Gallium arsenide has been implanted with nitrogen ions at 1–3 MeV and fluences between 3.3×1013 and 2.0×1017 ions/cm2. Room-temperature infrared spectra are presented which show major changes in the reststrahl region. A sample having the highest fluence was isochronally annealed with 2-h 100°C steps from 200 to 600°C, and the implantation-induced reflectivity changes are annealed by 600°C. Changes of the dispersion parameters were determined by Kramers-Kronig analysis as well as by curve fitting with classical dispersion (CD) analysis. Examples of dispersion parameters obtained by different analyses are compared and their validity is discussed. The data of nonimplanted and samples implanted with fluence up to 3.3×1014 ions/cm2 can be satisfactorily fitted with CD analysis assuming the material to be optically homogeneous. With this assumption, attempts to fit the data of samples with fluences ≥3.3 ×1015 ions/cm2 were unsuccessful. By extending the CD analysis to a layer model a reasonable fit was achieved. The analyses indicate changes in the transverse- and longitudinal-optic-mode frequencies. The latter changes were confirmed by Raman scattering measurements. Both the analyses and interference fringes observed in the near-infrared reflection spectra indicate some implantation-induced increase in the high-frequency dielectric constant.

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5-MHz resonators were fabricated from germanium-doped cultured quartz and were Co irradiated at room temperature. The quartz has a relatively low aluminum-impurity concentration, 0.5 ppm, and the aluminum is lithium compensated. Oscillator frequency offsets b fIf and resonator anelastic loss spectrum Q ' were measured and show an increase and subsequent decrease as a function of dose, known as radiation bleaching. At low irradiation levels, iaaf/f decreases with increasing dose, reaches at 50 krad a minimum of -4)&10, reverses and increases with additional dose, and at 1 Mrad it recovers to -1.2X10 '. (1 rad= 100 ergs/g. ) These values are surprisingly large in comparison with other lithium-compensated high-quality quartz. Resonator irradiation induces a Q ' peak centered at 246 K, which also bleaches with radiation. At 246 K the Q value is 2.25)& 10, decreases with irradiation, reaches at 50 krad a minimum of 0.65&(10, and recovers at 350 krad to 1.5&(10 . Electron paramagnetic resonance (EPR) measurements show Al hole, and germanium C and A centers, Ge(C)-Li and Ge(A)-Li, neutral defects of a trapped electron localized on a substitutional Ge site and stabilized by an adjacent Li+ ion. All three EPR spectra also radiation bleach at doses above 50 krad. This strongly suggests that the Ge(C)-Li defect is associated with the 246-K loss peak. The activation energy of the Q ' peak is E =0.22 eV, the corresponding relaxation time v. o --8& 10 " sec, and the peak anneals at 555 K.

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The effect of porosity on several material constants can be described by three types of empirical functions. One of these features linear increase from zero to unity of the relative bulk material constant when the relative density increases from π/6 to 1. An almost identical function results from application of a theoretical model with the following properties. (1) The porous compact is divided into two systems: first, isolated pores in a continuous solid matrix; second, solid grains mixed with continuous voids. (2) The geometry of both systems is assumed to be a cubic array of equal spheres. With this simplification, the relative bulk material constants of each system are calculated as functions of the relative density. The equations obtained are valid for those material constants which are ratios of corresponding fluxes and forces in the sense defined by Maxwell (e.g., the electric conductivity). (3) Weight factors for the presence of either system are introduced. (4) The weight factor for the system of isolated pores is assumed equal to the relative bulk material constant of the total compact for all values of relative density. The implications of this model to the mechanism of sintering are discussed.