Applied sciences

Opto-Electronics Review

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Opto-Electronics Review | 2024 | 32 | 4

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Abstract

Field-effect transistors (FETs) are efficient detectors of THz radiation. Despite over three decades of research, controversy still exists regarding the detection mechanism. The article attempts to solve this problem systemically. Existing approaches to modeling THz detection are critically reviewed, including plasmonic, resistive mixing, hot carrier and thermal models. Limitations and inconsistencies of the first two approaches, along with some classical physics principles and experiments conducted, were identified. These include the facts that some models were formulated independently of material relaxation time constraints, and the plasmonic approach does not take into account the conditions for the formation of surface plasmon-polarons and does not describe the case of p-type devices (hole plasmons have never been experimentally recorded). Relevant measurements and theoretical considerations illustrate the inadequacy of these models. As a result of this analysis, thermoelectric models are expected to explain THz sensing by FETs.
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Authors and Affiliations

Jacek Marczewski
1
ORCID: ORCID
Michał Zaborowski
1
ORCID: ORCID
Daniel Tomaszewski
1
ORCID: ORCID
Przemysław Zagrajek
2
ORCID: ORCID
Norbert Pałka
2
ORCID: ORCID

  1. Institute of Microelectronics and Photonics, Lukasiewicz Research Center, al. Lotników 32/46, 02-668 Warsaw, Poland
  2. Institute of Optoelectronics, Military University of Technology, ul. gen. S. Kaliskiego 2, 00-908 Warsaw, Poland
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Abstract

As part of the research and development project, a multi-touch multimedia system was implemented, working exclusively on the basis of optical technologies. The model of device with a diagonal of 42” was developed and made with 4K TV image technology and simultaneous detection in near infrared. The control of individual system modules was carried out on RaspberryPi microcomputers without typical operating system. The functionality of a conventional large-format display with unlimited multi-touch, QR code scanner, and a document scanner has been achieved in one housing. Luminance distribution tests were carried out in accordance with ANSI requirements and infrared radiation for detection work.
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Authors and Affiliations

Maciej Zajkowski
1
ORCID: ORCID
Piotr Kardasz
1
ORCID: ORCID
Łukasz Budzyński
1
ORCID: ORCID
Grzegorz Masłowski
2
ORCID: ORCID

  1. Faculty of Electrical Engineering, Department of Photonics, Electronic and Lighting Technology, Bialystok University of Technology, ul. Wiejska 45, 15-351 Białystok, Poland
  2. Faculty of Electrical and Computer Engineering, Department of Electrical and Computer Engineering Fundamentals, Rzeszow University of Technology, al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland
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Abstract

The paper describes the structural, optical, tribological, and mechanical properties of as‑prepared and annealed titanium dioxide (TiO2) coatings. TiO2 films were deposited by the electron beam evaporation (EBE) and additionally annealed at a temperature up to 800 °C using a tubular furnace. X-ray diffraction (XRD) analysis identified the amorphous phase of coatings as-prepared and annealed at 200 °C. The phase transition to anatase occurred at 400 °C, while annealing at 600 °C and 800 °C did not induce a phase transition to the rutile phase. The crystallite size increased with an annealing up to 40.4 nm at 800 °C. Raman spectroscopy confirmed the anatase phase in thin films annealed at 400 °C and above. A scanning electron microscope (SEM) images revealed surface morphology and grain structure changes after post-process high-temperature annealing. The optical transmission measurements showed a redshift in the fundamental absorption edge with increasing annealing temperature, accompanied by a decreased transparency level. The value of an optical band gap energy (Egopt) decreased to 2.77 eV for films annealed at 800 °C. Tribological tests revealed reduced scratch resistance with higher annealing temperatures, which was attributed to increased surface roughness and coating removal. Nanoindentation measurements showed a decrease in hardness with annealing temperature, attributed to changes in crystallite size and surface morphology. This comprehensive analysis of TiO2 thin-film coatings showed that the post-process annealing should be carefully controlled for films used in optoelectronic applications.
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Authors and Affiliations

