摘要
Ammonia （NH3） is a toxic gas released in different industrial, agricultural and natural processes. It is also a biomarker for some diseases. These require NH3 sensors for health and safety reasons. To boost the sensitiv- ity of solid-state sensors, the effective sensing area should be increased. Two methods are explored and compared using an evaporating pool of 0.5 mL NH4OH （28% NH3）. In the first method an array of Si nanowires （Si NWA） is obtained via metal-assisted-electrochemical etching to increase the effective surface area. In the second method CVD graphene is suspended on top of the Si nanowires to act as a sensing layer. Both the effective surface area as well as the density of surface traps influences the amplitude of the response. The effective surface area of Si NWAs is 100 × larger than that of suspended graphene for the same top surface area, leading to a larger response in amp- litude by a factor of -7 notwithstanding a higher trap density in suspended graphene. The use of Si NWAs in- creases the response rate for both Si NWAs as well as the suspended graphene due to more effective NH3 diffu- sion processes.
Ammonia （NH3） is a toxic gas released in different industrial, agricultural and natural processes. It is also a biomarker for some diseases. These require NH3 sensors for health and safety reasons. To boost the sensitiv- ity of solid-state sensors, the effective sensing area should be increased. Two methods are explored and compared using an evaporating pool of 0.5 mL NH4OH （28% NH3）. In the first method an array of Si nanowires （Si NWA） is obtained via metal-assisted-electrochemical etching to increase the effective surface area. In the second method CVD graphene is suspended on top of the Si nanowires to act as a sensing layer. Both the effective surface area as well as the density of surface traps influences the amplitude of the response. The effective surface area of Si NWAs is 100 × larger than that of suspended graphene for the same top surface area, leading to a larger response in amp- litude by a factor of -7 notwithstanding a higher trap density in suspended graphene. The use of Si NWAs in- creases the response rate for both Si NWAs as well as the suspended graphene due to more effective NH3 diffu- sion processes.
基金
financial support of EPSRC via the EEE department
