Ge nanocrystals formation on SiO₂ by dewetting: application to memory

¹ L2MP – CNRS UMR 6137, Faculté des Sciences et Techniques de Saint Jérôme, avenue Escadrille Normandie Niemen, Case 142, 13397 Marseille Cedex 20, France
² Laboratoire de Microscopies et d'Étude de Nanostructures (EA 3799), Bât. 6, Case 30, UFR Sciences, Université de Reims, 51687 Reims Cedex 2, France

Corresponding author: franck.bassani@l2mp.fr

Received: 26 July 2007
Revised: 23 October 2007
Accepted: 26 November 2007
Published online: 6 February 2008

Abstract

Ge nanocrystals (NCs) are produced by a dewetting process during annealing of an amorphous Ge layer deposited on an ultra thin SiO₂ layer. We have investigated the characteristics of the resulting NCs as a function of the nominal Ge layer thickness. Thanks to transmission electron microscopy images, we have extracted both the wetting angle and the NCs aspect ratio. We found that these characteristics remain constant whatever is the nominal thickness in the range of 1.5 to 10 nm. These results suggest that NCs have reached their equilibrium shape. We also experimentally determined the evolution of the NCs with the nominal thickness of the amorphous layer and found a linear relation. These results are in agreement with mass conservation and energetical considerations. Moreover a memory effect was evidenced in all the samples by C − V measurements. At last, we demonstrate that the use of a patterned SiO₂ surface improves considerably the ordering of NCs and reduces their size distribution. Such a process is promising for future integration of NCs in memory devices.