Nanovoid formationin helium-implanted single-crystal silicon studied by in situ techniques

In situ transmission electron microscopy and thermal desorption spectrometry have been employed to observe the evolution of vacancy-type extended defects and the corresponding helium state in helium implanted single crystal silicon during thermal ramping annealing. The structural evolution starting with the formation of a platelike cluster of high pressurized helium bubbles and ending in an empty nanovoid is performed conserving tha total volume of vacancy-type extended defects forming each cluster. Structural adjstements occur by surface diffusion inside each cluster following a migration and coalescence mechanism in presence of high pressure helium for 350°C /T/570°C. A conservative Ostwald ripening is observed for 570/T/700°C in presence of helium desorption.