Integrated capacitive and resistive humidity transduction via surface type nickel phthalocyanine based sensor

This paper reports the study of an organic semiconductor nickel phthalocyanine (NiPc) based thin film surface-type integrated capacitive and resistive type humidity sensor. The capacitance and resistance of the fabricated devices were evaluated at room temperature in the relative humidity (RH) range of 35-95% and 35-75% RH, respectively. In general, an increase in capacitance and decrease in resistance of the Ag/NiPc/Ag sensor was observed with the rise in humidity level. Humidity dependent capacitance and resistance properties of this sensor make it attractive for use in humidity sensors. The response and recovery characteristic of the humidity sensor were also investigated.Scopu

Capacitive and resistive response of humidity sensors based on graphene decorated by PMMA and silver nanoparticles

In this paper, we reported comparative study of the humidity characteristics of graphene/silver nanoparticles composite (Gr-AgNps) and graphene/silver nanoparticles/PMMA composite (Gr-AgNps-PMMA) based efficient humidity sensors. Aqueous solution of Gr-AgNps and Gr-AgNps-PMMA was drop casted over interdigitated copper electrodes with 50 μm gap embedded in the substrates in dust free environment. The band gap obtained from the UV-vis spectra for Gr-AgNps and Gr-AgNps-PMMA based humidity sensors was 4.7 and 4.1 eV respectively. The capacitive and resistive humidity response was studied using LCR meter (GW Instek817). Apparent increase in capacitance was observed (100-10,000 nF) with the increase in the humidity percentage (30-95%RH) at lower frequencies for both the sensors. Resistance of the sensors dropped to zero as the humidity level is increased from 30 to 95%RH in the chamber. The devices were tested for real time stability and for fast response/recovery time. Both the devices showed an excellent stability and response by recording their resistance and capacitance respectively. A lagging of RH decreasing response from RH increasing response was observed at 500 Hz frequency for both the sensors depicted from the hysteresis curve. The humidity response of Gr-AgNps was comparatively better than that of the Gr-AgNps-PMMA based humidity sensors

Pressure sensitive organic sensor based on CNT-VO2 (3fl) composite

In this paper, fabrication and investigation of organic pressure sensor based on Al/CNT-VO2 (3fl)/Cu composite is reported. The active layer of the composite was deposited by drop-casting of the blend CNT-VO2 (3fl) on a glass substrate (with prefabricated copper (Cu) electrode). The thin film of the blend consists of carbon nanotube CNT, (2.55 wt. %) and vanadium oxide (VO2 (3fl)) micropowder, (3 wt. %) in benzol (1 mL). The thickness of the composite was in the range of 20-40 μm. It was found that the fabricated sensor was sensitive to pressure and showed good repeatability. The decrease in resistance of the sensor was observed by increasing the external uniaxial pressure up to 50 kNm-2. The experimentally obtained results were compared with the simulated results and showed reasonable agreement with each other

Annealing effects on the structural and optical properties of thermally deposited tin antimony sulfide thin films

We report the deposition and characterization of tin antimony sulfide thin films on a soda glass substrate by a thermal evaporation technique. The thin films were annealed in argon gas at 150, 175, and 300 °C inside glass ampoules. The structural and optical properties of the deposited and annealed films are investigated. X-ray diffraction (XRD) patterns show that the films are polycrystalline in structure. Photoconductivity plot revealed good response in the NIR and visible regions, while the films show no transmittance below 700 nm. The absorption coefficient was of the order of 106 cm−1. Optical band gaps were also evaluated and a decrease in band gap was observed due to annealing. Hot point probe technique was employed for type of conductivit

Designing and development of polyvinylpyrrolidone-tungsten trioxide (PVP-WO3) nanocomposite conducting film for highly sensitive, stable, and room temperature humidity sensing

In the present research work, highly sensitive, stable, capacitive type humidity sensor based on polyvinylpyrrolidone and tungsten trioxide (PVP/WO3) nanocomposite was successfully developed. The sensing materials were prepared by using simple ultrasonication method and were characterized systematically through Fourier transform infrared spectroscopy, X-ray diffraction, high resolution transmission electron microscopy. Drop casting technique was used to develop sensing device using interdigitated copper electrode. Humidity sensing properties of PVP/WO3 nanocomposite sensors were investigated thoroughly and compared with pure PVP and WO3 sensors. It was observed that the humidity sensor with 20 wt% WO3 content showed high response of 44.73 nF/%RH, short response (10 s) and recovery time (15 s) as compared to pristine PVP and WO3 sensor. Low hysteresis value of 1.3 % was observed for PVP/WO3 20 wt% nanocomposite sensor along with excellent stability and repeatability