Semiconductor Nanowires (NWs) are ideally suited for efficient transport of charge carriers and excitons, and thus are expected to be critical building blocks for nanotechnology. In this thesis, we present a bottom-up approach to build up the future nanoelectronics, nanophotonics and nanosensors with semiconductor NWs.; We first present the size-selective synthesis of semiconductor NWs via a metal cluster-catalyzed vapor-liquid-solid (VLS) growth mechanism. The diameter and length of the NWs are controlled by the Au catalyst diameter and the growth time, respectively. High resolution transmission electron microscopy studies demonstrate that NWs have single crystal core sheathed with 1–3 nm amorphous oxide. The crystallographic growth orientation is size-dependent.; We then discuss NW electronic transport properties, functional nanoelectronic and nanophotonic devices. Semiconductor NWs are precisely doped into p- and n-type during synthesis. Carrier mobility of NWs estimated from field effect is significantly larger than the bulk material value. The electrical measurements through small diameter (∼10 nm) intrinsic NWs show evidence of ballistic transport. All these results suggest that NWs have high quality for nano functional devices. Moreover, NWs are assembled into functional nanoelectronic and nanophotonic devices including NW cross pn diodes and light-emitting diodes, bipolar transistors, inverters, and photodetectors. The facile way in assembling NWs into functional nano-devices represents a big step towards bottom-up nanotechnology.; Finally we describe how NW FETs are converted into electrical-based label-free, highly sensitive and selective chemical and biological sensors. NW nanosensor concepts are first approved by real-time detection of a variety of chemical and biological species including pH, proteins and metal ions. These NW sensors are applied to the multiplexing detection of cancer markers with high specificity and ultrahigh sensitivity down to femtogram/ml level, significant for cancer diagnostics and therapy. The sensitivity limit of NW sensors is further explored to detect the single molecule binding. This promises a new method to study single molecule.
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