One dimensional Semiconductor nanostructures: controlled synthesis, functionalization, and applications.

Abstract

Ultralong one-dimensional (1D) nanostructures can serve as the unique building blocks that interlink the nanometer-scale world with real macroscopic world. Here we report the vapor-liquid-solid (VLS) synthesis of millimeter-long silicon nanowires (SiNWs) by introducing disilane (Si2H6) as reactive gas source. For 1 hr growth, the longest SiNWs can reach ~3.5 mm and their aspect ratios extend up to ~100,000 while the diameters are uniform along the wires. The average growth rate at 400 ºC is 31 ?m/min, which is roughly 130 times higher than that for silane (SiH4) at the similar growth conditions. Significantly, millimeter-long SiNWs preferred to grow along the <110> direction without exhibiting diameter-dependent preference, which is contradictory to the previous experimental observations and the predictions based on thermodynamic models. The anomalous growth habits might be driven by growth kinetics, representing a new criterion that affects the crystallographic orientation during the precipitation in VLS synthesis. More importantly, these ultralong nanowire building blocks have been configured as multiple field-effect transistor (FET) arrays by wiring hundreds of electrodes onto the single wires. The transport measurements demonstrated uniform electrical properties along the entire length of wires, and each device can behave as a reliable FET with a current on/off ratio of 104-106, a subthreshold slop of 200-500 mV/dec, threshold voltage of 5-7 V, and peak transconductance of 160-270 nS with a maximum value of 360 nS. Electronic uniformity of millimeter-long SiNWs was further exploited to show multiplexed electrical sensing of cancer marker proteins.