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We investigate the propagation of laser-induced hypersound waves in polycrystalline diamond films by analyzing the spatial changes in the phase and amplitude of the probing laser beam reflected from the surface. We show that the velocity of bulk (longitudinal) acoustic waves is 14300 m/s in films with an average crystallite size of ≈ 0.2 μm and monotonically increases to 17200 m/s with increase in the crystallite size up to ≈ 2 μm. For surface waves, anomalous dispersion is observed, leading to a change in the phase velocity from ≈ 4800 to ≈ 6600 m/s, which is explained by the effective localization of the surface wave field in the diamond films. The values obtained can be used for the design of diamond films and membranes for applications in diamond photonics and acousto-electronics.

Ion-implanted and graphitized layers in diamond are considered as a key element of promising acousto-electronic devices, micro- and nano-electromechanical systems operating in the gigahertz frequency range. That is why their acoustical and photo-acoustical properties are of interest. In this work, we show that graphitized layers in diamond irradiated with femtosecond laser pulses are efficient generators of not only bulk but also surface waves. The nature of these waves is similar in structure to Rayleigh waves propagating along a free flat boundary of a half-space. In contrast to the undamaged diamond surface, the propagation of such a wave along the diamond surface with a buried graphitized layer leads to a considerable “spreading” of the surface wave caused by dispersion.

We employ here a picosecond ultrasonic technique to study Van der Waals heterostructures. Temporal variation of the reflection coefficient of the Al film that covers Van der Waals hBN/WSe$_2$/hBN heterostructures on a sapphire substrate after the femtosecond laser pulse excitation is carefully measured using an interferometric technique with spatial resolution. The laser pulse generates a broadband sound wave packet in aluminum film propagating perpendicular to the plane direction and partially reflecting from the heterostructural interfaces. The demonstrated technique has enough sensitivity to resolve a WSe$_2$ monolayer embedded in hBN. We apply a multilayered model of the optical and acoustical response that allows to evaluate the mechanical parameters, in particular, rigidity of interfaces, inaccessible from the other measurements. Mapping of the Fourier spectra of the response clearly visualizes different composition regions and can therefore serve as an acoustic tomography tool. Our findings demonstrate almost zero acoustic phonon dissipation below 150 GHz at the interfaces and in the layers that makes Van der Waals heterostructures perspective for nano-acoustical applications., 6 pages, 5 figures

—A compact pulse shaper described here for controlling broadband electro-optical modulators is capable of operating at frequencies from 0 to 1.5 MHz and allows the generation of control pulses with voltages up to 300 V or more and rise and fall edges of ~35 ns. The small dimensions of the shaper make it possible to combine it with an electro-optic modulator into a single unit, which significantly reduces parasitic electromagnetic radiation.

Using low-temperature (5 K) micro-photoluminescence measurements of a ZnSe/ZnMgSSe quantum well, isolated (quantum) emitters produced by interacting acceptor and hydrogen-like donor have been found and studied. These emitters enable optical probing of a single acceptor (donor) center if the nature of the donor (acceptor) constituting the distant donor-acceptor pair is known. Here we demonstrate the simplest realization of proposed optical probing: frequencies of optically active phonons are successfully determined for different types of single residual acceptors in a ZnSe-based quantum well.

Molecular responses to genotoxic stress, such as ionizing radiation, are intricately complex and involve hundreds of genes. Whether targeted overexpression of an endogenous gene can enhance resistance to ionizing radiation remains to be explored. In the present study we take an advantage of the CRISPR/dCas9 technology to moderately overexpress the RPA1 gene that encodes a key functional subunit of the replication protein A (RPA). RPA is a highly conserved heterotrimeric single-stranded DNA-binding protein complex involved in DNA replication, recombination, and repair. Dysfunction of RPA1 is detrimental for cells and organisms and can lead to diminished resistance to many stress factors. We demonstrate that HEK293T cells overexpressing RPA1 exhibit enhanced resistance to cell killing by gamma-radiation. Using the alkali comet assay, we show a remarkable acceleration of DNA breaks rejoining after gamma-irradiation in RPA1 overexpressing cells. However, the spontaneous rate of DNA damage was also higher in the presence of RPA1 overexpression, suggesting alterations in the processing of replication errors due to elevated activity of the RPA protein. Additionally, the analysis of the distributions of cells with different levels of DNA damage showed a link between the RPA1 overexpression and the kinetics of DNA repair within differentially damaged cell subpopulations. Our results provide knew knowledge on DNA damage stress responses and indicate that the concept of enhancing radioresistance by targeted alteration of the expression of a single gene is feasible, however undesired consequences should be considered and evaluated.

