Synthetic Crystalline Quartz Research Articles

Absorption Measurement in Ultrapure Crystalline Quartz with the Eliminated Influence of Ambient Air Absorption in the Time-Resolved Photothermal Common-Path Interferometry Scheme

We demonstrate measurements of the absorption coefficient α ≈ 2.5 × 10−7 cm−1 in synthetic crystalline quartz at a wavelength of 1071 nm with a signal-to-noise ratio of 10/1 using the Time-resolved photothermal common-path interferometry (TPCI) scheme. It utilized cells filled with flowing argon and eliminated the influence of ambient air absorption. The scheme elements limiting the sensitivity of measurements at the level of ≈7.8 × 10−8 cm−1 were revealed. When these elements are replaced by better ones in terms of their thermal influence, the sensitivity of absorption coefficient measurements in crystalline quartz is ~10−8 cm−1. The calculation of the correction due to these optical elements of the values of the measured absorption coefficients is also described, which makes it possible to achieve the same sensitivity without replacing the elements. The improved scheme confirms the presence of the spatial inhomogeneity of absorption with a minimum coefficient of 2.5 × 10−7 cm−1 in synthetic crystalline quartz. The discrepancy of the absorption coefficient values in different regions of the crystal in the presented series of experiments was 2.5 × 10−7 cm−1 to 4 × 10−6 cm−1. Taking into account the ratio of thermo-optical parameters and the heat diffusion effect, the calculation shows that for quartz glasses the corresponding sensitivity of the absorption coefficient measurements equals ≈1.5 × 10−9 cm−1.

Synthetic Crystalline Quartz as an Optical Material for Power Optics

We present the results of studying Russian synthetic crystalline quartz from the viewpoint of the possibility of its use for manufacturing optical elements of power optics. The results of experimental studies of the absorption and optical nonuniformity of crystal plates with dimensions of 12 × 8 × 1.7 cm as well as theoretical calculations of the thermooptical parameter for the disk configuration of the measured samples, which determines the value of the phase distortions of the wave front of heating radiation, are reported.

Quartz OSL emission spectra and the role of [AlO 4]° recombination centres

Synthetic crystalline quartz, with known concentrations of Al and alkali ions was used in this study. The wavelength-resolved OSL spectra were measured after different periods of optical stimulation, and more than one emission band were detected. A composite peak centred at 380 nm is seen; this is similar to the emission band for the 110 °C TL peak, that has been associated with the [AlO 4]° recombination centres. A direct correspondence between OSL signal intensity and the alkali ion concentration was observed; the signal intensity in bulk crystalline “swept out” quartz, i.e. quartz submitted to electro-diffusion, was found to be much lower than that from the ‘unswept’ quartz. These data suggest that alkali ions play an important role in the OSL phenomenon. Based on the data presented here and the existing TL studies it is inferred that OSL and the 110 °C and 325 °C TL peaks share a common recombination centre. This emission is assigned to electron recombination at Al centres with a trapped hole, [AlO 4]°. A preliminary phenomenological model of TL and OSL is proposed, which is based on a spatial association between the OSL and the 110 °C TL trap.

Ionic mechanisms in the optically stimulated luminescence of quartz

AbstractAmong the many centres found in crystalline quartz it is well known that Al, substitutional for Si, is always present in different concentrations giving rise at Room Temperature to ionic migration of the associated alkali ions. Many authors evidenced that these alkali ions are involved in trapping and recombination at the basis of Thermally and Optically Stimulated Luminescence, TL and OSL respectively. We have focused our attention on the OSL of quartz that is now widely used in sediment dating, although the trapping‐detrapping mechanisms have not yet been clarified. Bulk synthetic crystalline quartz, with known concentrations of Al and alkali ions has been used. There is evidence that an ionic migration is at the basis of the OSL phenomenon, linking OSL emission with the TL peaks known as “110 °C” and “325 °C”. This result is also supported by Radioluminescence (RL) measurements performed on swept and unswept quartzes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Anisotropic positronium in crystalline quartz

Abstract Positronium (Ps = (e+ e−)) in synthetic crystalline quartz is investigated by means of the positron spin relaxation (e+SR) technique. The set-up employed measures the change in the Doppler broadening of the 511 keV annihilation photon line caused by the reversal of large magnetic fields applied along the spin polarization axis of positrons (e+) emitted from a 68Ge/68Ga source. In contrast with other methods, the technique allows the detection of Ps in condensed matter even if the Ps-forming e+ fraction r is quite small. Moreover, because in single crystals the magnetic field defines a preferred crystallographic direction, the e+SR technique permits the study of the anisotropy of the hyperfine interaction of Ps in matter. The theory necessary to deduce the Ps hyperfine tensor from the e+SR measurements is developed. Room-temperature measurements show that in synthetic quartz crystals (i) the Ps-forming e+ fraction is r = 0.15, (ii) the electron density at the e+ in Ps is about 0.3 of the vacuum va...

