Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 13
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

IR spectroscopy, density and ultrasonic velocity measurements have been carried out for aluminum lithium phosphate glasses with and without MoO3. The observed changes in the FTIR spectra of the glasses were related to the modifier/former role of molybdenum ions. The results revealed that the density increases with increasing MoO<sub>3</sub> content, which was attributed to the increase in the compactness and packing of the glass network. The ultrasonic data were analyzed in terms of creation of new bonds of MoO<sub>3</sub> attached to phosphate units. The new bonds increased the average crosslink density and the number of network bonds per unit volume along with a strengthening of the different modes of vibrations which in its turn increased the ultrasonic velocity, the rigidity and hence the elastic moduli of the glasses.

Go to article

Authors and Affiliations

Yasser B. Saddeek
S.M. Abo-Naf
Download PDF Download RIS Download Bibtex

Abstract

The paper presents the results of studies on the influence of the 2010 Vistula flood on the humification process in the bottom sediments of the Goczałkowice Reservoir in southern Poland. Due to its location in the vicinity of farmlands, forests and urbanized areas, the Goczałkowice Reservoir is characterized by amplified and intense humification processes within its sediments. The studies were focused on the determining the influence of the flood wave containing organic and inorganic suspensions on these processes. Humic acids were analyzed using two spectroscopic methods: Electron Paramagnetic Resonance (EPR) and Fourier Transform Infrared Spectroscopy (FT-IR). Application of these methods allowed to determine the values of free radicals and of the g-factor, which are indicators of oxidation, aromatization and maturation of humic acids during the humification process, as well as the value of the 1650/1720 ratio, reflecting the dissociation of the COOH group to COO− and the formation of complexes of transitional metals with humic acids during the humification process.

Go to article

Authors and Affiliations

Karolina Czerwieńska
Waldemar Szendera
Waldemar Chmielewski
Download PDF Download RIS Download Bibtex

Abstract

The paper reports on the photoelectrical performance of the long wavelength infrared (LWIR) HgCdTe high operating temperature (HOT) detector. The detector structure was simulated with commercially available software APSYS by Crosslight Inc. taking into account SRH, Auger and tunnelling currents. A detailed analysis of the detector performance such as dark current, detectivity, time response as a function of device architecture and applied bias is performed, pointing out optimal working conditions.

Go to article

Authors and Affiliations

W. Gawron
P. Martyniuk
P. Madejczyk
A. Rogalski
J. Piotrowski
Download PDF Download RIS Download Bibtex

Abstract

Infrared detectors are usually characterized by 1/f noise when operating with biasing. This type of noise significantly reduces detection capabilities for low-level and slow signals. There are a few methods to reduce the influence of 1/f noise, like filtering or chopper stabilization with lock-in. Using the first one, a simple 1st-order analog low-pass filter built-in amplifier usually cuts off 1/f noise fluctuations at low frequencies. In comparison, the stabilization technique modulates the signal transposing to a higher frequency with no 1/f noise and then demodulates it back (lock-in amplifiers). However, the flexible tuned device, which can work precisely at low frequencies, is especially desirable in some applications, e.g., optical spectroscopy or interferometry. The paper describes a proof-of-concept of an IR detection module with an adjustable digital filter taking advantage of finite impulse response type. It is based on the high-resolution analog-to-digital converter, field-programmable gate array, and digital-to-analog converter. A microcontroller with an implemented user interface ensures control of such a prepared filtering path. The module is a separate component with the possibility of customization and can be used in experiments or applications in which the reduction of noises and unexpected interferences is needed.
Go to article

Authors and Affiliations

Krzysztof Achtenberg
1
ORCID: ORCID
Janusz Mikołajczyk
1
ORCID: ORCID
Zbigniew Bielecki
1
ORCID: ORCID

  1. Institute of Optoelectronics, Military University of Technology, Warsaw, Poland
Download PDF Download RIS Download Bibtex

Abstract

Non-intentionally doped GaSb epilayers were grown by molecular beam epitaxy (MBE) on highly mismatched semi-insulating GaAs substrate (001) with 2 offcut towards (110). The effects of substrate temperature and the Sb/Ga flux ratio on the crystalline quality, surface morphology and electrical properties were investigated by Nomarski optical microscopy, X-ray diffraction (XRD) and Hall measurements, respectively. Besides, differential Hall was used to investigate the hole concentration behaviour along the GaSb epilayer. It is found that the crystal quality, electrical properties and surface morphology are markedly dependent on the growth temperature and the group V/III flux ratio. Under the optimized parameters, we demonstrate a low hole concentration at very low growth temperature. Unfortunately, the layers grown at low temperature are characterized by wide FWHM and low Hall mobility.

