The effects of carbon and postdeposition annealing on white luminescence are studied in amorphous silicon oxycarbide (a-SiCxOy) films grown by chemical vapor deposition. The films showed strong room-temperature luminescence in a broad spectral range from blue-violet to near infrared, depending on excitation energy. Photoluminescence (PL) intensity exhibited good correlation with SiOC bond concentration. At low C (<5%), matrix PL was completely quenched after annealing in O2 even at 500 °C. PL was unaffected by O2 annealing at higher C, and could be enhanced when excited by an ultraviolet laser. These findings are correlated to C- and Si-related O defect centers as luminescence sources in a-SiCxOy.

Findings are presented from a systematic study of the effects of postdeposition thermal treatment on the optical characteristics of hydrogenated amorphous silicon-oxycarbide (a-SiCxOyHz) materials. Three different classes of a-SiCxOyHz films: SiC-like (SiC1.08O0.07H0.21), Si-C-O (SiC0.50O1.20H0.22), and SiO2-like (SiC0.20O1.70H0.24), were deposited by thermal chemical vapor deposition. The effects of thermal annealing on the compositional and optical properties of the resulting films were characterized using Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, nuclear reaction analysis, and spectroscopic ultraviolet-visible ellipsometry. As the Si-C-O system evolved from a SiC-like to SiO2-like matrix, its refractive index and optical absorption strength decreased, while its optical band gap increased. Thermal annealing between 500 and 1100 °C resulted in hydrogen desorption from and densification of the a-SiCxOyHz films. Concurrently, thermally induced changes were also observed for the optical properties of the films, as evidenced by an increase in film refractive index and an accompanying decrease in optical gap. These changes are analyzed in the context of the underlying physical processes, particularly modifications in the electronic configuration (bonding) and hydrogen desorption mechanisms. Furthermore, based on the observed structural and optical properties of the thermally treated a-SiCxOyHz films, the Si-C-O matrix was employed in the successful development of an Er-doped Si-C-O system with efficient Er excitation and strong room-temperature photoluminescence emission around 1540 nm within a broad (460–600 nm) excitation band. As such, a-Si-C-O represents a material system that provides considerably efficient energy transfer mechanisms at the same Er concentration level than previously investigated Si-based materials.

Silicon oxycarbide (SiCxOy) is a promising material for achieving strong room-temperature white luminescence. The present work investigated the mechanisms for light emission in the visible/ultraviolet range (1.5–4.0 eV) from chemical vapor deposited amorphous SiCxOythin films, using a combination of optical characterizations and electron paramagnetic resonance(EPR) measurements. Photoluminescence(PL) and EPR studies of samples, with and without post-deposition passivation in an oxygen and forming gas (H2 5 at. % and N2 95 at. %) ambient, ruled out typical structural defects in oxides, e.g., Si-related neutral oxygen vacancies or non-bridging oxygen hole centers, as the dominant mechanism for white luminescence from SiCxOy. The observed intense white luminescence (red, green, and blue emission) is believed to arise from the generation of photo-carriers by optical absorption through C-Si-O related electronic transitions,and the recombination of such carriers between bands and/or at band tail states. This assertion is based on the realization that the PL intensity dramatically increased at an excitation energy coinciding with the E04 band gaps of the material, as well as by the observed correlation between the Si-O-C bond density and the PLintensity. An additional mechanism for the existence of a blue component of the white emission is also discussed.

The composition, structure, morphology, and optical characteristics of hydrogenated amorphous silicon-oxycarbide (a-SiCxOyHz) materials were investigated as a function of experimental processing conditions and post-deposition thermal treatment. Thermal chemical vapor deposition (TCVD) was applied to the growth of three different types of a-SiCxOyHz films, namely, SiC-like (SiC1.08O0.07H0.21), Si-C-O (SiC0.50O1.20H0.22), and SiO2-like (SiC0.20O1.70H0.24). The resulting films were subsequently annealed at temperatures ranging from 500 °C to 1100 °C for 1 h in an argon atmosphere. The composition, structure, and morphology of as-deposited and post-annealed films were characterized by Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), nuclear-reaction analysis (NRA), and scanning electron microscopy. Corresponding optical properties were assessed by spectroscopic ultraviolet-visible ellipsometry (UV-VIS-SE). These studies led to the identification of an optimized process window for the growth of Er doped silicon oxycarbide (SiC0.5O1.0:Er) thin film with strong room-temperature photoluminescence emission measured around 1540 nm within a broad (460 nm to 600 nm) wavelength band. Associated modeling studies showed that the effective cross section for Er excitation in the SiC0.5O1.0:Er matrix was approximately four orders of magnitude larger than its analog for direct optical excitation of Er ions.

The present report presents results from the fabrication, structural, and optical characteristics of sub-100 nm thermal chemical vapor deposition-grown silicon-oxycarbide (SiC x O y ) nanowire (NW) arrays fabricated by e-beam lithography and reactive-ion-etching. The composition of SiC x O y materials follows closely the silicon-oxycarbide stoichiometry [SiC x O 2(1Àx) , (0 , x , 1)] as observed by compositional and structural analysis. The corresponding structural and bonding evolution of SiC x O y are well-correlated with changes in their optical properties, as demonstrated by the linear dependence of their optical gap and refractive index with [Si-C]/[Si-O] bond-area ratio. By virtue of these advantages, properly tailored SiC x O y NWs were fabricated, exhibiting strong room-temperature visible photoluminescence (PL) through engineering of [Si-C]/[Si-O] bonds. The current studies focused on the thermal-oxidation and excitation intensity behavior of SiC x O y NWs revealed their very good stability, as their luminescence characteristics remain unchanged upon annealing in oxygen ambient (250°C), while the PL intensity dependence on the excitation power-density exhibited a linear increase up to ;800 W/cm 2 .