Photoluminescence Studies Of Filament-Assisted CVD Grown Diamond Films

Abstract

Recent developments in diamond thin film growth using plasma, ion beam or hot filament assisted chemical vapor deposition (CVD) techniques have created the potential for a wide variety of applications for diamond in areas as diverse as cutting tool coatings and high speed electronic devices. In this paper we examine the impurity content of diamond films grown by filament-assisted CVD using photo-luminescence (PL) spectroscopy in the 1.6 - 2.5 eV energy range. We find that the dominant impurity in these films besides hydrogen is nitrogen, as determined by the presence of a strong luminescence peak at ~2.1 eV. This band is attributed to donor-acceptor pair recombination in analogy with a similar feature in the PL of natural diamonds. In films which show a sharp Rama feature at 1332 cm-1 and very little Raman activity in the 1550 cm-1 region, additional emis-sion appears at ~1.7 eV. This is in the vicinity of the 1.673 eV emission observed in natural diamonds, and is ascribed to a neutral vacancy. Other luminescence bands, which overlap the 1.7 eV emission and appear to be unique to CVD grown diamond, have yet to be assigned. We also include data on luminescent emission from a nitrogen vacancy complex which is referred to in the bulk as the H3 center This center was induced in the films by irradiation with 2 MeV He+ ions, with no post-irradiation anneal.