第三章一维纳米1概述.pptVIP

(c) When the concentrations of Si and O in the Ga ball are high enough, the Si and O will react to form many SiO2 nanoparticles on the surface of the lower hemisphere of the Ga ball. These particles act as the nucleation sites, initiating the growth of the first batch (batch I) of the SiO2 nanowires. The Ga ball is then pushed away from the silicon wafer by the growing SiO2 nanowires. From this stage, the Ga ball can only absorb Si species from the vapor. As this first batch of nanowires proceeds to grow, a second batch (batch II) of nanowires simultaneously nucleates and grows at nearly the same rate and direction above the first. As growth continues, the newly formed nanowires begin to exert a force on the batch below. Note that split growth proceeds during the entire nanowire growth process. (d) When the force is great enough, the second batch of nanowires will lift the Ga ball upward, thereby detaching the first batch of nanowires from the Ga ball and halting their growth. A third batch (batch III) of nanowires then nucleates and grows above the second. (e) The process of growth and detachment allows the formation of a tubular structure with regular stairlike inner wall. fishbone-like, gourd–like（葫芦形状）, spindle-like（纺锤形）, badminton-like （羽毛球形）, and octopus-like（章鱼形） Figure 1. Schematic diagram of the position and corresponding temperature range of the five deposition zones inside the reaction chamber. The representative morphologies of the products in these zones are shown. 实 例 3.2.2　固液固生长机制(ＳＬＳ) ＳＬＳ法和ＶＬＳ法很相似,二者的主要差别在于ＳＬＳ法纳米线成长的液态团簇来源于溶液相,而ＶＬＳ法则来自蒸气相. 尽管该方法比较有前景,但是,在制备过程中要求催化剂的熔点低于溶剂的沸点,因而限制了其广泛应用. SLS生长机制制备多种纳米结构SiO2 1　实验部分 图1为制备纳米结构的SiO2水平管式炉的结构示意图.石英管的内径为50 mm,长度为500 mm.炉子存在2个控温区,其中A为高温区,B为低温区,气体从左端通入. 实 例 实验过程 将1 g左右分析纯的Bi(NO3)3粉末置于陶瓷舟中,把舟放入单端开口的刚玉管(Φ20 mm×300mm)封闭端.用RF溅射方法在清洁Si片上镀一层Au膜,Au膜厚度分别为10、20、30 nm.把Au/Si衬底置于刚玉管的开口端.然后,将此小石英管置于管式炉的石英管中,使放Bi(NO3)3粉末的陶瓷舟位于A处,衬底位于B处,且A、B间相距约25 cm(如图1所示).在加热之前,先抽真空10 min,再通入高纯氩气10 min;最后在氩气的保护下加热高温区至1 20