Jorge L. B. Maciel

Bio: Jorge L. B. Maciel is an academic researcher from University of São Paulo. The author has contributed to research in topics: Thin film & Evaporation (deposition). The author has an hindex of 2, co-authored 3 publications receiving 29 citations.

Numerical simulation of the liquid phase in SnO2 thin film deposition by sol-gel-dip-coating

Abstract: The fluid flow of the liquid phase in the sol-gel-dip-coating process for SnO2 thin film deposition is numerically simulated. This calculation yields useful information on the velocity distribution close to the substrate, where the film is deposited. The fluid modeling is done by assuming Newtonian behavior, since the linear relation between shear stress and velocity gradient is observed. Besides, very low viscosities are used. The fluid governing equations are the Navier–Stokes in the two dimensional form, discretized by the finite difference technique. Results of optical transmittance and X-ray diffraction on films obtained from colloidal suspensions with regular viscosity, confirm the substrate base as the thickest part of the film, as inferred from the numerical simulation. In addition, as the viscosity increases, the fluid acquires more uniform velocity distribution close to the substrate, leading to more homogenous and uniform films.

Growth of Al2O3 thin film by oxidation of resistively evaporated Al on top of SnO2, and electrical properties of the heterojunction SnO2/Al2O3

Abstract: Aiming for the investigation of insulating properties of aluminum oxide (Al2O3) layers, as well as the combination of this oxide with tin dioxide (SnO2) for application in transparent field effect transistors, Al thin films are deposited by resistive evaporation on top of SnO2 thin films deposited by sol–gel dip-coating process. The oxidation of Al films to Al2O3 are carried out by thermal annealing at 500 °C in room conditions or oxygen atmosphere. X-ray diffraction data indicate that tetragonal Al2O3 is indeed obtained. A simple device and electric circuit is proposed to measure the insulating properties of aluminum oxide and the transport properties of SnO2 as well. Results indicate a fair insulation when four layers or Al2O3 are grown on the tin dioxide film, concomitant with thermal annealing between each layer. The current magnitude through the insulating layer is only 0.2% of the current through the semiconductor film, even though the conductivity of the SnO2 alone is not very high (the average resistivity is 2 Ω cm), because no doping is used. The presented results are a good indication that this combination may be useful for transparent devices.

Recent progress in direct patterning technologies based on nano-imprint lithography

Abstract: Nano-imprint lithography (NIL) is one of the most promising patterning technologies, in which nano- and micro-patterns are fabricated on various substrates. NIL provides high throughput and low cost in fabricating nano-structures due to its simple process and allows resolution below 10 nm without issues of light diffraction with conventional lithographic techniques. Its patterning mechanism is based on mechanical deformation of a polymer resist, which is simply done by pressing with a mold. This patterning mechanism also enables inorganic and organic-inorganic hybrid materials to be directly patterned by NIL. This article covers the recent progress of NIL-based direct patterning techniques and their applications to devices. Recently, functional nano- and micro-patterns have been applied to various electronic devices for the enhancement of overall performance. Fabrication methods of these devices are difficult using convention lithographic techniques due to complex processes, high cost and low throughput. Direct NIL technique using functional resist can simply fabricate functional nano- and micro-structures and thus can be usefully applied to various industries.

Performance and Stress Analysis of Metal Oxide Films for CMOS-Integrated Gas Sensors

Abstract: The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250°C and 550°C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed.

Dip-coating deposition of BiVO4/NiO p–n heterojunction thin film and efficiency for methylene blue degradation

Abstract: This paper deals with a simple FTO/p–n heterojunction electrode assembly formed by BiVO4 and NiO thin films, where the precursor solution is obtained by solution combustion synthesis and precipitation in aqueous media techniques, respectively, whereas the thin films were deposited by the dip-coating deposition process. The FTO/p–n electrodes are characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and UV–Vis spectroscopy. The performance analysis based on the methylene blue degradation reaction have shown that the p–n electrodes, FTO/p-NiO/n-BiVO4 and FTO/n-BiVO4/p-NiO have higher electroactivity under visible light irradiation condition when compared to single BiVO4 thin film, deposited separately, with estimated k obs value of 340 × 10−4 min−1, 270 × 10−4 min−1 and 150 × 10−4 min−1, respectively.