We propose a new spintronic emitter based on the Co/WSe2 heterostructure. The time of ultrafast demagnetization is estimated. It is shown that the two-dimensional ferromagnet/semiconductor interface exhibits strong spin-orbit coupling. Approaches to the description of the mechanism of generation of THz radiation are implemented. It is shown that the polarization orientation of THz radiation depends on the direction of magnetization.

In this work, the piezoelectric and ferroelectric properties in the Zn/Dy single-ion molecular complex have been studied by local piezoresponse force microscopy and switching spectroscopy. It is demonstrated that the chosen strategy for the synthesis of integrated magnetoelectric molecular systems makes it possible to grow molecular single crystals in the polar group. Switching of the intrinsic domain structure in Zn/Dy single crystal at a bias voltage of +15 V and the possibility of changing the induced domain structure at a bias voltage of -20 V were demonstrated. The effective piezoelectric coefficient d33 was attained of about 14 pm/V at a bias voltage of 50 V.

We report on a high-sensitive THz plasmonic-enhanced photoconductive antenna (PCA)-detector based on an InGaAs/InAlAs superlattice heterostructure. A noticeable increase in the sensitivity and signal-to-noise ratio of the proposed PCA-detector is shown compared to a similar detector without plasmonic electrodes. The efficiency of plasmonic electrodes has been experimentally confirmed via pulsed THz time-domain spectroscopy by measuring the dependence of the THz amplitude of the detector’s signal on the polarization of laser excitation.

The parameters of the generated terahertz radiation in a two-dimensional WSe2 film grown by chemical vapor deposition were investigated for the first time. The main mechanism of the generated terahertz radiation in the studied sample was determined. The terahertz amplitude dependence on azimuthal angle in the two-dimensional WSe2 film was studied. The distribution of the laser pump electric field in the WSe2 / SiO2 / Si structure was calculated as a function of the silicon dioxide thickness. The choice of the optimal structural geometry for the effective generation of terahertz radiation by a monolayer WSe2 was theoretically justified

AbstractThe influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the reflection coefficient of the InGaAs/InAlAs superlattice heterostructures is analyzed. A model is built for the reflection coefficient of the InAlAs barrier layer, depending on the excitation photons energy. The resonance behavior of the reflection coefficient is explained.

AbstractLow-temperature gallium arsenide (LT-GaAs) films were grown by the method of molecularbeam epitaxy (MBE) at a reduced temperature (230°C) on GaAs(100) substrates and subjected to postgrowth annealing in various regimes. Photoconductive antennas (PCAs) with flag geometry formed on the film surface were characterized by terahertz (THz) response power at various bias voltages. The method of THz spectroscopy was used to study the characteristics of PCAs based on LT-GaAs films annealed in various regimes and the optimum interval of postgrowth annealing temperatures (670–720°C) was established.

The results of experimental studies of the time dynamics of photoexcited charge carriers in In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As superlattices grown by molecular-beam epitaxy on a GaAs substrate with a metamorphic buffer are reported. On the basis of the results of the numerical simulation of band diagrams, the optimal thickness of the In 0.52 Al 0.48 As barrier layer (4 nm) is chosen. At this thickness, the electron wave functions in In 0.53 Ga 0.47 As substantially overlap the In 0.52 Al 0.48 As barriers. This makes it possible to attain a short lifetime of photoexcited charge carriers (τ ~ 3.4 ps) at the wavelength λ = 800 nm and the pumping power 50 mW without doping of the In 0.53 Ga 0.47 As layer with beryllium. It is shown that an increase in the wavelength to λ = 930 nm (at the same pumping power) yields a decrease in the lifetime of photoexcited charge carriers to τ ~ 2 ps. This effect is attributed to an increase in the capture cross section of trapping states for electrons with lower energies and to a decrease in the occupancy of traps at lower excitation densities.

AbstractThe results of experimental studies of the time dynamics of photoexcited charge carriers in In_0.53Ga_0.47As/In_0.52Al_0.48As superlattices grown by molecular-beam epitaxy on a GaAs substrate with a metamorphic buffer are reported. On the basis of the results of the numerical simulation of band diagrams, the optimal thickness of the In_0.52Al_0.48As barrier layer (4 nm) is chosen. At this thickness, the electron wave functions in In_0.53Ga_0.47As substantially overlap the In_0.52Al_0.48As barriers. This makes it possible to attain a short lifetime of photoexcited charge carriers (τ ~ 3.4 ps) at the wavelength λ = 800 nm and the pumping power 50 mW without doping of the In_0.53Ga_0.47As layer with beryllium. It is shown that an increase in the wavelength to λ = 930 nm (at the same pumping power) yields a decrease in the lifetime of photoexcited charge carriers to τ ~ 2 ps. This effect is attributed to an increase in the capture cross section of trapping states for electrons with lower energies and to a decrease in the occupancy of traps at lower excitation densities.

Методом терагерцевой спектроскопии исследована эффективность генерации и детектирования ТГц-излучения в диапазоне до 3 ТГц пленками LT-GaAs, содержащими легирующие эквидистантные delta-слои Si и выращенными методом молекулярно-лучевой эпитаксии на подложках GaAs с ориентациями (100) и (111)А. На поверхности пленок были изготовлены микрополосковые фотопроводящие антенны. Генерация ТГц-излучения происходила при облучении зазора антенны фемтосекундными оптическими лазерными импульсами. Показано, что интенсивность ТГц-излучения от фотопроводящей антенны на LT-GaAs/GaAs (111)A в 2 раза больше, чем от такой же антенны на LT-GaAs/GaAs (100), а чувствительность антенны на LT-GaAs/GaAs (111)A как детектора ТГц-излучения в 1.4 раза превосходит чувствительность антенны на LT-GaAs/GaAs (100). DOI: 10.21883/FTP.2017.04.44347.8408

The efficiency of the generation and detection of terahertz radiation in the range up to 3 THz by LT-GaAs films containing equidistant Si doping δ layers and grown by molecular beam epitaxy on GaAs (100) and (111)Ga substrates is studied by terahertz spectroscopy. Microstrip photoconductive antennas are fabricated on the film surface. Terahertz radiation is generated by exposure of the antenna gap to femtosecond optical laser pulses. It is shown that the intensity of terahertz radiation from the photoconductive antenna on LT-GaAs/GaAs (111)Ga is twice as large as the intensity of a similar antenna on LT-GaAs/GaAs(100) and the sensitivity of the antenna on LT-GaAs/GaAs (111)Ga as a terahertz-radiation detector exceeds that of the antenna on LT-GaAs/GaAs(100) by a factor of 1.4.

Методами оптического зондирования при фемтосекундной лазерной накачке (optical pump-probe) и терагерцевой спектроскопии во временной области исследовано влияние эпитаксиальных напряжений на динамику неравновесных носителей заряда, а также спектр терагерцевого излучения в пленках InyGa1-yAs. Продемонстрировано снижение времени жизни неравновесных носителей заряда и увеличение ширины спектра терагерцевого излучения для пленки InyGa1-yAs с большим механическим напряжением. DOI: 10.21883/PJTF.2017.22.45260.16958