Due to its high surface area ratio, excellent electrical properties, flexible and transparent properties, 2D materials have shown great promise in the field of humidity sensors. Among them, the transition metal chalcogenide, represented by molybdenum disulfide, possesses the possibility of its application in electronic devices because of its excellent current switching ratio, mobility and other characteristics. Since molybdenum disulfide itself is an n-type semiconductor, when its surface adsorbs water molecules, it is equivalent to p-type doping, its electrical properties will show a corresponding change, the use of this principle can be used to perceive Moisture sensor for changes in molecular weight of water in the outside world. At present, the research of MoS2 humidity sensor is mainly affected by the contamination of the surface of the material caused by the remnant glue introduced by the processing itself, which affects the adsorption of water molecules, resulting in the problems of low sensitivity and long response time. Therefore, how to get a highly sensitive and fast response time molybdenum disulfide humidity sensor to become the most important factor restricting its application.
In response to the above problems, Dr. Zhao Jing from the Institute of Physics, Chinese Academy of Sciences / N07 group at the Laboratory of Nanophysics and Devices, Beijing Condensed Matter Physics Laboratory under the guidance of researcher Zhang Guangyu used a new gold stripping method to obtain a surface with a clean surface Molybdenum disulfide field effect transistor, in order to achieve a sensitive response to water molecules. This processing method is mainly to use the force between the molybdenum disulfide and gold is far greater than the force between the gold and the substrate so that the excess sample of molybdenum disulfide can be completely stripped from the substrate while at the same time The surface of molybdenum disulfide used for the device clean, the use of this method on the one hand to effectively avoid the process of reactive ion etching after surface adhesive on the performance of the device, on the other hand greatly simplifies the process has been obtained The ultra-clean surface molybdenum disulfide field-effect transistor, the optical and electrical properties of the significant increase from another aspect of this process has proved that the sample obtained with better performance.
Since the molybdenum disulfide field-effect transistor obtained by using the gold peeling method has an ultra-clean surface, the invention can sense the change of the outside humidity sensitively and greatly improve the sensitivity of the molybdenum disulfide humidity sensor. For the doping effect of water molecules, the current of the device decreases obviously with the increase of humidity. When the relative humidity changes from 0% to 35%, the resistance increases by nearly 104. Compared with the previous molybdenum disulfide humidity sensor Research has increased by nearly three orders of magnitude, and the corresponding mobility and current switching ratio also decrease linearly with increasing humidity. In addition to its ultra-high sensitivity, the adsorption of water molecules on the surface of MoS2 is purely physical adsorption due to the absence of dangling bonds on the MoS2 surface, so the device can be desorbed easily and the response time and recovery time are effectively shortened, respectively 10s and 60s, and this device has a very good recoverability, after a month of testing the initial resistance of the basic unchanged, with a longer life. In addition, due to the uniform growth of molybdenum disulfide film grown by CVD, a series of molybdenum disulfide humidity sensor arrays with excellent performance can be processed to locate the spatial distribution of different humidity in the outside world for real-time Monitor changes in humidity distribution outside. In addition, the MoS2 humidity sensor with ultra-high sensitivity can work well on a flexible substrate, and its performance is basically unchanged from the change of applied stress, thus providing the field of future application in the field of flexible electronic devices may.
This ultra-clean surface molybdenum disulfide sample processing humidity sensor with high sensitivity, response time and recovery time is short, long life, high spatial resolution characteristics, can be widely used in the future non-contact positioning system and two-dimensional material Multifunction flexible sensor array field. This work has been funded by the pilot project of Chinese Academy of Sciences (B) (XDB07000000) and the National Natural Science Foundation of China (61325021).
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