Decoration of buried surfaces in Si detected by positron annihilation spectroscopy

The terminations of buried surfaces of two different cavity types (nano- and microcavities) produced in the same $He+–H+$ co-implanted $p$-type Si (100) sample annealed at $900°C$⁠, are studied and characterized by positron annihilation spectroscopy. The characterization was carried out by means of three complementary positron techniques: Doppler broadening and coincidence-Doppler broadening spectroscopy with a continuous slow positron beam, and lifetime spectroscopy with a pulsed slow positron beam. It was found that the nanocavities have a pristine surface of Si, while the surfaces of the microcavities, formed below protruding blisters, are oxygen decorated. This case study opens the interesting use of the positron spectroscopy tool in the topical subject of empty space for microelectronics applications.