NH3

Sensor materials with significant sensitivity, selectivity, and limit of detection (LOD) play a crucial role in monitoring and control of industrial process and environmental pollution. Herein density functional theory and ab initio molecular dynamics simulation are used to identify a hexagonal Be 2 P 4 ( h ‐Be 2 P 4 ) monolayer as a new sensor material for toxic gases. Adsorption properties of 10 target gases (CO, NO, NO 2 , SO 2 , H 2 S, NH 3 , PH 3 , AsH 3 , COCl 2 , and HCN) and three environmental gases (N 2 , CO 2 , and H 2 O) are investigated. The results demonstrate that the h ‐Be 2 P 4 ‐based sensor behaves with significant sensitivity, high selectivity, short recovery time, and fine adsorption stability for all target gases in the presence of CO 2 and N 2 . The presence of H 2 O decreases the selectivity partially. Nevertheless, the LODs imply that the h ‐Be 2 P 4 ‐based sensor can only detect six target gases in increased LOD order: NO 2  < NH 3  < HCN < SO 2  < CO < PH 3 at 298.15 K. The low detection limits are found to be 7.3 × 10 −10 , 2.14 × 10 −6 , and 14 ppm for NO 2 , NH 3 , and HCN, respectively, which are substantially lower than half of the corresponding immediately dangerous to life or health (IDLH) limits, demonstrating an excellent sensor performance to detect NO 2 , NH 3 , and HCN.

This study presents a synergistic patterning technique integrating directed self-assembly lithography (DSA) and sequential infiltration synthesis (SIS) to fabricate silicon nanowires with small critical dimension, high aspect ratios, and high density on silicon-on-insulator (SOI) substrates. Through optimization of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) guiding templates and SIS cycles, polymer templates were in situ converted into aluminum oxide (Al₂O₃) hard masks with high etching selectivity. Coupled with a single-layer silicon dioxide (SiO₂) intermediate mask strategy, this approach significantly simplifies the device fabrication workflow while leveraging the flexibility of SiO₂ etching to achieve progressive scaling of silicon nanowires. Focused ion beam-transmission electron microscopy (FIB-TEM) characterization confirmed nanowire profiles with a top width of ∼6.6 nm, bottom width of ∼14.9 nm, pitch of 28 nm, and height of ∼53.5 nm, which are further used in multiple applications. The exposed sub-10 nm silicon nanowire channels exhibited ultrasensitive gas-sensing capabilities, demonstrating a 49.8% response to 2.5 ppm ammonia (NH₃), significantly outperforming conventional NH₃ sensors. The silicon nanowire was further combined with a high-k/metal gate process to demonstrate its application in fin field-effect transistors (FinFETs). The device shows a switching ratio exceeding 10⁷ and a subthreshold swing as low as 69.59 mV/dec, demonstrating exceptional electrostatic control of the Fin channel fabricated by the DSA-SIS process. This work not only provides a cost-effective manufacturing solution of high-density silicon nanowires but also demonstrates the application potential of DSA-SIS technology in semiconductor devices with a nanostructure for both sensing and integrated circuit operations.