Two-dimensional materials have shown great potential applications in the field of humidity sensors because of their superb body-surface ratio, excellent electrical properties, flexible and transparent properties, etc. Among them, the transition metal chalcogenide represented by molybdenum disulfide has excellent Current switching ratio, mobility and other characteristics for its application in electronic devices may be available.As molybdenum disulfide itself is an n-type semiconductor, so when the surface of the water molecules, the equivalent of their p-type Doped, its electrical properties will show a corresponding change, the use of this principle can be used to detect changes in the external water molecular weight humidity sensor.At present the research of MoS2 humidity sensor is mainly subject to the process itself into the residual adhesive pairs The contamination of the surface of the material affects its adsorption to water molecules, which leads to the problems of low sensitivity and long response time, etc. Therefore, how to obtain a MoS2 sensor with high sensitivity and quick response time has become the most important factor restricting its application major factor.
In response to the above problems, under the guidance of researcher Zhang Guangyu, Dr. Zhao Jing, Institute of Physics, Chinese Academy of Sciences / Beijing Condensed Matter Physics Laboratory (chip) N07 group laboratories using a new method of gold stripping processing has been clean Surface molybdenum disulfide field effect transistor, so as to achieve a sensitive response to water molecules.This processing method is mainly the use of force between the molybdenum disulfide and gold is far greater than the force between the gold and the substrate, which can be Excess sample of molybdenum disulfide is peeled off completely from the substrate while ensuring the cleanliness of the molybdenum disulfide surface for the device. On the one hand, the method effectively avoids the surface after the reactive ion etching The effect of the residue on the device performance, on the other hand greatly simplifies the process, has been obtained with ultra-clean surface molybdenum disulfide field-effect transistor, the optical and electrical properties of a significant increase also proved from another aspect of this processing method The resulting sample has better performance.
Since the molybdenum disulfide field effect transistor obtained by using the gold exfoliation method has an ultra-clean surface, the sensor can sensitively sense the change of the external humidity and greatly improve the sensitivity of the molybdenum disulfide humidity sensor. For the doping effect of water molecules, When the relative humidity changes from 0% to 35%, the resistance has an increase of nearly 104, which is nearly three orders of magnitude higher than that of the previous MoS2 humidity sensor The mobility and the current switching ratio also decrease linearly with increasing humidity.In addition to having ultra-high sensitivity, since the surface of molybdenum disulfide has no dangling bonds and the adsorption of water molecules is purely physical adsorption, the device can easily Desorption, effectively reducing the response time and recovery time, respectively, up to 10s and 60s, and this device has a good recoverability, after a month of testing the initial resistance of the basic unchanged, with a longer Life.In addition, due to CVD growth of molybdenum disulfide uniform film can be processed to obtain a series of excellent performance of the disulfide Molybdenum humidity sensor array, so as to the spatial distribution of different humidity play a role in positioning, used to real-time monitoring of changes in the external humidity distribution.In addition, this highly sensitive molybdenum disulfide humidity sensor on the flexible substrate can still be very Good work, the basic performance is not changed by the application of stress changes, which for future applications in the field of flexible electronic devices may provide.
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 Multi-functional flexible sensor array field. Relevant results published in the "Advanced Materials." This work has been the CAS Class B strategic pilot science and technology projects, the National Natural Science Foundation of funding.
Figure 1. (a) Device Fabrication Process Using Gold Stripping Method. (B) Photodischarge of Molybdenum Disulfide Field Effect Transistor Array Processed on Silicon Oxide Substrate.
Figure 2. (a) Variation in Output Characteristics of Molybdenum Disulfide Field-Effect Transistor with Increasing Humidity (b) Change in Transfer Characteristic with Increasing Relative Humidity (c) Corresponding Relationship between Resistance Variation and Relative Humidity.
Figure 3. Time response of molybdenum disulfide humidity sensor (a) Response time and decay time of molybdenum disulfide humidity sensor for a single humidity pulse are ~ 10s and ~ 60s, respectively (b) Lifetime of molybdenum disulfide humidity sensor test.
(A) When the finger approaches the MoS2 sensor, the resistance of the device increases exponentially as the distance decreases. (B) and (c) show the response of the device array to ambient humidity Distribution of resistance distribution values and calculated relative humidity values.
