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Quasi-one-dimensional silicon nanostructures for gas molecule adsorption: a DFT investigation
摘要： Porous structures offer an enormous surface suitable for gas sensing, however, the effects of their quantum quasi-confinement on their molecular sensing capacities has been seldom studied. In this work the gas-sensing capability of silicon nanopores is investigated by comparing it to silicon nanowires using first principles calculations. In particular, the adsorption of toxic gas molecules CO, NO, SO2 and NO2 on both silicon nanopores and nanowires with the same cross sections was studied. Results show that sensing-related properties of silicon nanopores and nanowires are very similar, suggesting that surface effects are predominant over the confinement. However, there are certain cases where there are remarked differences between the nanowire and porous cases, for instance, CO-adsorbed nanoporous silicon shows a metallic band structure unlike its nanowire counterpart, which remains semiconducting, suggesting that quantum quasi-confinement may be playing an important role in this behaviour. These results are significant in the study of the quantum phenomena behind the adsorption of gas molecules on nanostructure’s surfaces, with possible applications in chemical detectors or catalysts.
关键词： Sensing,Chemical sensors,Silicon nanowires,Density functional theory,Molecule adsorption,Porous silicon
更新于2025-09-23 15:23:52
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Investigation of carrier density and mobility variations in graphene caused by surface adsorbates
摘要： Conductivity, carrier concentration and carrier mobility in graphene were investigated as a function of time in response to ionized donor and acceptor adsorbates. While a reduction in conductivity and hole density in graphene was observed upon exposure to a weak electron donor NH3, the carrier mobility was found to increase monotonically. The opposite behavior is observed upon exposure to NO2, which is expected based on its typical electron withdrawing property. Upon exposure to C9H22N2, a strong donor, it resulted in the transformation of graphene from p-type to n-type, although the inverse variation of carrier concentration and mobility was still observed. The variational trends remained unaltered even after intentional introduction of defects in graphene through exposure to oxygen plasma. The responses to C9H22N2, NH3 and NO2 exposures underline a strong influence by ionized surface adsorbates that we explained via a simple model considering charged impurity scattering of carriers in graphene.
关键词： Carrier density,Gas molecule adsorption,Graphene,Graphene mobility,NH3,NO2
更新于2025-09-10 09:29:36