Infrared and Photoluminescence Study of Rapidly Thermally Annealed SiO_x Thin Films

Abstract

Silicon suboxide, SiOx thin films with different oxygen contents (1.15≤x≤1.70) were prepared by thermal evaporation of silicon monoxide at a residual oxygen pressure of 1·10-3 Pa and deposition rates of 0.2, 1.0, 3.0 and 6.0 nm/s. Rapid thermal annealing (RTA) of films was carried out at 1100°C in vacuum for 15 and 30 s and the films were analyzed by infrared (FTIR) and photoluminescence (PL) spectroscopy. In the FTIR spectra of SiOx annealed samples, a blue-shift of the stretching band with initial oxygen content, x, is observed. This band is shifted to a much lower frequency with prolonged RTA time. This behavior can be interpreted in terms of the partial decrease of oxygen content and film density upon annealing in vacuum. With annealing time increase a new band at 1106 cm-1 appears. Therefore, infrared spectra of SiOx films are significantly affected by the oxygen content. PL spectra of these films also change drastically with increasing annealing time. In the PL spectra of films annealed for 15 s two bands are easily visible: broad redorange band at 2.2 eV and a green band at 2.4 eV, while for 30 s annealing only low-energy band exists. Green band is connected with the defects in the SiOx matrix while red-orange band can be deconvoluted into several bands at 2.0, 2.3 and 2.5 eV. Two types of defects can be responsible for the PL band at about 2 eV: defects in a-Si (amorphous silicon) nanoparticles separated during RTA, and nonbridging oxygen hole recombination centers (NBOHC) formed by loosing of oxygen during RTA. The PL band at 2.3 eV is associated with the defects formed at a-Si/SiOx interfaces while a hardly visible band at 2.5 eV is related to the defects connected with the oxygen deficiency formed in the SiOx matrix during RTA.

Influence of Temperature and Time on Nd2O3-SiO2Composite Prepared by the Solgel Process

“…In addition, it was also observed that TO mode of the Si-O-Si slightly shifts towards a higher wave number with increasing sintering temperature and time. Similar behaviors of Si-O-Si band in annealed SiO x (x -contents) sample were noticed by many workers [26][27][28]. They pointed out that the peak position of the asymmetric stretching broad band of the SiO x sample depends on the oxygen contents.…”

“…They pointed out that the peak position of the asymmetric stretching broad band of the SiO x sample depends on the oxygen contents. Nakamura et al [26] and Milutinovic et al [27] found that the oxygen contents decreases with increasing annealing temperature and time and as a result the peak position shifts towards higher wave number and eventually the density of SiO x increases. Figure 3 shows morphologies of the sintered composites systems (Nd 2 O 3 -SiO 2 ) as viewed under SEM.…”

Structural evolution of nanocrystalline Nd2O3 supported on silica: Effect of sintering time

“…In investigation the shifting of the Si-O-Nd peak towards higher spatial frequency is a consequence of higher ionic radius of Nd than Pr. In addition, it was also observed that TO mode the Si-O-Si slightly shifts towards a higher wave number with increasing sintering growth temperature and interruption time [14][15][16]. Fig.…”

Silver nanoparticle (AgNPs) doped gum acacia–gelatin–silica nanohybrid: An effective support for diastase immobilization

“…Enzyme impregnated AgNps doped gum acacia-gelatin silica hybrids (H 3 -Enz) shows nearly the same spectrum as that of H 3 indicating immobilization by physical entrapment and not by covalent bonding. In all the IR spectra, bending vibrations due to water are observed at around 1628 cm −1 indicating the hygroscopic character of the powdered samples [44]. Stretching peak due to C O at gum acacia is observed at 1710 cm −1 , which after silver doping shifts to 1705 cm −1 .…”