A5039857694- Advanced Memory and Neural Computing
- Conducting polymers and applications
- Neuroscience and Neural Engineering
- Thin-Film Transistor Technologies
- Organic Electronics and Photovoltaics
- Semiconductor materials and devices
- Semiconductor materials and interfaces
- Ferroelectric and Negative Capacitance Devices
- Organic Light-Emitting Diodes Research
- Transition Metal Oxide Nanomaterials
- Neural dynamics and brain function
- Molecular Junctions and Nanostructures
- Diamond and Carbon-based Materials Research
- Nanomaterials and Printing Technologies
- Analytical Chemistry and Sensors
- Force Microscopy Techniques and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Sensor and Energy Harvesting Materials
- Phase-change materials and chalcogenides
- Electrochemical sensors and biosensors
- Electrochemical Analysis and Applications
- Integrated Circuits and Semiconductor Failure Analysis
- Electronic and Structural Properties of Oxides
- Nanowire Synthesis and Applications
- Supercapacitor Materials and Fabrication
University of Coimbra
2021-2025
Instituto de Telecomunicações
2016-2025
University of Oxford
2025
University of Algarve
2011-2020
Universidade Nova de Lisboa
2016
Hospital de Faro EPE
2012-2015
Centro Universitário do Leste de Minas Gerais
2011-2014
University of Lisbon
2011
Johannes Kepler University of Linz
2011
Universidade Federal de São Carlos
2010
The electrical instability of organic field-effect transistors is investigated. We observe that the threshold-voltage shift (see figure) shows a stretched- exponential time dependence under an applied gate bias. activation energy 0.6 eV common for our and all other reported so far. constant supports charge trapping by residual water as origin.
A quantitative study of the dynamics threshold-voltage shifts with time in gallium-indium zinc oxide amorphous thin-film transistors is presented using standard analysis based on stretched exponential relaxation. For devices thermal silicon as gate dielectric, relaxation 3×105 s at room temperature activation energy 0.68 eV. These approach stability transistors. The threshold voltage shift faster after water vapor exposure suggesting that origin this instability charge trapping...
An investigation into the stability of metal-insulator-semiconductor (MIS) transistors based on α-sexithiophene is reported. In particular, kinetics threshold voltage shift upon application a gate bias has been determined. The follow stretched-hyperbola-type behavior, in agreement with formalism developed to explain metastability amorphous-silicon thin-film transistors. Using this model, quantification device possible. Temperature-dependent measurements show that there are two processes...
We report on the detailed electrical investigation of all-inkjet-printed thin-film transistor (TFT) arrays focusing TFT failures and their origins. The were manufactured flexible polymer substrates in ambient condition without need for cleanroom environment or inert atmosphere at a maximum temperature 150 °C. Alternative manufacturing processes electronic devices such as inkjet printing suffer from lower accuracy compared to traditional microelectronic methods. Furthermore, usually methods...
Resistive switching in nonvolatile, two terminal organic memories can be due to the presence of a native oxide layer at an aluminum electrode. Reproducible solid state realized by deliberately adding thin sputtered Al2O3 nominal electron-only, hole-only, and bipolar diodes. Before memory operation, devices have formed electric field 109V∕m, corresponding soft breakdown Al2O3. After forming, structures show pronounced negative differential resistance local maximum current scales with...
Abstract Microelectrode arrays (MEA) record extracellular local field potentials of cells adhered to the electrodes. A disadvantage is limited signal-to-noise ratio. The state-of-the-art background noise level about 10 μVpp. Furthermore, in MEAs low frequency events are filtered out. Here, we quantitatively analyze Au electrode/electrolyte interfaces with impedance spectroscopy and measurements. equivalent circuit charge transfer resistance parallel a constant phase element that describes...
The impact of a parylene top-coating layer on the illumination and bias stress instabilities indium-gallium-zinc oxide thin-film transistors (TFTs) is presented discussed. coating substantially reduces threshold voltage shift caused by continuous application gate light exposure. operational stability improves 75%, induced instability reduced 35%. quantified fitting with stretched exponential model. Storage time as long 7 months does not cause any measurable degradation electrical...
