We report direct measurements of electrical transport through poly(dA)-poly(dT) and poly(dG)-poly(dC) DNA molecules containing identical base pairs. The observed experimental results suggest that electrical transport through DNA molecules occurs by polaron hopping. We have also investigated the effect of gate voltage on the current-voltage curve. It demonstrates the possibility of a DNA field-effect transistor operating at room temperature. Moreover, the gate-voltage dependent transport measurements show that poly(dA)-poly(dT) behaves as an n-type semiconductor, whereas poly(dG)-poly(dC) behaves as a p-type semiconductor.

The Cu-O pair-distribution function in a Bi 2 Sr 2 CaCu 2 O 8ϩy superconductor has been measured by polarized Cu K-edge extended x-ray-absorption fine structure at TϽT c . The results show an anomalous long Cu-O ͑planar͒ distance, 1.96 Å, assigned to distorted CuO 2 stripes of width W intercalated with undistorted stripes of width L. From the measurement of Lϭ15Ϯ0.5 Å we have calculated the energies E n of the bottom of the one-dimensional subbands of the superlattice and found that the Fermi level E F is tuned to a ''shape resonance'' E F ϪE n Ͻប D , where D is the Debye frequency, giving the T c amplification.

Inelastic electron tunneling spectroscopy is a powerful technique for investigating lattice dynamics of nanoscale systems including graphene and small molecules, but establishing a stable tunnel junction is considered as a major hurdle in expanding the scope of tunneling experiments. Hexagonal boron nitride is a pivotal component in two-dimensional Van der Waals heterostructures as a high-quality insulating material due to its large energy gap and chemical-mechanical stability. Here we present planar graphene/h-BN-heterostructure tunneling devices utilizing thin h-BN as a tunneling insulator. With much improved h-BN-tunneling-junction stability, we are able to probe all possible phonon modes of h-BN and graphite/graphene at Γ and K high symmetry points by inelastic tunneling spectroscopy. Additionally, we observe that low-frequency out-of-plane vibrations of h-BN and graphene lattices are significantly modified at heterostructure interfaces. Equipped with an external back gate, we can also detect high-order coupling phenomena between phonons and plasmons, demonstrating that h-BN-based tunneling device is a wonderful playground for investigating electron-phonon couplings in low-dimensional systems.

Epidermal electronics are extensively explored as an important platform for future biomedical engineering. Epidermal devices are typically fabricated using high‐cost methods employing complex vacuum microfabrication processes, limiting their widespread potential in wearable electronics. Here, a low‐cost, solution‐based approach using electroconductive reduced graphene oxide (RGO) sheets on elastic and porous poly(dimethylsiloxane) (PDMS) thin films for multifunctional, high‐performance, graphene‐based epidermal bioelectrodes and strain sensors is presented. These devices are fabricated employing simple coatings and direct patterning without using any complicated microfabrication processes. The graphene bioelectrodes show a superior stretchability (up to 150% strain), with mechanical durability up to 5000 cycles of stretching and releasing, and low sheet resistance (1.5 kΩ per square), and the graphene strain sensors exhibit a high sensitivity (a gauge factor of 7 to 173) with a wide sensing range (up to 40% strain). Fully functional applications of dry bioelectrodes in monitoring human electrophysiological signals (i.e., electrocardiogram, electroencephalography, and electromyogram) and highly sensitive strain sensors for precise detection of large‐scale human motions are demonstrated. It is believed that our unique processing capability and multifunctional device platform based on RGO/porous PDMS will pave the way for low‐cost processing and integration of 2D materials for future wearable electronic skin.

The statistical distribution of the Cu site conformations in the Cu02 plane of Bi2Sr2CaC~208+y (Bi 2212) has been measured by a fast and local probe Cu K-edge extended X-ray absorption f i e structure ( E M S ) as a function of temperature. The Cu site conformations are frozen at T < T* = 120 K -1.4 T, in two well-defined conformations characterized by two Cu-O(apica1) bond lengths separated by 0.17 2 0.02 k The Cu site conformations with short bond 2.38 2 0.02 A have a probability of 41 f 2% at T < T* . The diffraction experiments show that the Cu site conformations exhibit a one-dimensional anharmonic modulation, with period 1, = 25 b, that has been measured by electron diffraction. These data show that the modulation is anharmonic and the plane is decorated with stripes of distorted lattice characterized by the short Cu-O(apica1) bonds of width W = 11 f 1 A at T < T* that form domain walls for the stripes of width L -1 4 2 1 A, characterized by the long Cu-O(apica1) bond. The stripes of distorted lattice run below the lines of interstitial oxygen ions in the BiO plane, playing the role of acceptors. The lattice modulation is therefore assigned to polaronic impurity states ordered in linear arrays. The measure of the width W of the stripes provides the measure of the area of the polarons S, -4a2 (a = 5.4 A) where each hole dressed by the lattice distortion spans a domain of 8 Cu sites. with the same orbital symmetry [ll giving a correlated electron gas with 1 + d i holes per Cu site. There is experimental evidence at low doping, in the insulating phase, for a second class of holes with different orbital symmetry k(a), forming a polaron gas with local density el [2-51. In the metallic phase the polarons are indicated by the local structure which diverges from the average crystallographic structure [6-131. There are experiments showing that the L_(a) holes are trapped by the negative countercharges in the rocksalt layer forming polaronic impurity 0 Les Editions de Physique