ABSTRACT
We report the fabrication of two terminal and three terminal gas sensor using Al-doped ZnO nanostructured-films and polymer electrolyte gate dielectric on glass substrate using vacuum free chemical method. The Al doped ZnO films are characterized by UV-vis Spectrometer, SEM, EDX and XRD. The characterization results have revealed the polycrystalline structure of both undoped and doped ZnO; with loosely packed, porous, and spherical granny nanostructure with mean grain size 20-10 nm and bandgap of the films is within the range of 3.12-3.16 eV. The conductivity of the ZnO film is tuned by Al concentration and the maximum value of conductivity was observed in 3 % Al doped ZnO films. Similarly, the best performance index of TFT such as current ON/OFF ratio, high transconductance and low threshold voltage was observed in 3 % Al doping concentration. The ordinary (two-terminal) sensor and three-terminal (FET) sensors' responses towards three different concentrations 50, 250, 500 ppm of ethanol and methanol vapors have been studied. The sensitivity of the film is modulated by Al concentration and higher value of sensitivity was achieved at 3 % Al doped ZnO films. The use of polymer electrolyte enhanced the sensitivity of the device which is more effective in methanol vapor. The Response-Recovery time of the sensor is significantly improved in three terminal devices than the two terminal devices.
ABSTRACT
Nanostructured Zincoxide thin-film is widely used as a sensing material because of its tunable surface microstructure and wide optical bandgap but synthesizing a film with desired value of resistance and reproducibility of film is challenging, particularly by chemical method. In this work, we showed how a ZnO film of arbitrary resistance can be used as a sensor without application of heat using operational amplifier. Zinc oxide thin film was synthesized by using the Sol-gel method (Spin coating) and was characterized by XRD and SEM which revealed wurtzite polycrystalline nature of Zinc oxide film with average grain size 17-25 nm. In this report, we designed a noble electronic circuit capable of detecting analyte gas molecule even if very small change in film resistance occurs due to the influence of gas molecule. In recently available sensors, the quality of the film degrades over time due to repeated heating and cooling, resulting in a reduced lifetime for the sensor. To address this issue and achieve higher sensitivity, as well as to fabricate an affordable, portable, precise, energy-efficient and durable device, this electronic model offers advantages over classical temperature-dependent sensors.
ABSTRACT
AIM: The present study attempted to find out the relationship between positive and negative clinical symptoms and Wisconsin Card Sorting Test (WCST) performance in a group of schizophrenia patients. METHODOLOGY: Fifty schizophrenia patients were assessed using the Positive and Negative Syndrome Scale (PANSS) by a trained psychiatrist (TKA) and two groups, each of 25 positive symptom and 25 negative symptom schizophrenia patients were formed. On these fifty patients with schizophrenia and 15 normal control groups, WCST measures were applied by a clinical psychologist (SS) who remained blind to the PANSS score. RESULTS: Schizophrenia diagnosis significantly affects WCST performances. One-way analysis of variance (ANOVA) revealed schizophrenia patients showed a significant impairment on all WCST indices compared with normal subjects except versus total number of correct responses. Post hoc comparison (Tukey HSD Test) between means revealed that negative schizophrenia patients showed significantly worse performance on most WCST performance parameters: percent errors, perseverative responses, percent perseverative responses, perseverative errors, percent perseverative errors, and conceptual level responses. CONCLUSIONS: Both positive and negative symptom schizophrenia patients have some distinct WCST measures deficits.
