Abstract
The photoluminescence characteristics of films consisting of Si nanocrystals either coated with or embedded into Spin on Glass (SOG) were studied. Si nanocrystals showing red or blue luminescence when suspended in alcohol solution were obtained from porous silicon films. These were then either deposited in Si substrates and coated with SOG, or mixed in an SOG solution that was later spun on Si substrates. Both types of films were thermally annealed at 1100 °C for three hours in N2 atmosphere. Transmission electron microscopy measurements showed a mean diameter of 2.5 nm for the Si nanocrystals, as well as the presence of polycrystalline Si nanoagglomerates. These results were confirmed by X-ray diffraction studies, which revealed the (111), (220) and (311) Bragg peaks in Si nanocrystals. Fourier transform infrared spectroscopy studies showed that the coated films present higher chemical reactivity, promoting the formation of non-stoichiometric SiO2, while the embedded films behave as a stoichiometric SiO2 after the thermal annealing. The PL (photoluminescence) characterization showed that both embedded and coated films present emission dominated by the Quantum Confinement Effect before undergoing any thermal treatment. After annealing, the spectra were found to be modified only in the case of the coated films, due to the formation of defects in the nanocrystals/SiO2 interface.
Highlights
In the past, many efforts have been devoted to the fabrication of light emitting films that are compatible with silicon technology [1]
Porous silicon obtained by electrochemical methods has been used to produce colloidal solutions
Porous silicon obtained by electrochemical methods has been used to produce colloidal with silicon nanocrystals that show red or blue PL emission
Summary
Many efforts have been devoted to the fabrication of light emitting films that are compatible with silicon technology [1]. Temperatures of around 1100 ◦ C are needed to promote the nucleation and activation of radiative Si nanopoints, crystalline or not [3,4,19,20] Examples of these materials are the silicon rich oxides obtained by chemical vapor deposition (CVD), Ionic implantation of Si in a dielectric matrix, and thermally treated chemical solutions [4,21,22,23]. Si-NCs obtained separately by a variety of techniques and mixed with SiO2 solutions, such as Spin on Glass (SOG), have been of particular research interest because they are usually easy and low cost methods that do not need to be thermal treated to produce emissive films. The coated and embedded films were studied with and without thermal annealing at 1100 ◦ C to look deeply into its effects
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