The early stages of stress development during epitaxial growth of Ag/Cu multilayers
- PDF / 298,497 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 89 Downloads / 252 Views
Q5.32.1
The early stages of stress development during epitaxial growth of Ag/Cu multilayers S. Labat, F. Bocquet, T. Bigault*, L. Roussel#, G. Mikaelian, C. Alfonso, A. Charai, O. Thomas TECSEN, Université Aix-Marseille III, case 262, Faculté de St Jérôme, Marseille 13397 Cedex 20 France
ABSTRACT The early stages of stress development during epitaxial growth of metal layers with a large misfit in lattice parameters still need in-depth understanding. In this particular study we have focused on Ag-Cu system, which is immiscible and exhibit a large 14% misfit in lattice parameters. Ag/Cu multilayers have been grown by ultrahigh-vacuum evaporation on Si (111) maintained at -20°C, 35°C or 110°C. The thickness of the individual layers is about 100 Å. All the films present the same (111) orientation with a well defined in-plane orientation: Cu or Ag // Si. The stress was monitored during growth with a home-made laser curvature measurement device. The stress vs thickness behaviour is highly asymmetric when comparing Ag/Cu and Cu/Ag. Indeed Ag grown on Cu does not develop any measurable stress at any thickness or temperature, whereas Cu grows on Ag under tensile temperature and thicknessdependent stress. The temperature dependence of this stress relaxation cannot be interpreted with a standard relaxation model including dislocation motion. A possible way to understand the stress temperature dependence is to consider the evolution of microstructure during growth.
INTRODUCTION Thin films deposited on solid substrates invariably develop elastic stresses. The coherent two-dimensional (2D) growth of a film with a small difference in lattice parameter with the substrate is a well described and understood situation 1. Other cases such as systems with a large misfit in lattice parameters 3-6 and/or with a 3D growth behavior 7 still need an in-depth understanding. When the relative difference in lattice parameters between the film and the substrate exceeds typically 10%, the usual mechanisms, which describe a coherent pseudomorphous regime followed by plastic 1 or elastic 8, 9 relaxation, do not seem to work any more. There are indications that interfacial mixing 10 may play a role or growth of a relaxed superstructure may occur from the early stages on 11, 12. This article reports on an in situ study of stress development during the growth of Ag on Cu (111) and Cu on Ag (111). The binary Ag-Cu system is immiscible and characterized by a very large size difference of 14%. The stress has been monitored in situ during UHV evaporation by measuring substrate bending. In the following we discuss: the stress related to the growth of Ag on Cu(111) and Cu on Ag(111) at different temperatures. -------------------------------------------------------------------------------------------------------------------*
Present address : ESRF - BM05, BP 220, 38043 Grenoble Cedex France Present address : FRESNEL, Université Aix-Marseille III, Faculté de St Jérôme, Marseille 13397 Cedex 20 France
#
Q5.32.2
EXPERIMENTAL Ag-Cu multilayers, with 4 per
Data Loading...
