Capacitive Mode Methanol Sensing by ZnO Nanorods Based Devices

Abstract

Abstract-Capacitive mode methanol sensing performance of ZnO hexagonal nanorods based MIS devices having diameters of 40-60 nm and lengths of 460-480 nm, is reported in this paper. ZnO nanorods were synthesized on p-Si substrate by chemical bath deposition method (CBD) using 50 ml aqueous solution of Zinc acetate dihydrate and HMT. The as deposited sensor with Pd catalytic contact in metal-insulator-metal (MIS) configuration offered 99% response magnitude (RM) in the temperature range of (300-325) º C towards 700 ppm methanol concentration. The response time (Rs:140s) and recovery time (Rc:110s) of the methanol sensor at 325º C were also obtained. The sensor was able to detect methanol even down to 10 ppm.Index Terms-Capacitive sensor, CBD, ZnO hexagonal nanorods, methanol sensing. I. INTRODUCTIONRecent advances in nanomaterials provide the opportunity to dramatically increase the response of these materials, as their performance is directly related to exposed surface volume. Detection of toxic and flammable gases is a subject of growing significance in both domestic and industrial environments [1]. Various air pollutants coming from industrial plants, households or automobiles should be controlled in order to keep them below a safe level. This has motivated the researchers to develop various types of gas sensors based on different principles. The conductometric semiconducting metal oxide gas sensors currently constitute one of the most investigated groups of gas sensors. Metal-insulator-semiconductor (MIS) structure attracts the interests as its capacitance (based on surface space charge of semiconductor) is delicately influenced by effective voltage applied on metal electrode for detecting combustible, reducing, or oxidizing gases by conductive measurements [2] The gas sensors used noble metal electrode as a sensing material. The following oxides show a gas response in their conductivity: Capacitive-type sensors have good prospects given that the capacitor structure is so simple enabling miniaturization and achieving high reliability and low cost. In addition, amplification of capacitance is easily performed by oscillator Manuscript

Synthesis and Fabrication of ZnO Nanorods on Silicon for Methanol Gas Sensor

“…It can also be seen from Figure 14 that the response and recovery time at methanol gas concentration of 200 ppm and temperature of 200 °C, are the 60s and 80 s, respectively. These values were found to be quite consistent with the reported data at 200 ppm and even at a higher temperature (300 °C) [43].…”

Hydrothermal Growth of Zinc Oxide (ZnO) Nanorods (NRs), Structural, and Chemical Composition Studies for pH Measurement Sensor Applications

“…One-dimensional (1D) Zinc oxide (ZnO) which have a direct wide band gap (3.37eV) semiconductor with a large excitation binding energy (60 meV) at room temperature. They have attracted considerable attention because of their potential application in different area (15), ZnO Nanorods (NRs) has been applied in various applications, such as in light-emitting diode, optoelectronics application (16)(17) gas and chemical sensors (18)(19)(20)(21), capacitive sensors (22) dye-sensitized solar cell (23)(24)(25)(26) and biosensors (27)(28).…”

“…Varying the precursor material, solvents and annealing temperature the different type of ZnO nanostructures can be formed, such as nanowires (NWs) (28,33), nanoflakes (34), nanorods (35), nanobelts (36), and nanotubes (37). NRs based miniaturized pH sensor (38) ultrasensitive nanosize Schottky junctions formed within bottom-up grown dopant-free arrays of assembled silicon NRs pH Sensors(39), Metal oxide-based electrochemical pH sensor (40), ZnO NRs based capacitive methanol sensing (22), humidity sensors (41) and Printed Flexible Electrochemical pH Sensors are reported (42).…”