We report on blue-white luminescence from amorphous silicon oxycarbide a-SiCxOy≤1.68 (0.25<x<0.36) thin
films, synthesized by thermal chemical vapor deposition (TCVD) process. The luminescence from SiCxOy was found to
exhibit a broad band in the blue-violet to near infrared range (370 - 750 nm), visible to the naked eye in a bright room.
The effects of carbon concentration (8.4 at.% < C < 13.6 at.%) in the material and post-deposition annealing treatments
(Ar and forming gas 5% of H2 ambient up to 1100°C) on the observed luminescence were studied. The emission intensity
slightly decreased with increasing carbon content but was appreciably enhanced in the samples following post-deposition
annealing treatment in forming gas 5% of H2 ambient.
We have previously demonstrated strong room-temperature luminescence at 1540 nm from erbium-doped
amorphous silicon oxycarbide (a-SiCxOyHz:Er) materials. In this study, pertinent details are presented regarding the
role of growth conditions and post-deposition thermal treatment in engineering the structural and optical characteristics
of these novel Si-based materials for optimized luminescence performance. Three different classes of a-SiCxOyHz
materials were synthesized by thermal chemical vapor deposition, as classified by their carbon and oxygen
concentrations: SiC-like; Si-C-O; and SiO2-like. Fourier-transform infrared spectroscopy, x-ray photoelectron
spectroscopy, nuclear reaction analysis, and spectroscopic ellipsometry were used to characterize the effects of thermal
annealing, as performed at temperatures in the range of 500 - 1100°<i>C</i>, on the structural and optical properties of the
resulting films. As the material evolves from the SiC-like, through the Si-C-O, to the SiO2-like matrix, the mass density
and refractive index are found to decrease, whereas the optical band gap actually increases. Thermal annealing also
resulted in hydrogen desorption from and densification of the a-SiCxOyHz films and in an accompanying decrease in optical gap and an increase in film refractive index. This work suggests that silicon oxycarbide could be a promising Si-based
matrix for high-performance Er-doped waveguide amplifiers.
The present investigators have previously reported on strong room-temperature luminescence at 1540 nm from
erbium-doped amorphous silicon oxycarbide (a-SiCxOy:Er) thin films. An enhancement of ~20 times was found for asgrown
SiC0.5O1.0:Er compared to SiO2:Er control samples under continuous wavelength (cw) pumping at 496.5 nm.
Here, we report the effects of post-deposition annealing on the photoluminescence (PL) properties of Er-doped silicon
oxycarbide. The amorphous SiCxOy films were grown by thermal chemical vapor deposition (TCVD) at 800°C and postdeposition annealing was conducted in the temperature range 500-1100°C. The thin films were then implanted with
260keV Er ions and subsequently annealed at 900°C. Strong room-temperature photoluminescence around 1540 nm was
observed, with efficient Er+3 ion excitation occurring for pumping wavelengths ranging from 460 nm to 600 nm.
Modeling of the power dependence of Er luminescence yielded an effective Er excitation cross-section about four orders
of magnitude larger than that for a direct optical excitation of Er+3 ions. Additionally, Fourier transform infrared
spectroscopy (FTIR) studies of post-deposition annealed samples revealed a strong correlation between the Er PL
intensity and the C-O bond concentration in the materials. The work suggests a novel method for achieving efficient Er
luminescence in Si-based materials through controlled engineering of the Si-C-O system.