When 3:30 PM - 5:00 PM Mar 12, 2010
Where 1670 CSE
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Electronic Transport in Nanostructures: Why Size Matters

Alec Talin, NIST

Nanowires continue to fascinate researchers, who are often motivated by the combination of high crystalline quality and nanoscale dimensions not easily accessible by ‘top-down’ lithographic means.  The ‘size-effect’ frequently sited in nanowire literature is that of quantum confinement, i.e., where the density of states assumes a 1-dimensional character.  These dimensions, typically <20 nm in diameter, are, in fact, seldom fabricated in practice.  In my talk, I will discuss how finite dimensions, far from the quantum confinement limit, affect bulk and contact mediated transport in nanowires. Specifically, I will show that the onset of space charge limited conduction in nanowires occurs at a lower critical voltage, and has a different geometric scaling as compared to low aspect ratio specimens (i.e. thin films). I will also discuss the transport characteristics of metal catalyst/nanowire contacts in the Au /Ge-nanowire system, demonstrating the presence of a Schottky barrier at the interface. Surprisingly, the small bias conductance increases with decreasing diameter in these nanodiodes. Our model suggests that this effect arises because electron-hole recombination in the depletion region is the dominant charge transport mechanism, with a diameter dependence of both the depletion width and the electron-hole recombination time. Time permitting, I will also discuss our recent characterization of transport in InAs nanowires, including real-time observation of thermal breakdown, and its implications for both electronic and thermal transport in this system.

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