Lee Jongyeong, Lee Yeongdong, Kim Jaemin, Lee Zonghoon
Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan 44919, Korea.
Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.
Nanomaterials (Basel). 2020 Oct 6;10(10):1977. doi: 10.3390/nano10101977.
The exit wave is the state of a uniform plane incident electron wave exiting immediately after passing through a specimen and before the atomic-resolution transmission electron microscopy (ARTEM) image is modified by the aberration of the optical system and the incoherence effect of the electron. Although exit-wave reconstruction has been developed to prevent the misinterpretation of ARTEM images, there have been limitations in the use of conventional exit-wave reconstruction in ARTEM studies of the structure and dynamics of two-dimensional materials. In this study, we propose a framework that consists of the convolutional dual-decoder autoencoder to reconstruct the exit wave and denoise ARTEM images. We calculated the contrast transfer function (CTF) for real ARTEM and assigned the output of each decoder to the CTF as the amplitude and phase of the exit wave. We present exit-wave reconstruction experiments with ARTEM images of monolayer graphene and compare the findings with those of a simulated exit wave. Cu single atom substitution in monolayer graphene was, for the first time, directly identified through exit-wave reconstruction experiments. Our exit-wave reconstruction experiments show that the performance of the denoising task is improved when compared to the Wiener filter in terms of the signal-to-noise ratio, peak signal-to-noise ratio, and structural similarity index map metrics.
出射波是均匀平面入射电子波在穿过样品后、且在原子分辨率透射电子显微镜（ARTEM）图像因光学系统像差和电子的非相干效应而被修改之前立即出射时的状态。尽管已经开发出出射波重建技术以防止对ARTEM图像的误判，但在二维材料结构和动力学的ARTEM研究中，传统出射波重建技术的使用存在局限性。在本研究中，我们提出了一个由卷积双解码器自动编码器组成的框架，用于重建出射波并对ARTEM图像进行去噪。我们计算了实际ARTEM的对比度传递函数（CTF），并将每个解码器的输出作为出射波的振幅和相位分配给CTF。我们展示了用单层石墨烯的ARTEM图像进行的出射波重建实验，并将结果与模拟出射波的结果进行比较。首次通过出射波重建实验直接识别了单层石墨烯中的铜单原子取代。我们的出射波重建实验表明，与维纳滤波器相比，在信噪比、峰值信噪比和结构相似性指数图指标方面，去噪任务的性能得到了改善。
