Electron spin resonance (ESR) and infrared absorption (IR) experiments have provided information about the role of aluminum in the radiation response of commercially available high‐quality synthetic quartz. Samples obtained from two separate sources were investigated, and identical radiation responses were found for the two materials. Interstitial ions such as H+, Li+, and Na+ as well as radiation‐induced holes trapped at oxygen ions act as charge compensators for the ever‐present substitutional aluminum ions. Usually the charge compensator is located adjacent to the aluminum, and this gives rise to Al‐OH−, Al‐Li+, Al‐Na+, and [Ale+]0 centers. Absolute concentrations of these compensated aluminum centers have been determined as a function of irradiation and annealing temperature for a variety of samples, both swept and unswept. The various treatments simply exchange one type of compensator for another at the aluminum sites, and within experimental error, the sum of the aluminum centers remains constant fo...

Radiation effects in crystalline SiO2: The role of aluminum

: The fundamentals of quartz frequency standards are reviewed. The subjects discussed include: crystal resonators and oscillators, oscillator types, and the characteristics arid limitations of temperature-compensated crystal oscillators (TCXO) and oven-controlled crystal oscillators (OCXO). The oscillator instabilities discussed include: aging, noise, frequency vs. temperature, warmup, acceleration effects, magnetic field effects, atmospheric pressure effects, radiation effects, and interactions among the various effects. Guidelines are provided for oscillator comparison and selection. Discussions of specifications are also included, as are references and suggestions for further reading. Oscillator, clock, frequency standard, frequency control, frequency stability, time, timing devices, quartz, quartz crystal, quartz oscillator, atomic clock, atomic frequency standard, stability, aging, noise, phase noise.

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Introduction to Quartz Frequency Standards

The frequency instabilities of precision bulk acoustic wave (BAW) quartz crystal oscillators are reviewed. The fundamental limits on the achievable frequency stabilities, and the degree to which the fundamental limits have been approached to date are examined. Included are the instabilities as a function of time, temperature, acceleration, ionizing radiation, electromagnetic fields, humidity, atmospheric pressure, power supply, and load impedance. Most of the fundamental limits are zero or negligibly small, a few are finite. We speculate about the progress which may be achievable in the future with respect to approaching the fundamental limits. Suggestions are provided about the paths that may lead to significant stability improvements. >

Fundamental limits on the frequency stabilities of crystal oscillators

Electron‐spin resonance (ESR) has been used to investigate defect formation, anneal, and migration effects in commercially available high‐quality synthetic quartz. Electronic‐Grade and premium Q material, both unswept and swept, were included in the study and an electron accelerator was used for all irradiations. Previously unreported holelike and electronlike paramagnetic defects have been observed and their production and decay properties are described. The concentration of aluminum‐associated trapped hole centers (now known as [Ale+]° centers) was found to be a strong function of irradiation temperature and previous electrodiffusion (sweeping) treatments. Irradiation of an as‐received unswept sample at 77 K produced very few [Ale+]° centers. If the same unswept sample was irradiated at room temperature and then reirradiated at 77 K, the [Ale+]° center concentration was enhanced by one to two orders of magnitude. The intermediate irradiation at room temperature is believed to remove interstitial Na+ ion...

Defects in synthetic quartz: Radiation-induced mobility of interstitial ions

The aging of quartz crystal resonators, filters, and oscillators is reviewed, including such topics as the impacts of aging, typical aging characteristics, aging specifications, aging mechanisms, temperature dependence of aging, frequency and overtone dependence of aging, drive level dependence of aging, the effects of aging interruptions, the dependence of aging on material and mode type, state-of-the-art in low-aging oscillators, and aging acceleration effects. The aging mechanisms discussed include contamination transfer effects, stress effects, electrode effects, diffusion effects, changes in the quartz material, and circuit and other electrical changes. Isothermal and thermal step stress aging acceleration methods are reviewed. >

The aging of bulk acoustic wave resonators, filters and oscillators

Radiation effects on 5 MHz 5th overtone AT cut Premium-Q quartz resonators are evaluated, comparing sweeping processes and resonator fabrication procedures. The resonators were irradiated at operating temperatures in oven controlled oscillator test beds with pulsed 10 MeV electrons from 200 rads up to 1 Mrad as well as with continuous 60Co gamma rays. Steady-state (permanent) and transient radiation-induced frequency changes were measured, the persistence of radiative preconditioning was investigated and the effect on drift rate was evaluated. From saturation characteristics of the steady-state frequency offset as function of total electron dose, the formation rate cross sections of several radiation-induced crystal defects have been evaluated. Formation of at least one defect is sensitive to differences in the sweeping process. In some resonators, frequency recovery after irradiation is dominated by an exponential decay mechanism with a time constant of 3.7 days. Under continuous gamma ray exposure with dose rates between 10 and 90 rad/hour, the frequency response is characterized by a steep initial rise followed by different patterns of saturation and recovery.

Steady-State and Transient Radiation Effects in Precision Quartz Oscillators

Two possible causes for the observed frequency shift of a crystal oscillator due to a small radiation dose to the crystal have been analyzed. Removal of mass from the surface of the crystal by the radiation does not appear to be a plausible cause for the frequency shift. However, the electric fields and voltages created in the crystal by charge that is photoemitted from the walls of the can around the crystal and is then trapped in the crystal are relatively large and could possibly produce the observed frequency shift. These trapped charges produce both normal and tangential electric fields inside the crystal. Consequently, the difference in this radiation-induced frequency shift for SC-cut resonators, which are primarily sensitive to normal stresses, and for AT-cut resonators, which are primarily sensitive to tangential stresses, is less than the difference in their normal voltage sensitivities.

https://ieeexplore.ieee.org/iel5/10320/32753/01537872.pdf

Evaluation of Mechanisms for Low-Dose Frequency Shifts in Crystal Oscillators

: Studies are presented of the effects of the interaction of radiation with matter. Displacement damage in compound semiconductors is considered, with emphasis on GaAs. The temperature dependence of electron damage is determined, as well as the relative damage as a function of electron and neutron energy. Transient conductivity measurements on GaAs have been able to detect carrier lifetime at 300K in the nanosecond range. The response of AlSiO2Si (n-type) MOS devices to pulsed 30-MeV electron irradiations has led to the identification of a new charge-transfer effect. Models are presented of this effect and of gate threshold shifts for clean oxides and aluminum ion-implanted clean oxides using the PN code. Also presented is a study of the dependence of the charge released to an external circuit by a capacitor subsequent to burn-in through both thermal and radiation-induced depolarization of the space-charge fields.

Terry M. Flanagan

Papers

Steady-State and Transient Radiation Effects in Precision Quartz Oscillators

Evaluation of Mechanisms for Low-Dose Frequency Shifts in Crystal Oscillators

Evaluation of Mechanisms for Low-Dose Frequency Shifts in Crystal Oscillators

Transient Radiation Effects.