| Records |
| Author |
Mitin, Vladimir; Antipov, Andrei; Sergeev, Andrei; Vagidov, Nizami; Eason, David; Strasser, Gottfried |
| Title |
Quantum Dot Infrared Photodetectors: Photoresponse Enhancement Due to Potential Barriers |
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Journal Article |
| Year |
2011 |
Publication |
Nanoscale Research Letters |
Abbreviated Journal  |
Nanoscale res lett |
| Volume |
6 |
Issue |
1 |
Pages |
6 |
| Keywords |
Quantum dots; Infrared detectors; Photoresponse; Doping; Potential barriers; Capture processes |
| Abstract |
Potential barriers around quantum dots (QDs) play a key role in kinetics of photoelectrons. These barriers are always created, when electrons from dopants outside QDs fill the dots. Potential barriers suppress the capture processes of photoelectrons and increase the photoresponse. To directly investigate the effect of potential barriers on photoelectron kinetics, we fabricated several QD structures with different positions of dopants and various levels of doping. The potential barriers as a function of doping and dopant positions have been determined using nextnano3 software. We experimentally investigated the photoresponse to IR radiation as a function of the radiation frequency and voltage bias. We also measured the dark current in these QD structures. Our investigations show that the photoresponse increases ~30 times as the height of potential barriers changes from 30 to 130 meV. |
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RPLAB @ gujma @ |
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712 |
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Tretyakov, I.; Svyatodukh, S.; Perepelitsa, A.; Ryabchun, S.; Kaurova, N.; Shurakov, A.; Smirnov, M.; Ovchinnikov, O.; Goltsman, G. |
| Title |
Ag2S QDs/Si heterostructure-based ultrasensitive SWIR range detector |
Type |
Journal Article |
| Year |
2020 |
Publication |
Nanomaterials (Basel) |
Abbreviated Journal |
Nanomaterials (Basel) |
| Volume |
10 |
Issue |
5 |
Pages |
1-12 |
| Keywords |
detector; quantum dots; short-wave infrared range; silicon |
| Abstract |
In the 20(th) century, microelectronics was revolutionized by silicon-its semiconducting properties finally made it possible to reduce the size of electronic components to a few nanometers. The ability to control the semiconducting properties of Si on the nanometer scale promises a breakthrough in the development of Si-based technologies. In this paper, we present the results of our experimental studies of the photovoltaic effect in Ag2S QD/Si heterostructures in the short-wave infrared range. At room temperature, the Ag2S/Si heterostructures offer a noise-equivalent power of 1.1 x 10(-10) W/ radicalHz. The spectral analysis of the photoresponse of the Ag2S/Si heterostructures has made it possible to identify two main mechanisms behind it: the absorption of IR radiation by defects in the crystalline structure of the Ag2S QDs or by quantum QD-induced surface states in Si. This study has demonstrated an effective and low-cost way to create a sensitive room temperature SWIR photodetector which would be compatible with the Si complementary metal oxide semiconductor technology. |
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Laboratory of nonlinear optics, Zavoisky Physical-Technical Institute of the Russian Academy of Sciences, Kazan 420029, Russia |
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English |
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2079-4991 |
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PMID:32365694; PMCID:PMC7712218 |
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1151 |
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González, F. J.; Boreman, G. D. |
| Title |
Comparison of dipole, bowtie, spiral and log-periodic IR antennas |
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Journal Article |
| Year |
2005 |
Publication |
Infrared Physics & Technology |
Abbreviated Journal |
Inf Phys & Technol |
| Volume |
46 |
Issue |
5 |
Pages |
418-428 |
| Keywords |
optical antennas; Microbolometer; Infrared antennas; Antenna efficiency; Antenna-coupled detectors |
| Abstract |
Antenna-coupled microbolometers use planar lithographic antennas to couple infrared radiation into a bolometer with sub-micron dimensions. In this paper four different types of infrared antennas were fabricated on thin grounded-substrates and coupled to microbolometers. Dipole, bowtie, spiral and log-periodic IR antenna-coupled detectors were measured at 10.6 μm and their performance compared. A new method to calculate the radiation efficiency based on the spatial and angular response of infrared antennas is presented and used to evaluate their performance. The calculated radiation efficiency for the dipole, bowtie, spiral and log-periodic IR antennas was 20%, 37%, 25% and 46% respectively. A dipole-length study was performed and shows that the quasistatic value of the effective permittivity accurately describes the incident wavelength in the substrate at infrared frequencies for antennas on a thin substrate. |
