Shinsuke Kawanishi

A novel approach to scanning electron microscopy at ambient atmospheric pressure

Scanning electron microscopy (SEM) for observing samples at ambient atmospheric pressure is introduced in this study. An additional specimen chamber with a small window is inserted in the main specimen chamber, and the window is separated with a thin membrane or diaphragm allowing electron beam propagation. Close proximity of the sample to the membrane enables the detection of back-scattered electrons sufficient for imaging. In addition to the empirical imaging data, a probability analysis of the un-scattered fraction of the incident electron beam further supports the feasibility of atmospheric SEM imaging over a controlled membrane-sample distance.

A novel approach for scanning electron microscopic observation in atmospheric pressure

Atmospheric scanning electron microscopy (ASEM) for observing samples at ambient atmospheric pressure is introduced in this study. An additional specimen chamber with a thin membrane allowing electron beam propagation is inserted in the main specimen chamber. Close proximity of the sample to the membrane enables the detection of backscattered electrons (BSEs) sufficient for imaging. A probability analysis of the un-scattered fraction of the incident electron beam and the beam profile further supports the feasibility of atmospheric SEM imaging over a controlled membrane-sample distance. An image enhancement method based on the analysis is introduced for the ASEM.

Reduction of Electron Scattering Image Blur for Atmospheric Scanning Electron Microscopy

Recently, methods for observing samples under atmospheric pressure in a scanning electron microscope (SEM) have been reported by some investigators. We proposed a novel atmospheric SEM (ASEM) technique for observing samples which are present in ambient air conditions but are separated from the membrane [1]. In our system, the environment around the sample can be kept in ambient air conditions (Fig. 1(a)). While wet materials is clearly observed without direct sample membrane contact at an optimized distance, typical atmospheric SEM image taken in atmosphere is more blurred compared to conventional SEM image taken in vacuum condition. The reason why ASEM images looks like “blurred” is because electron beam is scattered by electron scattering region shown in Fig. 1(b). In order to reduce the electron scattering effect, some methods utilizing light element gas [2] or additional vacuum pump to reduce pressure [1] (10 4 ~10 5 Pa) have been developed. A typical atmospheric SEM image is shown in Fig. 1(c). Brightness of point B is brighter than that of point A, although the edge of number “9” is clear. The image gives us a consideration that the profile of electron beam arriving at sample is estimated as sum of scattered and un-scattered electrons beam. As a result, the image in Fig. 1(c) seems to be blurred. Based on the consideration, we develop an image enhancement algorism for ASEM (electron scattering corrector: ES-Corrector). By using this algorism, blurring created by scattered electrons in ASEM image can be improved after detection of SEM image. Figure 2 shows SEM images of Cu mesh (Fig. 2(a)(b)) taken in atmospheric pressure. Figure 2(c) and (d) are restored images using ES-Corrector. The images show great improvements in clarity and edge sharpness than the observed images. The microstructures on Cu mesh observed in Fig. 2(c) and (d) are compatible to those in SEM images taken in vacuum Fig. 2(e) and (f). Figure 3 shows SEM images of a filter paper (Fig. 3(a)), renal glomerulus without metal staining (Fig. 2(b)), a leaf surface of the Japanese radish(Fig. 3(c)), and blood cells fixed with 1% glutaraldehyde and immune-stained with gold particles (Fig. 3(d)) taken in atmospheric pressure at room temperature. Figure 3(a)-(h) is the original and restored images. The images show great improvements in clarity and edge sharpness than the observed images. It has been shown that the ES-Corrector algorism to reduce effect of scattered electrons from ASEM image can improve image quality.

Observation of Wet Samples Using a Novel Atmospheric Scanning Electron Microscope

The scanning electron microscope (SEM) has been used as a powerful tool for providing surface information of micro and nanostructures. In recent years, SEM methods for observing wet samples under atmospheric pressure have been reported by some investigators [1-2]. With these methods, the sample space is separated by a thin transparent membrane from vacuum environment where electron beam is propagated, and samples attaching to the membrane are observed by SEM.