Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires
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Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires Francesca Iacopi1, Philippe M Vereecken1, Marc Schaekers1, Matty Caymax1, Nele Moelans2, Bart Blanpain2, Christophe Detavernier3, Jan D'Haen4, and Hefin Griffiths5 1 SPDT, IMEC, Kapeldreef 75, Leuven, 3001, Belgium 2 Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Leuven, 3001, Belgium 3 Solid State Physics, Universiteit Gent, Gent, 9000, Belgium 4 IMOMEC, Hasselt, 3590, Belgium 5 Plasma Technology, Oxford Instruments, Bristol, BS49 4AP, United Kingdom ABSTRACT The use of Au nanoparticles as catalysts for growth of Si nanowires poses fundamental reliability concerns for applications in Si semiconductor technology. In this work we show that the choice of catalysts can be broadened when the need for catalytic precursor dissociation is eliminated. However, the requirements for selective deposition in a gas phase transport ñlimited regime become stringent. When competing deposition of amorphous Si can bury the particles faster than the incubation time for VLS growth, no nanowire growth will be initiated. We show that the use of a catalyst such as In, already in a liquid form at the growth temperature, is effective. Therefore, the choice of VLS catalysts among the low melting point metals from the III, IV and V groups is suggested.
INTRODUCTION Catalyst ñassisted 1D crystal growth through the Vapour-Liquid-Solid (VLS [1,2,3]) mechanism is a widely demonstrated method for growing semiconductor nanowires. Nevertheless, a complete understanding and control of all the mechanisms governing precise and reproducible whisker growth with defined characteristics is still lacking. Until now, the vast majority of the work reported in literature makes use of Au as the metal catalyst, which appears to be a sort of ëuniversalí choice for growing the most diverse types of semiconductor nanowhiskers (e.g. Si, SiGe [4], Ge [5] and III-V [6]). In the case of III-V and II-VI compound semiconductors, nanowire growth at moderated temperatures has been demonstrated from a metal catalyst that is also one of the compound elements [7]. A few sporadic studies have assessed the feasibility for VLS growth of Si nanowhiskers mediated by Ga [8], Cu [9], and Vapour-Solid-Solid (VSS) growth with Al [10] and Ti [11]. All these studies reported a lesser efficiency as compared to Au ñcatalysed VLS growth. Early growth trials using In catalysts with Chemical Vapour Deposition technique were not successful [3]. The availability of alternative catalysts to Au may be enabling for some specific applications, i.e. the use of nanowires for Si ñbased devices. Au is an unfavourable metal for Si ñbased devices, since Au diffusion into Si would lead to the creation of mid- band gap states, and be a performance killer by reducing the minority carrier lifetime [12]. Therefore, in this study we focus on possible alternative metals compatible with Si technology, which could also be efficient catalysts for VLS growth of Si nanowires [13]. The general requ
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