Abstract
Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra.
Highlights
Quantum confinement effects have been found to improve the efficiency of radiative recombination in silicon [1]
Owing to the inherently poor sensitivity of Rutherford backscattering spectrometry (RBS) in measuring lower atomic number elements such as nitrogen, the values obtained from the fits have been rounded to the nearest percent, and values measured below 0.5% have been labelled as
Combined with the large changes measured in the PL spectra for annealing times on the order of seconds, these results suggest that silicon nanoclusters (Si-ncs) form much more rapidly than has been conventionally believed and it is likely the result of a fast transient diffusion mechanism for excess silicon in a silicon nitride film
Summary
Quantum confinement effects have been found to improve the efficiency of radiative recombination in silicon [1]. In accordance with Heisenberg’s uncertainty principle, the spatial confinement of the charge carriers induces a spread in their momenta, allowing for quasidirect radiative transitions to occur in an indirect bandgap semiconductor Utilizing these quantum confinement effects, efficient light emission has been achieved from silicon nanoclusters (Si-ncs) formed in a dielectric host matrix. Si-ncs formed in SRSN films deposited with varied compositions using three different chemical vapour deposition (CVD)-based systems are compared and discussed: plasma-enhanced CVD (PECVD), inductively coupled plasma CVD (ICP CVD), and electron cyclotron resonance PECVD (ECR PECVD). Results from these studies have been previously reported in two conference proceedings [18,19]. Information on the bulk of the film was provided by the TEY spectra at the Si K-edge and the FLY spectra at the Si L3,2-edge
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