We introduce a new concept for the solution-based fabrication of conductive gold nanowires using DNA templates. To this end, we employ DNA nanomolds, inside which electroless gold deposition is initiated by site-specific attached seeds. Using programmable interfaces, individual molds self-assemble into micrometer-long mold superstructures. During subsequent internal gold deposition, the mold walls constrain the metal growth, such that highly homogeneous nanowires with 20-30 nm diameters are obtained. Wire contacting using electron-beam lithography and electrical conductance characterization at temperatures between 4.2 K and room temperature demonstrate that metallic conducting wires were produced, although for part of the wires, the conductance is limited by boundaries between gold grains. Using different mold designs, our synthesis scheme will, in the future, allow the fabrication of complex metal structures with programmable shapes.
DNA origami nanostructures have been used extensively as scaffolds for numerous applications such as for organizing both organic and inorganic nanomaterials, studying single molecule reactions, and fabricating photonic devices. Yet, little has been done toward the integration of DNA origami nanostructures into nanoelectronic devices. Among other challenges, the technical difficulties in producing well-defined electrical contacts between macroscopic electrodes and individual DNA origami-based nanodevices represent a serious bottleneck that hinders the thorough characterization of such devices. Therefore, in this work, we have developed a method to electrically contact individual DNA origami-based metallic nanowires using electron beam lithography. We then characterize the charge transport of such nanowires in the temperature range from room temperature down to 4.2 K. The room temperature charge transport measurements exhibit ohmic behavior, whereas at lower temperatures, multiple charge transport mechanisms such as tunneling and thermally assisted transport start to dominate. Our results confirm that charge transport along metallized DNA origami nanostructures may deviate from pure metallic behavior due to several factors including partial metallization, seed inhomogeneities, impurities, and weak electronic coupling among AuNPs. Besides, this study further elucidates the importance of variable temperature measurements for determining the dominant charge transport mechanisms for conductive nanostructures made by self-assembly approaches.
The complex physics of the interaction between short pulse high intensity lasers and solids is so far hardly accessible by experiments. As a result of missing experimental capabilities to probe the complex electron dynamics and competing instabilities, this impedes the development of compact laser-based next generation secondary radiation sources, e.g. for tumor therapy [1,2], laboratory-astrophysics [3,4], and fusion [5]. At present, the fundamental plasma dynamics that occur at the nanometer and femtosecond scales during the laser-solid interaction can only be elucidated by simulations. Here we show experimentally that small angle X-ray scattering of femtosecond X-ray free-electron laser pulses facilitates new capabilities for direct in-situ characterization of intense short-pulse laser plasma interaction at solid density that allows simultaneous nanometer spatial and femtosecond temporal resolution, directly verifying numerical simulations of the electron density dynamics during the short pulse high intensity laser irradiation of a solid density target. For laser-driven grating targets, we measure the solid density plasma expansion and observe the generation of a transient grating structure in front of the pre-inscribed grating, due to plasma expansion, which is an hitherto unknown effect. We expect that our results will pave the way for novel time-resolved studies, guiding the development of future laser-driven particle and photon sources from solid targets.The solid density plasmas created in the interaction of an ultra-short, ultra-high intensity (UHI) laser pulse with a solid target are a source of femtosecond, highcharge electron[6] and ion bunches[7-10], extreme ultraviolet (XUV) radiation [11][12][13], and neutrons [14], making them promising candidates for future particle accelerators or radiation sources. Until now a fundamental impediment of the ongoing research of UHI laser-solid interactions has been the limited experimental capability of diagnosing the basic processes during the laser interaction on the relevant scales that range from sub-femtosecond to hundreds of femtoseconds and from few nanometers to few hundred nanometers. Some of the most important physical processes are, for example, the generation of plasma oscillations [15] and plasma waves [16], electron transport and plasma * .kluge@hzdr.de heating [17,18], instability development [16,[19][20][21][22][23][24], and the generation of strong magnetic fields [17]. A fundamental process is the expansion of the irradiated plasma into vacuum [25][26][27] during the laser interaction, governing the surface dynamics and laser absorption both prior to and during the laser main pulse.For each application a correspondingly tailored surface structure can enhance laser absorption and interaction, electron acceleration, and hence all subsequent processes. In fact, it has been shown that a preplasma density gradient, e.g. generated by laser intensity prior to the main pulse, strongly affects absorption[28] and the generation of secondary radiation such...
A laboratory measurement of the α-decay half-life of 190 Pt has been performed using a low background Frisch grid ionisation chamber. A total amount of 216.60(17) mg of natural platinum has been measured for 75.9 days. The resulting half-life is (4.97 ± 0.16) × 10 11 years, with a total uncertainty of 3.2%. This number is in good agreement with the half-life obtained using the geological comparison method.
A method for cross-sectional doping of individual Si/SiO core/shell nanowires (NWs) is presented. P and B atoms are laterally implanted at different depths in the Si core. The healing of the implantation-related damage together with the electrical activation of the dopants takes place via solid phase epitaxy driven by millisecond-range flash lamp annealing. Electrical measurements through a bevel formed along the NW enabled us to demonstrate the concurrent formation of n- and p-type regions in individual Si/SiO core/shell NWs. These results might pave the way for ion beam doping of nanostructured semiconductors produced by using either top-down or bottom-up approaches.
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