Abstract
In this work, we report a novel and efficient silicidation method to synthesize higher manganese silicide (HMS) nanowires with interesting characterization and physical properties. High density silicon nanowire arrays fabricated by chemical etching reacted with MnCl2 precursor through a unique double tube chemical vapor deposition (CVD) system, where we could enhance the vapor pressure of the precursor and provide stable Mn vapor with a sealing effect. It is crucial that the method enables the efficient formation of high quality higher manganese silicide nanowires without a change in morphology and aspect ratio during the process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to characterize the HMS nanowires. High-resolution TEM studies confirm that the HMS nanowires were single crystalline Mn27Si47 nanowires of Nowotny Chimney Ladder crystal structures. Magnetic property measurements show that the Mn27Si47 nanowire arrays were ferromagnetic at room temperature with a Curie temperature of over 300 K, highly depending on the relationship between the direction of the applied electric field and the axial direction of the standing nanowire arrays. Field emission measurements indicate that the 20 μm long nanowires possessed a field enhancement factor of 3307. The excellent physical properties of the HMS nanowires (NWs) make them attractive choices for applications in spintronic devices and field emitters.
Highlights
Transition metal silicide nanowires have been widely studied [1,2,3,4,5,6,7,8,9]
Higher manganese silicides represented by MnSi2-x, MnSi1.75 or MnSi1.8 are excellent thermoelectric materials due to their low thermal conductivity leading to a figure of merit of 0.7–0.8 [29,30]
higher manganese silicides (HMS) are of Nowotny Chimney Ladder (NCL) structures, described as chimneys of manganese atoms with silicon atoms, belonging to homologous series of specific HMS phases [21]
Summary
Transition metal silicide nanowires have been widely studied [1,2,3,4,5,6,7,8,9]. Fascinating materials from them with diverse features are recognized to be excellent candidates in various applications, including complementary metal-oxide semiconductor devices [10,11], electronics [12,13], photovoltaics [14,15], spintronics [16,17], field emission [18,19,20] and thermoelectrics [19,20,21,22,23]. HMS are of Nowotny Chimney Ladder (NCL) structures, described as chimneys of manganese atoms with silicon atoms, belonging to homologous series of specific HMS phases [21]. Some interesting pathways synthesized by thermal evaporation and Si nanostructures have been explored [22,31,32]; the conversion of Si nanostructures into HMS nanostructures by precursor vapor has not been completely studied. It is hard for the Si nanowires to react with precursor vapor of Mn source and to completely form HMS nanowires with the original nanoscale morphology preserved. The method facilitated efficient synthesis of high-quality HMS nanowires
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