Go to article

Authors and Affiliations

D. Benyahia
Łukasz Kubiszyn
ORCID: ORCID
Krystian Michalczewski
ORCID: ORCID
A. Kębłowski
Piotr Martyniuk
ORCID: ORCID
J. Piotrowski
A. Rogalski
Download PDF Download RIS Download Bibtex

Abstract

Insulin receptor substrate 2 (IRS-2) modulates the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, which controls the suppression of gluconeogenic genes; IRS-2 is also a critical node of insulin signaling. Because of the high homology between pig and human IRS-2, we investigated the expression pattern and function of porcine IRS-2. QPCR and immunoblotting were used to detect the IRS-2 expression level in different tissues. There were high IRS-2 levels in the cerebral cortex, hypothalamus, and cerebellum in the central nervous system. In peripheral tissues, IRS-2 was expressed at relatively high levels in the liver. Immunohistochemistry analysis revealed that IRS-2 was mainly distributed in the hypothalamus and cerebral cortex. Furthermore, IRS-2 knockdown porcine hepatocytes and porcine aortic endothelial cells (PAECs) were generated. The IRS-2 knockdown induced abnormal expression of genes involved in glycolipid metabolism in hepatocytes and reduced the antiatherosclerosis ability in PAECs. In addition, we disrupted IRS-2 in porcine embryonic fibroblasts (PEFs) using the CRISPR/Cas9 genome editing system, before finally generating IRS-2 knockout embryos by somatic cell nuclear transfer (SCNT). Taken together, our results indicate that IRS-2 might be a valuable target to establish diabetes and vascular disease models in the pig.

Go to article

Authors and Affiliations

Z. Yin
M. Cai
X. Weng
Z. Liu
G. Zhang
Download PDF Download RIS Download Bibtex

Abstract

In this paper the experimental results of piezoelectric and magnetostrictive ultrasonic stimulation are comparatively analyzed in the evaluation of impact damage in a graphite epoxy composite sample chosen for a round robin test. By comparing theoretical and experimental results, it is shown that the equivalent power of internal friction can reach some hundreds mill watt per a single crack.

Go to article

Authors and Affiliations

W. Swiderski
V. Vavilov
Download PDF Download RIS Download Bibtex

Abstract

Noise spectroscopy as a highly sensitive method for non-destructive diagnostics of semiconductor devices was applied to solar cells based on crystalline silicon with a view to evaluating the quality and reliability of this solar cell type. The experimental approach was used in a reverse-biased condition where the internal structure of solar cells, as well as pn-junction itself, was electrically stressed and overloaded by a strong electric field. This gave rise to a strong generation of a current noise accompanied by local thermal instabilities, especially in the defect sites. It turned out that local temperature changes could be correlated with generation of flicker noise in a wide frequency range. Furthermore, an electrical breakdown in a nonstable form also occurred in some specific local regions what created micro-plasma noise with a two-level current fluctuation in the form of a Lorentzian-like noise spectrum. The noise research was carried out on both of these phenomena in combination with the spectrally-filtered electroluminescence mapping in the visible/near-infrared spectrum range and the dark lock-in infrared thermography in the far-infrared range. Then the physical origin of the light emission from particular defects was searched by a scanning electron microscope and additionally there was performed an experimental elimination of one specific defect by the focused ion beam milling.
Go to article

Authors and Affiliations

Lubomir Skvarenina
Robert Macku
Download PDF Download RIS Download Bibtex

Abstract

The dual-band avalanche photodiode (APD) detector based on a HgCdTe material system was designed and analysed in detail numerically. A theoretical analysis of the two-colour APD intended for the mid wavelength infrared (MWIR) and long wavelength infrared (LWIR) ranges was conducted. The main purpose of the work was to indicate an approach to select APD structure parameters to achieve the best performance at high operating temperatures (HOT). The numerical simulations were performed by Crosslight numerical APSYS platform which is designed to simulate semiconductor optoelectronic devices. The current-voltage characteristics, current gain, and excess noise analysis at temperature T = 230 K vs. applied voltage for MWIR (U = 15 V) and LWIR (U = –6 V) ranges were performed. The influence of low and high doping in both active layers and barrier on the current gain and excess noise is shown. It was presented that an increase of the APD active layer doping leads to an increase in the photocurrent gain in the LWIR detector and a decrease in the MWIR device. The dark current and photocurrent gains were compared. Photocurrent gain is higher in both spectral ranges.
Go to article

