The role of radicals and clusters in thermal plasma flash evaporation processing

The prominent features of plasma flash evaporation may be caused by cluster deposition under high net flux of radicals. In order to clarify such features quantitatively, the atomic oxygen flux (Γ0) and cluster size (d) in 200 Torr RF thermal Ar-O2 plasma were measured on the substrate. It was found that Γ0 higher than 1019 atoms/cm2·s can be easily acheived in this processing and this value corresponds to frozen atomic oxygen fraction 7 %. The cluster size of YBCO was estimated to be about 0.3 to 10 nm. 0.8 nm cluster deposition under Γ0 higher than 6 × 1018 atoms/cm2·s made it possible to deposit fine epitaxial YBCO films with Tc = 90K on SrTiO3 (100) with extremely high deposition rate around 2.2 μm /min.