| Semiconducting chalcogenide nanowires can be grown in solution from metal catalyst particles via a solution-liquid- solid (SLS) mechanism. However, subsequent deposition of these nanowires onto electrodes while ensuring good electrical contact e.g. for field-effect transistors (FETs) is challenging. In this work, we present a new method to grow n-type CdSe nanowires from bismuth catalyst nanoparticles that are formed in-situ from a thin layer of bismuth at elevated temperatures. The evaporated thin bismuth layer on top of Ti/Pd source and drain electrodes breaks up at 250-270°C forming bismuth catalyst particles which induce heterogeneous nucleation of CdSe nanowires. The direct electrical contact between semiconductor nanowires and electrodes via Bi particles reduces contact resistance compared to nanowires deposited after synthesis in the solution improving transistor current-voltage characteristics. Pre-treatment of the palladium layer with oxygen plasma was found to be crucial for the formation of bismuth nanoparticles. Moreover, other parameters such as the thickness of the evaporated bismuth layer, preparation conditions of the Cd and Se precursors, injection and growth temperatures, etc. were found to influence the final length and diameter of the CdSe nanowires. These nanowires bridged 5 µm channels between the photolithographically patterned electrodes. To study the charge transport properties of these on-chip grown CdSe nanowires, we used electrolyte gating with ionic liquids and found reasonably high electron mobilities µ(lin) = 0.5 cm2/(V*s) at gate voltages below 2 V. This technique could also be applied to the fabrication of electrolyte-gated FETs with other semiconductor nanowires, e.g. ambipolar PbSe nanowire FETs. |
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