交叉束PLD法制备Co-Cu纳米颗粒膜的结构和巨磁电阻
Structure and giant magnetoresistance of granular Co-Cu nanolayers prepared by cross-beam PLD
摘要：
本文研究了Co_（xCu_{100-x}）（x = 0，40. 75，100）层，其厚度在13 nm和55 nm之间，使用交叉束脉冲激光沉积在硅衬底上制备。广角X射线衍射（WAXRD），透射电子显微镜（TEM）和电输运测量揭示了一个结构组成的分解钴和铜晶粒的晶粒尺寸约为10 nm。讨论了钴含量和镀层厚度对晶粒尺寸的影响。电子衍射（ED）表明存在Cu 3Au结构类型的金属间化合物Co-Cu相。在525 K和750 K之间的温度下的热处理导致Co和Cu的逐步分解，晶粒尺寸增加到约100 nm。这可以通过控制退火的温度和持续时间来调节，并且可以在WAXRD图案和TEM图像中直接观察到。通过考虑相干和非相干散射，对所用辐射的粒度和相干长度进行仔细分析，可以准确解释X射线衍射图案。该合金薄膜具有巨磁电阻效应，其值为1。2.3%，在725 K左右退火后获得最大值。
英文摘要：
A series of Co_xCu_{100-x} (x = 0, 40...75, 100) layers with thicknesses in-between 13 nm and 55 nm were prepared on silicon substrates using cross-beam pulsed laser deposition. Wide-angle X-ray diffraction (WAXRD), transmission electron microscopy (TEM) and electrical transport measurements revealed a structure consisting of decomposed cobalt and copper grains with grain sizes of about 10 nm. The influence of cobalt content and layer thickness on the grain size is discussed. Electron diffraction (ED) indicates the presence of an intermetallic Co-Cu phase of Cu3Au structure-type. Thermal treatment at temperatures between 525 K and 750 K results in the progressive decomposition of Co and Cu, with an increase of the grain sizes up to about 100 nm. This is tunable by controlling the temperature and duration of the anneal, and is directly observable in WAXRD patterns and TEM images. A careful analysis of grain size and the coherence length of the radiation used allows for an accurate interpretation of the X-ray diffraction patterns, by taking into account coherent and non-coherent scattering. The alloy films show a giant magnetoresistance of 1...2.3 % with the maximum obtained after annealing at around 725 K.
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