The effect of Sb on the oxidation of Ge quantum dots Y.S. Lim, F. Bassani, A. Portavoce, A. Ronda, S. Nozaki, I. Berbezier * CRMC2-CNRS Case 913 Campus de Liminy, 13288 Marseille Cedex 9, France Abstract A study on the dry thermal oxidation of Ge quantum dots is proposed. To find the effect of Sb on the oxidation, two kinds of Ge quantum dots were grown on Si (001) substrate with or without a predeposition of Sb. They were oxidized with conventional dry thermal oxidation method at 900 8C and characterized using transmission electron microscopy. Like in the numerous reports on the dry thermal oxidation of SiGe layers, the oxidation rate of Ge quantum dots directly grown on Si layer without Sb was the same to that of pure Si. However, the oxidation rate of the Ge islands grown with a Sb monolayer was significantly enhanced. This result suggests that the lower activation barrier due to the catalytic effect of Sb is the origin of the enhancement of the oxidation rate of the Ge quantum dots grown on Si. # 2003 Elsevier B.V. All rights reserved. Keywords: SiGe; Quantum dot; Oxidation; Doping; Transmission electron microscopy PACS numbers: 81.65.Mq; 61.72.Tt; 61.16.Gg 1. Introduction Due to the large difference of the heat of formation between SiO 2 and GeO 2 at high temperature oxidation, SiO 2 is more stable oxide than GeO 2 in the thermal oxidation of SiGe layer [1]. As a result, the thermally grown oxide is nearly pure SiO 2 , and Ge atoms are rejected from the oxide and piled up below the oxide layer [2  /5]. This Ge pileup layer has been regarded as the critical problem of using the conventional Si oxidation technology in the SiGe process, but recently it has been reported that this effect could be minimized by the oxidation of a graded SiGe layer [6,7]. Because the oxidation rate of Si can depend on many factors such as doping, stress, and pressure, and because the SiGe layer has different strain and chemical bonds depending on the Ge fraction, the oxidation rate of the SiGe layer should be different from that of pure Si layer [8]. However, although the Ge  /Ge bond has much lower binding energy than the Si  /Si bond, it has been reported that the dry thermal oxidation rate of the SiGe layer is the same to the rate of pure Si layer in the literature [9,10]. Recently, a study on the enhanced oxidation rate in the dry thermal oxidation of SiGe layer has been proposed, but the produced oxide in the experiment was mixed oxides of SiO 2 and GeO 2 , not pure SiO 2 [11]. Even though some studies on the oxidation of SiGe layer with alternative oxidation methods such as atomic oxygen-assistant oxidation, carbon-containing SiGe oxidation, showed the enhancement of the oxidation rate [12,13], the details on the oxidation kinetics of the SiGe layer have not been. Moreover, the doping effect on the oxidation of the SiGe layer has not been reported yet. Here, we propose a study on the oxidation of Ge quantum dots. To find the effect of Sb on the oxidation, two kinds of Ge nanostructure were grown on Si (001) substrate with or without a predeposition of Sb. They were oxidized with conventional dry thermal oxidation method at 900 8C and characterized using transmission electron mictoscopy. Like in numerous reports on the dry thermal oxidation of SiGe layer, the oxidation rate of the Ge layer without Sb was the same to that of pure Si [9,10]. However, compared to pure Si oxidation, the Ge quantum dots grown on a Sb monolayer showed a significant enhancement of the oxidation rate. It is the first report on the Sb effect on the oxidation of Ge/Si * Corresponding author. Tel.:  /33-6-6036-2813; fax:  /33-4-9141- 8916. E-mail address: berbezier@crmc2.univ-mrs.fr (I. Berbezier). Materials and Engineering B101 (2003) 190 /193 www.elsevier.com/locate/mseb 0921-5107/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-5107(02)00716-X