J.W. Chai

Enhancement of visible photoluminescence in the SiNx films by SiO2 buffer and annealing

The authors report a simple method to significantly enhance the photoluminescence (PL) of SiNx films by incorporating a SiO2 buffer and annealing treatment under N2 protection. Strong visible PL is achieved with annealing temperature above 650°C. Optimal PL is obtained at 800°C. The composition and structure analysis reveal that strong PL is directly related to the content of the Si–O and Si–N bonds in the SiNx films. These bonds provide effective luminescent centers and passivate the interface between Si core and the surrounding oxide.

SYNTHESIS AND CHARACTERIZATION OF TERNARY AL-C-N COMPOUND

An attempt for modification of carbon nitride material by introduction of Al to form a ternary Al-C-N compound in a thin film deposited using inductively coupled plasma (ICP) assisted DC magnetron sputtering is reported. Optical emission spectroscopy (OES) is used for in-situ observation and identification of reactive species. The films were characterized using x-ray photoelectron spectroscopy (XPS) and x-ray diffraction spectroscopy (XRD). The results indicate that C-N bond is formed in the plasma. The XPS narrow scam spectra confirm the existence of C-Al, sp2C-N and sp3C-N bonds. Elemental proportion of carbon increases with the CH4/N2 flow rate ratio, and has a tendency to saturate. The film is dominated by c-AlN (111), mixed with Al4C3 and AlCN ternary compound.

Visible photoluminescence from plasma-synthesized SiO2-buffered SiNx films: Effect of film thickness and annealing temperature

The effect of the film thickness and postannealing temperature on visible photoluminescence (PL) from SiNx films synthesized by plasma-assisted radio frequency magnetron sputtering on SiO2 buffer layers is investigated. It is shown that strong visible PL is achieved at annealing temperatures above 650°C. The optimum annealing temperature for the maximum PL yield strongly depends on the film thickness and varies from 800to1200°C. A comparative composition-structure-property analysis reveals that the PL intensity is directly related to the content of the Si–O and Si–N bonds in the SiNx films. Therefore, sufficient oxidation and moderate nitridation of SiNx∕SiO2 films during the plasma-based growth process are crucial for a strong PL yield. Excessively high annealing temperatures lead to weakened Si–N bonds in thinner SiNx films, which eventually results in a lower PL intensity.

CdS NANORODS FABRICATED BY ICP-ASSISTED MAGNETRON SPUTTERING AT ROOM TEMPERATURE

Cadmium sulfide (CdS) nanocrystals are successfully fabricated on glass and silicon substrates at room temperature with low-frequency (460 kHz) inductively coupled plasma assisted magnetron sputtering technique. Both size and shape can be controlled by changing deposition parameters and substrates. Field-emission scanning electron microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction are adopted to measure the properties of CdS nanorods.