Field effect devices have been formed in which the active layer is a thin film of poly(3-methylthiophene) grown electrochemically onto preformed source and drain electrodes. Although field present after electrochemical undoping, stable device characteristics with high modulation ratio are obtained only vacuum annealing at an elevated temperature, then if held vacuo. The polymer shown to be p type operate accumulation only. hole mobility thermally annealed under around 10-3 cm2 V-1 s-1. On...
It is reported that the electrical instability known as bias stress caused by presence of trapped water in organic layer. Experimental evidence provided observation an anomaly occurring systematically at around 200K. This observed a variety materials, independent deposition techniques and remarkably coincides with phase transition supercooled water. Confined does not crystallize 273K but forms metastable liquid. behaves electrically charge trap, which causes instability. Below 200K finally...
A detailed investigation both of the DC and AC electrical properties Schottky barrier formed between aluminium electrodeposited poly(3-methylthiophene) is reported. The devices show rectification ratios up to 2*104 which can be increased further after post-metal annealing. reverse characteristics follow predictions based on image-force lowering barrier, from doping density estimated. As forward voltage increases, device current limited by bulk resistance polymer with some evidence for...
The electronic conduction of thin-film field-effect-transistors (FETs) sexithiophene was studied. In most cases the transfer curves deviate from standard FET theory; they are not linear, but follow a power law instead. These results compared to models “variable-range hopping” and “multi-trap-and-release”. accompanying IV Poole-Frenkel (exponential) dependence on drain voltage. explained assuming huge density traps. Below 200 K, activation energy for found be ca. 0.17 eV. energies mobility...
Solution-based indium–gallium–zinc oxide (IGZO) nanoparticles deposited by spin coating have been investigated as a resistive switching layer in metal–insulator–metal structures for nonvolatile memory applications. Optimized devices show bipolar behavior, low programming voltages of ±1 V, on/off ratios higher than 10, high endurance, and retention time up to 104 s. The better performing were achieved with annealing temperatures 200 °C using asymmetric electrode materials titanium silver....
Integration of technological solutions aims to improve accuracy, precision and repeatability in farming operations, biosensor devices are increasingly used for understanding basic biology during livestock production. The aim this study was design validate a miniaturized tri-axial accelerometer non-invasive monitoring farmed fish with re-programmable schedule protocols.The device attached the operculum gilthead sea bream European bass juveniles their physical activity by measurements movement...
Abstract Specific detection of dopamine (DA) is achieved with organic neuromorphic devices no specific recognition function in an electrolyte solution. The response to voltage pulses consists amplitude‐depressed current spiking mimicking the short‐term plasticity (STP) synapses. An equivalent circuit hints that STP timescale device arises from capacitance and resistance poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) series resistance. Both PEDOT:PSS change solution...
Organic–inorganic nanocomposites (RF/VOX) were prepared through sol–gel synthesis and pyrolysis treatment using a resorcinol–formaldehyde carbon matrix enriched with vanadium nanoparticles.
The study of quantum reference frames (QRFs) is motivated by the idea taking into account properties used, explicitly or implicitly, in our description physical systems. Like classical frames, QRFs can be used to define quantities relationally. Unlike their analogue, they relativise notions superposition and entanglement. Here, we explain this feature examining how configurations locations are identified across different branches superposition. We show that, presence symmetries, whether a...
Abstract An investigation into the stability of metal insulator semiconductor (MIS) transistors based on α ‐sexithiophene is reported. In particular kinetics threshold voltage shift upon application a gate bias has been determined. The follow stretched‐hyperbola type behavior, in agreement with formalism developed to explain metastability amorphous–silicon thin film transistors. Using this model, quantification device possible. Temperature‐dependent measurements show that there are two...
Extracellular electrode recording demonstrates acid-triggered electrical activity in glioma cell populations.