Dust cloud dynamics during silicon particle deposition
Résumé
Dust cloud dynamics and behaviour are studied during dust particle successive generations in a silane based plasma. Silicon particle growth is known to exhibit a periodic behaviour, depending on experimental conditions. By having a look to the inner structure of the periodic signal (and especially to the electrical signal increase leading to the second dust particle generation), a complex unstable behaviour can be evidenced. This behavior is characterized by at least two distinct phases: a high-ordered one and a less-ordered one. Thanks to correlation between electrical measurements, laser light scattering, optical emission spectroscopy and video imaging, we show that these different phases are closely linked to the steps of dust particle formation. These diagnostics prove the presence of a void region (strongly speculated in our plasma until now). Spatially resolved depositions performed during dust successive generations show that new dust particles appear in the void region. This fact leads to an important spatial inhomogeneity in silicon particle size and density deposited on the substrate. We especially show that in some cases, the deposited dust density drastically increases between a sample deposited in the plasma center and one deposited at the plasma edge. Those phenomena of instabilities are known to be linked to dust formation in silane-based plasma [1]. They are also observed in dust cloud containing a void [2-4]. These two aspects could be linked, and further investigations are underway. [1] M. Cavarroc, M.C. Jouanny, K. Radouane, M. Mikikian, L. Boufendi, J. Appl. Phys. 99, 064301 (2006) [2] G. Praburam, J. Goree, Phys. Plasmas 3(4), 1212 (1996) [3] D. Samsonov, J. Goree, Phys. Rev. E 59, 1047 (1999) [4] M. Mikikian, L. Boufendi, Phys. Plasmas 11, 3733 (2004)