The patterns of propagation of gigahertz surface acoustic waves (SAWs) are obtained for cuts of CdZnTe single crystals with different crystallographic orientations. By comparing the experimental patterns with the calculated ones, the existence of at least two SAW modes, one of which is a Rayleigh mode, is demonstrated. It is shown that the anisotropy of propagation of different SAW modes makes it possible to determine the local crystallographic orientation of the CdZnTe surface and detect local imperfections of the crystal structure. Strong anisotropic scattering of the Rayleigh wave by coherent twin boundaries is found.

The dynamics of low-temperature (T = 5 K) photoluminescence spectra of Si/Si1-xGex/Si heterostructures (x = 0.045) under the influence of a stream of nonequilibrium phonons (heat pulses) propagating in the structure is investigated. The rapid evaporation of the electron–hole liquid in the quantum well of the structure is observed as the liquid is heated by nonequilibrium phonons. It is established that an increase in the exciton-gas density in the quantum well is caused by the evaporation of the electron–hole liquid and by an increase in the rate of exciton capture by the quantum well. It is shown that the interaction with nonequilibrium phonons results in the dissociation of bound-exciton complexes in the Si layers, which is accompanied by an increase in the exciton concentration and lifetime.

We show that the low-temperature (5 K) emission spectrum of InSe nanoflakes, obtained by mechanical exfoliation of β-InSe, is characterized by unusual luminescence bands that are not present in the source material. These bands were observed both in the center and at the edges of the flakes, and their location at 30–70 meV below the expected position of the excitonic band bottom rules out intrinsic emission. In addition, the most intense luminescence band exhibits line narrowing and a pronounced blue shift of ~40 meV with the increase of excitation power from 40 to 1000 W/cm2. The shift is not observed in the low-temperature emission spectra of ultra thin (four monolayers) InSe flakes. Our data suggest that producing InSe flakes using mechanical exfoliation leads to the generation of optically active structural defects, presumably associated with a violation of the layer sequence and/or layer spacing inherent to β-InSe. The simplest type of these defects are bubbles and/or folds, the formation of which is accompanied by an increase in the distance between InSe layers and, as a consequence, produces repulsive (attractive) potential for electrons (holes). At low temperatures, these defects govern the luminescent properties of the flakes up to 6 monolayers by suppressing the intrinsic (exciton) emission. Some qualitative changes were observed only in ultrathin flakes with a thickness of ~4 monolayers.

This work studies the scattering of coherent acoustical phonons within the frequency range of 30−200 GHz in strained SiGe/Si heterostructures with uniform SiGe layers and layers where the initial stage of self-organized islands formation was observed. Coherent phonon pulses reflected by single SiGe layers were detected, and phonon interference in the systems composed of two thin (approximately 10 nm) SiGe layers was observed. Acoustical properties were determined for single SiGe layers, and lateral acoustical inhomogeneity of the layers was estimated in the subterahertz frequency range. The results show that within the range of germanium content of 10%−32% acoustical properties of an approximately 10-nm SiGe layer are insensitive to internal strains governed by lattice mismatch and non-uniformities caused by initial stage of Stranski–Krastanov growth. The sound velocity and wave impedance of SiGe layers can be determined within 5% error, using the corresponding parameters of relaxed SiGe solid solutions with the same germanium content.

The lifetime of free photoexcited carriers in epitaxial films of “low-temperature” gallium arsenide (LT-GaAs) is determined by the pump-probe optical reflection method. The dark resistivity of LT-GaAs layers is estimated. Emission spectra of LT-GaAs photoconductive antennas are measured in the terahertz frequency region by the Fourier transform spectroscopy.

Heat propagation at liquid nitrogen temperature in a heterostructure consisting of a polycrystalline diamond film deposited from hydrocarbon plasma on an oriented silicon substrate is studied. A technique for measuring the cooling kinetics of a thin-film indium thermometer deposited on a diamond film after heating by nanosecond pulses of a nitrogen laser is used. The experimental data are compared with the results calculated within the theory of heat conduction for multilayer systems. The analysis performedmade it possible to simultaneously determine the thermal conductivity of the diamond film and the interfacial heat resistance of diamond/Si and In/diamond interfaces at liquid nitrogen temperature.

