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首页> 外文会议>International Conference on Solidification and Gravity; 20040906-09; Miskolc-Lillafured(HU) >Grain Boundary Influence on the Electrical Properties of Tellurium Microstructure Ingots and Nanocluster Crystals
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Grain Boundary Influence on the Electrical Properties of Tellurium Microstructure Ingots and Nanocluster Crystals

机译：晶界对碲微结构锭和纳米团簇晶体电学性能的影响

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The high sensitivity of the low temperature electrical properties of p-type pure tellurium (Te) to impurities, structural boundaries, point defects and dislocations allows to investigate the structural imperfection profiles in crystals grown under different conditions. Our interest was focused on studying the influence of grain boundaries on the electrical properties of the samples that were remelted and directionally solidified in space (μg) without a seed (W-μg), in comparison with the sample grown under the normal earth conditions (1g_0) and a nanocluster sample obtained by filling with melted Te of dielectric opal matrix voids (Opal < Te > sample). The W-μg ingot of Te was prepared in the "Crystallizator" furnace under microgravity conditions aboard the "Mir" space station.rnThe concentration variation of electrically active defects and neutral defects along the samples were studied by galvanomagnetic methods (Hall effect and electrical resistivity) in a wide temperature range from 0.4 to 300 K. In these measurements, the following effects caused by the micro- and nano- crystalline structure were found: low hole mobility, high concentration of neutral defects, and anomalous positive magnetoresistance in low magnetic fields at low temperatures. Besides, the specific resistivity of the space sample was found to oscillate (up to 20%) along the length which can be correlated with the presence of a few contact points of the melt with the ampoule wall. This ingot was formed as a result of rapid homogeneous spontaneous solidification, accompanied by forming a micro-block structure.rnThe appearance of the anomalous positive magnetoresistance was observed in the micro-block W- sample and the nanocluster Opal < Te > sample. It is a consequence of intensive hole scattering at the grain boundaries which leads to an increase of the intervalley transition probability and to a change of the spin sign of holes in a low symmetry Te crystal. According to the weak localization theory, the spin variation during the scattering results in a positive magnetoresistance of the sample in low magnetic fields, in contrast to bulk Te crystals.
机译：p型纯碲（Te）的低温电性能对杂质，结构边界，点缺陷和位错的高度敏感性允许研究在不同条件下生长的晶体中的结构缺陷。与在正常地球条件下生长的样品相比，我们的兴趣集中在研究晶界对在无晶种（W-μg）的空间（μg）中重新熔化和定向凝固的样品的电性能的影响（ 1g_0）和通过填充熔化的电介质蛋白石基质空隙的Te（Opal 样品）而获得的纳米簇样品。 Te的W-μg锭是在“ Mir”空间站上的微重力条件下在“结晶器”炉中制备的。rn用电磁方法研究了样品中电活性缺陷和中性缺陷的浓度变化（霍尔效应和电阻率）。 ）在0.4至300 K的宽温度范围内。在这些测量中，发现了由微晶体和纳米晶体结构引起的以下效应：低空穴迁移率，高浓度的中性缺陷以及在低磁场中的异常正磁电阻在低温下。此外，发现空间样品的比电阻率沿长度方向振荡（高达20％），这与熔体与安瓿壁的一些接触点的存在有关。该锭是由于快速均匀自发固化而形成的，并伴随着形成微块结构。在微块W样品和纳米簇Opal 样品中观察到异常正磁电阻的出现。这是由于在晶界处的大量空穴散射而导致的结果，即在低对称性的Te晶体中，晶格跃迁概率增加，并且空穴的自旋符号发生变化。根据弱局部化理论，与块状Te晶体相比，散射过程中的自旋变化会导致样品在低磁场中具有正磁阻。

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