Journal of Crystal Growth 308 (2007) 26–29 Epitaxial growth of Ge on a thin SiO 2 layer by ultrahigh vacuum chemical vapor deposition M. Halbwax a,b , C. Renard a,b,Ã , D. Cammilleri a,b , V. Yam a,b , F. Fossard a,b , D. Bouchier a,b , Y. Zheng c , E. Rzepka d a IEF, CNRS, UMR 8622, Orsay F-91405, France b Univ Paris-Sud, Orsay F-91405, France c Institut des Nanosciences de Paris, UMR 7588, Universite´Denis Diderot-Paris 7, Paris, France d Laboratoire de Physique des Solides et de Cristallogene`se (LPSC), CNRS (UMR 8635), Universite´de Versailles Saint-Quentin-en-Yvelines 1, place Aristide Briand, 92195 Meudon Cedex, France Received 21 June 2007; received in revised form 20 July 2007; accepted 25 July 2007 Communicated by R. Kern Available online 6 August 2007 Abstract In this work, the growth of germanium by ultrahigh vacuum chemical vapor deposition on a 0.6 nm thick SiO 2 layer formed on Si(0 0 1) is investigated by in situ reflection high-energy electron diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Because Ge does not grow from germane on SiO 2 , nucleation sites were created by exposure of the surface to SiH 4 at 650 1C prior to the Ge deposition, which is initiated at 600 1C. The first stage of Ge growth proceeds via the formation of dots that exhibit the same crystalline orientation as the Si substrate. They are assumed to grow from small apertures opened in the silica layer due to the reduction of SiO 2 by Si. For further deposition time, {1 1 1}- and {1 1 3}-facetted Ge crystals are formed and the growth remains monocrystalline. The so-formed Ge crystals are found to be completely relaxed and contain some emerging defects, identified as stacking faults. No misfit or threading dislocations are observed. Consequently, the interface between Ge and the SiO 2 layer remains perfectly sharp and free of defects. This relaxation without misfit dislocation is due to SiO 2 layer which acts as a buffer layer that prevents the Si substrate from imposing its lattice parameter on the Ge crystal. r 2007 Elsevier B.V. All rights reserved. PACS: 81.15.Gh; 68.47.Fg; 68.35.Fx Keywords: A1. Crystal structure; A1. Reflection high energy electron diffraction; A3. Chemical vapor deposition processes; B1. Germanium silicon alloys 1. Introduction The interest paid to the heteroepitaxy of germanium on Si(0 0 1) has never failed in the last years because of the ability of germanium to be integrated in novel devices built on silicon. However, due to the large lattice mismatch with Si (4.2%), it is not easy to obtain Ge films with suitable characteristics. Even if a relevant deposition procedure can keep free of defect the most part of the epilayer, the relaxation process of Ge on silicon implies the presence of a high density of misfit dislocations located at the very interface between Si and Ge [1,2]. This renders these layers inappropriate for applications involving the interfacial region in electronic transport. On the other hand, the fabrication of Ge quantum dots, via the Stranski–Krasta- nov growth mode, implies the formation of a wetting layer [3] which can create a short circuit between dots. Recently, the growth of Ge dots without the Strans- ki–Krastanov transition has been achieved on 1.2–7 nm thick SiO 2 thin layers by ultrahigh vacuum chemical vapor deposition (UHV-CVD) [4,5], or on a 0.3 nm thick SiO 2 film by molecular beam epitaxy (MBE) [6]. Moreover, ARTICLE IN PRESS www.elsevier.com/locate/jcrysgro 0022-0248/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2007.07.047 Ã Corresponding author. IEF, CNRS, UMR 8622, Orsay F-91405, France. E-mail address: charles.renard@ief.u-psud.fr (C. Renard).