Phosphorescence from tungsten clusters during laser-assisted chemical-vapor deposition of tungsten

Abstract

Phosphorescent light emission was investigated upon irradiation of WF&-12/noble gas (Ar, Kr, Ne, Xe) mixtures by At-F excimer laser. The continuous, broadband phosphorescence emission originates from excited tungsten clusters. The phosphorescence ceased with increased Xe and H, concentrations. Xe inhibits the formation of tungsten clusters and H, quenches the phosphorescence. The H, quenching rate and the unperturbed phosphorescence lifetime were determined to be 2.8X lo4 mbar-t s-' and 23 ,us, respectively. The intensity dependence of phosphorescence on the WF, partial pressure shows a rising part, then a declining part, and finally an increasing part again. It was shown that the declining part can be interpreted by scattering of the emitted phosphorescence. The phosphorescence intensity was dependent on the noble gas/H, concentration ratio. This effect was explained in terms of the thermal conductivity of the WF&-$/noble gas mixture, which influences the lifetime of the activated subfluorides and, thus, the cluster formation and growth rate. The intensity of the laser beam had a nonlinear effect on the phosphorescent light intensity due to the nonlinearly coupled photolytical steps of WF, and of the subfluorides. 0 1995 American Institute of Physics.

Light emission from tungsten nanoparticles during laser-assisted chemical vapor deposition of tungsten

“…The agreement between the measured/corrected spectra and the Planck curves is very good so the conclusion is that the radiation emerging from WF 6 /H 2 /Ar ͑and therefore WF 6 /H 2 /noble gas͒ 8 mixtures, illuminated by ArF excimer laser, is blackbody-like and not phosphorescence as stated before. 8,10 Since it was proven that the broadband radiation originates from tungsten nanoparticles 6 it is obvious that the blackbody-like radiation comes from these nanoparticles.…”

“…8,10 Briefly, a stainless steel vacuum chamber with quartz top and front windows was used as a reaction chamber in flow through arrangement. Reactor cross section was ϳ12 cm 2 and the laser beam was aligned parallel to it.…”

“…7 Moreover, a broadband radiation was also observed and assigned to phosphorescence of tungsten nanoparticles. 6,8 In this work supplementary results to this broadband emission are presented, and it is shown that the phosphorescence is in fact a blackbody-like emission. This allows measuring the temperature of the hot particles heated by subsequent laser pulses following the particle formation.…”

“…4,5 It was shown that for a wide range of parameter sets, the tungsten deposition goes through nanoparticle formation from WF 6 /H 2 /M (MϭAr, Kr, Ne, Xe) gas mixtures irradiated by an ArF excimer laser (ϭ193 nm). [6][7][8][9] This is due to gas phase reactions, since the laser beam is aligned parallel to and just above the substrate surface. For metallization purposes the particle formation is an avoidable effect, on the other hand, this LCVD process may be utilized for nanoparticle-film deposition.…”

Electromagnetic excitation of nano-carbon in vacuum

“…Its transforming efficiency is found to be more than 80%, which is quite different from the normal photoluminescence. In this paper, we show that it is the thermal radiation from nano-carbon (nano-radiation) which often makes us confuse it with photoluminescence (PL) [9,10]. With good color rendering, this white radiation from nano-carbon may be an ideal lighting source, even as a white point source in the scientific experiments.…”