Structural evolution and photoluminescence of SiO2 layers with Sn nanoclusters formed by ion implantation

Abstract

Samples of SiO2 (600 nm)/Si have been implanted with Sn ions (200 keV, 5 × 1016 cm−2 and 1 × 1017 cm−2) at room temperature and afterwards annealed at 800 and 900°C for 60 minutes in ambient air. The structural and light emission properties of “SiO2 +Sn-based nanocluster” composites have been studied using Rutherford backscattering spectroscopy, transmission electron microscopy in cross section and plan-view geometry, electron microdiffraction, and photoluminescence (PL). A strict correspondence of Sn concentration profiles and depth particle distributions has been found. In the case of 1 × 1017 cm−2 fluence, the impurity accumulation in the subsurface zone during the thermal treatment leads to swelling and to the formation of dendrites composed of large and coalesced nanoparticles of grey contrast. The appearance of dendrites is most probably due to the SnO2 phase formation. The as-implanted samples are characterized by a weak emission with maximum at the blue range (2.9 eV). The PL intensity increases by an order of magnitude after annealing in an oxidizing atmosphere. The narrowest and most intense PL band has maximum at 3.1 eV. Its intensity increases with increasing fluence and annealing temperature. This emission can be attributed to the formation of the SnO2 phase (in the form of separate clusters or shells of Sn clusters) in the subsurface region of the SiO2 matrix.