Fracturing microscale constrictions in metallic wires, such as tungsten, platinum, or platinum-iridium, is a common fabrication method used to produce atomically sharp tips for scanning tunneling microscopy (STM), field-emission microscopy and field ion microscopy. Typically, a commercial polycrystalline drawn wire is locally thinned and then fractured by means of a dislocation slip inside the constriction. We examine a special case where a dislocation-free microscale constriction is created and fractured in a single crystal tungsten rod with a long side parallel to the [100] direction. In the absence of dislocations, vacancies become the main defects in the constriction which breaks under the tensile stress of approximately 10 GPa, which is close to the theoretical fracture strength for an ideal monocrystalline tungsten. We propose that the vacancies are removed early in the tensile test by means of deformation annealing, creating a defect-free tungsten constriction which cleaves along the W(100) plane. This approach enables fabrication of new composite STM probes which demonstrate excellent stability, atomic resolution and magnetic contrast that cannot be attained using conventional methods.

中文翻译：

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结晶钨的变形断裂及复合STM探针的制备

在金属丝（如钨、铂或铂铱）中压裂微缩颈是一种常见的制造方法，用于生产用于扫描隧道显微镜 (STM)、场发射显微镜和场离子显微镜的原子级锐利尖端。通常，商用多晶拉制线会局部变薄，然后通过收缩部内部的位错滑移而断裂。我们研究了一种特殊情况，即在长边平行于 [100] 方向的单晶钨棒中产生和断裂无位错的微观收缩。在没有位错的情况下，空位成为缩颈中的主要缺陷，在大约 10 GPa 的拉应力下断裂，这接近理想单晶钨的理论断裂强度。我们建议在拉伸试验的早期通过变形退火去除空位，从而产生沿 W(100) 面解理的无缺陷钨收缩。这种方法能够制造新的复合 STM 探针，该探针表现出使用传统方法无法实现的出色稳定性、原子分辨率和磁对比度。