Single Crystal Quartz Research Articles

Narrowband surface-acoustic-wave filters in RF identification systems

Low-loss narrowband surface-acoustic-wave filters designed for operation in RF identification devices in the frequency range 860–890 MHz are developed and investigated. Software is developed on the basis of the theory of coupled modes. A procedure for calculating a resonator transversely coupled structure is presented. This procedure provides good agreement between experimental and theoretical results. The manufactured filters are based on the resonance structures made on single-crystal quartz substrates by means of liftoff (explosive) photolithography and a batch-fabrication technique.

Raman Studies of Monolayer Graphene: The Substrate Effect

Graphene has attracted a lot of interest for fundamental studies as well as for potential applications. Till now, micromechanical cleavage (MC) of graphite has been used to produce high-quality graphene sheets on different substrates. Clear understanding of the substrate effect is important for the potential device fabrication of graphene. Here we report the results of the Raman studies of micromechanically cleaved monolayer graphene on standard SiO2 (300 nm)/Si, single crystal quartz, Si, glass, polydimethylsiloxane (PDMS), and NiFe. Our data suggests that the Raman features of monolayer graphene are independent of the substrate used; in other words, the effect of substrate on the atomic/electronic structures of graphene is negligible for graphene made by MC. On the other hand, epitaxial monolayer graphene (EMG) on SiC substrate is also investigated. Significant blueshift of Raman bands is observed, which is attributed to the interaction of the graphene sheet with the substrate, resulting in the change o...

Irradiation effect on the electrical properties of corundum and quartz single crystals

The radiation effects in corundum and quartz crystals have been assessed at temperatures from 25 to 450°C and gamma doses from 104 to 109 rad. The radiation effects on the conductivity and dielectric losses of the crystals have been shown to be nonlinear, with extrema and inflections. The conductivity of corundum is characterized by three-step kinetics, with pronounced carrier generation in the range 100–200°C and restoration of parameters at 400°C in crystals irradiated to high doses. Both corundum and quartz crystals have extrema tanδ(t) in at different gamma doses. The peaks (200–250 and 50–150°C) grow with increasing frequency, without shifting to higher temperatures. The peaks seem to be due to different mechanisms of dielectric losses. The dose dependences of tanδ and σ have been compared up to 5 × 109 rad and have been shown to correlate with one another. The extrema have been interpreted in terms of the Vul model. We have analyzed the possible origins of the loss maxima and have evaluated the activation energies for ionic polarization and conduction in the materials studied. We assume that the dielectric losses in the irradiated crystals are determined by conduction and polarization.

X-ray diffraction in AT-cut quartz single crystal at acoustic excitation at the fundamental frequency

X-ray diffraction on different atomic planes of an AT-cut quartz crystal is studied experimentally in the Laue geometry in case of excitation by acoustic waves at the first resonant (fundamental) frequency. Acoustic waves lead to an increase in the integral intensity of the reflection-diffracted beam. The amplification coefficients in reflection are measured in dependence on the amplitude of a.c. voltage applied to the crystal at the resonant frequency. The frontal distributions of the intensity of the beam diffracted in the reflection direction are obtained for different atomic planes.

Positron states and nanoobjects in proton-irradiated quartz single crystals: Positronium atom in quartz

The influence of proton bombardment and metal atom impurities on the structure of quartz single crystals has been studied. The related defects have been studied using positron annihilation spectroscopy (angular correlation of positron-annihilation photons), acoustic absorption, and optical absorption measurements. It is shown that the presence of a narrow component f in the angular distribution of annihilation photons (ADAP), which is related to the formation of parapositronium, determines a high sensitivity of this method with respect to features of the crystal structure of quartz. It is established that the defectness of the structure of irradiated quartz crystals can be characterized by the ratio f/f0 of the relative intensities of narrow components in the ADAP curves measured before (f0) and after (f) irradiation. Any process leading to a decrease in the probability of positronium formation (e.g., positron loss as a result of the trapping on defects and the interaction with impurity atoms and lattice distortions) decreases the intensity of the narrow component. Based on the ADAP data, estimates of the radii and concentrations of nanodefects in quartz have been obtained and their variation upon annealing at temperatures up to T = 873 K has been studied.