Agata Obstarczyk
1
ORCID: ORCID
Ewa Mańkowska
1
ORCID: ORCID
Wiktoria Weichbrodt
1
ORCID: ORCID
Paulina Kapuścik
1
ORCID: ORCID
Wojciech Kijaszek
1
ORCID: ORCID
Michał Mazur
1
ORCID: ORCID

  1. Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science & Technology, ul. Janiszewskiego 11/17, 50-372 Wroclaw, Poland
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Abstract

One of the important directions of research in photovoltaics is the development of new thin-film technology, which can replace the currently used, more expensive bulk silicon technology. The article discusses the findings from research focused on optimizing the parameters for the deposition of silicon thin films with P-type electrical conductivity for applications in photovoltaics. The growth rate was determined depending on the change in substrate temperature using reflectometry and the influence of deposition time on optical properties was determined using UV/VIS spectroscopy. Photovoltaic structures were made on substrates with an ITO layer and their electrical parameters were measured. The authors applied the magnetron sputtering method to deposit the layers, selecting it over the commercially used the chemical vapor deposition (CVD) method. This replacement could alleviate the necessity for high temperatures and broaden the potential applications of thin-film solar cells.
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Authors and Affiliations

Marek Szindler
1
ORCID: ORCID
Magdalena M. Szindler
2
ORCID: ORCID
Krzysztof Lukaszkowicz
2
ORCID: ORCID
Krzysztof Matus
3
ORCID: ORCID
Paweł Nuckowski
3

  1. Scientific and Didactic Laboratory of Nanotechnology and Material Technologies, Faculty of Mechanical Engineering, Silesian University of Technology, ul. Towarowa 7, 44-100 Gliwice, Poland
  2. Department of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland
  3. Materials Research Laboratory, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland
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Abstract

The aim of this work was to improve the quality of the GaSb buffer layers on GaAs substrates using the molecular beam epitaxy (MBE) technology. The high quality of the GaSb buffer layers is one of the most important elements enabling the synthesis of good quality of type II superlattices (T2SL) structures for infrared applications. The main challenges in this regard are: compensation of the difference in lattice constants between GaAs and GaSb and obtaining the highest achievable surface quality of the final GaSb layer. In the literature, many authors describe different techniques to obtain the best quality of a GaSb buffer layer. In this work, we present the results of HRXRD, AFM, TOF-SIMS, SEM, and Nomarski optical microscope measurements obtained for 2 μm thick GaSb buffer layers. The GaSb layers are made according to different techniques and these results are compared with a GaSb buffer construction technique according to our own technology. During the processes, we also obtained an unintentional structure of one of the buffer layers, which allowed us to obtain very good results in terms of surface structure and crystallographic quality where FWHM in ωRC scan was equal to 138 arcsec and RMS 0.20 nm proving that there is still a lot of work to be done in this area.
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Authors and Affiliations

Dawid Jarosz
1
ORCID: ORCID
Ewa Bobko
1
ORCID: ORCID
Małgorzata Trzyna-Sowa
1
ORCID: ORCID
Ewa Przeździecka
2
ORCID: ORCID
Marcin Stachowicz
2
ORCID: ORCID
Marta Ruszała
1
ORCID: ORCID
Piotr Krzemiński
1
ORCID: ORCID
Anna Juś
1
ORCID: ORCID
Kinga Maś
1
ORCID: ORCID
Renata Wojnarowska-Nowak
1
ORCID: ORCID
Oskar Nowak
1
Daria Gudyka
1
Brajan Tabor
1
Michał Marchewka
1
ORCID: ORCID

  1. Institute of Materials Engineering, Center for Microelectronics and Nanotechnology, University of Rzeszow, al. Rejtana 16, 35-959 Rzeszow, Poland
  2. Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland