Search results

1

Submicrometric Heavily Doped n-GaAs Structures for Microwave Detection

100%

Ašmontas S., Gradauskas J., Kozič A., Shtrikmann H., Sužiedėlis A.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

147-150

EN

Strong coupling between electrons and phonons in heavily doped semiconductors impedes, in general, investigation of hot carrier phenomena in the material. Investigations of hot electron electromotive force arising in symmetrically and asymmetrically shaped structures of heavily doped n-GaAs under microwave radiation are presented in this paper. Mesas of MBE grown n-GaAs layers with neck shaped down to submicron dimensions revealed strong dependence of voltage sensitivity of the structure on the size of the neck. Slight frequency dependence of voltage sensitivity of the microwave diodes with both symmetrically and asymmetrically shaped n-n^+ junctions was observed experimentally in K_a frequency range, which coincides well with theoretical predictions.

2

Phase Separation and Microwave Response of Epitaxial and Polycrystalline Manganite Films

80%

Ašmontas S., Abrutis A., Gradauskas J., Lučun A., Oginskis A., Plaušinaitienė V., Sužiedėlis A., Vengalis B.

Acta Physica Polonica A

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2004

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vol. 105

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issue 1-2

141-147

EN

The resistance, magnetoresistance, and resistance response under microwave irradiation (f=10 and 35 GHz) were measured for epitaxial and polycrystalline La_{0.67}Ca_{0.33}MnO_3 and La_{0.67}Sr_{0.33}MnO_3 thin films in the temperature range 78÷300 K. The microwave induced resistance increase observed for the epitaxial films in a narrow temperature range below the ferromagnetic to paramagnetic transition temperature T_c certifies coexistence of low resistance (ferromagnetic) and high resistance (paramagnetic) regions in the manganites. Resistance of polycrystalline films decreased under microwave irradiation in a wide temperature range below T_c. The effect was explained in terms of microwave assisted hopping of carriers in high resistance regions formed at grain boundaries of the polycrystalline films.

3

Growth and Investigation of Oxide Heterostructures Based on Half-Metallic Fe3O4

80%

Vengalis B., Šliužienė K., Lisauskas V.

Acta Physica Polonica A

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2004

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vol. 105

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issue 6

659-665

EN

We report thin films of ferromagnetic Fe_3O_4 (magnetite) grown by a reactive magnetron sputtering at T=300÷450°C on lattice-matched MgO, and bilayer structures composed of Fe_3O_4 and underlying epitaxial films of highly conductive electron-doped In_2O_3〈Sn〉, LaNiO_3, and antiferromagnetic CoO. The prepared Fe3O4/MgO films and the bilayer structures demonstrated clearly defined resistance anomaly at Verwey transition point (T_V≈100-120 K). Formation of high resistance interlayer was indicated between the adjacent conducting Fe3O4 and LaNiO3 layers. However, relatively low interface resistivity of about 0.1 Ω cm^2 (at T=300 K) was estimated for the patterned Fe3O4/In2O3〈Sn〉 bilayer structures. Vertical electrical transport measurements revealed strong nonlinearity in the I-U dependences of the Fe3O4/In2O3 〈Sn〉 interface at T

4

Fast Bolometric Response of Bulk La_{0.7}Sr_{0.3}MnO_{3} Electroceramic Structures

80%

Nikolaenko Y., Maksimov I., Medvedev Y., Ulyanov A., Grishin A.

Acta Physica Polonica A

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2000

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vol. 97

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issue 6

991-995

EN

We report on the performance of a microwave electroceramic bolometer of hybrid La_{0.7}Sr_{0.3}MnO_{3}/Al_{2}O_{3} (0.2×2×4 mm^{3}) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature. When compared with the high-T_{c} superconducting bolometers, the La_{0.7}Sr_{0.3}MnO_{3} microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T=230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.

5

Terahertz Detection of Quantum Cascade Laser Emission by Plasma Waves in Field Effect Transistors

80%

Teppe F., Consejo C., Torres J., Chenaud B., Solignac P., Fathololoumi S., Wasilewski Z., Zholudev M., Dyakonova N., Coquillat D., El Fatimy A., Buzatu P., Chaubet C., Knap W.

Acta Physica Polonica A

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2011

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vol. 120

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issue 5

930-932

EN

We report on the resonant detection of a 3.1 THz radiation produced by a quantum cascade laser using a 250 nm gate length GaAs/AlGaAs field effect transistor at liquid nitrogen temperature. We show that the physical mechanism of the detection is related to the plasma waves excited in the transistor channel. The detection is enhanced by increasing the drain current and driving the transistor into saturation regime. These results clearly show that plasma wave nanometer-size transistors can be used as detectors in all-solid-state terahertz systems where quantum cascade lasers act as sources.

6

Magnetoresistance of Polycrystalline La_{0.7}Ca_{0.3}MnO_3 Films in a Microwave Magnetic Field

80%

Lučun A., Butkutė R., Maneikis A., Kiprijanovič O., Anisimovas F., Gradauskas J., Sužiedėlis A., Vengalis B., Kancleris Ž., Ašmontas S.

Acta Physica Polonica A

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2007

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vol. 111

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issue 1

147-152

EN

We present new experimental evidence indicating the importance of magnetic field component of microwave field (f=9.4 GHz) for magnetoresistive properties of polycrystalline La_{0.7}Ca_{0.3}MnO_3 films. The microwave measurements revealed a different character of the temperature-dependent electrical resistance of polycrystalline La_{0.7}Ca_{0.3}MnO_3 films placed in the centre (maximal amplitude of H_{10} wave vector) and at a narrow wall of the wave-guide (reduced H_{10} amplitude). Theoretical estimations of the influence of substrate onto distribution of microwave electric and magnetic fields in the waveguide were performed using the finite-difference time-domain method.

7

THz Double-Grating Gate Transistor Detectors in High Magnetic Fields

80%

But D., Dyakonova N., Coquillat D., Teppe F., Knap W., Watanabe T., Tanimoto Y., Boubanga Tombet S., Otsuji T.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1080-1082

EN

Double-grating-gate field-effect transistors have a great potential as terahertz detectors. This is because the double grating gate serves not only for carrier density tuning but also as an efficient THz radiation coupler. In this paper, we present characterization of these transistors using high magnetic fields. Low and high magnetic field data are used to determine the electron mobility and electron concentration, respectively, in different parts of the transistor channel.

8

Laser Induced Self-Organization of Nanohills/Nanowires in SiO_2/Si Interface

80%

Medvid A., Onufrijevs P., Dmitruk I., Pundyk I.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

1067-1070

EN

The aim of this work is to study optical properties of self-organized Si nanohills formed on the SiO_2/Si interface after pulsed Nd:YAG laser irradiation. Nanohills on Si surface give strong photoluminescence in the visible range of spectrum, with a long wing in red portion. This property is explained by charge carrier quantum confinement in nanohills/nanowires.

9

Experimental Investigation of High Pulse Power Microwave Resistive Sensor with Flat Frequency Response

80%

Kancleris Ž., Simniškis R., Dagys M., Tamošiūnas V., Ragulis P.

|

EN

Two types of resistive sensors with flat frequency response for microwave pulse power measurements in X-band rectangular waveguide WR-90 up to 100 kW were developed and experimentally investigated. The first type of the sensors demonstrates higher sensitivity and larger output signal, while the second one exhibits better linearity of the output signal. The experimental investigations revealed the sensitivity variation within ± 10% in 8.2-12.2 GHz frequency band.

10

High Power Microwave Detection in Asymmetrically Shaped n-Al_xGa_{1-x}As Structures

80%

Ašmontas S., Čerškus A., Gradauskas J., Kundrotas J., Lučun A., Petkun V., Sužiedėlis A., Šilėnas A.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

315-318

EN

Investigations of detection of high power microwaves in planar asymmetrically shaped microwave diodes on the basis of Al_xGa_{1-x}As ternary semiconductors with various AlAs mole fraction are presented. The principle of operation of the microwave diodes is based on carrier heating phenomena in asymmetrically shaped homogeneous semiconductor structure due to different distribution of the electric field strength along the sample. Experimental results of microwave detection on the barrier-less asymmetrically shaped diodes are presented paying special attention to the homogeneity of Al_xGa_{1-x}As which was monitored by photoluminescence technique.

11

Reversible Resistive Switching in Electrically Nonhomogeneous La_{0.67}Ca_{0.33}MnO_3 Thin Films by Short Electrical Pulses

80%

Lučun A., Kiprijanovič O., Ašmontas S., Anisimovas F., Maneikis A., Sužied.lis A., Vengalis B.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

1059-1062

EN

Resistance changes in thin electrically nonhomogeneous La_{0.67}Ca_{0.33}MnO_3 films were investigated using electrical pulses of nanosecond duration in the 80-300 K temperature range. Two types of reversible switching to higher resistive states with different starting temperature induced by series of the positive pulses were observed. Possible mechanisms of the resistance switching by short electrical pulses in the vicinity of T_m and at 80-90 K are discussed.

12

Response of Superconductor Bolometer to Phonon Fluxes

80%

Danilchenko B., Jasiukiewicz C., Paszkiewicz T., Wolski S.

Acta Physica Polonica A

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2003

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vol. 103

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issue 4

325-338

EN

A metallic film bolometer with heat capacity C is in contact with thermal bath and with crystalline specimen and is biased by a constant current I_b. The thermal contact of the bolometer is characterized by the thermal conductance G. The bolometer operates in the linear regime of dependence of resistance on temperature characterized by a constantα. Experiments which allow one to measureα, C, and G are proposed. The characteristic timeτ=C/G and characteristic current I_m=√{G/α} affect the effective relaxation rateΛ of the bolometer resistance R_b(t). The knowledge of the power W(t) absorbed by detector allows one to calculate R_b(t). The inverse problem of calculation of W(t) from known R_b(t) is also solved. The suitable algorithms are proposed. Deconvoluted absorbed power is obtained for experiments performed on GaAs and compared with phonoconductivity signal of two-dimensional electron gas structure as well as with results of Monte Carlo computer experiments.

13

Hot Electron Effect in Degenerate Semiconductor Tunnel Junction

80%

Ašmontas S., Gradauskas J., Petkun V., Seliuta D., Sužiedėlis A., Urbelis A.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

198-202

EN

We report on the results of experimental study of free carrier heating in degenerate GaAs tunnel p-n diodes when the carriers are excited by pulsed microwave radiation. Free carrier heating is responsible for the electromotive force in the diode. The magnitude of the electromotive force linearly depends on pulsed microwave power and increases with the decrease in semiconductor lattice temperature. It is almost independent of the pulsed microwave frequency and of p-n junction plane orientation in respect to electric field direction. In the tunnelling regime the dark current in the diode is reduced, however, at high enough forward bias the diffusive current is stimulated due to hot carrier phenomenon.

14

Frequency Dependence of Electrical Response of Polycrystalline LCMO Thin Films

80%

Ašmontas S., Anisimovas F., Balevičius S., Cimmperman P., Gradauskas J., Lučun A., Stankevič V., Sužiedėlis A., Vengalis B., Žurauskienė N.

Acta Physica Polonica A

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2005

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vol. 107

|

issue 1

193-197

EN

Influence of strong electric field in wide frequency range (from DC to 35 GHz) on electrical resistance of thin La_{0.67}Ca_{0.33}MnO_3 polycrystalline manganite films was investigated in the range of (78÷300) K. Different behavior of resistance change vs. temperature was observed when pulsed DC electric field and microwaves were applied to the films. When pulsed DC electric field is applied the electric-field-induced resistance change ("electroresistance") of manganite film depended nearly monotonically on temperature. However, in microwave electric fields a non-monotonic character of the electroresistance temperature dependence was observed. The dependence of the electroresistance on quality of manganite films was observed in case of microwaves. The experimental findings are explained assuming different electrical current mechanisms in case of DC and microwave fields. The applied voltage drops mainly across the grains of polycrystalline film due to a presence of displacement currents in case of microwaves, whereas in DC case the voltage drop is across the grain boundaries.

15

Terahertz Detection by the Entire Channel of High Electron Mobility Transistors

80%

Sakowicz M., Łusakowski J., Karpierz K., Knap W., Grynberg M., Köhler K., Valusis G., Gołaszewska K., Kamińska E., Piotrowska A., Caban P., Strupiński W.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1343-1348

EN

GaAs/AlGaAs and GaN/AlGaN high electron mobility transistors were used as detectors of THz electromagnetic radiation at liquid helium temperatures. Application of high magnetic fields led to the Shubnikov-de Haas oscillations of the detection signal. Measurements carried out with a simultaneous modulation of the intensity of the incident THz beam and the transistor gate voltage showed that the detection signal is determined by the electron plasma both in the gated and ungated parts of the transistor channel. This result is of importance for understanding the physical mechanism of the detection in high electron mobility transistors and for development of a proper theoretical description of this process.

16

Mechanism of Radiation Coupling to Plasma Wave Field Effect Transistor Sub-THz Detectors

80%

Sakowicz M., Łusakowski J., Karpierz K., Grynberg M., Gwarek W., Knap W., Boubanga S.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1337-1342

EN

Detection of 100 GHz and 285 GHz electromagnetic radiation by GaAs/AlGaAs field effect transistors with the gate length of 150 nm was investigated at 300 K as a function of the angleαbetween the direction of linear polarization of the radiation and the symmetry axis of the field effect transistors. The angular dependence of the detected signal was found to be Acos²(α-α₀)+C. A response of the transistor chip (including bonding wires and the substrate) to the radiation was numerically simulated. Calculations confirmed experimentally observed dependences and allowed to investigate the role of bonding wires and contact pads in coupling of the radiation to the transistor channel.

17

THz Reflection Spectra of Different Materials, Including Explosives, Measured at a Distance up to 5 m

71%

Walczakowski M., Palka N., Czerwiński A., Sypek M., Szustakowski M.

Acta Physica Polonica A

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2015

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vol. 127

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issue 3

689-692

EN

This work presents a terahertz system designed for the reflection spectroscopy of different materials located at a distance up to 5 m. The source of the radiation is a tunable solid-state optical parametric oscillator, which generates a narrow-band nanosecond pulses in the range of 0.7-2.5 THz. The signal is detected with relatively fast and having big sensitivity hot electron bolometer. The detailed description of each device and the functioning of the experimental setup are provided as well as the methodology of the measurement is explained. Investigations were performed in the 0.7-2.2 THz range in free space with relative humidity of about 40%. The experiment was divided into three series, each of which was carried out with different distance between the examined sample and the system - 1 m, 3 m, and 5 m. Obtained spectra of selected materials, including explosives, are similar to the results received from a purged time domain spectroscopy system. The observed small deviations are connected with fluctuations of the laser wavelength and the instability of the bolometer.

18

Terahertz Spectra of Explosives Measured by Optical Parametric Oscillator-Based System and Time Domain Spectroscopy

71%

Palka N., Trzcinski T., Szustakowski M.

Acta Physica Polonica A

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2012

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vol. 122

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issue 5

946-949

EN

In this paper, we report on measurements of absorption spectra of hexogen, penthrite, and octogen. The measurements were carried out by means of time domain spectroscopy and compared to spectra obtained from a setup, which bases on an optical parametric oscillator combined with a Golay cell. For time domain spectroscopy measurement, Teraview TPS 3000 unit with accessories in transmission configuration was used.

19

High Magnetic Field Effects on Plasma Wave THz Detection in Field-Effect Transistors

71%

Boubanga-Tombet S., Nogajewski K., Teppe F., Knap W., Karpierz K., Łusakowski J., Grynberg M., Dyakonov M.

Acta Physica Polonica A

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2009

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vol. 116

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issue 5

939-940

EN

Experiments on terahertz radiation detection with InGaAs/InAlAs field-effect transistor in quantizing magnetic field are reported. We observed oscillations of the photovoltaic signal analogous to the Shubnikov-de Haas oscillations, as well as their strong enhancement at the cyclotron resonance conditions. The results are described quantitatively within the frame of a theory which takes into account a new source of nonlinearity related to the Landau quantization of the conduction band.

20

Influence of TDMAAs Acceptor Precursor on Performance Improvement of HgCdTe Photodiodes

71%

Madejczyk P., Gawron W., Piotrowski A., Kłos K., Rutkowski J., Rogalski A.

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issue 6

1199-1204

EN

One of the key factor which determine HgCdTe photodiode quality is acceptor doping efficiency. This paper presents significant progress made over the past three years in development of acceptor doping technology in metalorganic chemical vapour deposition HgCdTe photovoltaic detectors. High acceptor doping is required for P^{+}-contact layers, whereas low doping is necessary for p-type absorbing base layer. Previously, AsH_3 precursor was used as an acceptor dopant. This precursor is partially incorporated as electrically neutral As-H pairs, which are likely to be recombination centres in HgCdTe and in consequence influence on the carriers lifetime lowering. Substituting of AsH_3 by TDMAAs resulted in higher carrier lifetimes and thereby about one order of magnitude higher R_0A product of HgCdTe photodiodes in temperatures close to 230 K.

Refine search results

Submicrometric Heavily Doped n-GaAs Structures for Microwave Detection

Phase Separation and Microwave Response of Epitaxial and Polycrystalline Manganite Films

Growth and Investigation of Oxide Heterostructures Based on Half-Metallic Fe3O4

Fast Bolometric Response of Bulk La_{0.7}Sr_{0.3}MnO_{3} Electroceramic Structures

Terahertz Detection of Quantum Cascade Laser Emission by Plasma Waves in Field Effect Transistors

Magnetoresistance of Polycrystalline La_{0.7}Ca_{0.3}MnO_3 Films in a Microwave Magnetic Field

THz Double-Grating Gate Transistor Detectors in High Magnetic Fields

Laser Induced Self-Organization of Nanohills/Nanowires in SiO_2/Si Interface

Experimental Investigation of High Pulse Power Microwave Resistive Sensor with Flat Frequency Response

High Power Microwave Detection in Asymmetrically Shaped n-Al_xGa_{1-x}As Structures

Reversible Resistive Switching in Electrically Nonhomogeneous La_{0.67}Ca_{0.33}MnO_3 Thin Films by Short Electrical Pulses

Response of Superconductor Bolometer to Phonon Fluxes

Hot Electron Effect in Degenerate Semiconductor Tunnel Junction

Frequency Dependence of Electrical Response of Polycrystalline LCMO Thin Films

Terahertz Detection by the Entire Channel of High Electron Mobility Transistors

Mechanism of Radiation Coupling to Plasma Wave Field Effect Transistor Sub-THz Detectors

THz Reflection Spectra of Different Materials, Including Explosives, Measured at a Distance up to 5 m

Terahertz Spectra of Explosives Measured by Optical Parametric Oscillator-Based System and Time Domain Spectroscopy

High Magnetic Field Effects on Plasma Wave THz Detection in Field-Effect Transistors

Influence of TDMAAs Acceptor Precursor on Performance Improvement of HgCdTe Photodiodes