Papers by Keyword: Hydrogen Plasma

Abstract: Metallic nanoparticles have various potential applications. Recent studies have showed that their morphology had a strong influence on their optical and electrical properties. In this work, rapid thermal annealing was used to produce gold nanoparticles on silicon substrates. Morphology control of the gold nanoparticles was made by changing inert annealing gases. Spherical gold nanoparticles were obtained with nitrogen while hemispherical gold nanoparticles were formed with argon.

Abstract: The evolution of the CVD diamond coatings morphology after perpendicular direction reactive ion etching was investigated. During the surface treatment, the average surface roughness was reduced. The efficiency of the etching decreases with the increasing of the processing time, until the surface roughness has been reduced by 30±5%. The height points spread over the surface were measured. The quality of the obtained films was investigated using the Raman spectroscopy.

Abstract: In this paper, we use PLASIMO to investigate the effect of discharge current on hydrogen plasma in the cascaded arc, the effects of discharge current on plasma properties were investigated. temperature, conductivity, and the distribution of electron density along the symmetry axis of hydrogen plasma is analyzed in the simulation area. The simulation results show that plasma temperature is 0.9503×104, 1.09862×104, 1.26675×104, 1.65102×104 K in the symmetry axis when the discharge current is 35, 50, 75 and 100A, meanwhile, electric conductivity is 1738.03, 2272.72, 2819.86, 3820.73 s/m.

Abstract: Hydrogen occurs ionization under high temperatures and high pressures. Considered the interaction between the electrons and ions of fully ionized hydrogen plasma, and the translational motion of hydrogen ion obey Boltzmann distribution, Coulomb interactions between charged particles can be used Hartree-Fock integrals and described by approximants, and obtained the statistical mechanics model and equation of state of full ionized hydrogen plasma.

Abstract: The ion-ion interaction contribution to the Helmholtz free energy is one of thermodynamic properties which discribing full ionized hydrogen plasma. Based quantum statistical theory and its simulation results to construct the free energy model of statistical mechanics, it is great significant to understand the properties of full ionized hydrogen plasma under high temperatures and pressures. Using Fortran program, we calculated the isotherms with some sensitive parameters, making comparison between our results and the formers. We find that former formula proposed by Chabrier appears variation at ultra-high temperatures ( > Κ ), implying a prominent limit of low temperature, while we developed a more reasonable formula of the ion-ion interaction contribution to the Helmholtz free energy. Analyses on isotherm curves indicate that the thermodynamic properties of the ion-ion interaction contribution to the Helmholtz free energy described by our approximant is very stable at all temperatures and pressures without any unphysical effects at low temperatures.

Abstract: Multi-wall carbon nanotube (MWCNT) structures were grown on cobalt catalyst layer through Plasma Enhanced Chemical Vapor Deposition (PECVD) process. Acetylene (C2H2) and hydrogen (H2) are used as precursors during the PECVD process. The morphology structures of the MWCNTs grown under different PECVD time were investigated and characterized using Scanning Electron Microscope (SEM). The effect of the PECVD time on the MWCNT growth is studied by varying the PECVD time at 45 sec and 600 sec. The morphology structures suggest that the growth rate is proportional to the PECVD time under the similar setting condition of pressure, acetylene flow-rate and temperature.

Abstract: The SiC surfaces were cleaned by the hydrogen plasma with ECRPEMOCVD plasma system at low temperature of 200°C, after the traditional wet cleaning. The surfaces were investigated by RHEED and X-ray Photoelectron Spectroscopy before and after hydrogen plasma treatment. The RHEED imagines showed that the SiC surfaces by hydrogen plasma treatment were more flatter than the SiC surfaces by the traditional wet cleaning, and we found the result that more treatment time, more flatter. The XPS spectra examinations indicated that the surface oxides reduced obviously and the C/C-H compounds on the SiC surface were removed by hydrogen plasma treatment, so the antioxidant ability of the SiC surface was improved.

Abstract: Describing the electron-electron interaction contribution to the Helmholtz free energy, we obtained a new fitting formula by revising the electronic exchange contribution to the Helmholtz free energy of the previous fitting formula. Using Fortran program, we calculated the curves with some sensitive parameters like the electron-electron interaction contribution to the free energy and the Coulomb coupling parameter , temperature , the mean distance between the electrons making a comparison between the revised fitting formula and the formers. It is concluded that the theoretical value of the revised fitting formula basically has agreement with the previous theoretical value at , when , the revised value completely has a consistent with the previous results. It is illustrated that the curve of the revised fitting formula is more smooth, perfect, and we obtained a very good agreement between the theoretical result of the revised Helmholtz free energy and the theoretical result of the former Padé formulas, which illustrates us to get a more accurate fitting formula and result. Therefore, the revised fitting formula is a more complete and accurate description of the thermodynamic properties of the electron-electron interaction contribution to the Helmholtz free energy.

Abstract: In future, thin wafers (< 100µm) will be employed in silicon heterojunction solar cell to decrease modules cost-per-Watt-Peak. However, in order to maintain excellent cell efficiency a higher device surface/volume ratio will demand stricter requirements on surface passivation. In this frame, the status of the crystalline surface (c-Si) prior to amorphous silicon (a-Si:H(i)) plasma deposition (PECVD) plays an important role: the c-Si chemical termination influences the quality of the interface layer a-Si:H(i)/c-Si, and affect the open circuit voltage (V_oc). Previous studies have shown that smooth and fully hydrogenated c-Si surface [ lead to best quality heterojunction. These surfaces can be obtained by different wet cleaning procedures, usually terminated by an immersion in diluted HF. However, after this step, the wafer surface is highly reactive and can re-oxidize rapidly: contaminants presents in air can be adsorbed and affect wafer passivation [. For this reason, in-situ Hydrogen (H₂) plasma cleaning prior to a-Si:H(i) deposition might be an interesting option to decrease the amount of contaminant on the surface. However, the experimental window is extremely narrow, since phenomena like epitaxial growth and ion-bombardment damage can easily occur [[ and worsen the surface passivation operated by a-Si:H(i) layers. In this contribution, we present an in-situ H₂ plasma clean and show a decrease of Oxygen and Carbon on wafer surface after a short time (<10 sec), without detrimental effects on the subsequent passivation.

Abstract: The Padé approximation is a very important description of thermodynamic properties of fully ionized hydrogen at high pressures and temperatures. By comparing of several reported Padé approximants via calculation of the ion-electron interaction contribution to the Helmholtz free energy of the fully ionized hydrogen plasma, we find that Padé approximant proposed by Stolzman gives an unphysical odd local minimal appears at low temperature( ), and gradually fade away with the increase of temperature, implying a prominent limit of low temperature. While Chabrier et al. developed a more reasonable Padé approximant for the contribution of ion-electron interaction on the Helmholtz free energy. Analyses on isotherm curves indicate that the thermodynamic properties of the ion-electron interaction contribution to the Helmholtz free energy described by the revised Padé approximant is very stable at all temperatures and pressures without any unphysical effects at low temperatures.