Francisco Paulo Rouxinol

University of Campinas | UNICAMP · Departamento de Física da Matéria Condensada (DFMC)

Over the past several decades, a rich series of experiments has repeatedly verified the quantum nature of superconducting devices, leading some of these systems to be regarded as artificial atoms. In addition to their application in quantum information processing, these `atoms' provide a test bed for studying quantum mechanics in macroscopic limits...

Mechanisms of gas sensing in sensors based on multi-wall carbon nanotubes decorated by Ti nanoparticles have been studied. Tests were performed with N-2, Ar and O-2 at low temperatures. Chemi-resistor sensor configurations with supported and suspended nanotubes were tested. Contributions from two gas sensing mechanisms (chemical and electrothermal)...

Molybdenum oxide thin films find diverse applications as catalysts, gas sensors, and electrochromic devices. Such films are produced mainly by reactive sputtering and thermal evaporation but other techniques such as chemical vapor deposition and electrochemical deposition have been used. In the present work, the feasibility of an alternative method...

Method to prepare suspended multilayer graphene (MLG) flakes and to form highly conductive (contact resistivity of similar to 0.1 k Omega mu m(2)) 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, followe...

Flexible self-standing supercapacitor devices (FSSS) have attracted great attention in several areas due to their potential use in a wide range of applications, such as roll-up displays, wearable electronics, and storage energy devices. However, the success of FSSS devices is highly dependent on their electrochemical properties. Here, we presented...

We show that a recent proposal for simulating planar hyperbolic lattices with circuit quantum electrodynamics can be extended to accommodate also higher dimensional lattices in Euclidean and non-Euclidean spaces if one allows for circuits with more than three polygons at each vertex. The quantum dynamics of these circuits, which can be constructed...

Superconducting metamaterials are a promising resource for quantum-information science. In the context of circuit QED, they provide a means to engineer on-chip dispersion relations and a band structure that could ultimately be utilized for generating complex entangled states of quantum circuitry, for quantum-reservoir engineering, and as an element...

https://arxiv.org/abs/1812.02579

Superconducting metamaterials are a promising resource for quantum information science. In the context of circuit QED, they provide a means to engineer on-chip, novel dispersion relations and a band structure that could ultimately be utilized for generating complex entangled states of quantum circuitry, for quantum reservoir engineering, and as an...

The present work aims to combine multilayer graphene (MLG) nanoparticles with Ordinary Portland Cement (OPC) mortar specimens, evaluating possible improvements on their mechanical properties and ultimately coming up with an ideal and effective concentration for future applications. Mortars with water/cement ratio of 0.4, MLG dosage varying from 0.0...

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 t...

Superconducting thin-film metamaterial resonators can provide a dense microwave mode spectrum with potential applications in quantum information science. We report on the fabrication and low-temperature measurement of metamaterial transmission-line resonators patterned from Al thin films. We also describe multiple approaches for numerical simulatio...

Superconducting systems have a long history of use in experiments that push the frontiers of mechanical sensing. This includes both applied and fundamental research, which at present day ranges from quantum computing research and efforts to explore Planck-scale physics to fundamental studies on the nature of motion and the quantum limits on our abi...

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...

Over the last decade, there has been an active effort to prepare and measure mechanical structures in the quantum regime for the purpose of sensing weak forces and for studying fundamental topics in quantum mechanics such as quantum measurement, entanglement and decoherence in new macroscopic limits. One promsing tool for such studies is the qubit-...

In recent years, various metamaterials have received substantial attention for their ability to exhibit simultaneous negative permittivity and permeability. Such systems are commonly referred to as left-handed materials and display a variety of counterintuitive properties. We are investigating one-dimensional metamaterials consisting of superconduc...

This book compiles articles from the Smart Nanocomposites Journal. Topics discussed include two different chemical routes to obtain graphene or few-later graphite; gas sensors based on multiwall carbon nanotubes decorated with different metal oxides nanoparticles; mechanism of multi-wall nanotube nucleation based on Mullins-Sekerka instability; sel...

The development of techniques to observe non-classical behavior of micro- and nano- scale mechanical structures has received considerable attention in recent years because of the potential to use these systems for fundamental studies of quantum mechanics as well as their possible role as new technologies for applications ranging from the sensing of...

The photothermally modulated magnetic resonance (PM-MR) technique was used to study thin films of Gd grown on fused quartz substrates. With this technique it was possible to observe the magnetic phase transitions for samples with different thickness and thermal treatments. Results were correlated with both magnetization and ESR measurements. The ef...

The study of gas sensors based on short MWCNTs in a chemical resistor configuration (where nanotubes can be heated considerably by current) has revealed two main effects occurring under exposure to simple low-pressure gases like Ar, N2 and O2, and manifestation of the effects is significantly different for supported (over SiO2) and suspended nanotu...

