Hite D A, McKay K S, Pappas D P
National Institute of Standards and Technology, Boulder, Colorado 80305, United States of America.
Department of Physics, University of Colorado, Boulder, Colorado 80309, United States of America.
New J Phys. 2021;23(10). doi: 10.1088/1367-2630/ac2c2c.
For the past two and a half decades, anomalous heating of trapped ions from nearby electrode surfaces has continued to demonstrate unexpected results. Caused by electric-field noise, this heating of the ions' motional modes remains an obstacle for scalable quantum computation with trapped ions. One of the anomalous features of this electric-field noise is the reported nonmonotonic behavior in the heating rate when a trap is incrementally cleaned by ion bombardment. Motivated by this result, the present work reports on a surface analysis of a sample ion-trap electrode treated similarly with incremental doses of Ar ion bombardment. Kelvin probe force microscopy and x-ray photoelectron spectroscopy were used to investigate how the work functions on the electrode surface vary depending on the residual contaminant coverage between each treatment. It is shown that the as-fabricated Au electrode is covered with a hydrocarbon film that is modified after the first treatment, resulting in work functions and core-level binding energies that resemble that of atomic-like carbon on Au. Changes in the spatial distribution of work functions with each treatment, combined with a suggested phenomenological coverage and surface-potential roughness dependence to the heating, appear to be related to the nonmonotonic behavior previously reported.
在过去二十五年里，来自附近电极表面的捕获离子异常加热持续展现出意想不到的结果。由电场噪声引起的离子运动模式加热，仍然是捕获离子可扩展量子计算的一个障碍。这种电场噪声的异常特征之一是，当通过离子轰击对陷阱进行逐步清理时，加热速率呈现出非单调行为。受此结果的推动，本研究报告了对经过类似增量剂量氩离子轰击处理的样品离子阱电极的表面分析。利用开尔文探针力显微镜和X射线光电子能谱来研究电极表面的功函数如何根据每次处理之间的残留污染物覆盖情况而变化。结果表明，制造后的金电极覆盖有一层烃膜，该膜在首次处理后会发生改变，导致功函数和芯能级结合能类似于金上类原子碳的情况。每次处理后功函数空间分布的变化，再加上所提出的现象学覆盖和表面势粗糙度对加热的依赖性，似乎与先前报道的非单调行为有关。
