Tuesday, July 03, 2007

four interesting ACS journal articles

Here are four recent articles ACS journals, two from Nano Letters and two from JACS, that made an impression on me.

Dattoli et al., Fully transparent thin-film transistor devices based on SnO2 nanowires
The authors of this paper have made fully functional n-type FETs based on lightly doped tin oxide nanowires with indium tin oxide source, drain, and gate electrodes, and the performance of these FETs is reasonable when compared with the ones currently driving the pixels in your flat panel display. Since the entire FET structure is very transparent in the visible, this could have some significant applications in display technologies.

Angus et al., Gate-defined quantum dots in intrinsic silicon
People have been making Coulomb blockade devices out of puddles of gate-confined two-dimensional electron gas for nearly two decades now. Mostly this has been done at the GaAs/AlGaAs interface, and more recently it's been achieved in nanotubes, semiconductor nanowires, and SiGe heterostructures. The authors of this work have managed to do this nicely at the Si/SiO2 interface in a MOSFET. What this really shows is how well the interface states at that junction are passivated, how nicely the authors can make gates without messing up the surrounding material, and that properly made Ohmic contacts in Si FETs can operate well down to cryogenic temperatures. This could be a very important paper if one can build on it to manipulating electron spins in these dots - unlike GaAs structures, there should be many fewer nuclear spins to worry about for effects like hyperfine-induced decoherence of electron spins.

Albrecht et al., Intrinsic multistate switching of gold clusters through electrochemical gating
Lots of people in the molecular electronics community have pointed out the similarities and differences between three-terminal (electrostatically gated) molecular devices and solution-based electrochemical oxidation/reduction experiments in electron transfer. These authors are some of the only experimentalists out there that I have seen really delving into this, trying to unravel how the electrochemical case really works. This experiment is analogous to the Coulomb blockade experiment of the preceding paper, but performed using an STM in an electrochemical medium, with ligand-protected gold clusters playing the role of the quantum dot.

Shim et al., Control and measurement of the phase behavior of aqueous solutions using microfluidics
This isn't particularly deep, but it sure is cool. Microfluidics has come a long way, and the extremely nice properties of polydimethylsiloxane (PDMS) have been a big help. That's the transparent silicone rubber used for many microfluidic applications, as well as being related to the silicone used for soft contact lenses and breast implants. The authors here have carefully used the water and gas permeability of thin PDMS layers to control the concentrations of solutes in water-based solutions, allowing them to do things like gently make supersaturated conditions to control crystallization of proteins. We're just at the leading edge of the potential applications for these kinds of systems.

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