The Development Of Single Layer Graphene Based Gas Sensor

The successful preparation of graphene breaks the long-standing prediction that two-dimensional crystal materials cannot stably exist due to thermal fluctuations,which greatly encouraged the enthusiasm of researchers to investigate graphene and promoted the progress of low-dimensional nanoscience and technology.Graphene has excellent electrical properties,unique band structure,ultra-high carrier mobility,good thermal conductivity and high mechanical strength.Therefore,it has enormous application prospects in many fields such as materials,physics,chemistry,biology,energy and information.To control the air pollution and ensure the human health and survival,the real-time environmental monitoring has become more and more important in daily life.In recent years,the application of graphene materials in the field of gas sensors has emerged as a hot issue,due to its excellent properties such as ultra-high carrier mobility,ultra-high specific surface area and extremely low resistivity.Although great progress has been made in the study of graphene,there are still many problems in the growth mechanism and the practical applications of gas sensors based on graphene and its derivatives that need to be solved.Therefore,the gas sensing properties of gas sensors based on CVD graphene films have been investigated in this thesis.The main contents and research results of this thesis have the following aspects:To explore the growth process,the important factors of graphene growth such as growth temperature,growth time and gas ratio were studied and analyzed.The large-area high quality single layer graphene was synthesized by optimizing the growth process.The graphene film were transferred on the Si O₂/Si substrate and sensors were fabricated using micro-nano processing technology.Based on the requirements of the gas sensing test,we designed and built a sensing measurement platform.The platform mainly includes multi-concentration gas configuration system,test chamber and data acquisition and processing software.The target gas concentration ranges from 10 ppb to 1%.The temperature of the sample stage in the test system can be adjusted from RT to 150°C.In order to study the effect of ultraviolet radiation on the performance of graphene gas sensor,UV-LEDs with four wavelengths of 265 nm,310 nm,365 nm and 405 nm were introduced into the test chamber.The gas sensing performance,such as the response-recovery characteristics,repeatability and stability,of CVD graphene-based gas sensor array was systematically investigated.Its results show that the response of the sensor is increased by seven times under UV irradiation.Meanwhile,UV irradiation reduces the detection limit of the sensor and shortens the recovery time,leading to better stability and repeatability.Finally,the gas sensitive response mechanism was discussed,and the potential application of graphene in the field of gas sensors was explored.