Francisco Rouxinol

Low contact resistivity and strain in suspended multilayer graphene

Method to prepare suspended multilayer graphene (MLG) flakes and to form highly conductive (contact resistivity of ∼0.1 kΩ μm2) and tight mechanical connection between MLG and metal electrodes is described. MLG flakes prepared from natural graphite were precisely deposited over tungsten electrodes using dielectrophoresis, followed by high-temperature thermal annealing in high-vacuum. Considerable strain induced in the suspended part of flakes was revealed by Raman imaging.

Li diffusion and electrochromism in amorphous and crystalline vanadium oxide thin film electrodes

Amorphous vanadium oxide films were synthesized onto ITO-coated glass substrates by the hot filament metal oxide deposition technique. The as-deposited samples were heat-treated in an argon atmosphere. X-ray diffraction analysis revealed that the films treated at 200 and 300 oC were still amorphous, while those treated at 400 and 500 oC were crystalline, with a V2O5 structure. All electrodes were electrochemically reversible for Li+ intercalation, exhibiting the electrochromic effect, observed from optical transmittance measurements at 632.8 nm. The Li-diffusion coefficient, DC, was measured by the galvanostatic intermittent titration technique (GITT) as function of the inserted charge. For the crystalline films it was observed that the optical absorbance and the DC increase with increasing Li insertion in the single-phase regions of crystalline LixV2O5 and decrease in the two-phase regions. For the latter, an effective DC was considered. The presence of other vanadium oxides mixed to the V2O5 matrix was inferred for the crystalline films from the chronopotentiometric and DC measurements.

Measurements of nanoresonator-qubit interactions in a hybrid quantum electromechanical system

Experiments to probe the basic quantum properties of motional degrees of freedom of mechanical systems have developed rapidly over the last decade. One promising approach is to use hybrid electromechanical systems incorporating superconducting qubits and microwave circuitry. However, a critical challenge facing the development of these systems is to achieve strong coupling between mechanics and qubits while simultaneously reducing coupling of both the qubit and mechanical mode to the environment. Here we report measurements of a qubit-coupled mechanical resonator system consisting of an ultra-high-frequency nanoresonator and a long coherence-time superconducting transmon qubit, embedded in a superconducting coplanar waveguide cavity. It is demonstrated that the nanoresonator and transmon have commensurate energies and transmon coherence times are one order of magnitude larger than for all previously reported qubit-coupled nanoresonators. Moreover, we show that numerical simulations of this new hybrid quantum system are in good agreement with spectroscopic measurements and suggest that the nanoresonator in our device resides at low thermal occupation number, near its ground state, acting as a dissipative bath seen by the qubit. We also outline how this system could soon be developed as a platform for implementing more advanced experiments with direct relevance to quantum information processing and quantum thermodynamics, including the study of nanoresonator quantum noise properties, reservoir engineering, and nanomechanical quantum state generation and detection.

Magnetism in Gd-W films

Vapor condensation techniques are useful to prepare magnetic alloys whose components have low or even negligible equilibrium mutual solubility. In this work, one of these techniques—sputtering—was used to obtain GdxW1−x alloys whose magnetic properties were investigated as a function of the Gd atomic concentration x. Gadolinium and various Gd-based alloys are promising materials for magnetic refrigeration and this was one of the motivations for this study. The Gdx–W1−x films were sputter deposited from Gd and W targets with x ranging from 0 to 1 as determined by x-ray energy-dispersive spectroscopic analyses. X-ray diffraction patterns indicate that crystalline structures were formed at low and high Gd concentrations, while at intermediate concentrations, the films were amorphous. Magnetization measurements, performed as a function of temperature and with static and alternating applied fields, reveal a spin glasslike behavior in all the W-containing samples for temperatures below the freezing temperature ...

Tungsten Oxide Films of High Electrochromic Efficiencies Obtained by Deposition

Amorphous tungsten oxide films of high electrochromic efficiency were produced by a chemical vapor deposition technique in which the precursors of film formation are generated at the surface of a heated tungsten filament by reactions of tungsten with oxygen. The film deposition rate was determined as a function of the filament temperature and oxygen pressure. Molecular structure investigations using X-ray photoelectron spectroscopy revealed that the tungsten oxide was in the WO 3 stoichiometry. The electrochromic properties of the films were studied for Li + intercalation. Optical efficiencies as high as 78 and 125 cm 2 /C at 632.8 and 950 nm, respectively, and absorbance changes from 0.07 to 1.1 were measured between the bleached and the colored states at 632.8 nm.

Development of a broadband reflective T-filter for voltage biasing high-Q superconducting microwave cavities

We present the design of a reflective stop-band filter based on quasi-lumped elements that can be utilized to introduce large dc and low-frequency voltage biases into a low-loss superconducting coplanar waveguide (CPW) cavity. Transmission measurements of the filter are seen to be in good agreement with simulations and demonstrate insertion losses greater than

Testing time reversal symmetry in artificial atoms

20\,{\rm dB}

Electron emission enhanced chemical vapor deposition (EEECVD) for the fabrication of diverse silicon-containing films☆

in the range of

Gas-phase and plasma-surface reactions in radiofrequency discharges of C2H2–N2–noble gas mixtures

{\rm 3\,to\,10\,GHz}

Superconducting metamaterials and qubits

. Moreover, transmission measurements of the CPWs fundamental mode demonstrate that loaded quality factors exceeding