Volume 96, Issue 8, 15 October 2004
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
96(2004); http://dx.doi.org/10.1063/1.1790577View Description Hide Description
Expanding thermal plasma chemical-vapor deposition has been used to deposit microcrystalline siliconfilms. We studied the behavior of the refractive index, crystalline fraction, and growth rate as a function of the silane flow close to the transition from amorphous to microcrystalline silicon. It was found that the refractive index, a measure for film density, increases when the average sticking probability of the depositing radicals decreases. Furthermore, we studied the influence of the position at which is injected in the expanding plasma on the film density. It was found that the film density becomes higher when the is injected closer to the substrate. Both findings strongly suggest that the film density benefits from a high contribution of the radical to the growth of microcrystalline silicon.
96(2004); http://dx.doi.org/10.1063/1.1786344View Description Hide Description
The characteristics of metal plasma launched by high-current electric arc in a vacuum-arc rail gun are determined by employing electrical and magnetic probes. These measurements are validated by results from theoretical simulations. The arc coupled nonlinear circuit equations are solved simultaneously with the Newtonian arc motion and revealed the undercritically damped behavior of the arc current identical to the arc-current signal recorded by the Rogowski magnetic probe. Similarly the arc velocity and displacement derived from the signatures of -dot probes are shown to concur closely with the results of propulsion from simulation. The heating of plasma is formulated in a three-electron population regime with direct arc energy coupling through magnetohydrodynamic, ion-acoustic, Coulomb, and neutral interactions. This results in high temperature of hundreds of eV in the arc as revealed by the simulation. Hence of the rapidly cooling and equilibrating plasma that emerged from the muzzle is high around , which is confirmed by Langmuir electric probe measurements. Density of this metal plasma is shown to be in the range and includes multiple ion charge states. The exit velocity of the plasmameasured by a pair of Langmuir probes is close to and matched well with the arc velocity determined by the -dot probes and the results from simulation.
Time-resolved cavity ringdown study of the and surface reaction probability during plasma deposition of at different substrate temperatures96(2004); http://dx.doi.org/10.1063/1.1793359View Description Hide Description
Time-resolved cavity ringdown spectroscopy (-CRDS) has been applied to determine the surface reaction probability of and radicals duringplasma deposition of hydrogenated amorphous silicon . In an innovative approach, our remote plasma is modulated by applying pulsed rf power to the substrate and the resulting time-dependent radical densities are monitored to yield the radical loss rates. It is demonstrated that the loss rates obtained with this -CRDS technique equal the loss rates in the undisturbed plasma and the determination of the gas phase reaction rates of and as well as their surface reaction probability is discussed in detail. It is shown that is mainly lost in the gas phase to [reaction rate ], while the probability for to react at an surface is for a substrate temperature of . is only lost in reactions with the surface and measurements of of for substrate temperatures in the range of show that , independent of the substrate temperature. The implications for film growth are discussed.
96(2004); http://dx.doi.org/10.1063/1.1787619View Description Hide Description
Measurements and analysis of the plasma flow in an ion source made for negative ion extraction are reported in this article. The plasma flow has been measured using a Mach probe having two orthogonal probe heads. The plasma flow along the axis is driven by the electron pressure gradient, dragging along the ions via a measured ambipolar electric field against the collisional drag on the background gas. The force on the ions created by the electric field is mainly balanced by the collisional drag force. The collision between the ions and the background gas creates a pressure gradient along the flow direction. The one-dimensional plasma dynamic analysis supports the consistency of the experimental observations. The presence of a transverse magnetic filter reduces the plasma flow velocity, which could affect the negative ion production on the cesiated grid surface. A simple analysis shows that a strong plasma flow could enhance the surface production of negative ions.