Volume 91, Issue 7, 01 April 2002
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
Control of plasma parameters and wall sheath voltage in radio frequency magnetron discharge by grid bias91(2002); http://dx.doi.org/10.1063/1.1454192View Description Hide Description
The plasma of a radio frequency (rf) magnetron discharge used for deposition of thin films was separated by a mesh grid into source (negative glow) and diffusion(deposition)plasmas.Langmuir probes were used to measure the potential, electron density, and electron temperature of both plasmas. While the change of the grid bias affected the diffusionplasma parameters, it did not change the sourceplasma parameters (except the potential). The use of the biased grid resulted in a decrease of temperature and an increase of density of plasma electrons in the film deposition region. With an increase of the grid biasing potential, the plasma potential increased in order to maintain a negative bias voltage across the grid sheath, the electron temperature increased, and the electron density decreased. The biased-grid-induced change of the plasma potential and the bias voltage across the wall sheath is explained based on the model of the asymmetric double probe, which is formed by the discharge chamber wall and the grid. The effect of the biased grid on the diffusionplasma parameters is discussed accounting for the particle transport phenomena in the system.
Distributions of and radical densities in laser-ablation carbon plumes measured by laser-induced fluorescence imaging spectroscopy91(2002); http://dx.doi.org/10.1063/1.1455151View Description Hide Description
We measured temporal variations of the distributions of and radical densities in carbon plumes produced by laser ablation of graphite in ambient He gas. Laser-induced fluorescence imaging spectroscopy was used for the measurement. The temporal variations of total numbers of and contained in plumes were evaluated by integrating the density distributions. The experimental observations have shown that the gas-phase production of is comparable to the direct production from the target, while is mainly produced in gas phase by three-body reactions between C and In addition, we have discussed a scenario for the temporal evolution of heavy clusters with The present results are useful for understanding initial formation processes of carbon clusters in laser-ablation plumes.
91(2002); http://dx.doi.org/10.1063/1.1455139View Description Hide Description
A global plasma model for an ionized physical vapor deposition (IPVD) system is described. The model predicts the density of electrons, excited state, Ar and ironized and the density of atomic N and and the electron temperature. The computed results are compared to experimental measurements of a titanium nitride IPVD reactor to confirm the validity of the model. The reactor consists of an inductively coupled plasma source that is fed by argon, nitrogen, and sputtered titanium. The dissociation of nitrogen in the discharge is typically found to be in the range of 10%–30%. The electron temperature is 1.8 eV, and the ion density is between and The ion density is found to decrease as nitrogen is added to the Ar discharge due to collisional losses associated with molecular states. In the metal mode of operation, the atomic nitrogen density is suppressed by the Ti-rich reactor walls. As the nitrogen flow rate is increased, the target and walls become nitrided and the density of N increases an order of magnitude to The ionization fraction for the depositing flux of titanium is typically 0.4–0.7. The model is easily adapted to other technologically relevant diffusion barrier layer materials such as WN and TaN.
91(2002); http://dx.doi.org/10.1063/1.1454194View Description Hide Description
Recently the dust charging and levitating in a collisionless cathodesheath with energetic electron beam were analyzed theoretically [D. Wang et al. J. Appl. Phys. 88, 1276 (2000)]. In this article, the model is extended in order to take into account the effects of the dust charge density on the plasma sheath equilibrium. The results show that dust density plays an important role both in the dust charging process and on the sheath potential profile.