Lee Jongmin, Farhangfar Shadyar, Lee Jaeyoung, Cagnon Laurent, Scholz Roland, Gösele Ulrich, Nielsch Kornelius
Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany.
Nanotechnology. 2008 Sep 10;19(36):365701. doi: 10.1088/0957-4484/19/36/365701. Epub 2008 Jul 28.
Arrays of thermoelectric bismuth telluride (Bi(2)Te(3)) nanowires were grown into porous anodic alumina (PAA) membranes prepared by a two-step anodization. Bi(2)Te(3) nanowire arrays were deposited by galvanostatic, potentiostatic and pulsed electrodeposition from aqueous solution at room temperature. Depending on the electrodeposition method and as a consequence of different growth mechanisms, Bi(2)Te(3) nanowires exhibit different types of crystalline microstructure. Bi(2)Te(3) nanowire arrays, especially those grown by pulsed electrodeposition, have a highly oriented crystalline structure and were grown uniformly as compared to those grown by other electrodeposition techniques used. X-ray diffraction (XRD) analyses are indicative of the existence of a preferred growth orientation. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) confirm the formation of a preferred orientation and highly crystalline structure of the grown nanowires. The nanowires were further analyzed by scanning electron microscopy (SEM). Energy dispersive x-ray spectrometry (EDX) indicates that the composition of Bi-Te nanowires can be controlled by the electrodeposition method and the relaxation time in the pulsed electrodeposition approach. The samples fabricated by pulsed electrodeposition were electrically characterized within the temperature range 240 K≤T≤470 K. Below T≈440 K, the nanowire arrays exhibited a semiconducting behavior. Depending on the relaxation time in the pulsed electrodeposition, the semiconductor energy gaps were estimated to be 210-290 meV. At higher temperatures, as a consequence of the enhanced carrier-phonon scattering, the measured electrical resistances increased slightly. The Seebeck coefficient was measured for every Bi(2)Te(3) sample at room temperature by a very simple method. All samples showed a positive value (12-33 µV K(-1)), indicating a p-type semiconductor behavior.
通过两步阳极氧化法制备的多孔阳极氧化铝（PAA）膜中生长出了热电碲化铋（Bi(2)Te(3)）纳米线阵列。在室温下，通过恒电流、恒电位和脉冲电沉积法从水溶液中沉积Bi(2)Te(3)纳米线阵列。根据电沉积方法以及不同生长机制的结果，Bi(2)Te(3)纳米线呈现出不同类型的晶体微观结构。Bi(2)Te(3)纳米线阵列，特别是通过脉冲电沉积生长的那些，具有高度取向的晶体结构，并且与使用其他电沉积技术生长的相比，生长得更加均匀。X射线衍射（XRD）分析表明存在择优生长取向。高分辨率透射电子显微镜（HRTEM）和选区电子衍射（SAED）证实了生长的纳米线形成了择优取向和高度结晶的结构。通过扫描电子显微镜（SEM）对纳米线进行了进一步分析。能量色散X射线光谱（EDX）表明，Bi-Te纳米线的成分可以通过电沉积方法和脉冲电沉积方法中的弛豫时间来控制。对通过脉冲电沉积制备的样品在240 K≤T≤470 K的温度范围内进行了电学表征。在T≈440 K以下，纳米线阵列表现出半导体行为。根据脉冲电沉积中的弛豫时间，估计半导体能隙为210 - 290 meV。在较高温度下，由于载流子 - 声子散射增强，测得的电阻略有增加。通过一种非常简单的方法在室温下测量了每个Bi(2)Te(3)样品的塞贝克系数。所有样品均显示正值（12 - 33 μV K(-1)），表明为p型半导体行为。
