Firmino, R., E. Carlos, J. V. Pinto, J. Deuermeier, R. Martins, E. Fortunato, P. Barquinha, and R. Branquinho,
"{Solution Combustion Synthesis of Hafnium-Doped Indium Oxide Thin Films for Transparent Conductors}",
Nanomaterials, vol. 12, no. 13, pp. 2167, jun, 2022.
Abstract{\textless}p{\textgreater}Indium oxide (In2O3)-based transparent conducting oxides (TCOs) have been widely used and studied for a variety of applications, such as optoelectronic devices. However, some of the more promising dopants (zirconium, hafnium, and tantalum) for this oxide have not received much attention, as studies have mainly focused on tin and zinc, and even fewer have been explored by solution processes. This work focuses on developing solution-combustion-processed hafnium (Hf)-doped In2O3 thin films and evaluating different annealing parameters on TCO's properties using a low environmental impact solvent. Optimized TCOs were achieved for 0.5 M{%} Hf-doped In2O3 when produced at 400 °C, showing high transparency in the visible range of the spectrum, a bulk resistivity of 5.73 × 10−2 $Ømega$.cm, a mobility of 6.65 cm2/V.s, and a carrier concentration of 1.72 × 1019 cm−3. Then, these results were improved by using rapid thermal annealing (RTA) for 10 min at 600 °C, reaching a bulk resistivity of 3.95 × 10 −3 $Ømega$.cm, a mobility of 21 cm2/V.s, and a carrier concentration of 7.98 × 1019 cm−3, in air. The present work brings solution-based TCOs a step closer to low-cost optoelectronic applications.{\textless}/p{\textgreater}
Branquinho, R., J. V. Pinto, T. Busani, P. Barquinha, L. Pereira, P. V. Baptista, R. Martins, and E. Fortunato,
"{Plastic Compatible Sputtered Ta O Sensitive Layer for Oxide Semiconductor TFT Sensors}",
Journal of Display Technology, vol. 9, no. 9, pp. 723–728, 2013.
AbstractThe effect of post-deposition annealing temperature on the pH sensitivity of room temperature RF sputtered Ta O was investigated. Structural and morphological features of these films were analyzed before and after annealing at various tem- peratures. The deposited films are amorphous up to 600 Cand crystallize at 700 C in an orthorhombic phase. Electrolyte-insu- lator-semiconductor (EIS) field effect based sensors with an amor- phousTa O sensing layer showed pHsensitivity above 50 mV/pH. For sensors annealed above 200 C pH sensitivity decreased with increasing temperature. Stabilized sensor response andmaximum pHsensitivitywas achieved after low temperature annealing at 200 C, which is compatible with the use of polymeric substrates and application as sensitive layer in oxides TFT-based sensors
Figueiredo, V., E. Elangovan, R. Barros, J. V. Pinto, T. Busani, R. Martins, and E. Fortunato,
"{p-Type Cu x O Films Deposited at Room Temperature for Thin-Film Transistors}",
Journal of Display Technology, vol. 8, no. 1, pp. 41–47, 2012.
AbstractThin-films of copper oxide @Cu OA were sputtered from a metallic copper (Cu) target and studied as a function of oxygen partial pressure @O??A. A metallic Cu film with cubic structure obtained from 0{%} O?? has been transformed to cubic CuPO phase for the increase in O?? to 9{%} but then changed to monoclinic CuO phase (for O?? PS7). The variation in crystallite size (calculated from x-ray diffraction data) was further substantiated by the variation in grain size (surface microstruc- tures). The Cu O films produced with O?? ranging between 9{%} and 75{%} showed p-type behavior, which were successfully applied to produce thin-film transistors.
Figueiredo, V., J. V. Pinto, J. Deuermeier, R. Barros, E. Alves, R. Martins, and E. Fortunato,
"{p-Type Cu O Thin-Film Transistors Produced by Thermal Oxidation}",
Journal of Display Technology, vol. 9, no. 9, pp. 735–740, 2013.
AbstractThin-films of copper oxide Cu O were produced by thermal oxidation of metallic copper (Cu) at different tempera- tures (150–450 C). The films produced at temperatures of 200, 250 and 300 C showed high Hall motilities of 2.2, 1.9 and 1.6 cm V s , respectively. Single Cu O phases were obtained at 200 Cand its conversion toCuO starts at 250 C. For lower thick- nesses 40 nm, the films oxidized at 250 Cshowed a complete conversion to CuO phase. Successful thin-film transistors (TFTs) were produce by thermal oxidation of a 20 nm Cu film, obtaining p-type Cu O (at 200 C) and CuO (at 250 C) with On/Off ratios of 6 10 and 1 10 , respectively.
Kiazadeh, A., D. Salgueiro, R. Branquinho, J. Pinto, H. L. Gomes, P. Barquinha, R. Martins, and E. Fortunato,
"{Operational stability of solution based zinc tin oxide/SiO2 thin film transistors under gate bias stress}",
APL Materials, vol. 3, no. 6, pp. 062804, 2015.