Authors and Affiliations

Tetiana Manyk
1
ORCID: ORCID
Kinga Majkowycz
1
ORCID: ORCID
Jarosław Rutkowski
1
ORCID: ORCID
Piotr Martyniuk
1
ORCID: ORCID

  1. Institute of Applied Physics, Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland
Download PDF Download RIS Download Bibtex

Abstract

The paper presents noise measurements in low-resistance photodetectors using a cross-correlation-based transimpedance amplifier. Such measurements usually apply a transimpedance amplifier design to provide a current fluctuation amplification. In the case of low-resistance sources, the measurement system causes additional relevant system noise which can be higher than noise generated in a tested detector. It mainly comes from the equivalent input voltage noise of the transimpedance amplifier. In this work, the unique circuit and a three-step procedure were used to reduce the floor noise, covering the measured infrared detector noise, mainly when operating with no-bias or low-bias voltage. The modified circuit and procedure to measure the noise of unbiased and biased detectors characterized by resistances much lower than 100 Ω were presented. Under low biases, the reference low-resistance resistors tested the measurement system operation and techniques. After the system verification, noise characteristics in low-resistance InAs and InAsSb infrared detectors were also measured.
Go to article

Bibliography

  1. Vandamme, L. J. Noise as a diagnostic tool for quality and reliability of electronic devices. IEEE Trans. Electron. Devices. 41, 2176–2187 (1994). https://doi.org/10.1109/16.333839
  2. Kotarski, M. & Smulko, J. M. Noise measurement set-ups for fluctuations-enhanced gas sensing. Metrol. Meas. Syst. 16, 457–464 (2009). http://www.metrology.pg.gda.pl/full/2009/M&MS_2009_457.pdf
  3. Jones, B. Electrical noise as a reliability indicator in electronic devices and components. IEE Proc. G 149, 13–22 (2002). https://doi.org/10.1049/ip-cds:20020331
  4. Dyakonova, N., Karandashev, S. , Levinshtein, M .E., Matveev, B. A. & Remennyi, M. A. Low frequency noise in p-InAsSbP / n-InAs infrared photodiodes. Semicond. Sci. Technol. 33, 065016 (2018). https://doi.org/10.1088/1361-6641/aac15d
  5. Ciura, L., Kolek, A., Michalczewski, K., Hackiewicz, K. & Martyniuk, P. 1/f noise in InAs/InAsSb superlattice photoconductors. IEEE Trans. Electron Devices. 67, 3205–3210 (2020). https://doi.org/10.1109/TED.2020.2998449
  6. Savich, G. , Pedrazzani, J. R., Sidor, D. E., Maimon, S. & Wicks, G. W. Dark current filtering in unipolar barrier infrared detectors. Appl. Phys. Lett. 99, 121112 (2011). https://doi.org/10.1063/1.3643515
  7. Cervera, C. et al. Dark current and noise measurements of an InAs/GaSb superlattice photodiode operating in the midwave infrared domain. Electron. Mater. 41, 2714–2718 (2012). https://doi.org/10.1007/s11664-012-2035-4
  8. Ciofi, C., Giusi, G., Scandurra, G. & Neri, B. Dedicated instrumentation for high sensitivity, low frequency noise measurement systems. Noise Lett. 4, L385–L402 (2004). https://doi.org/10.1142/S0219477504001963
  9. Horowitz, P. & Hill, W. The Art of Electronics (Cambridge University Press, 2015).
  10. Achtenberg, K. et al. Low-frequency noise measurements of IR photodetectors with voltage cross correlation system. Measurement 183, 109867 (2021). https://doi.org/10.1016/j.measurement.2021.109867
  11. Ciura, Ł., Kolek, A., Gawron, W., Kowalewski, A. & Stanaszek, D. Measurements of low frequency noise of infrared photodetectors with transimpedance detection system. Meas. Syst. 21,
    461–472 (2014). https://doi.org/10.2478/mms-2014-0039
  12. Giusi, G., Pace, C. & Crupi, F. Cross-correlation-based trans-impedance amplifier for current noise measurements. J. Circ. Theor. Appl. 37, 781–792 (2008). https://doi.org/10.1002/cta.517
  13. Jaworowicz, K., Ribet-Mohamed, I., Cervera, C., Rodriguez, J. & Christol, P. Noise characterization of midwave infrared InAs/GaSb superlattice pin photodiode. IEEE Photon. Technol. 23, 242–244 (2011). https://doi.org/10.1109/lpt.2010.2093877
  14. Taalat, R., Christol, P. & Rodriguez, J. Dark current and noise measurements of an InAs/GaSb superlattice photodiode operating in the midwave infrared domain. Electron. Mater. 41, 2714–2718 (2012). https://doi.org/10.1007/s11664-012-2035-4
  15. Ramos, D. et al. 1/f noise and dark current correlation in midwave InAs/GaSb Type-II superlattice IR detectors. Status Solidi A. 218, 2000557 (2020). https://doi.org/10.1002/pssa.202000557
  16. De Iacovo, A., Venettacci, C., Colace, L. & Foglia, S. Noise performance of PbS colloidal quantum dot photodetectors. Phys. Lett. 111, 211104 (2017). https://doi.org/10.1063/1.5005805
  17. Rais, M. et al. HgCdTe photovoltaic detectors fabricated using a new junction formation technology. Microelectron. J. 31, 545–551 (2000). https://doi.org/10.1016/s0026-2692(00)00028-8
  18. Achtenberg, K., Mikołajczyk, J., Ciofi, C., Scandurra, G. & Bielecki, Z. Low-noise programmable voltage source. Electronics 9, 1245 (2020). https://doi.org/10.3390/electronics9081245
Go to article

