| 1. |
- Cibiraite, D., et al.
(author)
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Thermal noise-limited sensitivity of FET-based terahertz detectors
- 2017
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In: 2017 International Conference on Noise and Fluctuations, ICNF 2017, Vilnius, Lithuania, 20-23 June 2017.
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Conference paper (peer-reviewed)abstract
- Here we present a detailed study on estimation of noise-dependent parameters, such as signal-to-noise ratio (SNR) or noise equivalent power (NEP), of field-effect-transistor based terahertz detectors (TeraFETs). Commonly, these parameters are estimated from a well-known assumption, that detector's performance is limited by the thermal noise of transistor's channel. However, practice shows that the influence of other noise sources or transient effects is considerable. We summarize TeraFET noise measurements performed on different material systems based transistors, such as AlGaN/GaN, AlGaAs/GaAs, silicon CMOS, and monolayer graphene. We have achieved a good agreement between thermal noise and measured data. However, attention has to be paid to gate leakage currents and slow defect charging and discharging effects, which can strongly influence TeraFET's performance estimation.
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| 2. |
- Lisauskas, A., et al.
(author)
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Colossal magnetoresistive La-0.7(Pb1-xSrx)(0.3)MnO3 films for bolometer and magnetic sensor applications
- 2001
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 89:11, s. 6961-6963
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Journal article (peer-reviewed)abstract
- We report on electrical and magnetic properties of a continuous series of solid solutions La-0.7(Pb1-xSrx)(0.3)MnO3 prepared by the pulsed laser deposition technique on LaAlO3 and SrTiO3 single crystals. Strict compositional control enables us to tailor the metal-to-semiconductor phase transition from 266 to 327 K, the maximum of temperature coefficient of resistance from 10.2% K-1 to 3.2% K-1, and maximum of magnetoresistance ratio at 7 kOe from 41% to 17% for x = 0 and x = 1 correspondingly. The ferromagnetic resonance linewidth ranges from 124 to 300 Oe, indicating low microwave loss and the films uniformity. Noise spectroscopy performed in the 2 Hz-20 kHz range reveals two components: Johnson noise (independent of frequency and bias current) and excess 1/f noise proportional to the square of the bias current. Very low excess noise (normalized value gamma /n varying in the range from 10(-20) to 10(-22) cm(3)) has been achieved due to the epitaxial quality of the fabricated films. Using these films, an infrared radiation bolometer and weak magnetic field sensor have been built and tested. The bolometer resolves the noise equivalent temperature difference as low as 120 nK/root Hz at 30 Hz frame frequency, while the magnetic field sensor shows the noise equivalent magnetic field difference of 50 mu Oe/root Hz at 1 kHz and optimum bias magnetic field applied.
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| 3. |
- Lisauskas, A., et al.
(author)
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Impedance fluctuations in epitaxial PZT films
- 2001
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In: Integrated Ferroelectrics. - 1058-4587 .- 1607-8489. ; 38:04-jan, s. 647-656
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Journal article (peer-reviewed)abstract
- We report on measurements of impedance of Au/PZT/La0.67Sr0.33MnO3/Pt80Ir20 thin film capacitors performed in the time domain. Ferroelectric PZT films pulsed laser deposited on bulk polycrystalline Pt80Ir20 substrates demonstrate good ferroelectric properties: dielectric permittivity epsilon' = 880 and loss tandelta = 0.039 at 1 kHz, remnant polarization as high as 20 muC/cm(2), induced polarization of 40 muC/cm(3) at 380 kV/cm, and coercive field of 52.5 kV/cm. Resistivity of PZT film at coercive field was found to be 3.10(12) Omega.cm. Instantaneous C-V and I-V characteristics have been recorded to study the relaxation of polarization. Transient current exhibits non-Debye type relaxation, which has been nicely fitted to Curie-von Schweindler law j = j(leak) + j(o) (t/1sec)(-n) with an exponent nsimilar to0.8 while the power law C proportional to f(-0.1) has been found in frequency dispersion of the capacitance. Impedance fluctuation spectrum in the true leakage and resistance degradation regimes was found to follow 1/f(1.5) dependence. Close to breakdown field voltage fluctuations in ferroelectric capacitor increase, become non-steady randomly spike-shaped.
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| 4. |
- Lisauskas, A., et al.
(author)
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Tailoring the colossal magnetoresistivity : La-0.7(Pb0.63Sr0.37)(0.3)MnO3 thin-film uncooled bolometer
- 2000
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 77:5, s. 756-758
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Journal article (peer-reviewed)abstract
- Epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature. Continuous series of solid solutions La-0.7(Pb1-xSrx)(0.3)MnO3 grown by the pulsed laser deposition technique were found to possess superior performance regarding the maximum of temperature coefficient of resistivity (TCR) @300 K. In these films phase transition temperature T-c ranges from 266 to 327 K. We have engineered the film of the optimum composition x = 0.37 exhibiting the maximum of TCR = 7.4% K-1 @295 K. Relatively low excess noise (normalized Value gamma/n of 3 X 10(-21) cm(3)) has been achieved due to the epitaxial quality of the fabricated film. Using this film, infrared radiation bolometer demonstrator, operating at room temperature, has been built and tested. The bolometer resolves the noise equivalent temperature difference as low as 120 nK/root Hz and shows signal-to-noise ratio SNR = 8 X 10(6) root Hz/K, responsivity R = 0.6 V/W, detectivity D = 0.9 x 10(7) cm root Hz/W, and noise equivalent power NEP 3 X 10(-8) W root Hz at 30 Hz frame frequency. For micromachined thermally isolated La-0.7(Pb0.63Sr0.37)(0.3)MnO3 thin-film bolometer one can expect to get responsivity about 4 x 10(3) V/W and detectivity higher than 10(9) cm root Hz/W @30 Hz.
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