Papers by Marco Roberto Cavallari
Energies
With the current worsening of climate change-associated risks, the transition to low-carbon energ... more With the current worsening of climate change-associated risks, the transition to low-carbon energy sources has become a global priority. In this context, the advances in the implementation of smart grids, which, in addition to greater efficiency and resilience, also allow greater penetration of renewable distributed energy resources, are becoming increasingly important. However, the necessary investments will be colossal. Many specialists see the process of opening up the electric energy markets as essential to boosting these new technologies. Greater decentralization of the decision-making process can potentially promote greater scalability. However, not all liberalization reforms have led to good results. Several researchers have been evaluating experiences in different countries. Brazil, a country with continental dimensions and peculiar characteristics, already counts with a mostly renewable electric energy generation mix. In recent decades, however, it has become increasingly d...
Journal of Integrated Circuits and Systems
This work is focused on the bias stress (BS) effects in Organic Thin-Film Transistors (OTFTs) fro... more This work is focused on the bias stress (BS) effects in Organic Thin-Film Transistors (OTFTs) from poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14) on both highly-doped Si and glass substrates. While the former had a thermally-grown SiO2 dielectric, the latter demanded an alternative dielectric that should be capable to withstand bottom contact lithography, as well as semiconducting thin-film deposition. In addition, it should represent one more step towards flexible electronics. In order to do that, poly(4-vinylphenol) (PVP) was blended to poly(melamine-co-formaldehyde) methylated (PMF). OTFTs on glass with a cross-linked polymer dielectric had a charge carrier mobility (μ) of 4.0x10-4 cm2/Vs, threshold voltage (VT) of 18 V, current modulation (ION/OFF) higher than 1x102, and subthreshold slope (SS) of -7.7 V/dec. A negative BS shifted VT towards negative values and produced an increase in ION/OFF. A positive BS, on the other hand, produced the opposite effect ...
2017 75th Annual Device Research Conference (DRC)
Journal of Integrated Circuits and Systems
Cross-linked polymer films with poly(melamine-co-formaldehyde) methylated (PMF) were investigated... more Cross-linked polymer films with poly(melamine-co-formaldehyde) methylated (PMF) were investigated in order to integrate flexible organic transistor-based sensors. By blending poly(methyl methacrylate) (PMMA) with PMF, solutions showed reduced viscosity for wet processing. Thin-films from poly (4-vinylphenol) (PVP) blends with PMF featured lower RMS roughness (0.37 nm) and higher dielectric constant (k ~ 3.7 – 5.7). The presence of enhanced cross-linking at higher PMF concentrations was confirmed for both polymers from chemical resistance essays and structural characterization.
Advanced Functional Materials
Journal of Applied Physics, 2003
Detailed investigations on shelf life and operation lifetime of polymer field-effect transistors ... more Detailed investigations on shelf life and operation lifetime of polymer field-effect transistors (PFETs) and circuits are reported. All examined devices consisted entirely of polymer materials except the electrodes. Regioregular poly(3-alkylthiophene) was used as a semiconductor. Unencapsulated devices were produced, stored, and measured under ambient conditions. The performance of PFETs was maintained for more than 12 months after production. Even under
MRS Proceedings, 2012
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Low Voltage Organic Devices with High-k TiOxNy and PMMA Dielectrics for Future Application on Fle... more Low Voltage Organic Devices with High-k TiOxNy and PMMA Dielectrics for Future Application on Flexible Electronics. [ECS Transactions 39, 455 (2011)]. Vinicius R. Zanchin, Marco Roberto Cavallari, Fernando J. Fonseca, Katia F. Albertin, Inés Pereyra, Adnei M. Andrade. ...
Materials Chemistry and Physics, 2015
IEEE Transactions on Device and Materials Reliability
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Polymeric semiconductors as poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PP... more Polymeric semiconductors as poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) have been widely studied in the last years thanks to their electronic and optical properties suitable for applications on opto-electronic devices such as Light-Emitting Diodes (LED) . These materials are well-suited for the fabrication of rigid and flexible ultra-thin displays, characterized by low power consumption and high-quality images [1]. π-conjugated polymers have been widely studied [2, 3], but despite their importance and all the acquired knowledge in the last years, the charge transport mechanisms are still not fully understood. A detailed description of the states and charge carrier mobility requires many efforts due to difficulties found in conventional techniques such as Time-of-Flight (ToF) and due to the small thickness of the films . In this context, our objective is to apply a new and powerful technique, Charge Extraction in a Linearly Increasing Voltage (CELIV), to determine charge carrier mobility in sandwiched structures where the active layer thickness is in the order of hundreds of nanometers. The validity of the results will be demonstrated by comparing them to more conventional techniques, such as Time-of-flight (ToF), Dark Injection in Space Charge Limited Current (DI-SCLC) and Current density versus Voltage (J vs. V) measurements, reaching the minimum thickness where other techniques fail to work. Results from CELIV measurements applied to PLEDs degradation studies by observing changes in carrier mobility and charge injection on samples exposed to air and kept in vacuum will be shown.
Journal of Integrated Circuits and Systems
Sensors, 2015
Electronic devices based on organic thin-film transistors (OTFT) have the potential to supply the... more Electronic devices based on organic thin-film transistors (OTFT) have the potential to supply the demand for portable and low-cost gadgets, mainly as sensors for in situ disease diagnosis and environment monitoring. For that reason, poly(3-hexylthiophene) (P3HT) as the active layer in the widely-used bottom-gate/bottom-contact OTFT structure was deposited over highly-doped silicon substrates covered with thermally-grown oxide to detect vapor-phase compounds. A ten-fold organochloride and ammonia sensitivity compared to bare sensors corroborated the application of this semiconducting polymer in sensors. Furthermore, P3HT TFTs presented approximately three-order higher normalized sensitivity than any chemical sensor addressed herein. The results demonstrate that while TFTs respond linearly at the lowest concentration values herein, chemical sensors present such an operating regime mostly above 2000 ppm. Simultaneous alteration of charge carrier mobility and threshold voltage is responsible for pushing the detection limit down to units of ppm of ammonia, as well as tens of ppm of alcohol or ketones. Nevertheless, P3HT transistors and chemical sensors could compose an electronic nose operated at room temperature for a wide range concentration evaluation (1-10,000 ppm) of gaseous analytes. Targeted analytes include not only biomarkers for diseases, such as uremia, cirrhosis, lung cancer and diabetes, but also gases for environment monitoring in food, cosmetic and microelectronics industries.
Journal of Solar Energy Engineering, 2014
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MRS Proceedings, 2012
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ECS Transactions, 2009
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28th Symposium on Microelectronics Technology and Devices (SBMicro 2013), 2013
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Papers by Marco Roberto Cavallari