Authors and Affiliations

Krzysztof Achtenberg 
1
ORCID: ORCID
Janusz Mikołajczyk
1
ORCID: ORCID
Zbigniew Bielecki
1
ORCID: ORCID

  1. Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego St., 00-908 Warsaw, Poland
Download PDF Download RIS Download Bibtex

Abstract

Magnetoabsorption in far and mid IR ranges in double HgTe/CdHgTe quantum wells with inverted band structure has been studied in high magnetic fields up to 30 T. Numerous intraband and interband transitions have been revealed in the spectra and interpreted within axial 8 × 8 k·p model. Splitting of dominant magnetoabsorption lines resulting from optical transitions from hole-like zero-mode Landau level has been discovered and discussed in terms of a built-in electric field and collective phenomena.

Go to article

Authors and Affiliations

L.S. Bovkun
A.V. Ikonnikov
V.Ya. Aleshkin
K.V. Maremyanin
N.N. Mikhailov
S.A. Dvoretskii
S.S. Krishtopenko
F. Teppe
B.A. Piot
M. Potemski
M. Orlita
V.I. Gavrilenko
Download PDF Download RIS Download Bibtex

Abstract

Photoelectrical characteristics of scanning IR detectors with implemented time delay and integration mode are analyzed. A new “shifted cellular” layout of photosensitive elements in the FPA structure is proposed. Advantages of the new FPA configuration in terms of threshold sensitivity for small-size/point objects are demonstrated. The analysis is based on the Monte Carlo simulation of the diffusion process of photogenerated minority charge carriers in the photosensitive layer photodiode arrays. The analysis is performed taking into account the main photoelectric parameters of FPA elements: photosensitive layer thickness, diffusion length of charge carriers, optical absorption length, their design parameters: geometric sizes of FPA elements, diameters of p-n junctions, and design parameters of the optical system: optical-spot diameter.

Go to article

Authors and Affiliations

S. A. Dvoretsky
A. P. Kovchavtsev
I. I. Lee
V. G. Polovinkin
G. Yu. Sidorov
M. V. Yakushev
Download PDF Download RIS Download Bibtex

Abstract

In virtual acoustics or artificial reverberation, impulse responses can be split so that direct and reflected components of the sound field are reproduced via separate loudspeakers. The authors had investigated the perceptual effect of angular separation of those components in commonly used 5.0 and 7.0 multichannel systems, with one and three sound sources respectively (Kleczkowski et al., 2015, J. Audio Eng. Soc. 63, 428-443). In that work, each of the front channels of the 7.0 system was fed with only one sound source. In this work a similar experiment is reported, but with phantom sound sources between the front loud- speakers. The perceptual advantage of separation was found to be more consistent than in the condition of discrete sound sources. The results were analysed both for pooled listeners and in three groups, according to experience. The advantage of separation was the highest in the group of experienced listeners.
Go to article

Authors and Affiliations

Piotr Kleczkowski
Aleksandra Król
Paweł Małecki

This page uses 'cookies'. Learn more