Oxide thin films for sustainable, multifunctional and flexible electronics

The growing range of applications of large-area electronics (LAE) in the last years is starting to require levels of performance, functionality and cost not compatible with the current thin-film technologies, such as a-Si or low-temperature polysilicon (LTPS) thin-film transistors (TFTs). This starts to be even more relevant when low-cost flexible substrates and processing technologies are considered. In this context, amorphous oxide semiconductors (AOS) are becoming essential materials in this field. AOS are recognized for their remarkable features such as good uniformity even when produced at room temperature, enabling applications in large area and flexible electronics; wide band gap (thus high transparency), making them suitable for transparent electronics; and good electrical performance despite their amorphous structure, enabling flexible circuitry operating at high-kHz to MHz range. Since the initial publication by Nomura et al. on indium-gallium-zinc oxide (IGZO) TFTs in 2004, these devices had a tremendous development and are now implemented in Gen10 display fabs for the production of low power consumption, high refresh rate and high resolution displays. But oxide electronics has a great potential for going well beyond display backplane applications: in fact, by combining new materials/structures, processing techniques and circuit design architectures having in mind conventional CMOS concepts adapted to the speed and (typically) unipolar limitations of oxide TFTs, these devices can be seen as a powerful platform for sustainable, multifunctional and flexible electronics. This presentation will precisely address these topics, which are currently being studied at CENIMAT: • Turning oxides into an even more sustainable approach for electronics, by replacing IGZO by indium- and gallium-free semiconductors, such as zinc-tin oxide (ZTO). Even if the initial reports on this material have shown largely inferior TFT performance and superior processing temperature when compared to IGZO TFTs, it will be shown that sputtered ZTO TFTs with On/Off ratio above 106, field effect mobility close to 10 cm2/Vs, subthreshold slope of 0.3 V/dec and non-significant performance variation under bending can now be obtained on PEN foil with only 150 C processing temperature. • Taking oxide TFTs towards the limits of microscale patterning, investigating the peculiarities found for oxide TFTs with channel lengths as low as 1 micron. While short channel effects as channel length modulation or drain induced barrier lowering start to be relevant, cut-off frequencies of oxide TFTs can exceed 100 MHz at this scale. The electrical characterization is being supported by TCAD simulations. [1, 2] • Integrating oxide TFTs in digital, analog and mixed-signal circuits with a significant level of complexity (100s of TFTs). To compensate for the intrinsic performance limitations compared to Si-based CMOS, high-gain topologies are being used to create logic gates, amplifiers, multipliers, phase-generators, among many other blocks. As examples, four-quadrant analog multipliers with a gain improvement of 7.2 dB over the Gilbert cell with the diode-connected load or amplifiers with a gain of 34 dB and a power consumption of 0.576 mW (load of 10 MOhm//16 pF) will be presented [3, 4]. These blocks are being used for different fields of applications, such as smart-bottles or flexible x-ray sensors. For this last application we recently found our oxide TFTs to have excellent ionizing-radiation hardness, showing to be insensitive even to exposure doses of 410 krad(SiO2) [5]. [1] Bahubalindruni, P. G. et al. Journal of Display Technology 12, 515-518 (2016) [2] Martins, J., Barquinha, P. & Goes, J. in Technological Innovation for Cyber-Physical Systems: 7th IFIP WG 5.5/SOCOLNET Advanced Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2016, Costa de Caparica, Portugal, April 11-13, 2016, Proceedings (eds M. Luis Camarinha-Matos, António J. Falcão, Nazanin Vafaei, & Shirin Najdi) 551-557 (Springer International Publishing, 2016) [3] Bahubalindruni, P. G. et al. Ieee Electron Device Letters 37, 419-421 (2016

Internship Report: AP/Portugal

The purpose of this report is to present the activities carried out during the six-month curricular internship at the company AP|PORTUGAL- Tech Language Solutions during the 2022/2023 academic year, in the 2nd semester of the 2nd year of the master's degree. This curricular internship was carried out to complete the Master's Degree in Intercultural Studies for Business at the Instituto de Contabilidade e Administração do Porto - Politécnico do Porto. Firstly, this document focuses on why I chose to do a curricular internship and what the expected objectives were when doing an internship at AP|PORTUGAL - Tech Language Solutions. This is followed by a detailed description of the host company, its mission, vision and objectives, the company's commitment to quality and a description of its departments. Finally, the activities and initiatives planned and carried out during the internship are presented, along with a brief analysis of them.O presente relatório tem como objetivo o relato das atividades realizadas ao longo do estágio curricular de seis meses na empresa AP|PORTUGAL– Tech Language Solutions durante o ano letivo 2022/2023, no 2.º semestre do 2º ano do mestrado. Este estágio curricular foi realizado para a conclusão do Mestrado em Estudos Interculturais para Negócios do Instituto de Contabilidade e Administração do Porto – Politécnico do Porto. Primeiramente, este documento centra-se na razão de ter escolhido fazer um estágio curricular e quais eram os objetivos esperados ao fazer um estágio na AP|PORTUGAL – Tech Language Solutions. Posteriormente, é feita descrição detalhada da entidade de acolhimento, a sua missão, visão e objetivos, o compromisso da empresa com a qualidade e descritos os departamentos desta. Por fim, apresentam-se as atividades e iniciativas previstas e desenvolvidas ao longo do estágio e uma breve análise destas

All-Standard-Cell-Based Analog-to-Digital Architectures Well-Suited for Internet of Things Applications

SMART-E-PTDC/CTM-PAM/04012/2022, IDS-PAPER-PTDC/CTM-PAM/4241/2020 and PEST (CTS/UNINOVA)-UIDB/00066/2020. This work also received funding from the European Community’s H2020 program [Grant Agreement No. 716510 (ERC-2016-StG TREND) and 952169 (SYNERGY, H2020-WIDESPREAD-2020-5, CSA)]. Publisher Copyright: © 2022 by the authors.In this paper, the most suited analog-to-digital (A/D) converters (ADCs) for Internet of Things (IoT) applications are compared in terms of complexity, dynamic performance, and energy efficiency. Among them, an innovative hybrid topology, a digital–delta (Δ) modulator (ΔM) ADC employing noise shaping (NS), is proposed. To implement the active building blocks, several standard-cell-based synthesizable comparators and amplifiers are examined and compared in terms of their key performance parameters. The simulation results of a fully synthesizable Digital-ΔM with NS using passive and standard-cell-based circuitry show a peak of 72.5 dB in the signal-to-noise and distortion ratio (SNDR) for a 113 kHz input signal and 1 MHz bandwidth (BW). The estimated (Formula presented.) is close to 16.2 fJ/conv.-step.publishersversionpublishe

Microwave-Assisted Hydrothermal Synthesis of Zn2SnO4 Nanostructures for Photocatalytic Dye Degradation

Zinc-tin oxide (ZTO) nanostructures appear as one of the most promising material systems for a new generation of nanodevices. In this work, a microwave-assisted hydrothermal synthesis to produce different shapes of Zn2SnO4 nanostructures (nanoparticles, octahedrons and nanoplates) is presented. Reproducible and homogeneous results were obtained with the advantage of reducing up to 20 h the synthesis time when compared to using a conventional oven. Furthermore, the photocatalytic activity of the Zn2SnO4 nanostructures in the degradation of rhodamine B under UV light was studied. Zn2SnO4 nanoparticles demonstrated better performance with >90% of degradation being achieved in 2.5 h.publishersversionpublishe

A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under positive gate bias stress

Thin film transistors (TFTs) employing an amorphous indium gallium zinc oxide (a-IGZO) channel layer exhibit a positive shift in the threshold voltage under the application of positive gate bias stress (PBS). The time and temperature dependence of the threshold voltage shift was measured and analysed using the thermalization energy concept. The peak energy barrier to defect conversion is extracted to be 0.75 eV and the attempt-to-escape frequency is extracted to be 107 s−1. These values are in remarkable agreement with measurements in a-IGZO TFTs under negative gate bias illumination stress (NBIS) reported recently (Flewitt and Powell, J. Appl. Phys. 115, 134501 (2014)). This suggests that the same physical process is responsible for both PBS and NBIS, and supports the oxygen vacancy defect migration model that the authors have previously proposed.The research leading to these results has received funding from the European Community’s 7th Framework Programme under grant agreement NMP3-LA-2010-246334. Financial support of the European Commission is therefore gratefully acknowledged. The work has also received funding from FEDER through the COMPETE 2020 Programme and National Funds through FCT–Portuguese Foundation for Science and Technology under the Project No. UID/CTM/50025/2013.This is the author accepted manuscript. The final version is available from AIP Publishing via http://dx.doi.org/10.1063/1.494324

Accurate determination of band tail properties in amorphous semiconductor thin film with Kelvin Probe Force Microscopy

