Abstract
Abstract The acicular Ni31Si12 nanowires (NWs) with twins and superlattice structure were described with a simple vapor phase deposition method at 650 ℃. The acicular NWs are several micrometers in length and with diameters of 60-100 nm and 20-40 nm at the streams and tip regions, respectively. The acicular Ni31Si12 NWs have a common {01-5} twin plane along the [01-5] growth direction and have the periodicity of 0.91 nm with one period that consists of four (01-5) planes of the superlattice nanostructure. The periodical twin and superlattice coexist in the Ni31Si12 NWs. The resistivity of the acicular Ni31Si12 NWs was measured to be 558 μΩ cm by two-terminal electrical measurement. The field-enhancement factor β can be calculated to be about 596 for the acicular Ni31Si12 NWs. The growth of vertically well-aligned single crystal Ni2Si and Ni31Si12 NWs arrays were respectively reported, for the first time. Highly oriented and large area arrays of NWs were epitaxially grown on Ni2Si and Ni31Si12 films and preferentially formed on Ni foil substrates with a simple vapor phase deposition method in one step. The Ni2Si and Ni31Si12 NWs are several micrometers in length and 20-50 nm and 50-80 nm in diameter, respectively. The resistivities of the Ni2Si and Ni31Si12 NWs were measured to be 21 and 51 μΩ cm by four-terminal electrical measurement, respectively. Both NWs can carry very high currents and possess excellent field emission properties. The growth of vertically well-aligned Ni2Si and Ni31Si12 NWs arrays shall lead to significant advantages in the fabrication of vertical Si nanodevices. The synthesis of free-standing single crystal NiSi2 NWs on Ni foil with a simple vapor transport method was reported. The growth of previously elusive Si-rich nickel silicide NWs was achieved with the addition of NiCl2 powders in front of the Ni substrate upstream. The presence of NiCl2 gas enhanced the condensation of Si and suppressed the supply of Ni atoms in the subsequent reactions. As the NWs maintain low resistivity, NiSi2 NWs can carry very high currents and possess excellent field emission properties. The growth of NiSi2 NWs shall lead to significant advantages in the fabrication of Si nanodevices. 摘 要 利用水平爐管結合氣相沉積的方法，成功地在鎳箔片上成長針狀式(acicular) 富鎳之鎳矽化合物(Ni31Si12)奈米線(nanowires, NWs)，此奈米線同時具有週期性雙晶面和超晶格結構(superlattice sturcutre)等兩項特點。針狀式(acicular) Ni31Si12 奈米線(acicular NWs)具有數十個微米長，其直徑於軀幹區(stems regions)為60-100奈米，於尖端區(tip regions)為20-40奈米。此針狀式奈米線屬{01-5}的雙晶面族，並沿著 [01-5]方向成長，且由四個 (01-5)面所組成超晶格結構之週期性間距為0.91奈米。上述之週期性的雙晶面和超晶格結構是同時共存於同一奈米線上。使用兩點電性量測其電阻率(resistivity)為558 μΩ cm。另其場發射因子(field-enhancement factor β)為596。 垂直生長且排列整齊的單晶富鎳之鎳矽化合物奈米線陣列(Ni2Si and Ni31Si12 NWs arrays)第一次被成功的報導。於850 和750 ℃下，利用水平爐管結合氣相沉積之一次反應步驟，於鎳箔片上成長磊晶 (epitaxially) 之Ni2Si和Ni31Si12 薄膜。藉此薄膜再次磊晶成長規則且大面積富鎳之鎳矽奈米線(Ni2Si和Ni31Si12 NWs)。成長出的Ni2Si和Ni31Si12奈米線其線長約為幾個奈米長，其直徑則分別約為20-50奈米和50-80奈米。以四點電性測量Ni2Si和Ni31Si12 的電阻率(resistivities)分別為21 和51 μΩ cm。 上述兩種奈米線皆能負荷極高的電流並且擁有極佳的場發射(field emission)特性。排列整齊的垂直奈米線陣列(Ni2Si和Ni31Si12 NWs arrays)，將有潛在的優勢應用於垂直矽奈米元件(Si nanodevices)之發展。 獨立於試片表面，利用氣相傳輸法於鎳片上任意方向生長單晶富矽之鎳矽矽化物奈米線(NiSi2 NWs)第一次被成功的報導。其主要的方法為緊鄰樣品區(鎳片)的前方放上氯化鎳的粉末(NiCl2 powders)，然氯化鎳粉末ㄧ經加熱則生成氯化鎳蒸氣，除有助於矽蒸氣的析出外，亦可與鎳片反應再生成回氯化鎳蒸氣，以消耗鎳原子的提供。此富矽之鎳矽矽化物(NiSi2)奈米線因具有良好之低電阻率(resistivities)、極高之負荷電流(high currents)與良好之場發射(field emission)特性，使其有顯著的優勢應用於矽奈米元件(Si nanodevices)之發展。