The impacts of surface conditions on the vapor-liquid-solid growth of germanium nanowires on Si (100) substrate

Abstract

The impacts of surface conditions on the growth of Ge nanowires on a Si ͑100͒ substrate are discussed in detail. On SiO 2 -terminated Si substrates, high-density Ge nanowires can be easily grown. However, on H-terminated Si substrates, growing Ge nanowires is more complex. The silicon migration and the formation of a native SiO 2 overlayer on a catalyst surface retard the growth of Ge nanowires. After removing this overlayer in the HF solution, high-density and well-ordered Ge nanowires are grown. Ge nanowires cross vertically and form two sets of parallel nanowires. It is found that nanowires grew along ͗110͘ directions. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2968201͔One-dimensional semiconductor nanostructures have attracted much attention because of their potential applications in the design of nanoelectronic, photonic, and sensing devices.1 Due to their high mobility of electrons and holes, Ge nanowires show their potential application in high-speed field-effect transistors.2-4 Moreover, Ge nanowires are potentially useful for high-speed quantum computing because of long decoherence time due to the predominance of spin-zero 5,6 nuclei and the advantage of a large excitonic Bohr radius in Ge ͑24.3 nm͒, allowing for quantum confinement to be observed in relatively large structures 7,8 and at high temperatures. In order to realize these applications, controllable and high-quality nanowire growth is important.

Organization of matter into one-dimensional units on designed media

“…Various pretreatments of the Si surfaces are described in the literature; some of them are the oxygen (O) and hydrogen (H) -terminations discussed in Ref. [14]. It is established that the growth mode of gold is significantly affected by them since the surface morphologies are changed.…”

“…It is established that the growth mode of gold is significantly affected by them since the surface morphologies are changed. For example, the Au ad-atoms nucleate and agglomerate to form stable islands on oxygen-terminated SiO 2 substrates, while on hydrogen-terminated Si surfaces the Au atoms form a wetting layer [14].…”

“…The growth techniques employed for the Au seeds vary in the literature [2,[14][15][16][17]. For example, in Ref.…”

“…[17] -sputtering, and in Refs. [2,14] -electron beam evaporation. The analyses for homogeneity of size and shape of the fabricated Au islands by various techniques conclude in favor of electron beam evaporation as the most adequate [2,[14][15][16][17], and this is therefore also applied in this work.…”

“…The thicknesses of the e-beam evaporated gold are usually between 0.5 and 2 nm [2,14]. Post annealing of Au/SiO 2 is utilized for size homogenization [16].…”