Priyanka Kakoty

This paper presents a simple method to fabricate a vertical closed membrane structured gas sensor on silicon substrate using micromachining technology for methanol detection at lower concentration. An undoped tin dioxide thin film is deposited by DC magnetron sputtering technique on a pair of gold interdigitated microelectrodes of dimension 820 µm ´ 925 µm. A meander shaped platinum micro heater of dimension 1025 µm ´ 1000 µm is incorporated to provide optimum operating temperature (about 350 0C) for sensing operation. Energy dispersive X-ray spectroscopy is done to confirm the chemical composition of the sensor. Temperature coefficient of resistance of the inbuilt micro heater is found to be 0.0941 /0C. The sensor resistance shows significant change when micro heater voltage is varied from 1.5 V-3 V. I-V analysis of the sensor is carried out at 25 0C, 50 0C and 75 0C, and shifts in current through the sensor at different temperatures are observed. I-V characterization is also carri...

A method is presented in this paper for the design of a high frequency CMOS operational amplifier (Op-Amp) which operates at 3V power supply using tsmc 0.18 micron CMOS technology. The OPAMP designed is a two-stage CMOS OPAMP followed by an output buffer. This Operational Transconductance Amplifier (OTA) employs a Miller capacitor and is compensated with a current buffer compensation technique. The unique behaviour of the MOS transistors in saturation region not only allows a designer to work at a low voltage, but also at a high frequency. Designing of two-stage op-amps is a multi-dimensional-optimization problem where optimization of one or more parameters may easily result into degradation of others. The OPAMP is designed to exhibit a unity gain frequency of 2.02GHz and exhibits a gain of 49.02dB with a 60.5 0 phase margin. As compared to the conventional approach, the proposed compensation method results in a higher unity gain frequency under the same load condition. Design has b...

An approach is made in this work to analyze sensitivity drift in a Pd doped SnO 2 sensor developed for detection of linalool, a significant aroma compound in tea.  Prior to the drift analysis, an attempt is made to choose the optimum loading percentage of Pd in SnO 2 for linalool sensing.  An inexpensive and simplistic hydrothermal method is used to develop five different Pd doped SnO 2 sensors (0.5 wt%, 2 wt%, 5 wt%, 6 wt% and 8 wt%) and compare their sensitivities when exposed to linalool vapour. The analysis shows that 6 wt% exhibits better sensitivity (62.7%) towards Linalool at a relatively lower temperature (100 0 C) as compared to all the other synthesized sensors. Henceforth, extensive experiments were performed on the 6 wt% Pd doped SnO 2 sensor for a period of one month to analyze its stability. Relative standard deviation and principal component analysis based drift analysis are performed to understand its changing attributes under repeated measurements.

SnO2 based sensing nano-material have been synthesized by simple chemical route using Stannic (IV) chloride-pentahydrate (SnCl4.5H2O) as precursor. The structural properties of the prepared SnO2 nano-particles annealed at different temperatures have been characterized by X-ray diffraction (XRD) analysis. The XRD patterns showed pure bulk SnO2 with a tetragonal rutile structure in the nano-powders. By increasing the annealing temperatures, the size of crystals were seen to increase, the diffraction peaks were found narrower and the intensity was higher. SnO2 films prepared by spin coating the prepared nano-material solution was tested at different temperatures for methanol vapour and it showed that the film prepared from SnO2 powder annealed at 500 °C shows the higher sensitivity to methanol vapour at 150 °C substrate temperature with significantly low response and recovery time.

This paper reports development of a robot that can sense the presence of hazardous gases in the environment. The robot aims at detection of hazardous gases and mapping global positioning system (GPS) locations of the detected gases to the navigation terrain in real-time. These information was transmitted to a hand-held device in a remote location for exploration of gas types, which holds promise for disaster management. The robot was equipped with a module of gas sensors, human detection sensor, GPS module and obstacle detection sensors in a coherent system. While navigating with collision avoidance to obstacles, the robot can transmit information about the presence of hazardous gases and human being in the area of navigation. It was tested in an uneven terrain to recognize the presence of hazardous gases like carbon dioxide, liquefied petroleum gas, vaporized alcohol gas vis-a-vis ambient gases in real-time. A ´ neural network-based classifier was implemented to recognize the gases...

SnO2 based MOS gas sensors are most popular for sensing a wide range of gases. Selection of a gas sensing material is crucial due to the fact that selectivity is an important characteristic for designing efficient gas sensing devices. An approach is made in this paper to analyze the advantages and disadvantages of SnO2 emphasizing on its fabrication process, adsorption chemistry, structure, material and dopants. Prior works has been discussed to encompass SnO2 as an efficient gas sensing material.

The purpose of this work is to design, simulate, and to evaluate the performance of a low power microheater for a gas sensing system. A microheater is a microstructure incorporated in a MOS gas sensor in order to elevate the temperature of the sensor to an operating range for the reliable performance of a gas sensor. An approach is made in this work to find an optimized microheater structure by considering different membrane sizes and geometries and taking into account the temperature distribution and power consumption problems. The materials used for the analysis are Platinum and Polysilicon. After analyzing various microheater designs, a novel design is developed by optimization and varying geometry, layer dimension, and materials of the device. For the developed design, thermal profile and power consumption analysis are carried out. The entire work is carried out in COMSOL MULTIPHYSICS 4.2.

A facile hydrothermal method was employed to synthesize a Pd doped SnO2 gas sensor. The sensor was experimented with four significant chemicals present in tea at four different operating temperatures. It is observed that the sensor could be used for linalool detection which is an important compound of black tea, responsible for its flavor. The optimum operating temperature is found to be 150 °C at which the sensor showed most favorable sensitivity, response time, and recovery time. Extensive experiments were carried out with different concentrations of linalool gas and the resistance variation of the sensor was observed with variation in gas concentration. The physical characteristics of the sensor were comprehended via X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, and atomic force microscopy analysis.

The work presented here focuses on the synthesis of Ag doped SnO2 based metal oxide semiconductor gas sensor using co-precipitation method and its performance evaluation towards some vital compounds responsible for the appealing aroma in tea. The sensor is tested to evaluate its response towards four noteworthy compounds (linalool, geraniol, methyl salicylate and trans-2-hexenal) present in the aroma matrix of black tea under diverse working temperature conditions. The prepared Ag doped SnO2 gas sensor exhibits improved sensitivity at a comparatively lesser working temperature (150°C) than the undoped SnO2 gas sensor. The proposed Ag doped sensor yields the highest sensitivity towards methyl salicylate(64.69%), an organic ester naturally synthesized by tea plants and is found in green, oolong and black tea. The physical characterization of the sensing material is carried out using XRD(x-ray diffraction), EDS(Energy dispersive X-ray spectroscopy) and SEM (scanning electron microscope...

—Microheater is a key element of a metal oxide semiconductor (MOS) gas sensor. Design and electro-thermal analysis of a platinum based microheater is presented in this work. The microheater was designed to achieve uniform heating over asensing area of 825µm ×1000µm. An electro-thermal finite element method (FEM) analysis was used to perform the Joule heating analysis of the microheater using COMSOL Multiphysics4.3. The geometric optimization of the microheater was carried out to obtain the optimum dimensions required for the application. The temperature profile of the microheater was analyzed and uniform heating was found across the active area with the temperature of 360 0 C, which is very decent for SnO 2 based gas sensor applications, when 2V is applied at the heater terminals. At the time of operation, the consumption of power is only 2.55mW which makes the design suitable for low power applications too.