Development of a process simulation capability for the formation of titanium nitride diffusion barriers

Titanium nitride (TiN) films deposited by chemical vapor deposition (CVD) techniques are of interest for a wide range of commercial applications. In this report, the authors describe a mechanism that predicts Tin film growth rates from TiCl{sub 4}/NH{sub 3} mixtures as a function of process parameters, including inlet reactant concentrations, substrate temperatures, reactor pressures, and total gas flow rates. Model predictions were verified by comparison with the results of TiN deposition experiments in the literature and with measurements made in a new stagnation-flow reactor developed for the purpose of testing deposition mechanisms such as this. In addition, they describe ab initio calculations that predict thermodynamic properties for titanium-containing compounds. The results of calculations using Moeller-Plesset perturbation theory, density functional theory, and coupled cluster theory are encouraging and suggest that these methods can be used to estimate thermodynamic data that are essential for the development of CVD models involving transition-metal compounds. Finally, measurements of the adsorption and desorption kinetics of NH{sub 3} on TiN films using temperature-programmed desorption are described and their relevance to TiN CVD and mechanism development are discussed

Radiative and SOL experiments in open and baffled divertors on DIII-D

The authors present recent progress towards an understanding of the physical processes in the divertor and scrape-off-layer (SOL) plasmas in DIII-D. This has been made possible by a combination of new diagnostics, improved computational models, and changes in divertor geometry. They have focused primarily on ELMing H-mode discharges. The physics of Partially Detached Divertor (PDD) plasmas, with divertor heat flux reduction by divertor radiation enhancement using D{sub 2} puffing, has been studied in 2-D, and a model of the heat and particle transport has been developed that includes conduction, convection, ionization, recombination, and flows. Plasma and impurity particle flows have been measured with Mach probes and spectroscopy and these flows have been compared with the UEDGE model. The model now includes self-consistent calculations of carbon impurities. Impurity radiation has been increased in the divertor and SOL with puff and pump techniques using SOL D{sub 2} puffing, divertor cryopumping, and argon puffing. The important physical processes in plasma-wall interactions have been examined with a DiMES probe, plasma characterization near the divertor plate, and the REDEP code. Experiments comparing single-null (SN) plasma operation in baffled and open divertors have demonstrated a change in the edge plasma profiles. These results are consistent with a reduction in the core ionization source calculated with UEDGE. Divertor particle control in ELMing H-mode with pumping and baffling has resulted in reduction in H-mode core densities to n{sub e}/n{sub gw} {approx} 0.25. Divertor particle exhaust and heat flux has been studied as the plasma shape was varied from a lower SN, to a balanced double null (DN), and finally to an upper SN

Divertor erosion in DIII-D

Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point (OSP) of two divertor plasma conditions: attached (T{sub e} > 40 eV) ELMing plasmas, and detached (T{sub e} 1,000x erosion rate of aligned surfaces). Leading edge erosion, and subsequent carbon redeposition, caused by tile gaps can account for half of the deuterium codeposition in the DIII-D divertor

Low-energy {sup 4}He{sup +} scattering from deuterium adsorbed on stepped Pd(331)

We have taken angle-resolved data for the scattering of low-energy (Pd ledge atoms. A strong quasi-elastic scattering signal of {sup 4}He{sup +} from D ({sup 4}He{sup +}/D) was observed at a forward scattering angle of {theta} = 25{degrees} and an incidence angle of {alpha} = 76{degrees} from the (331) normal. The results agree with shadow cone calculations of scattering first from Pd ledge atoms followed by a second event, {sup 4}He{sup +}/D. The resultant adsorption geometry shows D to reside in the quasi- threefold ledge site on the surface directly above the bulk fcc octahedral void. These results are consistent with the previous{sup 4}He{sup +} scattering study of the geometrically related Pd(110)- D(ads) system

Plasma–surface interactions on liquids

Liquid plasma-facing surfaces have been suggested as an option for advanced fusion devices, particularly in regions where solid materials may not survive over long operating periods. Because liquid surfaces can be replenished, they offer the possibility of tolerating intense particle bombardment and of recovering from off-normal events. As a preliminary step in understanding the nature of plasma-surface interactions on liquids, the authors consider some of the surface processes occurring in liquids undergoing irradiation by energetic particles. These include (1) sputtering, (2) segregation of liquid component species and impurities, (3) evaporation, and (4) trapping and release of incident particles. Aspects of these processes are examined for several candidate liquids, which represent three types of low-Z liquids: pure metals (Li), metallic alloys (Sn-Li), and compound insulators (Li{sub 2}BeF{sub 4})