J.D. Long

Inductively coupled Ar/CH4/H2 plasmas for low-temperature deposition of ordered carbon nanostructures

The study of inductively coupled Ar/CH 4/H 2 plasmas in the plasma enhanced chemical vapor deposition (PECVD) of self-assembled carbon nanostructures (CN) was presented. A spatially averaged (global) discharge model was developed to study the densities and fluxes of the radical neutrals and charged species, the effective electron temperature, and methane conversion factors under various conditions. It was found that the deposited cation fluxes in the PECVD of CNs generally exceed those of the radical neutrals. The agreement with the optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS) was also derived through numerical results.

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.

Self-organized ZnO nanodot arrays : effective control using SiNx interlayers and low-temperature plasmas.

An advanced inductively coupled plasma (ICP)-assisted rf magnetron sputtering deposition method is developed to synthesize regular arrays of pear-shaped ZnO nanodots on a thin SiNx buffer layer pre-deposited onto a silicon substrate. It is shown that the growth of ZnO nanodots obey the cubic root-law behavior. It is also shown that the synthesized ZnO nanodots are highly-uniform, controllable by the experimental parameters, and also feature good structural and photoluminescent properties. These results suggest that this custom-designed ICP-based technique is very effective and highly-promising for the synthesis of property- and size-controllable highly-uniform ZnO nanodots suitable for next-generation light emitting diodes, energy storage, UV nanolasers, and other applications.

Growth dynamics and characterization of SiC quantum dots synthesized by low-frequency inductively coupled plasma assisted rf magnetron sputtering

Self-assembled SiC quantum dots (QDs) are grown on Si substrates at a low substrate temperature of 400°C by means of low-frequency, inductively coupled plasma assisted rf magnetron sputtering from a sintered SiC target in a reactive Ar+H2 gas mixture. Effects of SiC target power and working gas pressure on the surface morphology and structural properties of SiC QDs are investigated. The growth dynamics of the QDs obeys cubic root-law behavior. With the increase of SiC target power, the growth rate increases greatly, resulting in nonuniform surface morphology and higher intensity of Si–C transmittance band. Scanning electron microscopy shows that (i) at pressure below 1Pa, SiC quantum dots are highly uniform and the average size of quantum dots increases with the increase of pressure; (ii) at pressure above 1Pa, SiC quantum dots are nonuniform, and the size of quantum dots decreases with the increase of pressure. These behaviors are explained by the scattering effects and the surface mobility of the sputte...

Growth of SiC nanoparticle films by means of RF magnetron sputtering

Plasma radio frequency (RF) magnetron sputtering growth of SiC nanoparticle films on AlN buffered Si(100) is investigated under different reactive gas flows. Introduction of hydrogen into the growth is found to yield a strongest photoluminescence (PL) at 620 nm. If the hydrogen gas flow is zero, or replaced by methane, the PL intensity decreases and the peak is red-shifted to round 680 and 660 nm. These results are discussed in relation to the morphological, compositional, and structural analysis.

In situ catalyzation of carbon nanostructures growth in low-frequency inductively coupled plasmas

A low-frequency inductively coupled plasma source has been employed for in situ catalyzed growth of carbon nanostructures. The catalyzing process depends strongly on the plasma parameters and controls the shape and alignment of nanostructures.

Plasma-reactive SiC quantum dots on polycrystalline AlN films

The self-assembly of SiC quantum dots (SiC QDs) formed on AlN films is investigated. Under optimized growth conditions, SiC QDs with a remarkably narrow size distribution on polycrystalline AlN films can be achieved with the presence of a wetting layer of SiC film by low-frequency inductively coupled plasma- (LF-ICP-) assisted magnetron sputtering. A transmission electron microscope (TEM), field-emission scanning electron microscope (FE-SEM) images, and an energy-dispersive x-ray (EDX) spectrometer clearly demonstrate that SiC QDs are formed on the polycrystalline AlN films.

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.

Chemically active plasmas for deterministic assembly of nanocrystalline SiC film

Silicon carbide thin films are self-assembled onto crystalline silicon substrate from a sintered SiC target at low substrate temperature of 400 °C in Ar + H2 discharge using inductively coupled plasma (ICP) assisted RF magnetron sputtering system. Surface morphology and structural properties of SiC films are investigated by SEM, XRD, FTIR and EDX. SEM, XRD and FTIR results show that the SiC film deposited at an ICP power of 800 W is 3C-SiC nanocrystalline film while the film deposited without ICP power exhibits an amorphous structure. At ICP power of 800 W, there exists a large amount of dissociated H in the plasma, leading to the structural relaxation of the amorphous network towards the crystalline state. The EDX result shows that elemental compositions of Si and C atoms in both the films are almost stoichiometric.

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.