We present the results of an experimental study of superconducting, disordered, thin films of amorphous indium oxide. These films can be driven from the superconducting phase to a reentrant insulating state by the application of a perpendicular magnetic field (B). We find that the high-B insulator exhibits activated transport with a characteristic temperature, TI. TI has a maximum value (TpI) that is close to the superconducting transition temperature (Tc) at B=0, suggesting a possible relation between the conduction mechanisms in the superconducting and insulating phases. Tp(I) and Tc display opposite dependences on the disorder strength.

We present the results of an experimental study of the current-voltage characteristics in strong magnetic field (B) of disordered, superconducting, thin-films of amorphous Indium-Oxide. As the B strength is increased superconductivity degrades, until a critical field (B c ) where the system is forced into an insulating state. We show that the differential conductance measured in the insulating phase vanishes abruptly below a well-defined temperature, resulting in a clear threshold for conduction. Our results indicate that a new collective state emerges in two-dimensional superconductors at high B.

We report a comprehensive study of the complex ac conductivity of thin effectively two-dimensional amorphous superconducting InO x films at zero applied field. Below a temperature scale T c0 where the superconducting order parameter amplitude becomes well defined, there is a temperature where both the generalized superfluid stiffness acquires a frequency dependence and the dc magnetoresistance becomes linear in field. We associate this with a transition of the Kosterlitz-Thouless-Berezinskii ͑KTB͒ type. At our measurement frequencies the superfluid stiffness at T KTB is found to be larger than the universal value. Although this may be understood with a vortex dielectric constant of ⑀ v Ϸ 1.9 within the usual KTB theory, this is a relatively large value and indicates that such a system may be out of the domain of applicability of the low-fugacity ͑lowvortex-density͒ KTB treatment. This opens up the possibility that at least some of the discrepancy from a nonuniversal magnitude is intrinsic. Our finite-frequency measurements allow us access to a number of other phenomena concerning the charge dynamics in superconducting thin films, including an enhanced conductivity near the amplitude fluctuation temperature T c0 and a finite dissipation at low temperature which appears to be a universal aspect of highly disordered superconducting films.

We present the results from an experimental study of the magneto-transport of superconducting wires of amorphous Indium-Oxide, having widths in the range 40 -120 nm. We find that, below the superconducting transition temperature, the wires exhibit clear, reproducible, oscillations in their resistance as a function of magnetic field. The oscillations are reminiscent of those which underlie the operation of a superconducting quantum interference device.PACS numbers: 74.78. Na, 85.35.Ds, 73.21.Hb The central challenge in the study of thin superconducting wires is to understand how superconductivity is affected when approaching the one-dimensional (1D) limit. Earlier studies have predicted that intrinsic thermal [1, 2] and quantum [3,4,5] fluctuations play an increasingly important role in this limit, causing the wires to remain resistive much below the superconducting transition temperature, T c . Recent theories [6,7], incorporating the effect of electron-electron interactions, describe the suppression of T c when approaching the 1D limit, which was observed in experiments [8].In recent years new experimental techniques enabling the fabrication of superconducting wires with a diameter approaching the 1D limit were developed. The experiments that followed [9] focused primarily on whether the quantum resistance for a Cooper-pair, R Q = h/4e 2 ≈ 6.45 kΩ (h is Planck's constant and e is the charge of the electron) is the resistance scale that solely controls the existence of superconductivity. While some works [9,10] provided evidence that wires with a normal state resistance R N < R Q are superconducting and those with R N > R Q become insulating at low T , this point is still under debate [11].In this letter we report on an experimental study of the magnetic field (B) dependence of the resistance of superconducting wires whose dimensions are close to the 1D limit. We find that, while a strong B drives our wires into an insulating state, the magnetoresistance is dominated by reproducible periodic oscillations similar to those observed in superconducting quantum interference devices (SQUIDs) [12]. We also find that wires with R N >> R Q can exhibit superconductivity.In order to fabricate our 1D wires we utilized the method of Bezryadin et al. [9], in which a non-conducting nanotube, suspended across a narrow gap etched in a semiconductor substrate, is used as a template on which the superconductor is deposited. There are two experimental differences between our work and that of Ref.[9]. First, instead of carbon, our nanotubes were made of WS 2 [13]. Being a semiconductor with a bandgap of about 2 eV [14], WS 2 nanotubes are electrically insulating at low T and do not create a parallel conduction channel. We have verified that the nanotubes are insulating before depositing the superconducting material.Second, and more importantly, for the disordered superconductor we chose amorphous indium-oxide (a:InO). This choice was influenced by several of its properties. Since a:InO is known to form relatively uniform, superco...

We demonstrate 100 ns write/erase speed of single-walled carbon nanotube field-effect transistor (SWCNT-FET) memory elements. With this high operation speed, SWCNT-FET memory elements can compete with state of the art commercial Flash memories in this figure of merit. The endurance of the memory elements is shown to exceed 104 cycles. The SWCNT-FETs have atomic layer deposited hafnium oxide as a gate dielectric, and the devices are passivated by another hafnium oxide layer in order to reduce surface chemistry effects. We discuss a model where the hafnium oxide has defect states situated above, but close in energy to, the band gap of the SWCNT. The fast and efficient charging and discharging of these defects is a likely explanation for the observed operation speed of 100 ns which greatly exceeds the SWCNT-FET memory speeds of 10 ms observed earlier for devices with conventional gate oxides.