D. Busquets-Mataix

Pentacene thin films on ferromagnetic oxide: Growth mechanism and spintronic devices

We investigated the growth mechanism of pentacene thin films on La0.7Sr0.3MnO3. A diffusion limited, thermally activated growth was found. Pentacene molecules formed flat islands that were a few microns in size and whose growth during deposition showed a strong anisotropy. We extracted a nucleation energy of 0.65 ± 0.05 eV and a diffusion barrier energy of 0.7 ± 0.2 eV. We also estimated a critical nucleus size of three molecules. We show that vertical pentacene-based spintronic devices with La0.7Sr0.3MnO3 and Co electrodes demonstrated magnetoresistive effects up to room temperature. We also propose a route for pentacene-based spintronic devices improvement.

Electrocapacitance of hybrid film based on graphene oxide reduced by ascorbic acid

Abstract A simple chemical approach was employed to reduce graphene oxide in order to fabricate electrode coatings in close correlation with industrial production standards for supercapacitors. The morphology, structure, thermal stability and the residual oxygen functional groups in chemically reduced graphene oxide were analyzed. Cyclic voltammetry and charge/discharge measurements were employed to study the electrochemical performance of the coatings as a function of active material loading. The results showed an increase in the specific capacitance for chemically reduced graphene oxide-based coatings in comparison to commercial activated carbon, while the desired value needs to be optimized with respect to the conductivity of such materials.

Effect of tin-doped indium oxide film on electrodeposition of ZnO nanostructures

Surface studies are reported for the deposition of ZnO nanostructures by one-step electrodeposition method. The electrosynthesis was perfomed at the surface of tin doped indium oxide coated glass substrates in the absence of any buffer layer. The growth of ZnO nanostructures was investigated with the morphology of substrate and the deposition mode. Combined nucleation mode was observed for the ZnO independently of substrate. The results indicated the growth, morphology and density of the ZnO nanostructures are markedly influenced by both the substrate and the deposition conditions. It was observed the ZnO formation is defect site driven in case of galvanostatic deposition mode, while in case of potentiostatic deposition mode, it is dependent on the roughness of the substrate.

Factorial electrochemical design for tailoring of morphological and optical properties of Cu2O

ABSTRACT The electrodeposition of cuprous oxide (Cu2O) onto FTO-coated glass substrate was studied by using a statistical approach in order to control the Cu2O morphology and optical properties. The factorial design considered four electrodeposition conditions at two representative levels as input variables (electrolyte temperature and pH, deposition potential and duration) and the deposition charge and morphology of obtained Cu2O as the output variables. The morphology analysis showed the highest influence on crystal shape was exhibited by electrolyte temperature and pH, reaching significance levels of 95 and 98%, respectively. Temperature as low as 35°C and pH 12.2 results in cubic morphology, while other parameters result in octahedron shape. The highest absorbance was exhibited by the Cu2O with cubic morphology.

Hybrid glider Alba14 with laser-acoustic data transfer as a low-cost independent instrumentation data-mule

The management of sensor nodes on the sea floor represents an important challenge due to the high difficulties associated to the deployment and recovering of untethered instruments on the seafloor. These difficulties are not only related to the management of the instruments themselves but also related to the valuable information that can be lost. Ambient sound and interferences, maritime traffic, marine mammals behavior, oceanographic data are all among this critical information suitable to be registered. The fact of part of these information being missed, represent a void gap in the spatio-temporal identification phenomena analysis. For reducing the risk of losing information and with the aim of providing a feasible and low cost systems for recovering information from seafloor, a hybrid glider vehicle equipped with acoustic and laser optical communications is proposed. Preliminary studies as well as experimental results of optical/acoustic communications integrated in the hybrid glider Alba14 as data mule are presented.

Seed layer technique for high quality epitaxial manganite films

We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.