The origin of white luminescence from silicon oxycarbide thin films

Abstract

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.

Strong visible light emission from silicon-oxycarbide nanowire arrays prepared by electron beam lithography and reactive ion etching

“…This is in contrast to nonstoichiometric compositions reported for SiC x O y samples with SiC/SiO 2 phases and free carbon, as it is shown in Fig. 1 27 The replacement of two bridging oxygen atoms by one carbon atom, as dictated by the SiC x O 2(1Àx) stoichiometry, results in the observed decrease in the Si-O-C intensity.…”

Influence of the oxygen content in obtaining tunable and strong photoluminescence from low-temperature grown silicon oxycarbide films

“…Thus, it is well reasonable that the behavior of yellow emission intensity with the oxygen flow rate exhibited a similar tendency to that of the intensity of SiAC bonds. In the C-rich SiC x O y films, it is considered that the oxygen may be doped as defect-related luminescent centers such as neutral oxygen vacancy (NOV) due to deviation from perfect stoichiometry [17]. The formation of NOV defects would further give rise to the blue emission via the electronic transition between the singlet ground state and the elevated state (triplet) of the Si-related NOV defect [31,32].…”

“…The main obstacle lies in the low light emission efficiency. In recent years, considerable attention has been paid to the light emission from silicon oxycarbide films, the advantages of which include strong light emission and wide tunable optical band gap, making it useful for the design of efficient light emitting devices [16,17]. In addition, silicon oxycarbide is also regarded as a promising host material for rare earth such as Er and Eu [18,19].…”

Photoluminescence of Carbon Incorporated Silica Nanopowder Fabricated Using Sucrose as Carbon Precursor

“…There are two general type of carbon related structural configurations that can be considered as light emitting sites: (1) carbon nanoclusters in form of 3D carbon nanodots, 2D grapheme nanodots or 3D/2D graphene oxide nanodots; (2) carbon related point defect in form of Si-O-C bonding [9] or ≡Si..C≡ defect [15]. In fact, ≡Si..C≡ bulk defect can be imagined as removing of oxygen atom from Si-O-C bulk bonding.…”