Ammonia sensing using arrays of silicon nanowires and graphene

Abstract

Ammonia (NH 3) is a toxic gas released in different industrial, agricultural and natural processes. It is also a biomarker for some diseases. These require NH 3 sensors for health and safety reasons. To boost the sensitivity 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 NH 4 OH (28% NH 3). 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 100x larger than that of suspended graphene for the same top surface area, leading to a larger response in amplitude by a factor of ~7 notwithstanding a higher trap density in suspended graphene. The use of Si NWAs increases the response rate for both Si NWAs as well as the suspended graphene due to more effective NH 3 diffusion processes.

Highly Sensitive Ammonia Gas Detection at Room Temperature by Integratable Silicon Nanowire Field-Effect Sensors

“…Ammonia (NH 3 ) gas is a typical reductive toxic gas that could harm human tissues, such as skin, eyes, mucous membranes of the respiratory organs, and cause even lung swelling and death in case of long-term exposure. , Therefore, the need for highly sensitive NH 3 sensors has been steadily increasing for industrial, medical, military, and living environment monitoring . So far, the most widely used NH 3 gas sensors are based on bulk or nanostructured metal oxide semiconductor materials that require a high working temperature of typically 200–450 °C. − This leads to a high-power consumption and limited application scenarios for wearable and portable electronics that are supposed to attach to or be in the close proximity of skin surfaces.…”

Improved NH3 Gas Sensing Performance of Femtosecond‐Laser Textured Silicon by the Decoration of Au Nanoparticles

“…Silicon-based gas sensors exhibit promising potential for room-temperature gas response sensing and can be highly integrated with modern integration technologies. Although preliminary investigations have been conducted on the gas sensing properties of various silicon-based materials, such as porous silicon, [1][2][3] structural silicon, [4] and silicon nanowires, [3,5,6] there are still some problems in terms of responsiveness, response time, and stability, and need further improvement. Recently, textured silicon (TSi) fabricated through femtosecond laser etching under specific conditions has attracted increasing interest.…”

High-performance pyramid-SiNWs biosensor for NH3 gas detection

“…To meet these requirements, electronic gas sensors have gained widespread application due to their low cost, ease of operation, rapid response, and real-time monitoring capabilities [10][11][12]. Various NH 3 electronic sensors based on carbon nanotubes [13][14][15][16][17][18][19], silicon nanowires (SiNWs) [20][21][22], metal oxides [23][24][25][26][27][28][29], and other hybrid materials [30][31][32][33][34][35] have been developed. However, most of these sensors still cannot well achieve the requirements such as high selectivity, sub-ppm level sensitivity, room temperature operation for environmental and health monitoring applications.…”