The near-surface nucleation and crystallization behavior of Ag+ ion-implanted lithia-alumina-silica glasses has been studied. For room-temperature Ag implants, crystallization of the glass ceramic phase was prevented by dissolution of Ag precipitates and migration of Ag atoms at temperatures below that necessary for formation of the glass ceramic phase. Crystallization was demonstrated after low-temperature or low-dose-rate implantations. Optical spectroscopy was used to monitor the size of colloidal Ag particles and to detect the presence of the crystalline phase. Rutherford backscattering spectroscopy (RBS) was used to obtain the depth distribution of Ag atoms in the glass and thus monitor Ag migration. For samples implanted at room temperature and at relatively high dose rates (∼1 μA/cm2), aggregation of the Ag atoms into colloids occurred during implantation and also during subsequent annealing to temperatures ?350 °C. The RBS spectra indicate some migration of the Ag to the surface at these temperatures. For annealing temperatures ≳350 °C, both optical and RBS measurements show that Ag is lost from the glass surface. The initial spatial distribution of the Ag for these high-dose-rate room-temperature implantations was distorted by interactions with the associated damage and possibly by local electric fields caused by neutralization of the implanted ions. It was possible to obtain dispersed Ag nuclei by implanting at low sample temperatures (80 K) or at low beam current (∼200 nA/cm2) to reduce ion-beam heating. Although some migration to the surface was seen in these samples, it occurred at higher temperatures and crystalline precipitation was achieved by annealing at 500 °C.
The production of SiC in single-crystal silicon by C12+ implantation to fluences of 1017/cm2-side followed by annealing has been detected by the characteristic infrared absorption of the TO phonon of SiC. Immediately following room-temperature implantation and after 20-min isochronal anneals up to temperatures ≤ 825°C, a previously unreported broad absorption band centered at 700–725 cm−1 is observed. SiC is observed to form at temperatures ≈ 850°C. For anneals ≥ 850°C, most of the broad absorption band shifts into the SiC-TO phonon absorption band. From the infrared absorption measurements together with the results of He+ backscattering, we conclude that about half of the implanted atoms are incorporated into microregions of SiC which are surrounded by bulk silicon.
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In this Letter we report observations of cyclotron resonance and approximate values for polaron masses in seven different ionic crystals. For the first time, the size of the polaron effect can be estimated in a variety of materials over a wide range of coupling constants. The measurements were carried out at 2-mm wavelengths and magnetic fields up to 140 kOe using an electron-heating technique previously applied to KBr at longer wavelengths. 1 The results can be used to compute band masses (effective masses in the absence of lattice polarization) for the purpose of comparison with recent band calculations. 2 " 4 Transient currents about 2 jusec in duration were excited in the insulating crystals studied by repeated flashes of a small xenon flash lamp. The alkali halides were either x rayed or additively colored with F centers, and electrons were excited by K-and L-band illumination. In the case of the silver and thallium halides, the carriers were produced by band-to-band excitation. Identical positive and negative voltage pulses were repetitively applied to the specimen, placed between blocking electrodes immersed in liquid helium. The small transient photo currents were then amplified by a low-
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