F. K. Euler

Infrared reflection of ion‐implanted GaAs

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...

Steady-State and Transient Radiation Effects in Precision Quartz 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.

Linewidth Reduction through Indium Substitution in Calcium‐Vanadium Garnets

On the garnets Y3−2xCa2xFe5−x−yVxInyO12, with x ≤ 1.5 and y ≤ 0.5, we have measured the polycrystalline linewidth ΔHpoly at X‐band and room temperature and have determined from single crystals the first‐order anisotropy constant, K1. Since the single‐crystal linewidth of these materials is but a few oersteds and the polycrystalline samples had less than 1% porosity and second phase, the observed ΔHpoly is attributed to anisotropy broadening, according to Schlomann. The introduction of indium reduces both | K1 | and ΔHpoly, for example: x = 0.63y = 0TC = 280°C4πMs = 650 GΔHpoly = 98 Oex = 0.80y = 0.50TC = 155°C4πMs = 750 GΔHpoly = 8 Oe. That last value is the lowest yet reported in the range of T ≈ 23 TC.

Localized Vibrational Mode Absorption of Ion‐Implanted Silicon in GaAs

Infrared absorption bands of localized vibrational modes for ion‐implanted Si in GaAs are observed. Room‐temperature implants were at energies of 1.0 and 1.5 MeV and fluences ∼ 1017 ions cm−2. The bands previously attributed to SiGa and SiAs defects were observed and the dependence of the absorption at liquid‐nitrogen temperature was studied for samples isochronally annealed from 200 to 900 °C. The strongest band due to (SiGa–SiAs) pairs was observed after 400 °C annealing. For most of the temperature range the different defect concentrations were found to either grow or show little change during the annealing cycle. However, between ∼ 500 and 650 °C substantial reverse annealing was observed for both SiGa and SiAs. This effect cannot be explained by direct pair formation and other possible explanations are suggested. For these high‐fluence, high‐energy implants the electrical data obtained during the anneal cycle show no apparent correlation with the Si defect concentrations as deduced from optical data....

Measurements of layer thicknesses and refractive indices in high‐energy ion‐implanted GaAs and GaP

Near normal incidence reflection and transmission measurements of GaAs and GaP samples implanted with large doses of ∼3‐MeV ions of 31P+ or 14N+ showed frequency‐dependent maxima and minima in the frequency range 800≲ν≲7500 cm−1. Assuming a layer model for the implanted material and considering reflections from layers surfaces, the interference fringes are analyzed to obtain the refractive index and thickness of both the cover and buried layers and substrate. With the same layer model the changes in the GaAs reststrahlen are shown to be quantitatively compatible with the results of the fringe measurements. Annealing GaAs at temperatures ≲400 °C reduced the implantation‐induced changes in the refractive index but the layer thicknesses remained constant. There was no evidence for regrowth by motion of the implant‐substrate interface as has been reported for silicon crystals. The analysis of the reststrahlen data for GaP is less satisfactory since the data could not be closely fitted with any choice of param...

Infrared reflection and Raman scattering of ion‐implanted nitrogen in gallium phosphide

Infrared reflection and Raman scattering measurements were performed on a set of GaP samples implanted at room temperature with 14N+ and 15N+ ions with an energy of 3 MeV and fluences in the range of 5×1013–2×1017 ions/cm2. The reflection data for all but the most heavily implanted samples were fitted with a classical dispersion layer model. Some of the parameters used in this model were obtained from the Raman data. An increased in the damping constant γ is the largest implantation‐induced change in the dispersion parameters. Annealing studies were performed on several samples implanted with 2×1017 ions/cm2. Raman and x‐ray measurements indicated that samples annealed at 773 °K recrystallized in a polycrystalline fashion but those annealed at 573 °K became single crystals. After both types of annealing procedure, structure resulting from the nitrogen localized vibrational mode was seen in the reflection spectra. This mode exhibited the expected isotope shift, appearing at ∼495 cm−1 for samples implanted ...

Ion‐implanted nitrogen in gallium arsenide

Several gallium arsenide samples were implanted at room temperature with 14N+ ions. Infrared absorption measurements at ≃ 80 °K showed a broad band near 480 cm−1 which is attributed to the localized vibrational mode of NAs,N substitutional on an As site. Measurements were made of the dependence of the integrated absorption I on the fluence φ for 1.0 × 1016 ≤ φ ≤ 2.0 × 1017 ions/cm2, on flux from 2.4 × 1012 to 1.2 × 1013 ions/cm2 sec, and on ion energies between 1.0 and 3.0 MeV. I increases linearly with φ until φ [inverted lazy s] 1017 ions/cm2 and decreases substantially at larger fluences probably due to the presence of short‐range lattice disorder. The implanted samples were annealed isochronally from 473 to 1073 °K, and isothermally at 973 °K. The isochronal anneal for φ≲1017 ions cm−2 showed no appreciable change in I up to 873 °K. The short‐range disorder in the φ≳1×1017 ions cm−2 samples annealed at much lower temperature. For all φ values the I decreased substantially after 973 °K anneal and after...

Simple Geometric Model for the Effect of Porosity on Material Constants

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 iso...

Characterization of Alkali Impurities in Quartz

Abstract : We report acoustic loss measurements from room temperature to above 500 degrees of C on resonator disks fabricated from high-grade as-grown and swept synthetic quartz, containing both Li(+) and Na(+) alkali impurities. As-grown quartz disks showed an exponential rise of acoustic loss 1/Q with temperature T, starting above 200 degrees of C. Swept samples show the onset of a rise above 400 degrees of C and show high-temperature losses which increase irreversibly with time and are tentatively attributed to the presence of residual alkali. Loss peaks above 300 degrees of C were found in the swept disks. Some of these disappear after exposure to temperatures above 400 degrees of C.

Anisotropy Linebroadening in Polycrystalline V–In Substituted YIG

Polycrystalline linewidth and magnetization have been measured between 77° and 300°K at 9.2 GHz on V–In substituted YIG in the composition range 0[equal to or less-than]x[equal to or less-than]1.50 and 0[equal to or less-than]y[equal to or less-than]0.50 for Y3−2xCa2xFe5−x−y VxInyO12. The linewidths were compared with theoretical values inferred from measurements of K1 (K2 negligible) and Ms on single crystals for 0[equal to or less-than]x[equal to or less-than]0.90 and 0[equal to or less-than]y[equal to or less-than]0.35 between 4° and 300°K on the basis of a recent theory by Schlomann. Data on dense, single‐phase polycrystals are in good quantitative agreement with Schlomanns theory for samples with weak anisotropy (Ha≪4πMs, where Ha = 2 | K1 | / M). For high anisotropy materials (Ha[equal to or greater-than]4πMs), linewidth derived from area fitting of the normalized curves follows ΔH = 0.5Ha. Moderately small (<3%) amounts of porosity yield additive linebroadening effects.