Pulsed-voltage atom probe tomography of low conductivity and insulator materials by application of ultrathin metallic coating on nanoscale specimen geometry

• Published in: Ultramicroscopy Vol. 181; pp. 150 - 159
• Main Authors: Adineh, Vahid R., Marceau, Ross K.W., Chen, Yu, Si, Kae J., Velkov, Tony, Cheng, Wenlong, Li, Jian, Fu, Jing
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.10.2017
• Subjects: Atom probe tomography; Nanospheres; Physical vapor deposition; Physical vapor deposition; Atom probe tomography; Nanospheres
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2017.05.002

•A novel approach to study low conductivity and insulator materials with conventional pulsed-voltage atom probe tomography (APT) by incorporating an ultrathin metallic coating.•The ultrathin coating was optimized through a series of computational and experimental studies, and an empirical model was also proposed for coating APT tips.•Nanospheres and resin embedded specimens were prepared using the optimized coating strategy, followed by successfully 3D atomic imaging. We present a novel approach for analysis of low-conductivity and insulating materials with conventional pulsed-voltage atom probe tomography (APT), by incorporating an ultrathin metallic coating on focused ion beam prepared needle-shaped specimens. Finite element electrostatic simulations of coated atom probe specimens were performed, which suggest remarkable improvement in uniform voltage distribution and subsequent field evaporation of the insulated samples with a metallic coating of approximately 10nm thickness. Using design of experiment technique, an experimental investigation was performed to study physical vapor deposition coating of needle specimens with end tip radii less than 100nm. The final geometries of the coated APT specimens were characterized with high-resolution scanning electron microscopy and transmission electron microscopy, and an empirical model was proposed to determine the optimal coating thickness for a given specimen size. The optimal coating strategy was applied to APT specimens of resin embedded Au nanospheres. Results demonstrate that the optimal coating strategy allows unique pulsed-voltage atom probe analysis and 3D imaging of biological and insulated samples.