Electrical properties, steady-state photoconductivity, and kinetics of photoconductivity have been studied in the samples of polycrystalline p-CdTe (as-grown by the method of low-temperature synthesis from thoroughly purified components; subjected to subsequent annealing in Cd vapors; and aged at room temperature). It is shown that electrical properties of as-grown p-CdTe are controlled by a complex defect with the level at Ev + 0.16 eV; the latter transforms into the level Ev + 0.25 eV as a result of annealing in Cd vapors and aging of the samples. In addition, the deep centers with the levels Ev + 0.6 eV and Ev + 0.86 eV were detected; these centers govern the decay of the photocurrent.

The Si/Si0.8Ge0.2/Si double quantum wells grown on a silicon substrate were probed in the reflection geometry with a flux of terahertz nonequilibrium acoustic phonons produced by the heat pulse technique. A comparison of the detected phonon arrival signals with those obtained under similar conditions from a silicon sample without a quantum well structure permits one to isolate the component due to the phonon reflection from quantum wells. This reflected signal was found to be strongly anisotropic.

Low-temperature (5K) photoluminescence of silicon substrates in the range 0.8–1.2 eV is studied before and after deposition of polycrystalline diamond films. The diamond films were deposited in the microwave plasma onto high-purity dislocation-free silicon (with the resitivity ρ ≈ 3 kΩ cm) subjected to mechanical polishing or more delicate chemical and mechanical polishing. The deposition temperature was 750–850°C. In the photoluminescence spectra of the samples with the substrates polished chemically and mechanically, two lines, D1 and D2, corresponding to the dislocation-related emission are recorded. Generation of dislocations in the substrates is caused by efficient adhesion of the diamond film and, as a result, by internal stresses that relax with the formation of dislocations. The experimental spectra are practically identical to the photoluminescence spectra observed in silicon (ρ ≈ 100 Ω cm) with the density of dislocations ∼104 cm−2.

The heat propagation at room temperature was studied in a heterostructure consisting of a polycrystalline diamond film deposited from a hydrocarbon plasma on an oriented silicon substrate. The dynamics of cooling of a thin-film indium thermometer evaporated atop the diamond film was measured following its heating by nanosecond nitrogen laser pulses. The experimental data were compared with the values calculated in the framework of the theory of thermal conductivity for multilayer systems. This analysis permitted the determination of both the thermal conductivity of the diamond film and the thermal resistance of the diamond/Si and In/diamond interfaces.

Propagation of nonequilibrium acoustic phonons in a coarse-grained ZnSe produced through chemical synthesis from a vapor phase was studied for phonons generated optically or by a metallic heater. The material is characterized by a microtwin structure in randomly oriented grains. Phonon transport studies, in combination with low-temperature photoluminescence, optical and electron microscopy, and x-ray diffraction analysis, made it possible to establish the decisive role played by extended defects in scattering of high-frequency acoustic phonons in this matterial.

A fast bolometric detector embedded in a plate of chemical-vapor-deposited polycrystalline diamond was developed and fabricated. The working element of the bolometer is a buried graphitized layer (with temperature-sensitive resistance) fabricated in the bulk of a diamond by C+ ion implantation followed by annealing. The kinetics of the response of the structure to irradiation with light from an LGI-21 pulsed nitrogen laser (λ = 337 nm, τP ∼ 8 ns) were studied. The room-temperature response width at half-maximum is ∼ 20 ns. Using the space-time distribution of responses of the structure, thermal (bolometric) signals were resolved from signals of different nature (photoconductivity or photovoltage).

The photoluminescence and nonequilibrium heat transfer observed in ZnSe single crystals grown by the free growth method on an oriented single-crystal ZnSe substrate in a hydrogen atmosphere were investigated. The nonequilibrium heat transfer (or propagation of nonequilibrium phonons) was studied by the heat pulse method. A region of local thermal equilibrium or “a hot phonon spot” was found to form in the material, and the threshold of its formation was determined. The constant of spontaneous anharmonic phonon decay in ZnSe was estimated from an analysis of the propagation of nonequilibrium phonons via comparison of the experimental responses with those calculated by the Monte Carlo method.

The propagation of acoustic phonons in IV and II-VI group materials with various types of interfaces embedded inside the samples was investigated. A reverberation-type phenomenon is observed in diamond samples with implanted layers. Measurements of phonon scattering in ZnTe and CdTe with different impurity concentrations, dislocation density, and twinning systems have shown that in a pure large-grain ZnTe with chaotically placed twinning systems separated by 1-10 μm, the scattering by twins dominated. The phonon free path in such samples is reduced compared to the twin-free (though more doped) material by more than an order of magnitude. Si/SiGe double quantum wells demonstrated a perfect quality of interfaces when probed by phonons from the substrate side.

