[en] The continuous transfer of (001)Si layers 0.2–1.7 μm thick by implanted hydrogen to the c-sapphire surface during direct bonding at high temperatures of 300–500°C is demonstrated for the first time. The formation of an intermediate silicon-oxide layer SiO_x during subsequent heat treatments at 800–1100°C, whose increase in thickness (up to 3 nm) correlates with an increase in the positive charge Q_i at the heterointerface to ~1.5 × 10¹² cm^–2 in contrast to the negative charge at the SiO_x/Al₂O₃ ALD heterointerface. During silicon-layer transfer to sapphire with a thermal silicon-dioxide layer, Q_i decreases by more than an order of magnitude to 5 × 10¹⁰ cm^–2 with an increase in the SiO₂ thickness from 50 to 400 nm, while the electron and hole mobilities barely differ from the values in bulk silicon. Based on these results, a qualitative model of the formation of positively charged oxygen vacancies in a 5-nm sapphire layer near the bonding interface is proposed.

[en] We show the possibility of producing a short bunch of nearly bandwidth-limited few-cycle attosecond pulses based on time-dependent resonant interaction of an incident radiation pulse with the bound states of hydrogen-like atoms. Time-dependence of an atomic resonance is provided by a laser pulse far from resonance with an intensity well below the atomic ionization threshold via time-dependent tunnel ionization from the excited states and time-dependent adiabatic Stark splitting of the excited energy levels. Without external matching of the spectral components it is possible to produce pulses with durations up to 80 as at the carrier wavelength of 13.5 nm in Li²⁺-plasma, as well as pulses with durations up to 600 as at the carrier wavelength of 122 nm in atomic hydrogen. (paper)

[en] The transformation of exponentially decaying waveform (the time dependence of detection probability) of a Mössbauer γ-ray photon into a regular sequence of short nearly bandwidth-limited pulses in a vibrating recoilless resonant absorber is studied. The case of dual-tone vibration at the fundamental frequency and its second harmonic under experimentally feasible conditions is considered. We show that this technique allows one to shorten pulses and increase the ratio of pulse separation to pulse length as well as to enlarge pulse amplitude compared to the pulses produced in harmonically vibrating absorber. The obtained results pave the way to the development of the time-resolved Mössbauer γ-ray spectroscopy and manipulation of quantum information in hard x-ray/γ-ray range. (paper)

[en] We establish a close physical analogy between coherent forward scattering of γ -ray radiation in the vibrating quasi-resonant nuclear absorber and the XUV field propagation in the quasi-resonant atomic medium in the presence of the moderately strong IR field. We prove that both processes, under certain conditions, are described by similar Maxwell–Bloch equations for a two-level medium with modulated parameters of the resonant transition. It results in similar transformation of both γ -ray and XUV fields at the exit from the medium, fully determined by the characteristics of applied modulation and spectral content of the incident fields. We find an appropriate analytical solution describing transformation of the electromagnetic field as a result of its propagation in the modulated medium. We show, in particular, that recently observed effects of (i) suppressed resonant absorption in coherent γ -ray scattering of vibrating absorber and (ii) ionization rate modulation in IR pump–XUV probe experiments, present themselves as different manifestations of the same general physical phenomenon of modulation induced transparency (MIT). That transparency is induced by modulating the parameters of the resonant transition. While only partial MIT was observed so far, we suggest certain conditions for conducting some realistic experiments, which should demonstrate nearly 100% transparency in both processes. (paper)

[en] Silicon wafers with an ultrathin buried high-k oxide were fabricated by the atomic layer deposition of high-k layers on sapphire and silicon substrates with subsequent silicon layer transfer onto their surfaces by bonding and rapid thermal annealing (RTA). An extremely high thermal stability of hafnia orthorhombic Pca2₁ ferroelectric phase of up to 1100 °C was observed in the silicon-on-ferroelectric structure on the sapphire substrate. Silicon–ferroelectric–silicon structures with hafnia BOX and alumina inclusions also demonstrated increased thermal stability for hafnia or hafnia–zirconia alloys during the RTA treatment up to 900 °C, which makes them fully compatible with current complementary metal oxide semiconductor technology, promising integrated circuits for neuromorphic computation and optoelectronic switching devices. (paper)

[en] The various methods of laser coherent photonic implementations of multiparametric classification are discussed in this paper. The holographic and optical data processing methods for medical application are considered. Inverse two-phase coding and analysis of light distribution in the correlation plane enables us to realize a number of algorithms: search for a precedent, Hamming distance measurement, Bayes probability algorithm, deterministic and ‘correspondence’ algorithms. The experimental holographic results for medicine prognosis are shown. (paper)

