The growth of small diameter silicon nanowires to nanotrees
Résumé
In this work we have studied a way to control the growth of small diameter silicon nanowires by the Vapour Liquid Solid (VLS) mode. We have developed a method to deposit colloids with good density control, which is a key point for the control of the nanowires (NWs) diameter. We also show the high dependence of the allowed growth diameter with growth conditions opening the door to the realization of as grown 2 nm silicon NWs. Finally we developed a smart way to realise nanotrees in the same run, by tuning the growth conditions and making benefit of gold on the sidewall of nanowires, without two catalyst deposition steps. 1 Introduction The growth of semiconducting nanowires is now of a great interest for nanoelectronics, biosensors, and solar cells technology, due to their particular electrical and optical properties arising from their one dimensional geometry [1]. In particular, small diameter (d) silicon nanowires (SiNWs) and nanotrees (SiNTs) are viewed as attracting building blocks for future devices operating in the quantum limit predicted for d<5 nm wires [2,3]. To fabricate devices with homogeneous properties, getting monodispersed diameter populations is also a prerequisite. In this communication, we present a method to grow silicon nanotrees (Si NTs) with small diameter branches (<10 nm) using a two step process. This method comes from our studies which showed that (i) in case of larger diameter nanowires (> 50 nm) we have observed gold droplets on Si NWs sidewalls, based on in situ gold diffusion, (ii) the growing condition could be adjusted to grow selectively small or large NWs. By combining the catalytic activity of the Au particles at the sidewalls with the selective growth condition for different diameter we can realise NTs with branches presenting diameter down to 2 nm and
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