Propagation of nonequilibrium acoustic phonons in coarse-grained ZnTe obtained through vacuum sublimation was studied using the heat pulse method under both optical and metallic-heater phonon generation. The phonon mean free paths in the samples studied were shown to be 14 µm and to be dominated by scattering from twin boundaries.

Propagation of nonequilibrium acoustic phonons in ZnTe single crystals at helium temperature was studied with phonons being both optically generated and produced by a metal-film heater. Experiments with [110] ZnTe allowed for the detection of the arrival of longitudinal and transverse acoustic phonons, which are particularly well resolved when generated by a heated metal film. A bolometer also detected emission of ZnTe material with a time constant τ ∼ 90 ns, which can apparently be attributed to the luminescence of oxygen complexes, because the lifetimes of other complexes and bound excitons are substantially shorter.

Propagation of nonequilibrium acoustic phonons in samples of high-purity CdTe (impurity content ∼1016 cm−3) was studied using the heat pulse technique under pulsed photoexcitation. An analysis of nonequilibrium phonon propagation made by comparing the experimental response with Monte Carlo calculations assuming samples to be without twins provided an estimate for the spontaneous anharmonic phonon decay constant AL=2×10−52 s−1 Hz−5. The probability of free phonon transit through a twin boundary in a sample with twin structure was estimated as AC=0.96.

A bolometer based on a buried graphitized layer built into a diamond matrix is described. The bolometer was formed by ion implantation on IIa-type diamond plate with subsequent annealing. The R ( T ) characteristic of the bolometer was linear with a resistance temperature coefficient −0.06 Ω/K. The bolometer response to a nitrogen laser pulse radiation was studied for temperatures 300 and 90 K. The bolometer operating speed was less than several nanoseconds. Calculation of the temperature distribution dynamics in the layered structure was carried out by the solution of a system of linear thermal conductivity equations.

Using a heat-pulse technique we investigated propagation of acoustic phonons in twinned CdTe, ZnTe crystals, in the vicinity of CdTe/ZnTe quantum well, and Si/CVD-diamond structures. Phonon mean free paths in CdTe were estimated. We studied the effect of phonon wind on the luminescence of narrow CdTe quantum well and observed an increase in the total luminescence intensity and the change of the luminescence band shape. We believe that this effect is due to a quasi-two-dimensional lateral propagation of subsurface and interface acoustic phonons in the ZnTe/CdTe structure. Preliminary data obtained on the Si/CVD-diamond interfaces suggest they are strongly damaged. To reduce the thermal boundary resistance of the interface between the material studied and the thin-film phonon detector we developed a buried bolometer based on a graphitized layer produced by ion implantation in diamond.

Characteristics of a phonon generator in the form of a pulse-heated metallic film, viz., the time dependences of the film temperature and the kinetics of phonon ejection from the film into a substrate, are considered. The time dependences of the film temperature are calculated for cadmium telluride, diamond, and silicon substrates. It is shown that the duration of film cooling substantially exceeds the heating pulse length and the film continues to generate phonons with lower frequencies at the end of heating pulse. The inference is drawn that the film cooling should be correctly taken into account in analysis of the propagation of nonequilibrium acoustic phonons, specifically for phonon processes occurring in nanostructures.

The heat-pulse technique was employed to study the heat transfer in laser-pulse excitation in a high-purity grain-oriented CdTe growth by multiple sublimation. Comparison of the heat pulses obtained in the experiment with the results of calculations by the Monte Carlo method allowed one to evaluate the mean free path of the acoustic phonons in this material. It is proposed on the basis of the results obtained that the scattering by planar defects (grain boundaries and twinning planes) is the main mechanism of phonon scattering at low temperatures.

We have studied the mechanism of heat transfer under pulsed excitation at low temperatures while measuring the propagation of non-equilibrium acoustic phonon packets across a CVD diamond film. Results are presented on the measurements of acoustic phonon packets propagating across the high quality CVD diamond films with 0.25 and 0.35 mm thickness. Two types of phonon generator were employed: laser heated Au/Ti films deposited onto the sample, and photoexcited buried implanted layers. A superconducting Al GR -based bolometer served as the phonon detector. The results obtained essentially differ from those for natural diamond: under photoexcitation of the buried implanted layer the bolometer response times are larger by an order of magnitude than those for natural diamond, and the shape of response has a clearly pronounced diffusive character. Possible mechanisms of response broadening are discussed, including the scattering of high-frequency phonons at grain boundaries.

