Ion exchange and radiation response of H-related point defects in natural quartz crystals
- PDF / 1,923,613 Bytes
- 13 Pages / 576 x 792 pts Page_size
- 105 Downloads / 179 Views
Infrared absorption measurements have been used to study the radiation response of various hydroxyl point defects present in natural quartz crystals in their unswept, Na-swept, and H-swept conditions for "low-H" and "high-H" samples with similar aluminum concentration. The irradiation was done at 77 K, 300 K, and finally again at 77 K in sequence. At low-temperature irradiation the A 1 - 0 H " bands equalize in their intensity-like H-swept or prior 300 K-irradiated cultured quartz. Among other major bands the alkali-related centers show a reduction in their strength at all stages of irradiation. Purely H-related centers show no steady-state room temperature effects; only the low-temperature irradiation reduces their band strength. The results have been discussed in terms of proton and alkali ion motion to shallow and deep traps and compared with cultured quartz.
I. INTRODUCTION Natural crystalline quartz is a strategic material in the fabrication of numerous precise optical components and precision oscillators. It is therefore important that under ordinary conditions the selected crystals would have a high degree of uniformity and stability for use in these devices. The limitations of quartz crystal-controlled oscillators subjected to radiation in earth-orbiting satellites are well known. Therefore, considerable attention has been given to radiation effects in crystalline quartz. It is now believed that a variety of impurities present as point defects in quartz crystals, both natural and synthetic (also called "cultured quartz"), incorporated during their growth are responsible for the performance of the oscillator crystals in a radiation environment.1"3 Aluminum is the most pervasive impurity in quartz and is present as Al 3+ at substitutional sites for Si 4 + . The charge compensation for Al 3+ is provided by one of the monovalent impurities such as Li + , Na + , and K + , proton interstitially placed in open oaxis channels or by an electron hole on one nonbonding oxygen p -orbital. In addition, there are other types of point defects also present in quartz.4 They include, e.g., oxygen vacancies, Ge-associated centers, and numerous OH" defects. The different OH" bonds exhibit their stretching vibrational frequencies in the 3300-3700 cm" 1 range and, therefore, can be studied using the near infrared absorption. The absorption of quartz in this range observed at low temperature contains a large number of narrow bands
a) Currently
with the National Physical Laboratory, Hillside Road, New Delhi-110012, India. J. Mater. Res., Vol. 9, No. 7, Jul 1994
http://journals.cambridge.org
Downloaded: 01 Apr 2015
superimposed on a broad background. These bands are as many as sixteen in natural crystals and four in cultured quartz. Infrared absorption studies involving electrodiffusion (also called "sweeping") and irradiation in natural quartz have been carried out in the past by several workers.5"9 Kats's work5 is encyclopedic. In this classic study of IR absorption in quartz crystals, he has reported numerous OH" related a
Data Loading...
