White light emission from amorphous silicon oxycarbide (a-SiCxOy) thin films: Role of composition and postdeposition annealing

Abstract

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.

The origin of white luminescence from silicon oxycarbide thin films

“…As in the case of the oxide luminescence centers mentioned above, the density of both EPR detected centers is expected to diminish, and their respective luminescence, if it were to exist in the SiC x O y samples, would be quenched following prolonged oxidation or hydrogen passivation. 5,16,17 This expectation did not actually materialize in the SiC x O y samples. 5 Another potential mechanism responsible for strong luminescence from C-rich materials could be small sp 2 -carbon clusters.…”

“…5,16,17 This expectation did not actually materialize in the SiC x O y samples. 5 Another potential mechanism responsible for strong luminescence from C-rich materials could be small sp 2 -carbon clusters. 18 Previous FTIR studies showed the absence of C¼C bonds at $1644 cm À1 , which would result from the sp 2 -carbon molecular orbitals.…”

“…5,6 In this case, the red, green, and blue emissions could be achieved simultaneously from the same SiC x O y thin film produced with a single deposition process, without the complications encountered in the case of using Si or SiC nanocrystals for white light emission. However, despite the advantages of SiC x O y thin films in white luminescence applications, the underlying mechanisms for light emission within the same SiC x O y matrix are not clear.…”

Investigation of photoluminescence of Si−O−C(−H) ceramics at an early stage of decarbonization by using high energy excitation

“…Various kinds of Si−O−C ceramics were synthesized by various methods, and many mechanisms have been proposed to explain the observed PL bands. [3][4][5][6][7][8][9] Their simple chemical composition with no special activator was promising for their use in LED systems, devices of radiation detectors or environmental resistant inorganic pigments with fluorescent colors.…”

“…Gallis et al proposed the idea of C-ODC (carbon modified oxygen deficiency related centers) to explain broad PL spectra of near-stoichiometric Si−O−C films. 8 Detailed discussion of the modified ODC (II) structure is, however, very difficult.…”