Hydrogen desorption from crystalline quartz and some related differential-scanning calorimetry and conductivity phenomena

Temperature-programmed desorption (TPD) and differential-scanning calorimetry (DSC) analyses were performed on synthetic crystalline quartz, both “as received” and “hydrogen swept”, from 200 to 600°C. The TPD measurements allowed us to establish that interstitial hydrogen ions, present as charge compensators near trivalent aluminium ions substitutional for silicon, are removed from the crystal in the considered temperature range, mostly in the form of H 2 molecules. In the hydrogen-swept samples, release of small amounts of other molecular groups, namely SiH 4 and NaOH, was also observed. The DSC studies revealed the existence of a weak exothermic peak (enthalpy change ⋍ 0.90 J g −1) in the temperature range from 350 to 400°C. The exothermic process, only observable in hydrogen-swept samples, may tentatively be attributed to the total-energy variation involved in processes leading to H 2 formation and to SiO 4 tetrahedra relaxation after H 2 release. The above results have been compared with the intensity variations, following annealing treatments, of near-infrared OH stretching vibrations and with time-transient effects observed in ionic conductivity measurements. The analysis contributes to a deeper understanding of the hydrogen-impurity dynamics in crystalline quartz.

Photoluminescence and optical absorption in neutron-irradiated crystalline quartz

Optical absorption measurements in the 3.5--6.5 eV spectral range and photoluminescence spectra, excited in the 4--8 eV range have been performed on neutron irradiated synthetic crystalline quartz as a function of temperature and of neutron fluence. The Gaussian deconvolution of the radiation-induced absorption spectrum in the 4.5--6 eV region reveals a complex structure: five distinct components, peaking at 4.85, 5.06, 5.35, 5.62, and 5.96 eV are detected. The complexity of the absorption pattern finds a correspondence in photoluminescence spectra excited in the 5 eV region: a detailed analysis of the emission spectra as a function of excitation energy indicates the presence of three emission bands centered at 3.91, 4.23, and 4.46 eV, excited at 5.25, 4.83, and 5.03 eV respectively. Excitation in the 5.62 and 5.96 eV absorption peaks does not produce emission. The features of the 4.23 eV and of the 4.46 eV bands are very similar to those of the ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{intrinsic}}$ emission, already well studied in amorphous ${\mathrm{SiO}}_{2}$: this suggests a possible correlation between these bands and the ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{}\mathrm{intrinsic}}$ center. The 3.91 eV band does not find a correspondence in amorphous ${\mathrm{SiO}}_{2}$, and so the responsible defect appears specifically related to the crystalline structure. The emission spectra excited in the E absorption band (\ensuremath{\approxeq}7.6 eV) present a weak band centered at 4.83 eV: its dependence on neutron irradiation dose suggests the attribution to an intrinsic center different from those responsible for the emission in the 3.8 -- 4.5 eV region. \textcopyright{} 1996 The American Physical Society.

Electron irradiation induced outgrowths from quartz

The irradiation of natural and ultrapure synthetic crystalline quartz by a stationary electron beam produces surface outgrowths, which have been analyzed using scanning electron microscopy, atomic force microscopy, cathodoluminescence spectroscopy, and microscopy. Oxygen enrichment of the quartz surface occurs due to electromigration resulting from the trapped charge induced electric field. It is proposed that the accumulated oxygen is incorporated into the quartz surface structure as peroxy linkages, the formation of which results in the permanent volume increase observed as amorphous outgrowths on crystalline quartz. A cathodoluminescence emission at 2.3 eV localized on the outgrowths, is attributed to an intrinsic process.

Thermally Stimulated Luminescence (TSL) and Conductivity (TSC) of synthetic crystalline quartz

A comparative and simultaneous study of TSL and TSC above room temperature (20–400°C) has been performed on “as-grown” and “hydrogen-swept” synthetic quartz crystals. Following X- irradiations, TSL spectra (heating rate = 1°C/s) feature a number of peaks: at 75°C an intense structure is observed (the well-known “100°C” peak of quartz); the analysis of this peak obtained by numerical methods has shown that it follows monomolecular kinetics, giving a value of 0.83 eV for the trap depth. Additional peaks are observed at 110°C and 160°C, followed by weaker and less resolved emissions above 200°C. TSC peaks at 80°C, 120°C and 160°C, particularly evident in as-grown samples when measured with the electric field applied along the x-axis, can be associated to the corresponding TSL peaks. However, spectra performed with the electric field applied along the z-axis evidence different features. In as-grown samples a strong and broad peak at approximately 132°C is observed, while hydrogen-swept samples are characterized by two peaks at 180°C and 275°C. Such an anisotropic character, and the fact that no TSL structures are observed in the same temperature range, support the hyporthesis of an ionic nature for the latter peaks. TSC “pre-dose” measurements of the 75°C peak show that no current enhancement is observed upon irradiational and heating treatment: this result is in accordance with previous radioluminescence and thermally stimulated exoelectron emission experiments and supports the proposed model of the dynamics of this effect.