High resolution X-ray diffraction is applied to study Mn3+ doped potassium dihydrogen phosphate (KDP) single crystals as it function of dopant concentration with quantitative dopant composition within the crystals being assessed using Rutherford backscattering spectroscopy (RBS). Synchrotron radiation high resolution X-ray multiple diffraction Stud...

Multi-wall carbon nanotubes decorated by Ti nanoparticles were used for gas (N2, Ar, O2) sensing at low temperatures. Chemiresistor sensor configurations with supported and suspended nanotubes were tested. Two gas sensing mechanisms (chemical and electrothermal) were demonstrated, with their relative contributions strongly depending on the sensor c...

Experimental procedures have been developed to prepare carbon nanotubes (CNTs) decorated by metal oxides nanoparticles for gas sensing applications. For decoration of carbon nanotubes with Sn and Cu oxides, the concentration of precursors and time of sonication were found to be crucial parameters, to control the size and density of nanoparticles on...

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...

Hot-filament metal oxide deposition (HFMOD) is a variant of conventional hot-filament chemical vapor deposition (HFCVD) recently developed in our laboratory and successfully used to obtain high-quality, uniform films of MOx, WOx and VOx. The method employs the controlled oxidation of a filament of a transition metal heated to 1000 °C or more in a...

Silicon-based polymers and oxides may be formed when vapours of oxygen-containing organosilicone compounds are exposed to energetic electrons drawn from a hot filament by a bias potential applied to a second electrode in a controlled atmosphere in a vacuum chamber. As little deposition occurs in the absence of the bias potential, electron impact fr...

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 crysta...

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 crysta...

Polymer films synthesized from plasmas of a tetramethylsilane - Ar mixture were modified by irradiation with 170 keV He ions at fluences ranging from 1 × 1014 to 1 × 1016 cm-2. As revealed by infrared spectroscopy, the ion beam produced intense bond rearrangements, such as the depletion of bonding groups (C-H and Si-H), and induced the formation of...

This work describes an XPS investigation of plasma-deposited polysiloxane films irradiated with 170 keV He+ ions at fluences, Phi, ranging from 1 x 10(14) to 1 x 10(16) cm(-2). Modifications in the atomic concentrations of the surface atoms with (D were revealed by changes in the [O]/[Si], [O]/[C] and [C]/[Si] atomic ratios. Surface chemical struct...

This work illustrates the advantages of using p-polarized radiation at an incidence angle of 70° in contrast to the conventional unpolarized beam at normal (or near-normal) incidence for the infrared spectroscopic study of polycarbosilane, polysilazane and polysiloxane thin films synthesized by plasma enhanced chemical vapor deposition (PECVD) and...

The effects of ion irradiation on the composition, structure, compactness, and surface hardness of polyorganosiloxane films synthesized by plasma-enhanced chemical vapor deposition were investigated as a function of the ion mass and fluence. The films were obtained from a glow discharge plasma of a hexamethyldisiloxane (HMDSO)-O2-Ar mixture, and th...

The present work describes the effects of diluting hexamethyldisilazane (HMDSN) vapor either in pure argon or in oxygen−argon mixtures on the solid film deposited from the resulting plasma. Such a dilution provides a manner of incorporating controllable amounts of Si−O groups into the solid film. The characterization of the films investigated here...

Thin films of tungsten oxide deposited by hot filament metal oxide deposition (HFMOD) were thermally annealed up to 800 °C and investigated by means of XRD, Raman spectroscopy, and infrared reflection−absorption spectroscopy (IRRAS). As clearly shown by the XRD and Raman spectroscopy data, the deposited films were amorphous and crystallized by ther...

This short report describes a novel method for the synthesis of metal oxide thin films. The experimental setup consists of a metal filament installed inside a vacuum chamber. The filament can be heated by an ac power supply while oxygen is admitted into the chamber using a mass flowmeter. From reactions between oxygen and the heated metal filament,...

Plasma-enhanced chemical vapor deposition (PECVD) of mixtures of hexamethyldisiloxane and acetylene can be used to synthesize thin films of nanocomposites constituted of hydrogenated amorphous carbon and siloxane networks, as evidenced by transmission electron micrographs and infrared spectroscopy.

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 oxyge...

Amorphous films (a-C:H:Si and a-C:H:Si:O) were grown in a vacuum chamber containing a hot filament on substrates held on a copper plate to which a bias voltage could be applied. This modified hot-filament chemical vapor deposition process was used to fabricate various types of amorphous thin film from mixtures of tetramethylsilane (TMS) or hexameth...

Actinometric optical emission spectrometry was used to determine the relative concentrations of the species H, CH, N2 and CN as a function of the ratio of the nitrogen flow rate to the acetylene flow rate in acetylene–nitrogen–helium–argon mixtures. The forms of these concentration functions are discussed in terms of gas-phase molecular fragmentati...