Synthesis and Magnetic Characterization of Coaxial Ge1鈥?i>xMnx/a-Si Heterostructures

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• 作者：Sven Barth ; Olga Kazakova ; Sonia Estrade ; Richard G. Hobbs ; Francesca Peiro ; Michael A. Morris ; Justin D. Holmes
• 刊名：Crystal Growth & Design
• 出版年：2011
• 出版时间：December 7, 2011
• 年：2011
• 卷：11
• 期：12
• 页码：5253-5259
• 全文大小：936K
• 年卷期：v.11,no.12(December 7, 2011)
• ISSN：1528-7505

文摘

A method for synthesizing Ge_1鈥?i>xMn_x/a-Si core鈥搒hell nanowires (x = 0.3(1)鈥?.0(2)) using a supercritical fluid deposition technique, with a homogeneous distribution of manganese along the entire lengths of the crystalline Ge cores but not in the a-Si shells, is reported. Investigations into the magnetic properties of the heterostructured nanowires revealed a significant influence of the amorphous Si shell covering the surface of the core Ge_0.997Mn_0.003 nanowires compared to pristine Ge_0.997Mn_0.003 nanowires with no a-Si coating. The magnetic data revealed diminished values of both the remanence and the saturation magnetization for pristine Mn-doped Ge nanowires at higher temperatures when compared to the Ge_1鈥?i>xMn_x/a-Si core鈥搒hell nanowires, whereas both parameters increased as the temperature dropped down to 5 K. Differences in the temperature-dependent evolution of the coercivity were observed in the magnetically harder core鈥搒hell nanowires compared to the pristine Ge_0.997Mn_0.003 nanowires, showing a drop of 26% at 5 K vs room temperature compared to a drop of 66% for the pristine nanowires. The low dopant concentration (0.3(1)%) of Mn in the core鈥搒hell nanowires, combined with the observed ferromagnetic properties, suggests a combination of hole-mediated exchange and confinement processes are responsible for the observed properties. Our observations show the importance of a protective layer in covering the oxidation-sensitive dilute magnetic semiconductor nanowires.