ performances were investigated as a function of glucose concentration, revealing a high sensitivity of 832 nm/RIU, a notable figure-of-merit of 1.46 × 10⁵ RIU⁻¹, a Q-factor exceeding 10⁵, and a minimum limit of detection of 3.4 × 10⁻⁷ RIU. Finally, we modified the [GaS/G]^ND[GaS/G]^Nstructure in order to enhance the sensitivity nearly 5-fold. The proposed biosensors offer the advantage of being label-free, making them promising platforms for the sensitive and reliable detection of blood glucose levels.

It is important to control the microstructure and surface of films to use them in gas sensors. Chemical mechanical polishing (CMP) processing is one of the most useful methods for improving the surface roughness of films. The effects of CMP on the surface morphology of WO3 thin films prepared by the rf sputtering system were investigated in this article. The removal rate of the films increased, and the rms surface roughness decreased with the addition of an oxidizer to the tungsten slurry. Within-wafer nonuniformity was improved to below 5% when oxidizers of 5.0 and 2.5vol%, respectively, were added to the tungsten slurry. The optimized oxidizer concentration, reflected by both the rms roughness values and a hillock-free surface with the good uniformity, was 5.0vol% as shown with atomic force microscopy analysis of thin film topographies. Our CMP results will be a useful reference for advanced technology of thin films for gas sensor applications in the near future.