利用柯肯道爾效應來製備中空奈米結構

Abstract

本研究藉由鎳/鍺、金/鈦之核殼奈米粒子進行固態反應來形成中空鍺化鎳、金鈦化合物化物奈米球殼，並利用臨場超高真空穿透式電子顯微鏡來觀察形成中空奈米球殼的反應過程。首先，利用電子束微影系統以及電子槍蒸鍍系統，將鎳/鍺核殼奈米結構製備於穿透式電子顯微鏡觀察用的氮化矽薄膜窗口試片上，此外亦藉由電子槍沉積系統鍍覆金薄膜於氮化矽薄膜窗口試片背面的二氧化矽側，並使用快速退火系統900℃下加熱10分鐘形成金奈米粒子，接著沉積鈦薄膜包覆所形成之金粒子來製備出金/鈦核殼奈米粒子。當此兩種核殼奈米粒子分別於450℃與600℃以上加熱時，因其核殼材料界面間的非平衡交互擴散，即為柯肯道爾效應，使得在內部具較大擴散係數的材料上產生空孔，並隨著反應的進行而逐漸形成中空形貌之金鈦化合物奈米球殼或是內部有鎳剩餘的鍺化鎳奈米球/殼結構。最後，由本研究中臨場加熱所觀察到的擴散行為，以及後續對形成的中空奈米結構所做的顯微結構、晶格結構、元素分布等分析，我們提出具有不同尺寸核顆粒的核殼奈米結構，其各自透過柯肯道爾效應來製備中空奈米結構的擴散機制。

In this work, we demonstrate the formation of hollow Ni germanide and AuTi compound nanospheres by a solid state reaction of Ni/Ge and Au/Ti core/shell nanoparticles, respectively. The structural evolution of hollow AuTi compound and Ni germanide nanospheres have been investigated in real-time ultrahigh vacuum transmission electron microscopy (UHV-TEM). When annealed above 450℃, the non-equilibrium counter-diffusion of core and shell species occurred through an interface. Therefore, Ni germanide and AuTi compound hollow nanospheres were formed by a solid state reaction involving the Kirkendall effect. Finally, we propose the mechanism with the effects of the size and annealing duration on solid state reaction based on the Kirkendall effect. And it can look forward to the application in the fabrication of other system with different hollow morphologies according to the mechanism proposed in this study.