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Vacuum Pressure Sensors Based on One-dimensional ZnO and ZnS Nanomaterials

Author: CaoZuoChao
Tutor: ZhengXueJun
School: Xiangtan University
Course: Microelectronics and Solid State Electronics
Keywords: Ⅱ-Ⅳ semiconductor nanomaterials Vacuum pressure sensor Bandtheory Pressure sensitive resistance Oxygen adsorption and desorption
CLC: TP212
Type: Master's thesis
Year: 2013
Downloads: 20
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Abstract


The continuous progress of nanotechnology strongly promotes the micromation,intellengence, and high integration of the micro-and nano-devices, and shows itspotential applications, therefore, nano-materials and nanotechnology have attractedconsiderable attention. ZnO and ZnS nanomaterials are two of the most widelystudied nanomaterials, and both of them belong to the direct band gap semiconductors.Due to the size effect and surface effect, ZnO and ZnS nanomaterials are sensitive tooxygen and can detect the change of oxygen concentration and pressure. With thisconclusion, this work described the preparation and characterization of ZnO/ZnSnanobelts and ZnO nanowires array, and they were fabricated to vacuum pressuresensors based on ZnO/ZnS nanobelts film and ZnO nanowires array withmicroelectronic technology. Current-voltage (I-V) characteristics of the three types ofsensors were tested under different pressure conditions, and the characteristics of theresistance, power, sensitivity and measurement range were analyzed based on the I-Vcharacteristics. With periodical variation of the vacuum pressure, the current-time (I-t)characteristics of the sensors were tested and discussed. Finally, the sensingmechanism of the sensors was reasonably interpreted by oxygen adsorption theoryand band theory. The main works of this thesis are given as below:(1) ZnO and ZnS nanobelts were prepared with thermal evaporation method, andthey could be observed with SEM that they are of flat belt structure, length of tens tohundreds of microns, width of about a few hundred nanometers. The vacuum pressuresensors based on ZnO and ZnS nanobelts film were fabricated by depositing thenanobelts on the interdigital electrodes. ZnO nanowires array was prepared withchemical vapor deposition method, and it can be seen by using SEM that thenanowires are vertically-aligned on the substrate, and of uniform height and diameter.The vacuum pressure sensor based on ZnO nanowires array was fabricated byinstalling electrodes on the top of the array.(2) I-V characteristics of the vacuum pressure sensors based on ZnO/ZnS nanobeltsfilm and ZnO nanowires array were tested under different vacuum pressure. It isfound that the response currents of the three sensors increase with the decreasingpressure, and the response current of the sensor based on ZnO nanowires array isthree orders of magnitude higher than those of the sensors based on ZnO/ZnS nanobelts film. The relationship between resistance and pressure is establishedaccording to the I-V characteristics, and it can be used to monitor the surroundingpressure. All the sensors are of wide measurement range, high sensitivity and lowpower consumption.(3) I-t characteristics of the sensors based on ZnO/ZnS nanobelts film and ZnOnanowires array were tested while the vacuum pressure changed periodically. Theresults show that the response currents periodical variation with the pressure, and theyshow certain lags while the pressure changes rapidly.(4) The sensing mechanism of the vacuum pressure sensors is reasonablyinterpreted by using oxygen adsorption theory and band theory, and they are used toexplain why the response current of the sensor based on ZnO nanowires array is highthan those of the sensor based on ZnO/ZnS nanobelts film.

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