Day Alec C, Breen Andrew J, Reinhard David A, Kelly Thomas F, Ringer Simon P
The University of Sydney, Australian Centre for Microscopy & Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering. Sydney, NSW 2006, Australia; Steam Instruments, Inc., Madison, WI 53703, USA.
The University of Sydney, Australian Centre for Microscopy & Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering. Sydney, NSW 2006, Australia.
Ultramicroscopy. 2022 Nov;241:113595. doi: 10.1016/j.ultramic.2022.113595. Epub 2022 Jul 26.
The operating temperature is a critical parameter in atom probe tomography experiments. It affects the spatial precision, mass resolving power and other key aspects of the field-evaporation process. Current commercially available atom probes operate at a minimum temperature of ∼25 K when measured at the specimen. In this paper, we explore and implement changes to the mechanical design of both the LEAP and EIKOS™ atom probe microscope systems manufactured by CAMECA to enable a specimen temperature in the sub-10 K regime. We use these modified instruments to analyze four materials systems: pure Al (in both pulsed-voltage and pulsed-laser mode), pure W (pulsed-voltage mode only), doped Si, and GaN (pulsed-laser mode only). The effects of conducting atom probe experiments in the sub-10 K regime were assessed with reference to a range of quantitative analysis metrics related to spatial precision, mass resolving power, stoichiometry and charge-state ratio. We demonstrate that the spatial precision is significantly improved with decreasing temperature, whilst the effect on mass resolving power is relatively minor. The enhanced spatial precision is significant insofar as it enables lattice planes from the doped Si samples to be resolved. Furthermore, mass spectral analysis, lower noise floors and changes in the field evaporation process enabled more accurate GaN compositional measurements. We discuss the significance of these findings for the semiconductor and metallurgical industries and the potential opportunities for further investigations of this parameter space.
在原子探针层析成像实验中，工作温度是一个关键参数。它会影响场蒸发过程的空间精度、质量分辨率以及其他关键方面。目前市售的原子探针在样品处测量时的最低工作温度约为25K。在本文中，我们探索并对CAMECA制造的LEAP和EIKOS™原子探针显微镜系统的机械设计进行了改进，以使样品温度能处于10K以下的范围。我们使用这些经过改进的仪器来分析四种材料体系：纯铝（脉冲电压模式和脉冲激光模式）、纯钨（仅脉冲电压模式）、掺杂硅以及氮化镓（仅脉冲激光模式）。参照与空间精度、质量分辨率、化学计量比和电荷态比相关的一系列定量分析指标，评估了在10K以下范围进行原子探针实验的效果。我们证明，随着温度降低，空间精度显著提高，而对质量分辨率的影响相对较小。增强的空间精度意义重大，因为它能够分辨掺杂硅样品的晶格平面。此外，质谱分析、更低的本底噪声以及场蒸发过程的变化使得氮化镓成分测量更加准确。我们讨论了这些发现对半导体和冶金行业的意义以及进一步研究该参数空间的潜在机会。