The low temperature (5 K) photoluminescence (PL) of silicon substrate in the range of 0.8–1.12 eV before and after microwave plasma assisted chemical vapor deposition of polycrystalline diamond films was studied. The diamond films were deposited onto the pure ( ρ ∼3 kOhm cm) dislocation-free silicon treated by mechanical polishing (MP) or by superior chemical–mechanical polishing (CMP). In the PL spectra of coated silicon substrates treated by CMP, the D 1 and D 2 lines related to the dislocation emission were registered. We suppose that the formation of dislocations in the substrate is caused by a strong adhesion of diamond film and as a consequence by the formation of inner tensions released as dislocations.

A simple method for detecting time-resolved weak light signals with a digital oscilloscope, which allows detection of several photons per one excitation period, is described. A system for detecting low-temperature photoluminescence with a resolution of 15 ns has been implemented on the basis of this technique and a method for attaining a resolution of 1–3 ns has been developed. The luminescence kinetics of Si/GexSi1 − x/Si quantum wells was measured in the near-IR region.

A theoretical model of the temperature distribution of biological tissue under pulsed laser illumination is developed. With the help of the elaborated miniature thermometer based on a shieldless silicon transistor, the spatial-temporal distribution of temperatures of the artery inner wall with atherosclerotic inclusions (in vitro) under excimer-laser illumination as a function of laser power and the distance between the thermometer and laser spot on the tissue surface was experimentally measured. From a comparison of experimental data with the results of the model developed, the thermal diffusivity of tissue and the size of the “region of damage” (i.e., the region where the temperature exceeds 43–45°C) under laser removal (ablation) of the tissue was determined, as well as the threshold energy density of the ablation onset.

The phonon pulses initiated by photoexcitation of structures containing Si0.8Ge0.2 double quantum wells under picosecond radiation of a MIRA 900P titanium-sapphire laser (λ = 760 nm) are studied. The propagation of nonequilibrium acoustic phonons is detected with a superconducting bolometer. The recorded bolometer response is found to differ substantially from that observed in photoexcitation of the same structure by nanosecond pulses of a nitrogen laser (λ = 337 nm). The generation of coherent acoustic phonons is suggested as an explanation.

The luminescence of highly calcified atherosclerotic plaque in comparison with the luminescence of a normal wall of the vessel was studied in vitro (the luminescence was excited by a CW argon laser with λ = 488 nm or a pulsed nitrogen laser with λ = 337 nm). The mass-spectroscopy analysis of the plaque was carried out with a LAMMA-1000 system. It is ascertained that the specific shape of the luminescence spectrum with maximum at λ = 560 nm (under argon laser excitation) and λ = 485 nm (under nitrogen laser excitation) is typical of a highly calcified plaque (Ca content ≈38 %) and is similar to the luminescence spectrum of ordinary chalk.

A nonlinear model is developed for the photoresponse of a bolometric structure taking into account the temperature dependences of the thermal constants of the YBaCuO/MgO structure and its boundary thermal resistance. The model also allows for the specific form of the currentvoltage characteristic of YBaCuO and the heat release from the transport current flow. A comparison between the experimental data and the model showed that the nonlinear thermal model accurately describes the temporal characteristics of the photoresponse.

The heat pulses produced by laser excitation were measured in Si using YBCO sensor. The observed pulse shapes confirm the existence of the phonon hot spot in certain experimental conditions. The exploiting of YBCO bolometer and rather thin Si sample allowed the direct measurement of the hot spot temperature and its life time. Measured hot spot parameters are in satisfactory agreement with those obtained by help of Kazakovtsev-Levinson theory. The Monte-Carlo simulation of phonon propagation was carried out with account of coalescence process. It was found that with increase of excitation energy density, the calculated response peak position shifts noticeably to greater time values.

The propagation of heat pulses produced in thin silicon wafers by photoexcitation is investigated before and after the YBCO laser ablation. The Monte-Carlo simulation and analysis of the heat pulse shape led to conclusion about the introducing into the Si substrate of the acceptor type additional centers in the process of laser ablation. These centers turn to be phonon scatterers and therefore change the heat transfer velocity.

