Low Energy Hydrogen Plasma Research Articles

Effects of hydrogen molecular desorption on the heat load on plasmafacing materials

Measurements of the heat load on C (isotropic graphite) and W targets wereperformed in linear steady plasma facility MAP-II (materials and plasma),which produces a low-energy hydrogen plasma 10-20 eV with an electron densityof (1.0-5.0)×1017 m-3. From the measurements of the heatremoved by the target coolant, heat flow to the target and Balmer intensitiesnear the targets we found that the heat load was larger on the C target than Wbecause of higher molecular hydrogen desorption. The population densities ofvibrational levels in the d 3Πu state of molecular hydrogenshifted to higher levels near the C target in the spectroscopy of the Fulcherband. From these results, it was found that molecular hydrogen desorptionplays an important role in the heat load on plasma facing materials and itdepends on the materials, which have different characteristics of hydrogenmolecular desorption and energy states of desorbed hydrogen.

Spectroscopic study on the reflected neutral particles from solid surface

Low energy hydrogen plasma was applied to copper, molybdenum and tungsten targets by the steady state linear plasma facility MAP (Material And Plasma) to study reflected neutral particles. The H α (656.285 nm) spectra emitted from the reflected hydrogen atoms were measured to investigate the energy distribution and the angular distribution of the reflected hydrogen atoms. We found that the spectrum was composed of two groups. One is the low energy component (group 1) and the other is the high energy (group 2). The backscattered hydrogen atoms is found to be included in the group 2 spectrum from the results of the spectrum broadening and shift. The relation between the characteristics of target materials and reflection processes was also discussed.

Study of Particle Reflection by Linear Plasma Facility Map

Low energy hydrogen plasma was applied to a graphite target by the linear steady plasma facility MAP(Materials And Plasma). The Hα (656.285 nm) spectrum emitted from reflected hydrogen atoms were measured to investigate hydrogen release processes from a graphite target. Broadening, peak shift and intensity of the Hα spectrum were compared with those in the previous experiments of tungsten target. The results indicated that a large fraction of hydrogen particles is released as molecules from the graphite surface.

The Role of Surface Chemistry in Bonding of Standard Silicon Wafers

Hydrophilic silicon surfaces become hydrophobic without microroughening after 200°C low energy hydrogen plasma cleaning. The fully hydrogen‐terminated silicon surfaces do not bond to each other, not even by the application of external pressure. A subsequent 400 to 600°C, 4 min thermal treatment in ultrahigh vacuum converts the wafer surfaces to hydrophilic and bondable which can be attributed to desorption of hydrogen from the surfaces. Hydrophobic silicon surfaces prepared by a dip in HF (without subsequent water rinse) are terminated by H and a small amount of F, or by H and a small amount of OH (after subsequent water rinse). Hydrogen bonding of Si‒F⋯(HF)⋯H‒Si or Si‒OH⋯(HOH)⋯OH‒Si across the two mating surfaces appears to be responsible for room temperature spontaneous hydrophobic or hydrophilic wafer bonding, respectively.

Process Optimization for the Fabrication of the Thin PtSi Schottky Barrier Diode IRCCD

AbstractHigh quality abrupt junction PtSi thin film prepared by the MBE system with in situ precleaning and annealing was obtained. Wet etching and low energy hydrogen plasma excitation to generate H-terminated Si surface and low temperature thermal desorption were used to clean the substrate. IRCCD thus fabricated achieved the quantum efficiency 0.8%. TEM, STM/AFM, AES/ESCA, and RBS were used to monitor the fabrication processes.

Dry Cleaning of Silicon Wafers in a Low Energy Hydrogen Plasma

Dry Cleaning of Silicon Wafers in a Low Energy Hydrogen Plasma

Hydrogen passivation of delta doped GaAs

We report on hydrogen passivation of Si and Be delta doped GaAs grown by molecular beam epitaxy. The delta doped structures were exposed to low energy and low frequency hydrogen and deuterium plasmas. Secondary ion mass analysis shows hydrogen and deuterium incorporation at the dopant sites. Electrical analysis of the samples reveals total deactivation of the Si atoms and only a partial (35%–50%) deactivation of the Be atoms. Photoluminescence measurements of the hydrogenated Si doped structures indicate a disappearance of above band gap transitions associated with free carriers and enhancement of transitions related to background acceptors.

The arcing behaviour of metals in contact with a low energy hydrogen plasma

Previous work has been extended under highly reproducible conditions in an attempt to ascertain the mechanism of arc initiation. Results show that only quite small potential differences, of the order of 10 volts, need exist between parent metal and inclusions therein in order to initiate arcing. The proposed mechanism leads to the production of a vapour of impurity atoms above the cathode surface and is based upon the electrical properties of the interface between metal and inclusions which are viewed as being semi-conducting in character.