Experimental investigation of discharge characteristics in enhanced glow discharge plasma immersion ion implantation

In enhanced glow discharge plasma immersion ion implantation (EGD-PIII) that involves a small pointed anode and large area tabular cathode, the high negative substrate bias not only acts as the plasma producer but also supplies the implantation voltage. Consequently, an electric field is created to focus the electrons and the electron focusing field in turn enhances the glow discharge process. In this work, the discharge characteristics of EGD-PIII are investigated experimentally. The discharge initiation and extinction characteristics during pulsed biasing are discussed. The duration of the post pulse-off plasma is explained from the viewpoint of particle motion and experimentally verified by employing an auxiliary disk. Our experiments show that a dual-pulse method may be utilized to determine the remnant plasma.     

Patterned uniformly orientated silicon nanocrystallite films and efficient field emission characteristics

Patterned uniformly (100)-orientated silicon nanocrystallite (SiNC) films were fabricated based on hydrogen ion implantation technique and typical electrochemical anodic etching method. The surface morphology and microstructure characteristics of the films were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and atomic force microscopy. The efficient field emission with low turn-on field of about 3.2 V/μm at current density of 0.1 μA/cm² was obtained. The emission current density from the SiNC films reached 1 mA/cm² under a bias field of about 11 V/μm. The experimental results demonstrate that the SiNC films have great potential applications for flat panel displays.     

Study of carboxylic functionalization of polypropylene surface using the underwater plasma technique

Non-equilibrium solution plasma treatment of polymer surfaces in water offers the possibility of more dense and selective polymer surface functionalization in comparison to the well-known and frequently used low-pressure oxygen plasma. Functional groups are introduced when the polymer surface contacts the plasma moderated solution especially water solutions. The emission of ions, electrons, energy-rich neutrals and complexes, produced by the ion avalanche are limited by quenching, with the aid of the ambient water phase. The UV-radiation produced in plasma formation also helps to moderate the reaction solution further by producing additional excited, ionized/dissociated molecules. Thus, monotype functional groups equipped polymer surfaces, preferably OH groups, originating from the dissociated water molecules, could be produced more selectively. An interesting feature of the technique is its flexibility to use a wide variety of additives in the water phase. Another way to modify polymer surfaces is the deposition of plasma polymers carrying functional groups as carboxylic groups used in this work. Acetic acid, acrylic acid, maleic and itaconic acid were used as additive monomers. Acetic acid is not a chemically polymerizing monomer but it could polymerize by monomer/molecular fragmentation and recombination to a cross linked layer. The other monomers form preferably water-soluble polymers on a chemical way. Only the fragmented fraction of these monomers could form an insoluble coating by cross linking to substrate. The XPS analysis was used to track the alterations in –O-CO- bond percentage on the PP surface. To identify the -COOH groups on substrate surface unambiguously, which have survived the plasma polymerization process, the derivatization with trifluoroethanol was performed.     

RF-CF4 plasma surface modification of paper: Chemical evaluation of two sidedness with XPS/ATR-FTIR

The study was performed to examine the correlation between the initial roughness and surface fluorination of paper under RF-CF₄ plasma environment.Based on the experimental observations, a correlation was observed between surface fluorination and plasma parameters, e.g. RF-power, treatment time and gas pressure. The level of fluorination with RF-CF₄ plasma treatment was found to be extensive in both side of paper. Even very short treatment time, as low as 1 min at 300 W power, provides effective implantation of fluorine (38.7%) on surfaces. It was observed that, CF₄ plasma treatment had a significant effect on the molecular fragmentation on both side of paper. However, the felt side have a much stronger effect on plasma-induced dissociation and fluorination than in the wire side of paper.     

Features of microarc oxidation coatings formation technology in slurry electrolytes

A group of electrolytes composed of different powders entered into electrolyte presents a separate direction in microarc oxidation (MAO) technology. This group of electrolytes is most complex and however it has not been sufficiently studied yet. This paper shows that addition of powders of different nature into electrolyte influences both on properties of obtained coatings and on speed of their formation. The MAO-coatings formed in similar electrolytes-suspensions or slurry electrolytes (SE) contain in their composition an essential share of powder material entered into electrolyte as corpuscles of disperse phase (DP). Different nonmetallic combinations are used: oxides, carbides, borides, nitrides of metals and others. The particular conditions of microarc discharge regime (high temperature and pressure in a zone of breakdown) cause a thermolysis of electrolyte together with weighed corpuscles of solid matter, the realization of plasma chemical reactions on oxidizing surface and provide the synthesis of chemical combinations in an oxide matrix. A new composition of slurry electrolyte which allows improving the quality of obtained coatings on the basis of held investigations was developed.     