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RPLAB @ gujma @ |
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739 |
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Krasnopolsky, Vladimir A.; Maillard, Jean Pierre; C. Owen, Tobias |
| Title |
Detection of methane in the martian atmosphere: evidence for life? |
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Journal Article |
| Year |
2004 |
Publication |
Icarus |
Abbreviated Journal |
Icarus |
| Volume |
172 |
Issue |
2 |
Pages |
537-547 |
| Keywords |
FTS, Mars atmosphere, methane absorption lines, IR spectroscopy, infrared spectroscopy, landfill gas |
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Using the Fourier Transform Spectrometer at the Canada–France–Hawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH4 band at 3.3 μm with resolving power of 180,000 for the apodized spectrum. Summing up the spectral intervals at the expected positions of the 15 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.7 sigma level which is exactly centered in the summed spectrum. The observed CH4 mixing ratio is 10±3 ppb. Total photochemical loss of CH4 in the martian atmosphere is equal to View the MathML source, the CH4 lifetime is 340 years and methane should be uniformly mixed in the atmosphere. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH4 during its diffusion through the regolith may be significant. There are no processes of CH4 formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. Outgassing from Mars is weak, the latest volcanism is at least 10 million years old, and thermal emission imaging from the Mars Odyssey orbiter does not reveal any hot spots on Mars. Hydrothermal systems can hardly be warmer than the room temperature at which production of methane is very low in terrestrial waters. Therefore a significant production of hydrothermal and magmatic methane is not very likely on Mars. The calculated average production of CH4 by cometary impacts is 2% of the methane loss. Production of methane by meteorites and interplanetary dust does not exceed 4% of the methane loss. Methane cannot originate from an extinct biosphere, as in the case of “natural gas†on Earth, given the exceedingly low limits on organic matter set by the Viking landers and the dry recent history which has been extremely hostile to the macroscopic life needed to generate the gas. Therefore, methanogenesis by living subterranean organisms is a plausible explanation for this discovery. Our estimates of the biomass and its production using the measured CH4 abundance show that the martian biota may be extremely scarce and Mars may be generally sterile except for some oases. |
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879 |
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Parrott, Edward P. J.; Zeitler, J. Axel; Fris<cc><152>c<cc><152>ic<cc><81>, Tomislav; Pepper, Michael; Jones, William; Day, Graeme M.; Gladden, Lynn F. |
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Testing the sensitivity of terahertz spectroscopy to changes in molecular and supramolecular structure: a study of structurally similar cocrystals |
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Journal Article |
| Year |
2009 |
Publication |
Crystal Growth & Design |
Abbreviated Journal |
Crystal Growth & Design |
| Volume |
9 |
Issue |
3 |
Pages |
1452-1460 |
| Keywords |
supramolecular recognition, infrared, terahertz, IR, THz, TDS |
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Terahertz time-domain-spectroscopy (THz-TDS) has emerged as a versatile spectroscopic technique, and an alternative to powder X-ray diffraction in the characterization of molecular crystals. We tested the ability of terahertz spectroscopy to distinguish between chiral and racemic hydrogen-bonded cocrystals that are similar in molecular and supramolecular structure. Terahertz spectroscopy readily distinguished between the isostructural cocrystals of theophylline with chiral and racemic forms of malic acid which are almost identical in molecular structure and supramolecular architecture. Similarly, the cocrystals of theophylline with chiral and racemic forms of tartaric acid, which are similar at the molecular level but dissimilar in crystal packing, were distinguished unequivocally. The investigation of the same cocrystals using X-ray powder diffraction and Raman spectroscopy suggested that THz-TDS is comparable in sensitivity to diffraction methods and more sensitive than Raman spectroscopy to changes in cocrystal architecture. The differences in spectra acquired by THz-TDS could be further enhanced by cooling the samples to 109 K. |
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1528-7483 |
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567 |
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