Abstract
The use of completely oxidized two-dimensional (2D) silicon nanosheets (SiNSs) represents a novel approach for the application of 2D silicon-based materials in the nanoelectronics field. Densely stacked and highly porous oxidized SiNSs (OSiNSs) act as a sensitive layer for humidity detection. Due to the oxidation-caused porosity of the SiNSs and the possibility functionalize the 2D surface with hydrophilic groups, this hybrid material exhibits an extremely good sensitivity towards relative humidity (RH). In this work, precise tuning of the SiNSs' sensing properties by their functionalization is demonstrated. In particular, the modification with methacrylic acid (MAA) groups, leading to SiNS-MAA, and the subsequent deposition on interdigitated electrodes double the capacitance value in the range of 20-85% RH. These values were achieved after the full oxidation of SiNS-MAA in ambient conditions. The mentioned changes in capacitance are extremely high compared to the response of the so far known common polymer humidity sensors. Contrary to that, this response is neutralized when the SiNSs are functionalized with tert-butyl acrylic acid ((t)BMA), a rather hydrophobic functional group. The fabricated devices show, how the specific functionalization of SiNSs serves as a reliable tool to provide sensitivity towards RH. Similar approach, based on tuning the functionality, can be applied to achieve e.g., sensor array selectivity. For this purpose, the functional groups on the surface of the nanomaterial can be further modified. Additional molecules with sensitivities towards various surrounding conditions could be attached. Furthermore, these functional molecules can be used for subsequent (bio) molecule immobilization, which can serve as sensitive molecular groups towards surrounding substrates and gases. However, one of the main challenges in sensor technology is to find a highly selective solution: a sensor system capable to differentiate among different vapor species. The described strategy can serve as an access towards new and promising solutions, which can help to face this issue in modern nanomaterials-based technology.