MAGNETIC PROPERTIES OF NANOCRYSTALLINE CO-FERRITE FILMS DEPOSITED ON SINGLE-CRYSTAL SiO2 SUBSTRATES USING PULSED LASER DEPOSITION

Co-ferrite films were prepared using pulsed laser deposition with both post-annealing and in situ heating processes. Magnetic properties of these films were studied in the function of temperature, film thickness, and substrate. The films using post-annealing processes exhibited isotropic microstructure, and the coercivity showed no obvious magnetic anisotropy and no strong dependence on film thickness. Co-ferrite films using in situ heating exhibited (111) highly textured structure and possessed perpendicular anisotropy as well as large coercivity. The preferential texture and magnetic anisotropy were closely associated with substrate temperature and thickness. Perpendicular Hc over 12.5 kOe was obtained in the 33 nm Co-ferrite film deposited on single crystal quartz substrate at 550°C. The high coercivity and perpendicular coercivity may be attributed to the nanocrystalline grain, textured orientation, and large residual strain in these films since large residual strain may induce strong stress anisotropy.

Grain size dependence of elastic anomalies accompanying theα–β phase transition in polycrystalline quartz

The effects of grain size on the elastic properties of quartz through theα–β phase transition have been investigated by resonant ultrasound spectroscopy.It is found that there are three regimes, dependent on grain size, withinwhich elastic properties show different evolutions with temperature. Inthe large grain size regime, as represented by a quartzite sample with∼100–300 µm grains, microcracking is believed to occur in the vicinity of the transition point, allowinggrains to pull apart. In the intermediate grain size regime, as represented by novaculite(1–5 µm grain size) andEthiebeaton agate (∼120 nm grain size), bulk and shear moduli through the transition follow closely the values expectedfrom averages of single crystal data. The novaculite sample, however, has a transition temperature∼7 °C higher than that of single crystal quartz. This is assumed to be due to the development of internalpressure arising from anisotropic thermal expansion. In the small grain size region, agates from Mexico(∼65 nm) andBrazil (∼50 nm) show significant reductions in the amount of softening of the bulk modulus as thetransition point is approached from below. This is consistent with a tendency for thetransition to become more second order in character. The apparent changes towards secondorder character do not match quantitative predictions for samples with homogeneous strainacross elastically clamped nanocrystals, however. Some of the elastic variations arealso due to the presence of moganite in these samples. True ‘nanobehaviour’ forquartz in ceramic samples thus appears to be restricted to grain sizes of less than∼50 nm.

Stress-induced second harmonic generation in silica glass

Second harmonic generation (SHG) was observed from external stress-applied silica glass. Since no SHG signal was obtained from stress-free silica glass, the SHG is considered to result from the strain caused by the externally stress. The intensity of SHG is about 0.1% of that of Y-cut quartz single crystal. The lost of centrosymmetry in the microstructure induced by external pressure seems to result in the SHG.

Fractoluminescense of crystalline quartz upon an impact

The kinetics of fractoluminescence of quartz single crystals subjected to an impact with a steel striker is investigated. It is established that, within several tens of microseconds after an impact, there appear two to three tens of fractoluminescence flashes. An analysis of the luminescence spectra demonstrates that fractoluminescence arises upon the transition from an excited electron level to the ground electron level in SiO. radicals formed as a result of the breaking of the Si-O-Si bonds. Acoustic emission signals are detected simultaneously with fractoluminescence. It is revealed that all except the first of the fractoluminescence flashes arise from vibrations of the crystal-striker system after the impact. Approximately ten cracks with linear sizes of several millimeters are observed on the surface of the plate. The SiO· radicals are assumed to be located at the surface of these cracks. The time of fractoluminescence excitation is determined by the growth rate of cracks and amounts to ≈1–3 μs. After the growth of the cracks is terminated, the fractoluminescence intensity decreases exponentially with a mean time of ≈12 μs, which does not depend on the temperature. This makes it possible to attribute the observed luminescence to fluorescence, i.e., to a singlet-singlet transition.

Positronics and nanotechnologies: Possibilities of studying nano-objects in technically important materials and nanomaterials

This article shows that an effective method to define the size of nano-objects (vacancies, vacancy, clusters, free pore volumes, cavities, and holes), and their concentration and chemical composition, is positron annihilation spectroscopy (PAS). A review of the state of the art of the application of the PAS technique to probe nanostructures in porous silicon, silicon and single crystal quartz samples is presented.

Measurement of specific surface free energy of ruby and quartz single crystals using contact angle of liquids

AbstractThe specific surface free energy of ruby and quartz single crystal was experimentally obtained using contact angle of water and formamide droplets on the crystal surfaces, and compared with the morphology of each crystal. The ruby crystals satisfied Wulff's relationship even though their shape were not equilibrium form. The specific surface free energies of the growing faces of synthetic quartz crystal, ‐X, +X, Z, and S faces were obtained as 51.9, 55.6, 57.4, and 58.9 mN/m, respectively. The growth rates of these faces were 0.09, 0.23, 0.28, and 0.33 mm/day, respectively. The growth rate of each face of the quartz crystal can be regarded as a function of the experimentally obtained specific surface free energy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dependence of the dielectric permittivity of single-crystal quartz on thermal deformation at cryogenic temperatures

