Temperature and thickness dependence of the sensitivity of nitrogen dioxide graphene gas sensors modified by atomic layer deposited zinc oxide films
Temperature and thickness dependence of the sensitivity of nitrogen dioxide graphene gas sensors modified by atomic layer deposited zinc oxide films
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DOI：
10.1039/c5ra03752b
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发表时间：
2015-03
期刊：
影响因子：
3.9
通讯作者：
Haifen Xie;Keke Wang;Zhiqiang Zhang;Xiaojing Zhao;F. Liu;H. Mu
中科院分区：
文献类型：
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作者：
Haifen Xie;Keke Wang;Zhiqiang Zhang;Xiaojing Zhao;F. Liu;H. Mu
采用原子层沉积法（ALD）制备了氧化锌（ZnO）修饰的化学气相沉积（CVD）石墨烯二氧化氮（NO2）气敏元件，并研究了其灵敏度与温度和ZnO膜厚的关系。发现ALD ZnO修饰石墨烯传感器（ZnO/graphene）在室温下对NO2的异常p型响应可能归因于ZnO薄膜中氧空位与氧之间的反应导致的n到p电导转变。在升高的温度下，ZnO/石墨烯传感器表现出p到n电导转变，并且转变温度从原始石墨烯的200 °C、5个ALD循环和Inm ZnO/石墨烯的300 °C增加到3、5和IOnm ZnO/石墨烯的350 °C。同时，传感器的灵敏度显示出强烈的温度依赖性，对于超薄5 ALD循环ZnO/石墨烯（包括原始石墨烯）的最佳温度为100 °C，对于其他ZnO/石墨烯传感器（ZnO膜厚度≥ 1 nm）的最佳温度为200 °C。这种转变和灵敏度对温度的依赖性可以归因于ZnO/石墨烯中的载流子类型和浓度随温度的变化而变化。此外，在各种温度下，ZnO膜厚度的强灵敏度依赖性也被证明，对于100 °C的相对较低的温度，最佳ZnO膜厚度为5个ALD循环，对于200 °C和300 °C的较高温度，最佳ZnO膜厚度为3 nm。讨论了传感器灵敏度随温度和ZnO薄膜厚度变化的机理。
The Chemical Vapor Deposition (CVD) grown graphene nitrogen dioxide (NO2) gas sensors modified by zinc oxide (ZnO) thin films via atomic layer deposition (ALD) were fabricated and their sensitivity dependence on the temperature and ZnO film thickness was investigated. The anomalous p-type response of the ALD ZnO modified graphene sensors (ZnO/graphene) to NO2 at room temperature was found which might be attributed to the n to p conductance transition due to the reaction between oxygen vacancies and oxygen in the ZnO films. At elevated temperature, ZnO/graphene sensors exhibited p to n conductance transition and the transition temperature increased from 200 °C for pristine graphene, 300 °C for 5 ALD cycles and 1 nm ZnO/graphene, to 350 °C for 3, 5 and 10 nm ZnO/graphene. Meanwhile, the sensors' sensitivity revealed strong temperature dependence with the optimal temperature of 100 °C for ultra thin 5 ALD cycles ZnO/graphene (including pristine graphene) and 200 °C for other ZnO/graphene sensors (ZnO films thickness ≥ 1 nm). Such transition and sensitivity dependence on temperature could be ascribed to the change of carrier type and concentration in the ZnO/graphene with the variation of the temperature. Besides, strong sensitivity dependence on the ZnO film thickness at various temperatures was also demonstrated with the optimal ZnO film thicknesses of 5 ALD cycles for relatively low temperature of 100 °C and 3 nm for higher temperatures of 200 °C and 300 °C. The mechanism responsible for the sensors' sensitivity dependence on the temperature and ZnO film thickness was discussed.