Self-assembly methods combined with standard top-down approaches are demonstrated to be suitable for fabricating three-dimensional ultracompact hybrid organic/inorganic electronic devices based on rolled-up nanomembranes. Capacitors that are self-wound and manufactured in parallel are almost 2 orders of magnitude smaller than their planar counterparts and exhibit capacitances per footprint area of around 200 microF/cm(2). This value significantly exceeds that which was previously reported for metal-insulator-metal capacitors based on Al(2)O(3), and the obtained specific energy (approximately 0.55 Wh/kg) would allow their usage as ultracompact supercapacitors. By incorporating organic monolayers into the inorganic nanomembrane structure we can precisely control the electronic characteristics of the devices. The adaptation of the process for creating ultracompact batteries, coils and transformers is an attractive opportunity for reducing the size of energy storage elements, filters, and signal converters. These devices can be employed as implantable electronic circuits or new approaches for energy-harvesting applications. Furthermore, the incorporation of functional organic molecules gives rise to novel devices with almost limitless chemical and biological functionalities.

We fabricate inorganic thin film transistors with bending radii of less than 5 μm maintaining their high electronic performance with on-off ratios of more than 10(5) and subthreshold swings of 160 mV/dec. The fabrication technology relies on the roll-up of highly strained semiconducting nanomembranes, which compacts planar transistors into three-dimensional tubular architectures opening intriguing potential for microfluidic applications. Our technique probes the ultimate limit for the bending radius of high performance thin film transistors.

Control over the autonomous motion of artificial nano/ micromachines is essential for real biomedical and nanotechnological applications. Consequently, a complete nanomachine should be able to be turned on and off at will. Developments over the last few years on synthetic catalytic nano/microengines and motors have enabled the harvesting of chemical energy from local molecules and transforming it into an effective autonomous motion.[1] Several impressive applications have recently reported the use of artificial micromachines for the detection of biomolecules with roving nanomotors, [2] transport of animal cells in a fluid, [3] and other microcargo delivery. [4][5][6][7] Recently, the use of a light source has been implemented to propel microparticle-based motors [8] generated by a selfdiffusiophoretic mechanism. Despite this interesting approach, the motion of the particles is limited by the dissolution of the materials and to the ultraviolet (UV) spectrum.[9] Moreover, a reversible method to start and stop the propulsion of micromotors by a visible-light source remains a challenge.Here we report the tuning of the propulsion power of Ti/ Cr/Pt catalytic microengines (m-engines) through illumination of a solution by a white-light source. We show that light suppresses the generation of microbubbles, stopping the engines if they are fixed-to or self-propelled above a platinum-patterned surface. The m-engines are reactivated by dimming the light source that illuminates the fuel solution. The illumination of the solution with visible light in the presence of Pt diminishes the concentration of hydrogen peroxide fuel and degrades the surfactant, consequently reducing the motility of the microjets. Electrochemical measurements and analysis of the surface tension support our findings. We also study the influence of different wavelengths over the visible spectrum (500-750 nm) on the formation of microbubbles.Rolled-up Ti/Cr/Pt catalytic m-engines with diameters of 5-10 mm and a length of 50 mm were prepared as described previously elsewhere [10][11][12] and in the Experimental Section.Microengines were immersed into solutions of aqueous H 2 O 2 (2.5 % v/v) as fuel and benzalkonium chloride (ADBAC) (0.5 % v/v), as the surfactant, to determine the influence of white light on the mobility of the m-engines. At lower concentrations of both chemicals, the generation of microbubbles is significantly reduced. Thus, the motility of the catalytic m-engines is controlled by a small change in the fuel (H 2 O 2 and/or surfactant) concentration. These conditions allow us to investigate a concentration range close to the metastable state, that is, where the probability of stopping the m-engines is high. Figure 1 A shows an optical microscopy image of a self-propelled mengine on a Pt-patterned silicon substrate (1 nm-thick Pt layer) placed in a Petri dish ( % 53 mm in diameter) under the illumination of a tungsten lamp (inset in Figure 1 A). The speed of the m-engines moving within the illuminated area is rapidly reduced and is zero afte...

