Electrical characterization of nanoparticle and protein networks

This thesis describes the research directed towards practical realization of an on-chip biosensing technology and that of understanding charge transport mechanisms in organic and biological nanoobjects. For this, silicon-based chips with metallic nanoelectrodes were fabricated using electron-beam lithography and metal evaporation. The final devices have source-drain separations of tens of nanometres, so that several up to one nanoobject can be trapped in between the electrodes, depending on its size. The electrical characterization is typically performed at room temperature. A current was induced in the sample by applying a voltage across the junction first before the deposition of nanoobject to characterize the bare junction as a reference, and subsequently after deposition. An increase of current after the deposition indicates that nanoobjects participate in the charge carrier flow through the device. For some nanoobjects it was possible to influence the current flow by inducing changes in the environment, for instance by varying the temperature (Chapter 4) or by changing the gas composition (Chapter 5 and Chapter 6). This thesis constitutes the results of two topics: two-dimensional (graphene) electrodes for contacting single nanoobjects (Chapter 3 and Chapter 4), and the electrical characterization of biological iron containing protein networks (Chapter 5 and Chapter 6).