We demonstrate the direct biosensing of the Ebola VP40 matrix protein, using a memristor mode of a liquid-integrated nanodevice, based on a large array of honeycomb-shaped silicon nanowires. To shed more light on the principle of biodetection using memristors, we engineered the opening of the current-minima voltage gap V_GAP by involving the third gap-control electrode (gate voltage, V_G) into the system. The primary role of V_G is to mimic the presence of the charged species of the desired sign at the active area of the sensor. We further showed the advantages of biodetection with an initially opened controlled gap (V_GAP ≠ 0), which allows the detection of the lowest concentrations of the biomolecules carrying arbitrary positive or negative charges; this feature was not present in previous configurations. We compared the bio-memristor performance, in terms of its detection range and sensitivity, to that of the already-known field-effect transistor (FET) mode by operating the same device. To our knowledge, this is the first demonstration of Ebola matrix protein detection using a nanoscaled electrical sensor.

A novel photosensitive hybrid field-effect transistor (FET) which consists of a multiple-shell of organic porphyrin film/oxide/silicon nanowires is presented. Due to the oxide shell around the nanowires, photoswitching of the current in the hybrid nanodevices is guided by the electric field effect, induced by charge redistribution within the organic film. This principle is an alternative to a photoinduced electron injection, valid for devices relying on direct junctions between organic molecules and metals or semiconductors. The switching dynamics of the hybrid nanodevices upon violet light illumination is investigated and a strong dependence on the thickness of the porphyrin film wrapping the nanowires is found. Furthermore, the thickness of the organic films is found to be a crucial parameter also for the switching efficiency of the nanowire FET, represented by the ratio of currents under light illumination (ON) and in dark conditions (OFF). We suggest a simple model of porphyrin film charging to explain the optoelectronic behavior of nanowire FETs mediated by organic film/oxide/semiconductor junctions.

We demonstrate a pH sensor based on ultrasensitive nanosize Schottky junctions formed within bottom-up grown dopant-free arrays of assembled silicon nanowires. A new measurement concept relying on a continuous gate sweep is presented, which allows the straightforward determination of the point of maximum sensitivity of the device and allows sensing experiments to be performed in the optimum regime. Integration of devices into a portable fluidic system and an electrode isolation strategy affords a stable environment and enables long time robust FET sensing measurements in a liquid environment to be carried out. Investigations of the physical and chemical sensitivity of our devices at different pH values and a comparison with theoretical limits are also discussed. We believe that such a combination of nanofabrication and engineering advances makes this Schottky barrier-powered silicon nanowire lab-on-a-chip platform suitable for efficient biodetection and even for more complex biochemical analysis.

We present novel Schottky barrier field effect transistors consisting of a parallel array of bottom-up grown silicon nanowires that are able to deliver high current outputs. Axial silicidation of the nanowires is used to create defined Schottky junctions leading to on/off current ratios of up to 10⁶. The device concept leverages the unique transport properties of nanoscale junctions to boost device performance for macroscopic applications. Using parallel arrays, on-currents of over 500 μA at a source-drain voltage of 0.5 V can be achieved. The transconductance is thus increased significantly while maintaining the transfer characteristics of single nanowire devices. By incorporating several hundred nanowires into the parallel array, the yield of functioning transistors is dramatically increased and deviceto-device variability is reduced compared to single devices. This new nanowirebased platform provides sufficient current output to be employed as a transducer for biosensors or a driving stage for organic light-emitting diodes (LEDs), while the bottom-up nature of the fabrication procedure means it can provide building blocks for novel printable electronic devices.