Electrical properties of strained off-stoichiometric Cu-Cr-O delafossite thin films.

Off-stoichiometric Cu-Cr-O delafossite thin films with different thicknesses were grown by metal organic chemical vapor deposition on substrates with different coefficients of thermal expansion. Seebeck thermoelectric coefficient and resistivity measurements were performed on the range of 300-850 K. A qualitative change in the temperature-dependence of the resistivity is observed at the temperature corresponding to the deposition process, where the transition from tensile to compressive strain takes place.

Two-Step Approach for Conformal Chemical Vapor-Phase Deposition of Ultra-Thin Conductive Silver Films.

Conductive ultra-thin silver films are commonly fabricated by physical vapor deposition methods such as evaporation or sputtering. The line-of-sight geometry of these techniques impedes the conformal growth on substrates with complex morphology. In order to overcome this issue, volume deposition technologies such as chemical vapor deposition or atomic layer deposition are usually preferred.

High Aspect Ratio Fin-Ion Sensitive Field Effect Transistor: Compromises toward Better Electrochemical Biosensing.

The development of next generation medicines demands more sensitive and reliable label-free sensing able to cope with increasing needs of multiplexing and shorter times to results. Field effect transistor-based biosensors emerge as one of the main possible technologies to cover the existing gap. The general trend for the sensors has been miniaturization with the expectation of improving sensitivity and response time but presenting issues with reproducibility and noise level.

Transparent Ferroelectric Capacitors on Glass.

We deposited transparent ferroelectric lead zirconate titanate thin films on fused silica and contacted them via Al-doped zinc oxide (AZO) transparent electrodes with an interdigitated electrode (IDE) design. These layers, together with a TiO₂ buffer layer on the fused silica substrate, are highly transparent (>60% in the visible optical range). Fully crystallized Pb(ZrTi)O₃ (PZT) films are dielectrically functional and exhibit a typical ferroelectric polarization loop with a remanent polarization of 15 μC/cm².

Twin-Induced InSb Nanosails: A Convenient High Mobility Quantum System.

Ultra narrow bandgap III-V semiconductor nanomaterials provide a unique platform for realizing advanced nanoelectronics, thermoelectrics, infrared photodetection, and quantum transport physics. In this work we employ molecular beam epitaxy to synthesize novel nanosheet-like InSb nanostructures exhibiting superior electronic performance. Through careful morphological and crystallographic characterization we show how this unique geometry is the result of a single twinning event in an otherwise pure zinc blende structure.

Confinement-modulated junctionless nanowire transistors for logic circuits.

We report the controlled formation of nanoscale constrictions in junctionless nanowire field-effect transistors that efficiently modulate the flow of the current in the nanowire. The constrictions act as potential barriers and the height of the barriers can be selectively tuned by gates, making the device concept compatible with the crossbar geometry in order to create logic circuits. The functionality of the architecture and the reliability of the fabrication process are demonstrated by designing decoder devices.

Magnetotransport subband spectroscopy in InAs nanowires.

We report on magnetotransport measurements in InAs nanowires under a large magnetic field (up to 55 T), providing a spectroscopy of the one-dimensional electronic band structure. Large modulations of the conductance mediated by a control of the Fermi energy reveal the Landau fragmentation, carrying the fingerprints of the confined InAs material. Our numerical simulations of the magnetic band structure consistently support the experimental results and reveal key parameters of the electronic confinement.

Persistent enhancement of the carrier density in electron irradiated InAs nanowires.

We report a significant and persistent enhancement of the conductivity in free-standing non-intentionally doped InAs nanowires upon irradiation in ultra-high vacuum. Combining four-point probe transport measurements performed on nanowires with different surface chemistries, field effect based measurements and numerical simulations of the electron density, the change in the conductivity is found to be caused by an increase in the surface free carrier concentration. Although an electron beam of a few keV, typically used for the inspection and the processing of materials, propagates through the entire nanowire cross-section, we demonstrate that the electrical properties of the nanowire are predominantly affected by radiation-induced defects occurring at the nanowire surface and not in the bulk.

Nonequilibrium fluctuation relations in a quantum coherent conductor.

We experimentally demonstrate the validity of nonequilibrium fluctuation relations by using a quantum coherent conductor. In equilibrium the fluctuation-dissipation relation leads to the correlation between current and current noise at the conductor, namely, the Johnson-Nyquist relation. When the conductor is voltage biased so that the nonlinear regime is entered, the fluctuation theorem has predicted similar nonequilibrium fluctuation relations, which hold true even when the Onsager-Casmir relations are broken in magnetic fields.

Self-aligned charge read-out for InAs nanowire quantum dots.

A highly sensitive charge detector is realized for a quantum dot in an InAs nanowire. We have developed a self-aligned etching process to fabricate in a single step a quantum point contact in a two-dimensional electron gas and a quantum dot in an InAs nanowire. The quantum dot is strongly coupled to the underlying point contact that is used as a charge detector.

Aharonov-Bohm oscillations in the presence of strong spin-orbit interactions.

We have measured highly visible Aharonov-Bohm (AB) oscillations in a ring structure defined by local anodic oxidation on a p-type GaAs heterostructure with strong spin-orbit interactions. Clear beating patterns observed in the raw data can be interpreted in terms of a spin geometric phase. Besides h/e oscillations, we resolve the contributions from the second harmonic of AB oscillations and also find a beating in these h/2e oscillations.