The whispering gallery mode technique applied to single-crystal quartz has been used as a precise method to determine the dependence of the dielectric permittivity of pure single-crystal quartz on temperature-induced dimensional changes at cryogenic temperatures. The anisotropic temperature coefficients of permittivity (TCP) perpendicular and parallel to the crystal axis have been determined between 4.7 and 280 K. The difference between TCPs perpendicular and parallel to the crystal axis, near 17 GHz, between 160 and 300 K is approximately half the thermal expansion coefficient perpendicular to the crystal axis. Over this temperature range, the fractional change in the relative permittivity values perpendicular and parallel to the crystal axis, as a result of thermal expansion of the perpendicular dimension of the crystal, only differs by a small constant value.

EXPERIMENTAL SETUP FOR STUDYING THERMOSTIMULATED CURRENTS IN SEMICONDUCTORS AND DIELECTRICS

An automated setup for studying thermostimulated currents (TSC) in semiconductor and dielectric materials is made. Unlike the existing equipment, it enables TSC to be measured in vacuum in a broad range of the linear heating rates (0.01-10 °C/s) and temperatures (20-400 °С). The signal, detected by the setup, varies within 10 -12 A to 10 -7 A. An electronic control system was designed to control the heating process. A microcontroller was used for digital data acquisition, processing and transfer to a personal computer. Test measurements of thermostimulated conductivity currents (TSCC) were carried for a quartz single crystal.

Nature of radiation defects in synthetic quartz according to the small-angle neutron scattering data

The supraatomic structure of single crystals of synthetic quartz in the initial state with a dislocation density of 570 cm−2 and after irradiation in the VVR-M reactor at the Petersburg Nuclear Physics Institute with fast neutrons having the energy E n > 1 MeV in the range of fluences F n = 7.7 × 1017 −2.1 × 1020 neutrons/cm2 has been studied by small-angle scattering of thermal neutrons. It is established that fast neutrons form point, linear, and volume lattice defects throughout the entire sample volume. Large-volume structures (nuclei of the amorphous phase) in quartz, reaching ∼100 nm in size, occupy a small total volume (∼1.5%) even at the maximum fluence 2.1 × 1020 neutrons/cm2. The majority of damage is related to the point defects with the radius of gyration of 1–2 nm and linear defects, which give comparable contributions up to several percent.

Investigation of the structure and properties of quartz in the α-β transition range by neutron diffraction and mechanical spectroscopy

The paper reports on the results of complex investigations into the physical properties of synthetic quartz single crystals and quartz powders in the temperature range of the α-β transition with the use of neutron diffraction and mechanical spectroscopy. The crystal structure of quartz powders with different average sizes of grains is determined in the temperature range up to 620°C and in the α-β transition temperature range. The temperature dependences of the internal friction and the resonant frequency for quartz samples in the vicinity of the phase transition temperature are obtained upon excitation of vibrations in the planes parallel and perpendicular to the Z axis of the quartz crystal. The temperatures at the maxima of the internal friction in the range 560–620°C are determined. The assumptions regarding the possible reasons for the shift of the phase transition temperature are made. It is revealed that the internal friction is characterized by a maximum that is observed in the vicinity of 350°C and is not related to the structural transformations in quartz.

PLD-grown Yb-doped Sesquioxide Films on Sapphire and Quartz Substrates

This paper focuses on the fabrication and characterization of crystalline Yb-doped sesquioxide films (Yb2O3, Yb:Lu2O3, Yb:Sc2O3) grown by pulsed laser deposition on single crystal sapphire (α-Al2O3) and quartz (α-SiO2) substrates as well as on lutetia (Lu2O3) and scandia (Sc2O3) substrates. Such ytterbium doped active films can be promising for use in a thin-disk laser setup. X-Ray diffraction measurements show that the films grow highly textured along <111> direction. The ω-scan (rocking curve) shows deviation of the crystallite orientation ∼4° in case of Lu2O3 and Yb2O3 films and <1° for Sc2O3 films. Yb2O3 films reveal no luminescence at room temperature and the well known Yb3+ emission in the 975-980 nm region (zero-phonon line) can only be observed at temperatures below 20 K. A similar effect is observed in a bulk Yb2O3 crystal. Ytterbium emission and excitation spectra measured at room temperature for Yb(5%):Lu2O3 and Yb(4%):Sc2O3 films resemble those of the bulk crystal very closely. Luminescence decay lifetimes are also comparable to those measured in a bulk crystal. This indicates a high quantum efficiency of the Yb3+-emission and allows application of such films as active media for thin disk lasers.