The role of heat-conducting walls in the measurement of heat and mass transport in transient grating experiments

We present a two-dimensional model to account for the role of heat-conducting walls in the measurement of heat transport and Soret-effect-driven mass transport in transient holographic grating experiments. Heat diffusion into the walls leads to non-exponential decay of the temperature grating. Under certain experimental conditions it can be approximated by an exponential function and assigned an apparent thermal diffusivity D_{th, app} < D_{th, s}, where D_th,s is the true thermal diffusivity of the sample. The ratio D_{th, app}/D_{th, s} depends on only three dimensionless parameters, d /l_s, κ_s/κ_w, and D_{th, s}/D_{th, w}. d is the grating period, l_s the sample thickness, κ_s and κ_w the thermal conductivities of sample and wall, respectively, and D_th,w the thermal diffusivity of the wall. If at least two measurements are performed at different d /l_s, both D_th,s and κ_s can be determined. Instead of costly solving PDEs, D_th,s can be obtained by finding the zero of an analytic function. For thin samples and large grating periods, heat conduction into the walls plays a predominant role and the concentration grating in binary mixtures is no longer one-dimensional. Nevertheless, the normalized heterodyne diffraction efficiency of the concentration grating remains unaffected and the true thermal and collective diffusion coefficient and the correct Soret coefficient are still obtained from a simple one-dimensional model.     

Synthesis of intrinsic fluorescent polypyrrole nanoparticles by atmospheric pressure plasma polymerization

Intrinsic fluorescent polypyrrole (ppy) nanoparticles with different shapes were fabricated by atmospheric pressure plasma polymerization. Gradient electrical field and polarization of active particles in the plasma induce change of shape of nanoparticles from spherical to rod, when the plasma power varied from 5 W to 10 W. Both X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results suggest that the atmospheric pressure plasma polymerization process (APPP) at the power of 5 W and 10 W can help to preserve the integrity of the structure of monomer due to the predominant role of radical polymerization in APPP at these powers. However, when the plasma power increased to 20 W, the ring structure of some pyrroles was destroyed, owing to existence of higher energy species. The polypyrrole nanoparticles exhibit the peak fluorescence around 415 nm. Fluorescent results show that the fluorescent properties of polypyrrole nanoparticles are related to the particle size of the polymer. The bigger particles would have more enlarged room for exciton diffusion, resulting in lower fluorescence intensity and red shift of the fluorescent peak.     

Hydrogenation of carbon fragments after femtosecond laser ablation of solid C60

We have observed several kinds of hydrocarbon cations after the nanosecond and the femtosecond laser ablation (nsLA and fsLA) of solid C₆₀. The observation indicates that the carbon fragments produced just after laser ablation of the C₆₀ molecule react with the hydrogen atoms and ions coexisting in the ablation plume. In the case of fsLA, clear dependence of the product hydrocarbon species on the ablation laser power has been observed although the dependence is not clearly observed in nsLA. The production of C_nH₅⁺ (n = 8, 10, and 12) is only observed in fsLA suggesting the unique nature of the transient carbon fragments produced by fsLA.     

CHF3 Dual-Frequency Capacitively Coupled Plasma by Optical Emission Spectroscopy

We investigate the intermediate gas phase in the CHFs 13.56 MHz/2 MHz dual-frequency capacitively couple plasma （CCP） for the SiCOH low dielectric constant （low-k） film etching, and the effect of 2MHz power on radicals concentration. The major dissociation reactions of CHF3 in 13.56MHz CCP are the low dissociation bond energy reactions, which lead to the low F and high CF2 concentrations. The addition of 2MHz power can raise the probability of high dissociation bond energy reactions and lead to the increase of F concentration while keeping the CF2 concentration almost a constant, which is of advantage to the SiCOH low-k films etching. The radical spatial uniformity is dependent on the power coupling of two sources. The increase of 2 MHz power leads to a poor uniformity, however, the uniformity can be improved by increasing 13.56 MHz power.     

Mass Spectrometry Investigation on Decamethylcyclopentasiloxane Electron Cyclotron Resonance Plasma for SiCOH Film Deposition

We investigate the fragmentation behaviour of decamethylcyclopentasiloxane （DMCPS） plasma using a quadrupole mass spectrometry, which is used as the precursor to deposit SiCOH film in an electron cyclotron resonance （ECR） plasma system. The structure of DMCPS molecules comprises a fivefold Si-O ring and ten -CH3 groups bonded at five Si atoms. In ECR discharge plasma, the main fragmentation behaviour of DMCPS includes two stages. One is the breaking of fivefold Si-O rings and then the formation of threefold Si-O rings and Si-O chain species. The other is the decomposing of hydrocarbon groups from Si atoms and then the crosslink of hydrocarbon species. Combined with the bonding configuration of SiCOH films, the relation between species in ECR plasma and films structures is analysed.