The effects of the polymerization temperature and of voltammetric cycling on the chain length and the resistivity of polypyrrole films are investigated. The studies provide further proof for the existence of at least two different types of polypyrrole, the so-called PPy I and PPy II. As the electropolymerization of conjugated systems in contrast to normal polymerization reactions is a fully activated process, the generation of these different types of PPy depends on experimental parameters such as temperature or formation potentials. UV-vis measurements demonstrate that PPy II comprises significantly shorter chains than PPy I (8-12 vs 32-64 units); moreover, film conductivity is found to increase with the fraction of PPy II. This fraction is changed via the polymerization temperature as well as by cyclic voltammetry, both of which can induce a metal-insulator transition. The counter-intuitive relationship between resistivity and chain length is interpreted in terms of disorder-dominated transport, in which the shorter chains of PPy II support the formation of delocalized electronic states, thereby increasing the localization length. Thus, our results are in agreement with recent broadband reflectivity measurements.

Bulky organic semiconductors have been widely applied on a variety of devices including transistors, sensors, and organic light-emitting diodes. Recently, the capability of producing stable ultrathin organic semiconductor-based junctions has opened the possibility of a variety of novel device concepts, including highspeed organic transistors, organic spin valves, and biosensors. In such context, the investigation of the charge transport mechanisms across ultrathin organic semiconductors is the key for the engineering of emerging organic-based technologies. Here, the charge transport mechanisms across heterojunctions based on physisorbed ultrathin copper phthalocyanine on gold are precisely determined and controlled over a wide range of temperatures and electric fields. We observe that the macroscopic electrical characteristics of Au/CuPc/Au heterojunctions are similar to what has been reported for chemisorbed molecular junctions. For instance, the transition from thermally activated transport to tunneling is verified regardless of the nature of the molecule-contact bonding. The Au/CuPc/Au heterojunction transport is dominated by charge localization sites at high temperatures and, upon cooling, a continuous transition from direct tunneling, via resonant tunneling, to field emission takes place by increasing the voltage bias. Such a continuous transition has not been reported for a hybrid metal/organic heterojunction yet. We have also determined the dielectric constant of the CuPc molecular layer via transport measurements, which allowed us to infer the possible molecule arrangements between the electrodes.

We report on a magnetophotoluminescence study of single self-assembled semiconductor nanorings which are fabricated by molecular-beam epitaxy combined with AsBr 3 in situ etching. Oscillations in the neutral exciton radiative recombination energy and in the emission intensity are observed under an applied magnetic field. Further, we control the period of the oscillations with a gate potential that modifies the exciton confinement. We infer from the experimental results, combined with calculations, that the exciton Aharonov-Bohm effect may account for the observed effects.

In this work, we combine self-assembly and top-down methods to create hybrid junctions consisting of single organic molecular monolayers sandwiched between metal and/or single-crystalline semiconductor nanomembrane based electrodes. The fabrication process is fully integrative and produces a yield loss of less than 5% on-chip. The nanomembrane-based electrodes guarantee a soft yet robust contact to the molecules where the presence of pinholes and other defects becomes almost irrelevant. We also pioneer the fabrication and characterization of semiconductor/molecule/semiconductor tunneling heterojunctions which exhibit a double transition from direct tunneling to field emission and back to direct tunneling, a phenomenon which has not been reported previously.

The charge transport in molecular systems is governed by a series of carrier-molecule quantum interactions, which result in a broad set of chemical and physical phenomena. The precise control of such phenomena is one of the main challenges toward the development of novel device concepts. In molecular systems, direct tunneling across 1−10 nm barriers and activated hopping over longer distances have been described as the main charge transport mechanisms. The continuous transition from one mechanism to the other, by increasing the transport distance, has mainly been reported for molecular chains covalently bonded to the electrodes. In elementary molecular junctions, like those formed by physisorbed organic semiconductor thin films, such transition remains unclear. Here, we report the first experimental evidence for sequential, long-range coherent tunneling across physisorbed ensembles by investigating the charge transport in copper phthalocyanine layers (5−60 nm thick films). Like observed for chemisorbed molecules, our junction exhibits a gradual transition from coherent tunneling to activated transport in the 10−22 nm thickness range. The present work contributes to connect the quantum transport to diffusive-related phenomena in such an elementary organic system.