The early history and future of the SEM

Abstract

The early history and development of the scanning electron microscope (SEM) up to the time of the first commercial SEMs has been described by Oatley.1 In the first instance, commercial SEMs were manufactured both in England 2 and in Japan.3 -5 The history of the SEM has also been described by many authors.6 -21 Improvements in the performance and in the ease of operation of commercial SEMs have been remarkable and are expected to continue. Knoll 22,24 achieved four important experimental results using the apparatus shown in Fig. 1: (i) He obtained the specimen of a current image from solid polycrystalline sample as shown in Fig. 2. (ii) This image shows orientationdependent contrasts between grains as would now appear to be caused by electron channeling contrast. (iii) He measured the secondary electron (SE) plus backscattered electron (BSE) coefficient as a function of incident beam energy E 0 from various materials and showed that there is a 'second crossover' value of ¾1.5 keV for E 0 when SE C BSE coefficient is unity. The charging of the specimen is then minimized and is also stable. (iv) He measured the potential to which a nonconducting particle is charged by the beam by an early version of quantitative voltage contrast. Figure 3 shows an electron scattering model for the generation of SE that was proposed by von Ardenne, 25 which shows initial beam-broadening; wide-angle scattering; diffusion; escape of BSE and the excitation of SE at every stage. He proposed two kinds of high-resolution SE images. The first (now called SE-I imaging following a detailed discussion by Peters 26 ) is with E 0 equal to several tens of kiloelectronvolts so that the penetration depth (a few micrometers) is many times greater than the SE escape depth

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A model for roughness statistics of heterogeneous fibrous materials

“…We proceed to compare the predictions of Eqs. 9and (15) to (18) with surface roughness data obtained from the literature and with experiments carried out using paper samples with systematically varying properties.…”

“…As might be anticipated given the long-standing and still ubiquitous use of printed paper, there is a substantial literature relating surface topography of paper to print quality, see, for example, [10][11][12][13][14]. Indeed, the first industrial application of scanning electron microscopy was the analysis of the surface of papers [15,16] to understand its influence on printability. Perhaps, the earliest quantitative analysis of paper topography is provided by Hsu [17,18], who reported lognormal, i.e.…”

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