No abstract

Silicon nitride thin.films are deposited on silicon woofers at room temperature when silane gas is injected in a nmogen .[lowing post-discharge. Reactive processes involving silane molecules and hmg-I(fctime nitrogen species are studied, pointing out the r, onreactivity of the N:( A 'v+ ) metastable state, the low contribution af the vibrationally excited nitrogen ground-state molecules, and the high reactivity of N('~S) atoms. Spectroscopic observations per/brined in the reaction region are correlated with thin-film characteristics.

The reaction of SiH4 with nitrogen is studied in a post-discharge device by means of a mass spectrometer. The atomic nitrogen is produced in a dc discharge and the silane is injected downstream and reacts mostly with the atomic nitrogen. Induced effects due to the vibrational excitation of the molecules (change in the ionization cross section when molecules are ionized in the ionization chamber of the mass spectrometer) are minimized by adding a buffer gas (N2) that is injected downstream with the silane. The reaction scheme of the silane injected in the nitrogen post-discharge, proceed via the dissociation of the silane with atomic nitrogen according to SiH4 + N⟶k1SiH2 + NH2. Then the two radicals SiH2 and NH2 produced react also with the atomic nitrogen via the reactions SiH2 + N⟶k2products and NH2 + N⟶k2products. These two radicals react also together via SiH2 + NH2⟶k4products. The absolute concentrations of the main species considered in the reaction mechanism are measured using different methods and absolute concentrations of the species are compared with results given by a kinetic model. A Runge-Kutta-Merson algorithm is used in order to resolve the set of ordinary differential equations. The experimental results are well fitted with a relative accuracy of 20%, using the reaction rate constants k1, k2, k3 and k4 in the ranges (1.2-1.7)×10-16 m3 s-1, (9.0-13.7)×10-16 m3 s-1, (5.8-8.8)×10-16 m3 s-1 and (4.2-6.2)×10-16 m3 s-1, respectively.

Experiments with coaxial plasma guns at currents in excess of ten megamperes have resulted in the production of high-voltage pulses (0.5 MV) and hard x radiation (10–200 keV). The x-radiation pulse occurs substantially after the high-voltage pulse suggesting that high-energy electrons are generated by dynamic processes in a very high speed (≳106 m/s), magnetized plasma flow. Such flows, which result from acceleration of relatively low-density plasma (10−4 vs 1.0 kg/m3) by magnetic fields of 20–30 T, support high voltages by the back electromotive force-u×B during the opening switch phase of the plasma flow switch. A simple model of classical ion slowing down and subsequent heating of background electrons can explain spectral evidence of 30-keV electron temperatures in fully stripped aluminum plasma formed from plasma flows of 1–2 × 106 m/s. Similar modeling and spectral evidence indicates tungsten ion kinetic energies of 4.5 MeV and 46 keV electron temperatures of a highly stripped tungsten plasma.

Abstract-Using a 1313-,F, 3-nH, 120-kV, 9.4-MJ SHIVA Star capacitor bank, we have performed vacuum inductive store/plasma flow switch (PFS) driven implosions of low mass (200-400 jig/cm2) cylindrical foil liners of 2-cm height and 5-cm radius. This technique employs a coaxial discharge through a plasma armature, which stores magnetic energy over 3-4 Its and rapidly switches it to an imploding load as the plasma armature exits the coaxial gun muzzle. The current transferred to the load by the PFS has a rise time of less than 0.2 As.With 5-MJ stored energy, we have driven fast liner implosions with a current of over 9 MA, obtaining an isotropic equivalent 2.7-TW 0.5-MJ X-ray yield.