Materials Science and Engineering, Saitama Institute of Technology, 1690 Fusaiji, Fukaya, Saitama 369-0293, Japan.
Microsc Microanal. 2012 Jun;18(3):603-11. doi: 10.1017/S1431927612000062. Epub 2012 Apr 12.
Scanning confocal electron microscopy (SCEM) is a new imaging technique that is capable of depth sectioning with nanometer-scale depth resolution. However, the depth resolution in the optical axis direction (Z) is worse than might be expected on the basis of the vertical electron probe size calculated with the existence of spherical aberration. To investigate the origin of the degradation, the effects of electron energy loss and chromatic aberration on the depth resolution of annular dark-field SCEM were studied through both experiments and computational simulations. The simulation results obtained by taking these two factors into consideration coincided well with those obtained by experiments, which proved that electron energy loss and chromatic aberration cause blurs at the overfocus sides of the Z-direction intensity profiles rather than degrade the depth resolution much. In addition, a deconvolution method using a simulated point spread function, which combined two Gaussian functions, was adopted to process the XZ-slice images obtained both from experiments and simulations. As a result, the blurs induced by energy loss and chromatic aberration were successfully removed, and there was also about 30% improvement in the depth resolution in deconvoluting the experimental XZ-slice image.
扫描共聚焦电子显微镜（SCEM）是一种新的成像技术，能够进行纳米级深度分辨率的深度切片。然而，在光轴方向（Z）上的深度分辨率比根据存在球差计算的垂直电子探针尺寸所预期的要差。为了研究退化的原因，通过实验和计算模拟研究了电子能量损失和色差对环形暗场 SCEM 深度分辨率的影响。考虑到这两个因素的模拟结果与实验结果吻合得很好，这证明电子能量损失和色差会在 Z 方向强度分布的离焦侧产生模糊，而不会大大降低深度分辨率。此外，采用了一种使用模拟点扩展函数的反卷积方法，该方法结合了两个高斯函数，用于处理实验和模拟获得的 XZ 切片图像。结果，成功消除了由能量损失和色差引起的模糊，并且在对实验 XZ 切片图像进行反卷积时，深度分辨率也提高了约 30%。
