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.
We describe a nanometer-scale manipulatoion and cutting method using ultrasonic oscillation scratching. The system is based on a modified atomic force microscope (AFM) coupled with a haptic device as a human interface. By handling the haptic device, the operator can directly move the AFM probe to manipulate nanometer scale objects and cut a surface while feeling the reaction from the surface in his or her fingers. As for manipulation using the system, nanometer-scale spheres were controllably moved by feeling the sensation of the AFM probe touching the spheres. As for cutting performance, the samples were prepared on an AT-cut quartz crystal resonator (QCR) set on an AFM sample holder. The QCR oscillates at its resonance frequency (9 MHz) with an amplitude of a few nanometers. Thus it is possible to cut the sample surface smoothly by the interaction between the AFM probe and the oscillating surface, even when the samples are viscoelastics such as polymers and biological samples. The ultrasonic nano-manipulation and cutting system would be a very useful and effective tool in the fields of nanometer-scale engineering and biological sciences.
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 4~1 0 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.
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.In the present study, we developed a table-top atmospheric SEM (ASEM) for observing samples which are present in ambient air conditions but are separated from the membrane (Fig.1). Our ASEM has an inner chamber inside a regular specimen chamber. This inner chamber is equipped with an attachable thin membrane on its roof. When a sample should be exchanged, the specimen stage is extracted from the inner chamber ( Fig. 1(b)). In this configuration, the environment around the sample can be kept in ambient air conditions and changed by evaporation with an additional vacuum pump (Fig. 1(c)). Moreover, the higher vacuum observation can be also performed after removing the membrane from the inner chamber (Fig. 1(d)). This means that our ASEM enables observation of samples under not only atmospheric but also various-ranged vacuum pressures.Using our ASEM, we observed wet regenerated cellulose fibers at atmospheric pressure (Fig. 2). After obtaining an image of wet fibers (Fig. 2(a)), the specimen chamber was evaporated using the additional vacuum pump and the same fibers were observed in different pressure conditions. Measurement from the SEM images shows that the fibers shrunk approximately 25 % in diameter after evaporation (Fig. 2(b) and (c)), indicating that the fibers swell with water. We also succeeded in observing wet biological samples including blood cells and renal glomerulus at atmospheric pressure (Fig. 3(a) and (b)). We further compared an ASEM image of the mildew fungus with its light microscopic image, (Fig. 3(c) and (d)). No additional preparation of samples are not required between light microscope and our ASEM, which allows to be widely used for evaluation of wet materials observed using ASEM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.