We define two laterally gated small quantum dots with less than 15 electrons in an Aharonov-Bohm geometry in which the coupling between the two dots can be changed. We measure Aharonov-Bohm oscillations for weakly coupled quantum dots. In an intermediate coupling regime we study molecular states of the double dot and extract the magnetic field dependence of the coherently coupled states.

Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO(3) template layer with superior piezoelectric coefficients (e(31,f) = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.

Spin blockade occurs when an electron is unable to access an energetically favourable path through a quantum dot owing to spin conservation, resulting in a blockade of the current through the dot 1-6 . Spin blockade is the basis of a number of recent advances in spintronics, including the measurement and the manipulation of individual electron spins 7,8 . We report measurements of the spin blockade regime in a silicon double quantum dot, revealing a complementary phenomenon: lifetimeenhanced transport. We argue that our observations arise because the decay times for electron spins in silicon are long, enabling the electron to maintain its spin throughout its transit across the quantum dot and access fast paths that exist in some spin channels but not in others. Such long spin lifetimes are important for applications such as quantum computation and, more generally, spintronics.Semiconductor quantum dots or 'artificial atoms' provide highly tunable structures for trapping and manipulating individual electrons [9][10][11] . Such quantum dots are promising candidates as qubits for quantum computation [12][13][14] , owing in part to the long lifetimes and slow dephasing of electron spins in semiconductors 7,15 . Si quantum dots are predicted to have especially long lifetimes and slow dephasing, due to low spin-orbit interaction and low nuclear spin density 16,17 . In the past several years, much activity has focused on the development of quantum dots in Si/SiGe (refs 18-22) and recent advances in materials quality and fabrication techniques have enabled the observation of coherent spin phenomena in such quantum dots 23 . Spin-to-charge conversion, in which spin states are detected through their effect on charge motion, enables measurement of individual electron spins in quantum dots 15 . Spin blockade is the canonical example of spin-to-charge conversion in transport, where charge current is blocked in a double quantum dot by a metastable spin state. The blockade occurs when one electron is confined in the left dot and a further electron enters the right dot forming a spin triplet state T(1,1) (Fig. 1a). Exiting the dot requires reaching the triplet T(2,0), with both electrons in the left dot, a state that is higher in energy. The electron is thus trapped in the right dot, unless relaxation from T(1,1) to S(1,1) occurs, opening a downhill channel through S(2,0). As we show below, this aspect of spin blockade in Si is virtually identical to that previously observed in other systems 1-3 . The unexpected effect presented here is lifetime-enhanced transport (LET). The energy level diagram for LET is the same as for spin blockade, except that current flows in the opposite direction (Fig. 1b). Flow through the triplet channel is now energetically downhill, whereas flow through the singlet channel is very slow, because it requires either an uphill transition or tunnelling directly from the left dot to the right lead. Transport current will be observable only if electrons flow almost exclusively through the triplet channel,...

The state of the art technology for the study of ion channels is the patch clamp technique. Ion channels mediate electrical current flow, have crucial roles in cellular physiology, and are important drug targets. The most popular (whole cell) variant of the technique detects the ensemble current over the entire cell membrane. Patch clamping is still a laborious process, requiring a skilled experimenter to micromanipulate a glass pipette under a microscope to record from one cell at a time. Here we report on a planar, microstructured quartz chip for whole cell patch clamp measurements without micromanipulation or visual control. A quartz substrate of 200 microm thickness is perforated by wet etching techniques resulting in apertures with diameters of approximately 1 microm. The apertures replace the tip of glass pipettes commonly used for patch clamp recording. Cells are positioned onto the apertures from suspension by application of suction. Whole cell recordings from different cell types (CHO, N1E-115 neuroblastoma) are performed with microstructured chips studying K(+) channels and voltage gated Ca(2+) channels.

GCNBs were prepared by chemical vapor deposition at Tokai Carbon Co. Ltd. The detailed preparation procedure has been reported previously [18]. The structure of GCNBs was studied by X-ray diffraction (XRD) (Rigaku, Rint2500), Raman spectroscopy (JovinYvon, T-64 000), and TEM (Hitachi-9000).For the fabrication of GCNB electrodes, each GCNB sample was mixed with a solution of poly(vinylidene difluoride)/N-methylpyrrolidinone (PVdF/NMP) (KF # 1120, Kureha) to make a slurry of a suitable viscosity. The weight ratio of GCNBs to PVdF was adjusted to 9:1. Then, the slurry was spread onto a copper foil thinly and evenly to fabricate the electrodes. The electrode was allowed to stand in a draft overnight to evaporate most of the NMP solvent, and was then vacuum dried at 80°C for 1 day. The electrode thickness was ca. 100 lm. For electrochemical measurements, 1 mol dm -3 LiClO 4 dissolved in PC and 1 mol dm -3 LiClO 4 dissolved in EC:DEC (1:1 by volume) were used as electrolytes. The former and the latter electrolytes are referred to as PC-and EC-based electrolytes, respectively. CV measurements were performed in a three-electrode cell using a HSV-100 (Hokuto Denko) instrument. Alternating current (AC) impedance measurements were also conducted with a three-electrode cell using a Solartron SI 1255 impedance analyzer coupled with a SI 1480 multi-channel electrochemical interface over a frequency range from 100 kHz to 10 mHz with an AC oscillation of 10 mV. Lithium metal was used as the counter and reference electrodes, and the GCNB electrode served as the working electrode. Unless otherwise stated, potentials were referenced to lithium metal.