The dose dependence and the firing effects on the thermoluminescence of quartz

AbstractPapers on the dose dependence of thermoluminescence of quartz have been published in recent years by research groups from various countries. These papers show that untreated quartz gives very strong superlinearity (up to slopes of 3 in a log‐log scale). Almost all the investigators who describe the above effects refer to a theoretical paper by Kristianpoller et al. (J. Phys. D: Appl. Phys. 7, 1063 (1974) [6]) which shows that adding a competing trap to the energy system of quartz, gives a set of equations which can be solved numerically for various sets of given parameters, when results explain all the above effects. Unlike other investigators who used quartz powders, we preferred to use single crystals of quartz. For better resolution of two or more neighboring thermoluminescence peaks, we reduced the rate of heating in the thermoluminescence measurements to 10 degrees per minute. We found that limiting the temperature in the TL heatings during the set of doses to 400‐450 K, gave extremely high superlinearity (slopes close to 7). A set of decreasing doses was found to reduce the high superlinearity and to increase the 430 K peak by more than 3 orders of magnitude without any firing. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

From an initial transient‐state to a steady‐state in metamorphic reactions: An experimental approach in the system dolomite‐quartz‐H2O

Abstract We carried out hydrothermal experiments in the system dolomite‐quartz‐H2O to track the temporal change in reaction rates of simultaneous reactions during the development of reaction zones. Two types of configurations for the starting materials were prepared: dolomite single crystals + quartz powder + water and quartz single crystals + dolomite powder + water, both sealed separately in gold capsules. Runs at 0.1GPa and 600°C with cold seal pressure vessels gave the following results. (i) In short duration (45–71 h) runs metastable layer sequences involving wollastonite and talc occur in the reaction zone, whereas they disappear in longer duration (168–336 h) runs. (ii) The layer sequence of the reaction zones in short duration runs differs from place to place on the dolomite crystal even in the same run. (iii) The diversity of layer sequences in the short duration runs merges into a unique layer sequence in the longer duration runs. (iv) The reaction zone develops locally on the dolomite crystal, but no reaction zone was observed on the quartz crystal in any of the runs. The lines of evidence (i)–(iii) show that the system evolves from an initial transient‐ to a steady‐state and that the kinetic effect is important in the development of reaction zones. A steady diffusion model for the unique layer sequence Qtz/Di/Fo + Cal/Dol + Cal/Dol shows that the Dol + Cal layer cannot be formed by diffusion‐controlled process and that the stability of the layer sequence Qtz/Di/Fo + Cal/Dol depends not only on L‐ratios (a = /LCaOCaO and b = /LMgOMgO) but also on the relative rate P = (−2ξ1 − ξ2)/(–ξ1 − 2ξ2) of competing reactions: Dol + 2Qtz = Di + 2CO2 (ξ1) and 2Dol + Qtz = Fo + 2Cal + 2CO2 (ξ2). For smaller P the stability field will shift to higher values of a and b. The steady diffusion model also shows that the apparent‐non‐reactivity on the quartz surface can be attributed to void formation in a large volume fraction in the diopside layer.

Effective hydrostatic limits of pressure media for high-pressure crystallographic studies

The behavior of a number of commonly used pressure media, including nitrogen, argon, 2-propanol, a 4:1 methanol–ethanol mixture, glycerol and various grades of silicone oil, has been examined by measuring the X-ray diffraction maxima from quartz single crystals loaded in a diamond-anvil cell with each of these pressure media in turn. In all cases, the onset of non-hydrostatic stresses within the medium is detectable as the broadening of the rocking curves of X-ray diffraction peaks from the single crystals. The onset of broadening of the rocking curves of quartz is detected at ∼9.8 GPa in a 4:1 mixture of methanol and ethanol and at ∼4.2 GPa in 2-propanol, essentially at the same pressures as the previously reported hydrostatic limits determined by other techniques. Gigahertz ultrasonic interferometry was also used to detect the onset of the glass transition in 4:1 methanol–ethanol and 16:3:1 methanol–ethanol–water, which were observed to support shear waves above ∼9.2 and ∼10.5 GPa, respectively, at 0.8–1.2 GHz. By contrast, peak broadening is first detected at ∼3 GPa in nitrogen, ∼1.9 GPa in argon, ∼1.4 GPa in glycerol and ∼0.9 GPa in various grades of silicone oil. These pressures, which are significantly lower than hydrostatic limits quoted in the literature, should be considered as the practical maximum limits to the hydrostatic behavior of these pressure media at room temperature.

Measuring shock-induced electrical conductivity in piezoelectrics and ferroelectrics. Single-crystal quartz

A method is proposed to measure shock-induced electrical conductivity in electrically active dielectrics — piezoelectrics and ferroelectrics. Results of measurements of electrical conductivity in single-crystal quartz are reported.