Hydrogen Afterglow Research Articles

UV and air stability of high-efficiency photoluminescent silicon nanocrystals

The effects of UV light and air exposure on the photoluminescent properties of nonthermal plasma-synthesized silicon nanocrystals (Si NCs) were investigated. Si NCs with high-efficiency photoluminescence (PL) have been achieved via a post-synthesis hydrosilylation process. Photobleaching is observed within the first few hours of ultra-violet (UV) irradiation. Equilibrium is reached after ∼4h of UV exposure wherein the Si NCs are able to retain 52% of the initially measured PL quantum yield (PLQY). UV-treated Si NCs showed recovery of PL with time. Gas-phase passivation of Si NCs by hydrogen afterglow injection improves PLQY and PL stability against UV and air exposure. Additionally, phosphorous doping can also improve UV stability of photoluminescent Si NCs.

In Situ Xps Studies of the Deposition of Thin Films from Tetrakis(Dimethylamido)Titaniumorganometaluc Precursor for Diffusion Barriers

AbstractWith the decreasing minimum feature size of integrated microcircuits, a low-temperature, chlorine-free CVD process is needed for the deposition of TiN diffusion barriers. A problem during the thermal deposition of titanium nitride from organometallic precursors, such as tetrakis(dimethylamido)titanium, is the high content of carbon in the films. In situ XPS study reveals that most of the carbon is present as CHx inclusions with a smaller but not negligible amount of carbidic component. This can be avoided by using ammonia, but the high rate of the reaction in the gas phase makes the control of the film growth difficult. Most of the problems can be resolved when using hydrogen afterglow.

Organometallic vapor-phase homoepitaxy of gallium arsenide assisted by a downstream hydrogen afterglow plasma in the growth region

In situ generated arsenic hydrides are reacted downstream with trimethylgallium (TMGa), both in the presence of and in the absence of a downstream hydrogen afterglow plasma. The homoepitaxial activation energy dramatically changes from 62 kcal/mol for the pure thermal to 21 kcal/mol for the plasma-assisted growth. The carbon incorporation mechanism for the plasma-assisted growth at temperatures less than 400 °C has a distinct activation energy for carbon incorporation of 23 kcal/mol, independent of V-III ratios. At temperatures above 400 °C, the level of carbon incorporated in the films reaches a level that appears to be dependent on the gas-phase precursor V-III ratio. The activation energy of the low-temperature region is consistent with the surface decomposition of arsenic hydrides.

High-resolution electron energy-loss spectrum of discharged hydrogen in the energy-loss region 10 to 12.5 eV

High-resolution electron energy-loss spectra of the hydrogen afterglow have revealed transitions from the first two vibrationally excited levels of the ground state to the B1 Sigma u+ state in the energy-loss range 10.5 to 11.2 eV. Franck-Condon factor calculations are used to obtain an estimate of the vibrational concentration in the ground state.

Reproducible control of the voltage of Langmuir probes in steady-state and afterflow plasma (regulation circuit)

A regulation circuit is described that makes possible very accurate probe measurements by virtually eliminating work function drift and plasma potential fluctuation effects on the probe characteristic. By the use of a reference probe and repeated measurement of the floating potential of the active probe in time intervals that are short compared to the time constant of the work function drift, a voltage scale can be established for the probe with an accuracy and repeatability of a few mV. As an application of the method, the rapid thermalization of the electrons and the appearance of the fundamental diffusion mode in a hydrogen afterglow are shown.

Electron Loss Process in the Hydrogen Afterglow

Electron loss processes in the afterglow of very pure hydrogen have been studied by the microwave technique. The conclusion is drawn that within the error of the experiment, no electron-ion recombination is observed, and that high-mode diffusion is very evident. By properly accounting for the high diffusion modes, the results are given as ${D}_{a}p=700\ifmmode\pm\else\textpm\fi{}50$ ${\mathrm{cm}}^{2}$-mm Hg ${\mathrm{sec}}^{\ensuremath{-}1}$ with the electron-ion recombination less than 3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ ${\mathrm{sec}}^{\ensuremath{-}1}$.