ABSTRACT
Radiation-generated point defects in solids often experience dynamic annealing-diffusion and interaction processes after the thermalization of collision cascades. The length scale of dynamic annealing can be described in terms of the characteristic defect diffusion length (Ld). Here, we propose to measure Ld by a pulsed beam method. Our approach is based on the observation of enhanced defect production when, for individual ion pulses, the average separation between adjacent damage regions is smaller than Ld. We obtain a value for Ld of ~30 nm for float-zone Si crystals bombarded at room temperature with 500 keV Ar ions.
ABSTRACT
Under ion irradiation, all crystalline materials display some degree of dynamic annealing when defects experience evolution after the thermalization of collision cascades. The exact time scales of such defect relaxation processes are, however, unknown even for Si at room temperature. Here, we use a pulsed ion-beam method to measure a characteristic time constant of dominant dynamic annealing processes of about 6 ms in Si bombarded at room temperature with 500 keV Ar ions.
ABSTRACT
We propose a new method of confining Au nanoparticles of a narrow size distribution at a precise depth in an SiO2 matrix. The process involves the formation of nanocavities in silicon by hydrogen implantation and annealing (at 850 degrees C), followed by Au gettering to and precipitation in such cavities and a wet oxidation at 900 degrees C. Starting with a silicon-on-insulator wafer, Au precipitates can be segregated behind a growing Si/SiO2 interface during wet oxidation and ultimately trapped in SiO2 at the front interface of a buried oxide layer. The shape of the precipitates has been examined by transmission electron microscopy and found to be spherical. The average diameters of these precipitates before and after oxidation have been determined as around 15 nm and 30 nm, respectively.
