Plasma parameter dependence of critical particle size at the moment of void formation in RF silane plasmas

Abstract

Although dust-free voids are frequently observed in many dusty plasmas, experiments regarding the critical particle size for the void formation have not been reported much. In this work, the dust particle size measurement at the critical moment of the void formation was performed by the polarization- sensitive laser light scattering method (PSLLS) as the input rf power was varied in the silane plasmas in which particles were created and grown. The electron temperature and ion density were also measured by a floating probe1, and the relation between the parameters was studied. The results show that the critical particle size was decreased from 50 nm to 35 nm as the rf power was increased from 30 W to 100 W. In addition, the electron temperature and ion density were increased from 4.7 eV to 6.2 eV and from 7.0×109 cm-3 to 1.4×1010 cm-3, respectively. To investigate the mechanism of the void formation, we calculated the critical particle size for the void with measured plasma parameters using a simple onedimensional force balance equation along the horizontal direction (parallel to the electrode). Consequently, the calculated particle sizes were in good agreement with the measured ones.