Lebeau James M, Stemmer Susanne
Materials Department, University of California, Santa Barbara, CA 93106-5050, USA.
Ultramicroscopy. 2008 Nov;108(12):1653-8. doi: 10.1016/j.ultramic.2008.07.001. Epub 2008 Jul 15.
This paper reports on a method to obtain atomic resolution Z-contrast (high-angle annular dark-field) images with intensities normalized to the incident beam. The procedure bypasses the built-in signal processing hardware of the microscope to obtain the large dynamic range necessary for consecutive measurements of the incident beam and the intensities in the Z-contrast image. The method is also used to characterize the response of the annular dark-field detector output, including conditions that avoid saturation and result in a linear relationship between the electron flux reaching the detector and its output. We also characterize the uniformity of the detector response across its entire area and determine its size and shape, which are needed as input for image simulations. We present normalized intensity images of a SrTiO(3) single crystal as a function of thickness. Averaged, normalized atom column intensities and the background intensity are extracted from these images. The results from the approach developed here can be used for direct, quantitative comparisons with image simulations without any need for scaling.
本文报道了一种获取原子分辨率Z衬度（高角度环形暗场）图像的方法，其强度已归一化至入射束。该过程绕过了显微镜的内置信号处理硬件，以获得连续测量入射束和Z衬度图像强度所需的大动态范围。该方法还用于表征环形暗场探测器输出的响应，包括避免饱和的条件以及导致到达探测器的电子通量与其输出之间呈线性关系的条件。我们还表征了探测器响应在其整个区域的均匀性，并确定其尺寸和形状，这些是图像模拟所需的输入。我们展示了SrTiO(3) 单晶的归一化强度图像随厚度的变化。从这些图像中提取了平均归一化原子列强度和背景强度。此处开发的方法所得结果可用于与图像模拟进行直接定量比较，而无需进行缩放。
