Nanovoid formation in 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 ramp annealing. The structural evolution, starting with the formation of a platelike cluster of highly pressurized helium bubbles and ending in an empty nanovoid, is performed conserving the total volume of vacancy-type extended defects forming each cluster. Structural adjustments occur by surface diffusion inside each cluster following a migration and coalescence mechanism in presence of high pressure helium for 350 degreesC