Developing Si samples with nanochannels connected to buried cavities for positronium collection

The possibility of combining ultrafast laser direct writing and electrochemical etching in Si to produce a network of nanochannels connected to buried cavities was preliminary explored. The final goal is the efficient collection of positronium atoms inside the cavities for spectroscopy experiments and studies of positronium-positronium interaction. Positron Annihilation Spectroscopy measurements were performed to investigate the formation of buried cavities, their connection to nanochannels, the diffusion of positronium from the nanochannels to the cavities, and its collection inside the cavities. According to the measurements, at least around 7% of positrons implanted into the region of Si with nanochannels form positronium atoms that reach the cavities where they self-annihilate via 3 gamma emission.