The silicon microwires were received as arrays grown on <111> silicon substrates. Different samples were grown using both Au and Cu catalysts. The microwires were p-type doped with boron (using BCl 3) as the dopant. All the samples had the metallic catalyst on the end of each microwire and also have some minor amounts deposited on the sides. A slow cool down procedure has been done after growth so that the metallic catalyst diffuses out readily from the Si. The etch procedure for removing the catalyst and for etching off the SiO 2 that results from the catalyst removal is as follow: 10 s, 10% aq. HF 30 min. 30 wt.% aq. FeCl 3 10 s, 10% aq. HF 1 min 20 wt.% aq. KOH 10 s, 10% aq. HF After each step, the microwires were rinsed thoroughly with DI water and dried under a stream of N 2. FeCl 3 was used to remove the metallic catalyst. The KOH was used to remove any leftover FeCl 3. Finally, buffered HF was used to remove the native oxide and any oxide formed during the catalyst removal process. XPS analysis confirmed the catalyst removal from the microwires after etching process (Figure A.1).

The photoelectrical properties and stability of individual p-silicon (Si) microwire/ polyethylenedioxythiophene/polystyrene sulfonate:Nafion/n-Si microwire structures, designed for use as arrays for solar fuel production, were investigated for both H-terminated and CH 3 -terminated Si microwires. Using a tungsten probe method, the resistances of individual wires, as well as between individual wires and the conducting polymer, were measured vs. time. For the H-terminated samples, the n-Si/polymer contacts were initially rectifying, whereas p-Si microwire/polymer contacts were initially ohmic, but the resistance of both the n-Si and p-Si microwire/polymer contacts increased over time. In contrast, relatively stable, ohmic behavior was observed at the junctions between CH 3 -terminated p-Si microwires and conducting polymers. CH 3 -terminated n-Si microwire/polymer junctions demonstrated strongly rectifying behavior, attributable to the work function mismatch between the Si and polymer. Hence, a balance must be found between the improved stability of the junction electrical properties achieved by passivation, and the detrimental impact on the effective resistance associated with the additional rectification at CH 3 -terminated n-Si microwire/polymer junctions. Nevertheless, the current system under study would produce a resistance drop of $20 mV during operation under 100 mW cm À2 of Air Mass 1.5 illumination with high quantum yields for photocurrent production in a water-splitting device. Broader contextPhotoelectrosynthetic splitting of water to store solar energy in the simplest chemical bond, H-H, would provide a globally scalable means of compensating for the intermittency of solar energy at a given region of the earth's surface. A working device will require: a light harvesting component; redox catalysts; and a membrane barrier, for separating the products of the oxidation and reduction reactions, while maintaining efficient ionic conductivity to maintain charge neutrality. Given the useable solar energy range and the energy requirements for both oxidation and reduction reactions, it is challenging to find a single light absorber that can function efficiently. As in the natural photosynthetic system, it is possible to combine two light absorbers across a product-separating, ionically conductive membrane; however, the membrane is then required to manage, with minimal resistance, electron transport between the two light absorbers. We report herein the photoelectrical properties of a test structure of this type of device, incorporating an individual semiconductor photoanode and photocathode (with no redox catalysts) embedded into a candidate conducting polymer membrane, to form a single functional unit.

PEDOTÀPSSÀNafion/microwire system would provide a suitable combination, from an electrical resistance perspective, to be used in a solar fuels generation device.' ASSOCIATED CONTENT b S Supporting Information. Metallic catalyst removal procedure, conductive polymer film preparation, microwire/polymer junction formation, and quantifying the applied mechanical force on the single silicon microwires. This material is available free of charge via the Internet at http://pubs.acs.org.

The surface polarization caused by traveling SAWs at 1.585 GHz has been imaged using a dynamic homodyne electrostatic force microscope technique. Instead of measuring topographic changes caused by the SAW, the reported technique measures polarization in the piezoelectric substrate arising from mechanical stress caused by the SAW. The polarization associated with this stress field modulates the scanning probe cantilever deflection amplitude, which is extracted using a lock-in-based technique. High-resolution imaging is presented with images of the interference arising from a metal reflector on a SAW device. A mathematical model combining SAW generation and force interactions between the probe and the substrate was used to verify the experimental data. In addition to overcoming the challenge associated with detecting and imaging polarization effects at gigahertz frequencies, this imaging technique will greatly assist the development of SAW-based devices that exploit the reflection and interference of SAWs in areas as diverse as microfluidic mixing, cell sorting, and quantum entanglement.

Considering the limitations of dynamic memory structures based on the "1 Transistor -1 Capacitor" design paradigm related to their complexity and scaling, non-transistor based designs are being actively pursued. Bulk resistive memory designs that do not require additional transistor components per bit, are desirable candidates. This article presents a layered approach for formation of tungsten oxide and conducting polymer junctions to be used as a redox memory structure. This system includes an electrochemically deposited tungsten oxide film covered by electrophoretically deposited conducting polymer material capable of producing transient current-voltage characteristics that can be controlled by electric fields and exhibiting memory effects. The approach presented in this paper is particularly attractive since it provides a means to form these junctions on CMOS-friendly contact metals such as copper. Junctions between tungsten oxide and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have been formed and characterized, demonstrating these junctions on copper substrates, significantly advancing this approach for making CMOS-compatible crossbar memory structures based on conducting polymer systems.