Impedance laser spectroscopy in a small RF-excited neon discharge

Laser impedance spectroscopy in a miniature neon RF-discharge operating at 0.27 bar was performed. The dominant role of the metastable atoms to the size and the sign of the RF-signal was investigated. Excellent linearity of the RF-signal but poor detection sensitivity of excited metastable neon atoms were found at low laser powers.     

Localized surface plasmon resonance of silicon compounds adsorbed on silver nanoparticles

A simple method to produce silver nanoparticles on a glass surface from silver nanolayer deposited by magnetron sputtering and thermal annealed is presented. Localized surface plasmon resonance of nanoparticles shows a red shift depending on the silver nanolayer thickness, the refractive index and the thickness of an ultra-thin silicon compound adsorbed on the surface. A highly enhanced Raman spectrum of the characteristic groups of a silicon compound adsorbed on the nanoparticles surface was obtained.     

Spectroscopic measurements of excited particles in a N2 gas RF plasma-assisted carbon laser ablation

In this work, we investigated a carbon plasma plume produced by laser ablation of a graphite target in a nitrogen gas environment. The spatial distributions of C and N atoms were measured by time-resolved absorption spectroscopy. The spatial distributions of the relative densities of CN radicals, C₂, and C₃ molecules were measured using time-resolved emission spectroscopy. We determined that nitrogen gas produced an increase in carbon atom and molecule densities in the ablation plume. It was observed that the addition of RF plasma to the plume increased the CN radicals and C atom densities, and decreased the C₂ and C₃ molecule densities. The RF plasma changed the evolution of various fractional species of C, N, CN, C₂, and C₃ in the ablation plume. The chemical reactions with and without RF plasma were explained using the evolution and density of the fractional species of C, N, CN, C₂, and C₃in the plume. PACS 52.38.Mf; 42.62.Fi; 33.20.-t; 81.05.Uw     

Hollow Cathode Effect with Double Axial Electron Injection

The paper presents a new type of HCE glow discharge obtained with double plane-conical cathodes. The two identical cathodes are tronconical and screened with 1 mm² mailed wire net with a 3.5 mm diameter central washer each. The discharge is obtained between the two cathodes and a ring shaped anode equally distant from both. Optimum intercathodic span is 4 mm, allowing for maximum amplifications at the optimum pressure values for the two gases. Employed helium and argon are spectral pure. At the given distance and depending on voltage and gas pressure, a double axial electron self injection cathode effect is obtained between the electrodes, consisting of very large increase of current and radiations.     

Amorphous carbon nitride film preparation by plasma-assisted pulsed laser deposition method

Amorphous carbon nitride (aCN_x) films were prepared by pulsed laser ablation of graphite in N₂ RF plasma. The film property was compared with that prepared in N₂ gas. The N₂ plasma was generated by a mesh electrode, which was inserted between a graphite target and a Si substrate. The gas pressure p_N2 was varied from 10 to 100 mTorr. The film deposition rate exponentially decreased with p_N2 for both the plasma and gas environment. X-ray photoelectron spectroscopy analysis showed that the ratio of nitrogen content to the carbon one ([N]/[C]) of the aCN_x film surface deposited in the N₂ plasma was 2 times higher than that obtained in the N₂ gas. The film structure was shown by Raman spectroscopy analysis that sp² clustering was enhanced with increasing the [N]/[C]. The effect of plasma on aCN_x film deposition was discussed. PACS 81.15.Fg; 79.60.-i; 81.05.Uw     

Growth of carbon nanotubes on Fe or Ni-coated Si substrate by feeding with carbon from a graphite ablation plume

By feeding with carbon clusters from the ArF excimer laser (=193 nm) ablation of graphite target, carbon nanotubes (CNTs) were grown on Fe and Ni films deposited on SiO₂/Si substrates, which were set inside a quartz tube with Ar gas pressure of 500 Torr operating at 1100 °C. Optical emission spectroscopic observation of the ablation plume of graphite and Ni/Y catalyst was performed in the Ar gas for a pressure range of 0–600 Torr at room temperature and 1000 °C. The emission band intensity of C₃ (ù_u) at the distance of 2 mm from the target increased with increasing Ar gas pressure. PACS 79.20.Ds; 81.07.De; 39.30.+w     

Attenuated total reflectance spectroscopy of simultaneous processes: Corrosion inhibition of cuprous oxide by benzotriazole

Attenuated total reflectance (ATR) spectroscopy was used to perform in situ studies of the corrosion inhibition of cuprous oxide (Cu₂O) by benzotriazole (BTA) in aqueous solution at concentrations from 1 to 20 μM. Because two separate processes occur simultaneously, that of Cu₂O corrosion and corrosion inhibition by BTA adsorption, the spectral information was subjected to deconvolution by a conjugate gradient minimization algorithm. Under these conditions, a solution phase concentration of 7-10 μM BTA nearly completely inhibited the corrosion of Cu₂O in deionized water. Using a Langmuir adsorption model, this represented only 25% of the maximally covered surface area.     

Attenuated total reflectance spectroscopy of coumarin organosilane molecules adsorbed on a fused silica surface

Attenuated total reflectance (ATR) spectroscopy was used to investigate the adsorption of coumarin organosilane molecules onto a fused silica surface. The difference between the absorption spectra of the molecules on the surface and in solution was explained by the interaction of the adsorbed coumarin organosilane molecules with the hydroxyl groups on the fused silica surface. This interaction produces a perturbation of the π electron distribution and the electronic transitions of the coumarin chromophore of the organosilane molecules adsorbed on the surface. From the kinetics adsorption curves, the calculated enthalpy values of 74.8 ± 5.2 kJ mol⁻¹ and free energy of −38.22 ± 0.70 kJ mol⁻¹ at 23 °C indicates a chemisorption process. The high sensitivity of ATR spectroscopy allows the detection of a monolayer formed by a 10 nM concentration of coumarin organosilane molecules, which covers more than half of the maximum surface coverage at 60 °C.     

Time-resolved Optical Emission Spectroscopy in Water Electrical Discharges

The characteristics of the plasma initiated in ultrapure water between pairs of tungsten and tantalum electrodes were investigated by time-resolved optical emission spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depended on the electrode material, but had been independent on the polarity of the applied voltage pulses. All the reactive species presented the same evolution with time and have been identified with high concentration in the emission spectra between the pulses. The current–voltage characteristics showed the features of a spark discharge for the both types of electrodes used in the process. When tantalum electrodes were used to generate the discharge, a broad emission continuum (350–940 nm) dominated the spectrum due to a transition to arc discharge.