We demonstrated capacitive-type chemical sensors (chemicapacitor sensors) based on two-dimensional (2D) tungsten diselenide (WSe2). The integration of 2D materials with high surface-to-volume ratios and a capacitor resulted in excellent chemical sensing with high selectivity, high sensitivity, and fast response. WSe2-based 2D chemicapacitors were fabricated by combining exfoliated WSe2 flakes with parallel-plate capacitors. The sensing ability of WSe2-based 2D chemicapacitors towards NO2 molecules was characterized by monitoring the changes in capacitance (ΔC/C0, ∼65%) and parallel resistance (ΔRp/Rp0, ∼−90%) due to the adsorption of NO2 molecules (200 ppm). Transient sensing characteristics with fast response and recovery were achieved with adequate reproducibility. Interestingly, ΔC/C0 and ΔRp/Rp0 exhibited different behaviors, which can be a useful value for distinguishing between different target gas molecules. Our novel approach provides a convenient and effective method for producing 2D chemicapacitor sensors at low cost and with low power consumption.

Conventional solar-blind photodetectors based on the conduction of photoexcited carriers are energy inefficient owing to the power dissipation caused by a resistive sensing mechanism and the narrow bandgap energy of the photon-absorbing layer. Herein, we demonstrate the energy-efficient capacitive sensing of deep-UV wavelengths by integrating an intrinsically solar-blind ultrawide bandgap (UWBG) β-Ga2O3 semiconductor with UV-transparent and conductive graphene electrode. A UWBG β-Ga2O3 eliminates the requirement of a solar-blind deep-UV bandpass filter. The high optical transmittance of the graphene enables UV-C light to be absorbed in the underlying β-Ga2O3, thereby facilitating carrier transport between the graphene electrode and β-Ga2O3. A capacitance change under UV-C excitation is observed, along with excellent reproductivity and spectral selectivity at various frequencies and bias conditions; the sensing performance improves with an increase in frequency. The average power dissipation of the fabricated photodetector in the stand-by (dark) and active (UV-C illumination) modes is 37.7 and 53.3 μW, respectively. Overall, this work introduces a new strategy for developing next-generation compact and energy-efficient solar-blind photodetectors.

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