The photoresponse of a YBaCuO/ZrO2 bolometric structure was measured under modulated (λ = 630 nm) and pulsed (τ ≈ 7 – 8 ns; λ = 337 nm) laser excitation. The shape of the measured photoresponse was interpreted by a thermal model; nevertheless, the pulse amplitude for vanishing YBaCuO film resistance was 5–6 times greater than predicted; the thermal boundary resistance RBd between YBaCuO and YSZ was evaluated ⋍ 10−2 K × cm2/Watt, which is considerably larger than estimated theoretically for the similar situation of YBaCuO/MgO [5].

A heated thin gold film as a generator of nonequilibrium phonons in diamond was studied both theoretically and experimentally. The cooling times τC of the film obtained theoretically are of the order of experimental bolometric response widths. Since τC>τB (time of phonon ballistic propagation in the sample under study), the “gold” phonon generator proved to be inadequate. A novel method of phonon generation is proposed – photoexcitation of buried implanted layer that allowed us to resolve the arrival of LA and TA phonons. Comparison of the heat pulses observed with those calculated by the Monte Carlo method yields the constant of elastic phonon scattering ASCAT=2×10−44 s−3, which coincides with that calculated by taking into account scattering only by the isotopes 13 C .

It is shown that an approximately 150 nm thick ion-implanted buried layer in diamond and excited by a pulsed laser at wavelength λ=337 nm is a source of nonequilibrium acoustic phonons propagating ballistically through the diamond sample at temperatures ∼2 K.

A fast bolometer built in a plate of diamond grown at high pressure by the gradient growth method is developed and fabricated. The parameters of this structure are compared with these of the structures investigated earlier, which were fabricated based on chemical vapour deposited (CVD) diamond and natural type IIa diamond.

A novel interest has arisen to the nature of boundary resistance (RBd) of solid/solid interface in connection with the fact, for example, that the photoresponse of such systems as HTSC/dielectric, inevitably is determined by the heat transfer (phonon) processes via the interface after energy relaxation of excited particles. Up to now the role of RBd for explanation of photoresponse features is almost unknown.

Since diamond can be used as both the substrate and the active medium in electronic devices, it is very important to obtain information concerning the temperature variations in the immediate vicinity of active elements and the conditions of heat removal from such elements. This task is solved by a bolometer built into a diamond plate, which is capable of measuring temperature increments induced by laser pulses in the diamond or in the diamond-supported surface structures. The bolometer, representing a buried graphitized layer formed by helium ion implantation with subsequent annealing, has a characteristic response time of ∼10 ns.

The heat propagation at room temperature in the heterostructure – polycrystalline diamond film deposited on a silicon substrate has been investigated by the pulse photothermal method. A thin In film evaporated onto the diamond was used as a thermometer. The experimental response was compared to that calculated by the solution of the heat propagation problem in the three-layer axial-symmetric structure with definite thermal boundary resistance on the interfaces. This analysis permitted the determination of both the thermal conductivity of the diamond film and the thermal resistance of the diamond/Si and In/diamond interfaces.

Diamond, with its unique combination of physical properties, is a promising material for electronic devices operating under extreme conditions. Due to its exceptionally high thermal conductivity, diamond-based bolometers should possess very short response time. A fast bolometric sensor was formed within a polycrystalline diamond plate by ion implantation and subsequent annealing. The response kinetics of the structure was studied under a nitrogen laser pulsed illumination. The response time at room temperature was less than 20 ns. The spatial-temporal distribution of responses allowed us to distinguish between thermal responses and those of different nature (e.g. photoconductivity). This study was supported by the Russian Foundation for Basic Research, project nos. 05-02-17545 and 07-02-00575.

ZnTe crystallites isolated from a druse of coarse-grained polycrystalline ZnTe, prepared by chemical vapor synthesis at a temperature of ∼650°C, were studied using x-ray diffractometry, luminescence, and the heat pulse technique. The crystallites are stacked in {110}-oriented macroscopic layers with a common twin system. The {111} twin planes separated at a distance of 50–100 μm are perpendicular to the (110) growth layers. Acoustic phonon propagation was studied using the heat pulse technique. A comparison of the responses to the arrival of differently polarized phonons in a given sample with the responses obtained on high-purity coarse-grained ZnTe with randomly distributed twin systems with a separation of 5–10 μm and on twin-free single-crystal ZnTe suggests that twins radically affect the scattering of acoustic phonons. The mean free paths of LA, FTA, and STA phonons were determined by comparing the experimental responses with Monte Carlo calculations.