“Background Self-assembled nanowires (NWs) of metal silici


“Background Self-assembled nanowires (NWs) of metal silicides have received much attention recently for their potential applications as electrical interconnects on a scale that cannot be attained with conventional lithographic methods [1–4]. In addition, such structures are expected to display novel physical

properties related to the structural anisotropy and quantum confinement effects and could be used as active elements for the new generation of electronic, optoelectronic, magnetic, and thermoelectric devices [5–7]. In the past decade, it has been reported that NWs of rare-earth silicides such as ScSi2[7], ErSi2[8, 9], DySi2[2, 10, 11], GdSi2[12, 13], and HoSi2[14, 15] and 3d transition metal silicides such as PSI-7977 cost FeSi2[1], CoSi2[3], NiSi2[16], and TiSi2[17–19] can be formed on silicon substrates by the molecular beam epitaxy method. While the NW shape of rare-earth silicides is thought to result from an anisotropic lattice mismatch that is small (<1%) in length direction Belnacasan and large (>5%) in width direction of the NW, the NW shape of FeSi2, CoSi2, and NiSi2 results from an ‘endotaxial’ growth mechanism which involves the growth of silicide into the Si substrate [1, 3]. Very recently, we have reported that MnSi~1.7 NWs can also be grown on the Si substrates with reactive epitaxy method at temperatures above approximately 500°C [20–22]. The growth mechanism of the

NWs was considered to be anisotropic lattice mismatch between the silicide and the Si substrates. The growth direction of the NWs is confined along Si<110>, resulting in the NWs orienting with the long axis along one direction (Si ), two orthogonal directions (Si and [011]), and three directions (Si , , and ) on the Si(110), (001), and (111) surfaces, respectively. However, for scientific investigation as well as device applications, it would be highly expected to grow NWs with a single orientation because either the NWs grown in this mode would never cross and have larger length. Parallel NW arrays can be used as nanomechanical devices [23], and using parallel NWs, the anisotropic electronic

structure of silicide NWs can be investigated by angle-resolved photoelectron spectroscopy [11]. On the other hand, the Si(110) surface is currently attracting renewed interests because of its unusual properties such as high hole mobility, unique surface reactivity, and strong structural anisotropy. The Si(110) surface has a potential use in fabricating vertical double-gate metal oxide semiconductor field effect transistors that enable much higher integration [24]. Although the formation of MnSi~1.7 NWs with sole orientation on Si(110) was demonstrated in our previous works [20], a detailed investigation on how the growth parameters affect the growth of MnSi~1.7 NWs on Si(110), which is of key importance for a comprehensive understanding of the growth kinetics and thus the controllable growth of the NWs, is still lacking.

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