Amorphous oxide semiconductors are receiving significant attention due to their relevance for large area electronics. Their disordered microscopic structure causes the formation of band tails in the density of states (DOS) that strongly affect charge transport properties. Bandtail properties are crucial to understand for optimizing thin film device performance. Among the available techniques to measure the DOS, KPFM is exceptional as it enables precise local electronic investigations combined with microscopic imaging. However, a model to interpret KPFM spectroscopy data on amorphous semiconductors of finite thickness is lacking. To address this issue, we provide an analytical solution to the Poisson's equation for a metal-insulator-semiconductor (MIS) junction interacting with the AFM tip. The solution enables us to fit experimental data for semiconductors with finite thickness and obtain the DOS parameters, such as band tail width (E_t), doping density (N_D), and flat band potential. To demonstrate our method, we perform KPFM experiments on Indium-Gallium-Zinc Oxide (IGZO) thin film transistors (IGZO-TFTs). DOS parameters compare well to values obtained with photocurrent spectroscopy. We demonstrate the potentials of the developed method by investigating the impact of ionizing radiation on DOS parameters and TFT performance. Our results provide clear evidence that the observed shift in threshold voltage is caused by static charge in the gate dielectric leading to a shift in flat band potential. Band-tails and doping density are not affected by the radiation. The developed methodology can be easily translated to different semiconductor materials and paves the way towards quantitative microscopic mapping of local DOS parameters in thin film devices

effect of physical parameters

POCI-01-0145-FEDER-007688. SFRH/BD/131836/2017. SFRH/BD/122286/2016.ZnSnO3 semiconductor nanostructures have several applications as photocatalysis, gas sensors, and energy harvesting. However, due to its multicomponent nature, the synthesis is far more complex than its binary counter parts. The complexity increases even more when aiming for low-cost and low-temperature processes as in hydrothermal methods. Knowing in detail the influence of all the parameters involved in these processes is imperative, in order to properly control the synthesis to achieve the desired final product. Thus, this paper presents a study of the influence of the physical parameters involved in the hydrothermal synthesis of ZnSnO3 nanowires, namely volume, reaction time, and process temperature. Based on this study a growth mechanism for the complex Zn:Sn:O system is proposed. Two zinc precursors, zinc chloride and zinc acetate, were studied, showing that although the growth mechanism is inherent to the material itself, the chemical reactions for different conditions need to be considered.publishersversionpublishe

Chapter Hydrothermal Synthesis of Zinc Tin Oxide Nanostructures for Photocatalysis, Energy Harvesting and Electronics

The massification of Internet of Things (IoT) and Smart Surfaces has increased the demand for nanomaterials excelling at specific properties required for their target application, but also offering multifunctionality, conformal integration in multiple surfaces and sustainability, in line with the European Green Deal goals. Metal oxides have been key materials for this end, finding applications from flexible electronics to photocatalysis and energy harvesting, with multicomponent materials as zinc tin oxide (ZTO) emerging as some of the most promising possibilities. This chapter is dedicated to the hydrothermal synthesis of ZTO nanostructures, expanding the already wide potential of ZnO. A literature review on the latest progress on the synthesis of a multitude of ZTO nanostructures is provided (e.g., nanowires, nanoparticles, nanosheets), emphasizing the relevance of advanced nanoscale techniques for proper characterization of such materials. The multifunctionality of ZTO will also be covered, with special attention being given to their potential for photocatalysis, electronic devices and energy harvesters

Microwave-Assisted Synthesis of Zn2SnO4 Nanostructures for Photodegradation of Rhodamine B under UV and Sunlight

Funding Information: This work is funded by National Funds through FCT—Portuguese Foundation for Science and Technology, Reference UIDB/50025/2020-2023. This work also received funding from the European Community’s H2020 program under grant agreement No. 716510 (ERC-2016-StG TREND) and No. 101008701 (EMERGE). Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.The contamination of water resources by pollutants resulting from human activities represents a major concern nowadays. One promising alternative to solve this problem is the photocatalytic process, which has demonstrated very promising and efficient results. Oxide nanostructures are interesting alternatives for these applications since they present wide band gaps and high surface areas. Among the photocatalytic oxide nanostructures, zinc tin oxide (ZTO) presents itself as an eco-friendly alternative since its composition includes abundant and non-toxic zinc and tin, instead of critical elements. Moreover, ZTO nanostructures have a multiplicity of structures and morphologies possible to be obtained through low-cost solution-based syntheses. In this context, the current work presents an optimization of ZTO nanostructures (polyhedrons, nanoplates, and nanoparticles) obtained by microwave irradiation-assisted hydrothermal synthesis, toward photocatalytic applications. The nanostructures’ photocatalytic activity in the degradation of rhodamine B under both ultraviolet (UV) irradiation and natural sunlight was evaluated. Among the various morphologies, ZTO nanoparticles revealed the best performance, with degradation > 90% being achieved in 60 min under UV irradiation and in 90 min under natural sunlight. The eco-friendly production process and the demonstrated ability of these nanostructures to be used in various water decontamination processes reinforces their sustainability and the role they can play in a circular economy.publishersversionpublishe