[en] The luminescence of Cr²⁺ and Fe²⁺ in Cr:Fe:ZnSe polycrystals excited at room temperature by pulsed lasers at wavelengths of 2.09 and 2.94 m was studied. For comparison, we also studied the luminescence in single crystals and polycrystals of Fe:ZnSe with iron ion concentration in the range from 5.6  ×  10¹⁸ to 5.7  ×  10¹⁹ cm⁻³. Doping of the polycrystalline samples was carried out using a high-temperature diffusion process with subsequent control of the dopants concentration distribution over the crystal depth. The dependence of the luminescence lifetime τ _lt of Fe²⁺ ions on the dopants concentration in crystals excited at a wavelength of 2.94 m was obtained. It was found that chromium quenches the luminescence of Fe²⁺ no less actively (if no more) than iron itself. The τ _lt values were measured for Fe:ZnSe excited at a wavelength of 2.94 m and Cr:Fe:ZnSe samples with the same maximum Fe²⁺ ions concentrations (≈0.9  ×  10¹⁹ cm⁻³) at wavelengths of 2.94 m and 2.09 m. A noticeable increase in τ _lt value and luminescence rise time was observed in Cr:Fe:ZnSe crystals excited at a wavelength of 2.09 m (τ _lt  ≈  460 ns) compared to 2.94 m (τ _lt  ≈  240 ns). For comparison, the value of τ _lt in Fe:ZnSe was about 340 ns. The obtained results confirm the fast energy transfer in Cr:Fe:ZnSe crystals from excited chromium ions to iron ions. The output characteristics of lasers on Fe:ZnSe and Cr:Fe:ZnSe polycrystalline active elements with pumping by HF laser radiation were compared. The slope efficiency with respect to the absorbed energy of Cr:Fe:ZnSe lasers was significantly lower, and the generation threshold was two times higher than for Fe:ZnSe lasers. The prospects for creating a room temperature laser, in which the excitation of iron ions will be carried out through energy transfer from chromium ions, are analyzed. (letter)

[en] Energy and spectral–temporal characteristics of lasers on heavily doped single crystals Fe:ZnSe are studied. With the cavity formed by faces of the crystal at a bivalent iron concentration of 2.8 × 10¹⁹ cm⁻³, the slope and total laser efficiencies with respect to the absorbed energy were 53% and ≈ 42%, respectively. Laser spectra with the cavity free of air and elements capable of forming Fabry–Perot interferometers were recorded using a monochromator with an HPL-256-500 (HEIMANN Sensor) pyroelectric line photodetector. The spectra have a periodical structure with the period of about ≈ 4 cm⁻¹. A similar periodical structure was observed in other cavity types with active elements differing in thickness, production technology, and even crystal material (Fe:ZnSe, Fe:ZnS). Presently, we have no adequate explanation for such a periodical structure. A simple method is suggested for obtaining nanosecond radiation pulses in the spectral range of 4–5 µm based on heavily doped Fe:ZnSe single crystals.

[en] Characteristics of a Fe:ZnSe laser are studied at room temperature. The laser active elements are heavily doped single crystals with the ${\text{Fe}}^{2+}$ ion concentration $n=0.64\times <!--\; ??\; -->{10}^{19}-<!--\; ???\; -->5.7\times <!--\; ??\; -->{10}^{19}{\text{cm}}^{-<!--\; ???\; -->3}$, grown from melt by the Bridgman method. The generated energy of 870 mJ is obtained at the total efficiencies with respect to the absorbed and incident energies ${\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{a}\mathrm{b}\mathrm{s}}=43\mathrm{\%<!--\; \%\; -->}$ and ${\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{i}\mathrm{n}\mathrm{c}}\approx <!--\; ???\; -->35\mathrm{\%<!--\; \%\; -->}$, respectively. The laser slope efficiency with respect to the absorbed energy is ${\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{s}\mathrm{l}\mathrm{o}\mathrm{p}\mathrm{e}}\approx <!--\; ???\; -->50\mathrm{\%<!--\; \%\; -->}$. In a heavily doped active element with the ${\text{Fe}}^{2+}$ concentration $n=5.7\times <!--\; ??\; -->{10}^{19}{\text{cm}}^{-<!--\; ???\; -->3}$, in which the medium excitation depth is just a part of the total element dimension along the optical axis (the element is completely non-transparent for the pumping radiation), the radiation spectrum of the Fe:ZnSe laser shifts to the long-wavelength range by more than 300 nm as compared to spectra of the laser on crystals excited along the whole element length. It is shown that Fe:ZnSe lasers on heavily doped single-crystal elements can be efficiently excited by a radiation of a Cr:ZnSe laser without tuning the spectrum of the latter to the longer wavelength range.