Positronium in α-Quartz. I. Observed Temperature Dependence of the Positronium Effective Mass and the Probability of Annihilation from Singlet Positronium State

The momentum distribution of photon pairs from positrons annihilating in synthetic crystalline quartz has been measured over a wide temperature range. The width of the narrow component in the distribution was analyzed to yield the positronium effective mass. The effective mass is found to be (1.6 7 ±0.15)×2 m e at low temperature, but appears to increase as the temperature is raised. This result will be discussed in Part II from the view-point of positronium-phonon interaction. The probability of annihilation from singlet positronium state (i.e., the intensity of the narrow component) also increases as the temperature is raised, and tends to approach to a constant value at sufficiently high temperatures. This result might be attributable to possible temperature dependence of positronium formation probability in quartz.

Defect Structure of Crystalline Quartz. II. Variation of Displacement Threshold Energy with Crystal Growth Rate

An optical-absorption maximum ($C$ band) is produced at about 220 m\ensuremath{\mu} in crystalline quartz by electron bombardment at 77\ifmmode^\circ\else\textdegree\fi{}K. The band is produced by the displacement of lattice atoms and not by ionization. Previously it was shown that the production rate of the band for constant integrated electron flux increases greatly with increased growth rate. In the present experiment, the threshold energy for the displacement which leads to $C$-band absorption was measured in synthetic crystalline quartz grown at 0.45 and 1.91 mm/day. Interpretations of the data lead to the conclusion that $C$-band absorption is caused by displacement of oxygen atoms and that the threshold energy for this displacement is a function of growth rate varying from 15\ifmmode\pm\else\textpm\fi{}5 eV for fast-growth (1.91 mm/day) material to 50\ifmmode\pm\else\textpm\fi{}5 eV for quartz grown at a slower rate (0.45 mm/day).

Defect Structure of Crystalline Quartz. I. Radiation-Induced Optical Absorption

Low-temperature bombardment (77\ifmmode^\circ\else\textdegree\fi{}K) of synthetic crystalline quartz with fast electrons induces optical absorption ($C$ band) near 220 m\ensuremath{\mu}. For 40\ifmmode^\circ\else\textdegree\fi{}C neutron irradiations the absorption maximum is near 210 m\ensuremath{\mu}. The absorption has an orientation dependence when produced by electron irradiation. This dependence is exhibited by a shift in the position of maximum absorption from 220 m\ensuremath{\mu} for samples cut perpendicular to the $c$ axis ($Z$ cut) to 217 m\ensuremath{\mu} for samples cut parallel to the $c$ axis ($Y$ cut). The absorption in the $Z$-cut samples is about twice that of the $Y$-cut samples for equal integrated flux. In neutron-irradiated material no such dependence is noted. The defect giving rise to the $C$-band absorption anneals near 225\ifmmode^\circ\else\textdegree\fi{}C. The electron or hole occupying the defect, however, is relased below room temperature, removing the optical absorption. After heating to temperatures below 225\ifmmode^\circ\else\textdegree\fi{}C, the original absorption obtained after electron irradiation at 77\ifmmode^\circ\else\textdegree\fi{}K can be regained by a brief re-irradiation at 77\ifmmode^\circ\else\textdegree\fi{}K (0.01 of the original integrated flux). A similar electron exposure at low temperature augments the absorption induced by fast neutrons at 40\ifmmode^\circ\else\textdegree\fi{}C and introduces a strong absorption at 230 m\ensuremath{\mu} which was not previously discernible. The magnitude of the $C$-band absorption in electron-irradiated material is strongly dependent on the crystal growth rate, increasing by a factor of about 17 for a growth rate increase of 4.5. The increase for the band produced by neutron bombardment [5\ifmmode\times\else\texttimes\fi{}${10}^{17}$ nvt (fast)] is only about 25%. The comparison of electron irradiation and x-ray bombardments, and noncorrelation of absorption with impurity content, indicate that the defect responsible for the $C$-band absorption is produced by direct Coulomb encounters with lattice constituents.

Anelasticity of Synthetic Crystalline Quartz at Low Temperatures

This is a preliminary report of an examination of the anelasticity and frequency-temperature behavior of synthetic quartz resonators, vibrating in thickness shear at low temperatures. The stress-induced relaxation absorption occurring at 50\ifmmode^\circ\else\textdegree\fi{}K for a frequency of vibration of 5 Mc/sec in natural quartz is found to be three orders of magnitude larger in some samples of the synthetic quartz. The magnitude of the 50\ifmmode^\circ\else\textdegree\fi{}K absorption is dependent upon the crystallographic orientation of the seed plate upon which the quartz is grown.The frequency-temperature behavior of the resonator over the region of maximum absorption is characteristic of a stress-induced relaxation. The crystal imperfection underlying the absorption at 50\ifmmode^\circ\else\textdegree\fi{}K is considered to be responsible for the apparent lowering of the rigidity modulus of synthetic quartz above the temperature region of stress relaxation. X-ray irradiation of synthetic quartz is found to produce a marked lowering of the defect concentration responsible for the 50\ifmmode^\circ\else\textdegree\fi{}K relaxation loss.