AbstractIn this study, we report solution-processed amorphous zinc tin oxide transistors exhibiting high operational stability under positive gate bias stress, translated by a recoverable threshold voltage shift of about 20{%} of total applied stress voltage. Under vacuum condition, the threshold voltage shift saturates showing that the gate-bias stress is limited by trap exhaustion or balance between trap filling and emptying mechanism. In ambient atmosphere, the threshold voltage shift no longer saturates, stability is degraded and the recovering process is impeded. We suggest that the trapping time during the stress and detrapping time in recovering are affected by oxygen adsorption/desorption processes. The time constants extracted from stretched exponential fitting curves are ≈106 s and 105 s in vacuum and air, respectively.
Morais, A. R. C., J. V. Pinto, D. Nunes, L. B. Roseiro, M. C. Oliveira, E. Fortunato, and R. Bogel-Łukasik,
"{Imidazole: Prospect Solvent for Lignocellulosic Biomass Fractionation and Delignification}",
ACS Sustainable Chemistry {&} Engineering: American Chemical Society, dec, 2015.
Abstractn/a
Cruz, M. M., R. C. Silva, J. V. Pinto, R. P. Borges, N. Franco, and A. Casaca,
"{Formation of oriented nickel aggregates in rutile single crystals by Ni implantation}",
Journal of Magnetism and Magnetic Materials, vol. 340: Elsevier, pp. 102–108, 2013.
AbstractThe magnetic and electrical properties of Ni implanted single crystalline TiO2 rutile were studied for nominal implanted fluences between 0.5?1017 cm−2 and 2.0?1017 cm−2 with 150 keV energy, corre- sponding to maximum atomic concentrations between 9 at{%} and 27 at{%} at 65 nm depth, in order to study the formation of metallic oriented aggregates. The results indicate that the as implanted crystals exhibit superparamagnetic behavior for the two higher fluences, which is attributed to the formation of nanosized nickel clusters with an average size related with the implanted concentration, while only paramagnetic behavior is observed for the lowest fluence. Annealing at 1073 K induces the aggregation of the implanted nickel and enhances the magnetization in all samples. The associated anisotropic behavior indicates preferred orientations of the nickel aggregates in the rutile lattice consistent with Rutherford backscattering spectrometry—channelling results. Electrical conductivity displays anisotropic behavior but no magnetoresistive effects were detected.
Nunes, D., T. R. Calmeiro, S. Nandy, J. V. Pinto, A. Pimentel, P. Barquinha, P. A. Carvalho, J. C. Walmsley, E. Fortunato, and R. Martins,
"{Charging effects and surface potential variations of Cu-based nanowires}",
Thin Solid Films: Elsevier B.V., pp. 1–9, 2015.
AbstractThe presentwork reports charging effects and surface potential variations in pure copper, cuprous oxide and cu- pric oxide nanowires observed by electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). The copper nanowires were produced by wet synthesis, oxidation into cuprous oxide nanowires was achieved throughmicrowave irradiation and cupric oxide nanowireswere obtained via furnace annealing in at- mospheric conditions. Structural characterization of the nanowireswas carried out byX-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. During the EFM experiments the electrostatic field of the positive probe charged negatively the Cu-based nanowires, which in turn polarized the SiO2 dielectric substrate. Both the probe/nanowire capacitance as well as the sub- strate polarization increased with the applied bias. Cu2O and CuO nanowires behaved distinctively during the EFMmeasurements in accordancewith their band gap energies. Thework functions(WF) of the Cu-based nano- wires, obtained by KPFM measurements, yieldedWFCuO N WFCu N WFCu2O
Casella, C., H. Costantini, a. Lemut, B. Limata, D. Bemmerer, R. Bonetti, C. Broggini, L. Campajola, P. Cocconi, P. Corvisiero, J. Cruz, a. D'Onofrio, a. Formicola, Z. Fülöp, G. Gervino, L. Gialanella, a. Guglielmetti, C. Gustavino, G. Gyurky, a. Loiano, G. Imbriani, P. a. Jesus, M. Junker, P. Musico, a. Ordine, F. Parodi, M. Parolin, J. V. Pinto, P. Prati, J. P. Ribeiro, V. Roca, D. Rogalla, C. Rolfs, M. Romano, C. Rossi-Alvarez, a. Rottura, F. Schuemann, E. Somorjai, F. Strieder, F. Terrasi, H. P. Trautvetter, a. Vomiero, and S. Zavatarelli,
"{A new setup for the underground study of capture reactions}",
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, vol. 489, pp. 160–169, 2002.
AbstractFor the study of astrophysically relevant capture reactions in the underground laboratory LUNA a new setup of high sensitivity has been implemented. The setup includes a windowless gas target, a 4$π$ BGO summing crystal, and beam calorimeters. The setup has been recently used to measure the d(p,$\gamma$)3He cross-section for the first time within its solar Gamow peak, i.e. down to 2.5keV c.m. energy. The features of the optimized setup are described. © 2002 Elsevier Science B.V. All rights reserved.