{"id":1669,"date":"2019-05-22T02:47:38","date_gmt":"2019-05-22T02:47:38","guid":{"rendered":"http:\/\/www.meetyoucarbide.com\/single-post-the-science-of-high-resolution-electron-micro-graphs\/"},"modified":"2020-05-04T13:12:07","modified_gmt":"2020-05-04T13:12:07","slug":"the-science-of-high-resolution-electron-micro-graphs","status":"publish","type":"post","link":"https:\/\/www.meetyoucarbide.com\/pt\/the-science-of-high-resolution-electron-micro-graphs\/","title":{"rendered":"A ci\u00eancia dos micro-gr\u00e1ficos eletr\u00f4nicos de alta resolu\u00e7\u00e3o"},"content":{"rendered":"
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Microscopia eletr\u00f4nica de transmiss\u00e3o de alta resolu\u00e7\u00e3o (HRTEM ou HREM) \u00e9 o contraste de fase (o contraste de imagens de microscopia eletr\u00f4nica de alta resolu\u00e7\u00e3o \u00e9 formado pela diferen\u00e7a de fase entre a onda projetada sintetizada e a onda difratada, \u00e9 chamada de contraste de fase). Microscopia, que fornece um arranjo at\u00f4mico da maioria dos materiais cristalinos.<\/div>\n
High-resolution transmission electron microscopy began in the 1950s. In 1956, JWMenter directly observed parallel strips of 12 \u00c5 copper phthalocyanine with a resolution of 8 \u00c5 transmission electron microscope, and opened high-resolution electron microscopy. The door to surgery. In the early 1970s, in 1971, Iijima Chengman used a TEM with a resolution of 3.5 \u00c5 to capture the phase contrast image of Ti2Nb10O29, and directly observed the projection of the atomic group along the incident electron beam. At the same time, the research on high resolution image imaging theory and analysis technology has also made important progress. In the 1970s and 1980s, the electron microscope technology was continuously improved, and the resolution was greatly improved. Generally, the large TEM has been able to guarantee a crystal resolution of 1.44 \u00c5 and a dot resolution of 2 to 3 \u00c5. HRTEM can not only observe the lattice fringe image reflecting the interplanar spacing, but also observe the structural image of the arrangement of atoms or groups in the reaction crystal structure. Recently, Professor David A. Muller’s team at Cornell University in the United States used laminated imaging technology and an independently developed electron microscope pixel array detector to achieve a spatial resolution of 0.39 \u00c5 under low electron beam energy imaging conditions.<\/div>\n
Atualmente, os microsc\u00f3pios eletr\u00f4nicos de transmiss\u00e3o geralmente s\u00e3o capazes de realizar HRTEM. Esses microsc\u00f3pios eletr\u00f4nicos de transmiss\u00e3o s\u00e3o classificados em dois tipos: alta resolu\u00e7\u00e3o e anal\u00edtico. O TEM de alta resolu\u00e7\u00e3o \u00e9 equipado com uma pe\u00e7a de p\u00f3lo objetivo de alta resolu\u00e7\u00e3o e uma combina\u00e7\u00e3o de diafragma, o que torna o \u00e2ngulo de inclina\u00e7\u00e3o da mesa de amostra pequeno, resultando em um menor coeficiente de aberra\u00e7\u00e3o esf\u00e9rica objetivo; enquanto o TEM anal\u00edtico requer uma quantidade maior para v\u00e1rias an\u00e1lises. O \u00e2ngulo de inclina\u00e7\u00e3o do est\u00e1gio de amostra, de modo que o suporte da haste da lente objetiva \u00e9 usado de maneira diferente do tipo de alta resolu\u00e7\u00e3o, afetando a resolu\u00e7\u00e3o. Em geral, um TEM de alta resolu\u00e7\u00e3o de 200 kev tem uma resolu\u00e7\u00e3o de 1,9 \u00c5, enquanto um TEM anal\u00edtico de 200 kev tem um 2,3 \u00c5. Mas isso n\u00e3o afeta a TEM anal\u00edtica que captura a imagem de alta resolu\u00e7\u00e3o.<\/div>\n

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As shown in Fig. 1, the optical path diagram of the high-resolution electron microscopy imaging process, when an electron beam with a certain wavelength (\u03bb) is incident on a crystal with a crystal plane spacing d, the Bragg condition (2dsin \u03b8 = \u03bb) is satisfied, A diffracted wave is generated at an angle (2\u03b8). This diffracted wave converges on the back focal plane of the objective lens to form a diffraction spot (in an electron microscope, a regular diffraction spot formed on the back focal plane is projected onto the phosphor screen, which is a so-called electron diffraction pattern). When the diffracted wave on the back focal plane continues to move forward, the diffracted wave is synthesized, an enlarged image (electron microscopic image) is formed on the image plane, and two or more large objective lens stops can be inserted on the back focal plane. Wave interference imaging, called high-resolution electron microscopy, is called a high-resolution electron microscopic image (high-resolution microscopic image).<\/div>\n
Como mencionado acima, a imagem microsc\u00f3pica eletr\u00f4nica de alta resolu\u00e7\u00e3o \u00e9 uma imagem microsc\u00f3pica de contraste de fase formada pela passagem do feixe transmitido do plano focal da lente objetiva e dos v\u00e1rios feixes difratados atrav\u00e9s da pupila objetiva, devido \u00e0 sua coer\u00eancia de fase. Devido \u00e0 diferen\u00e7a no n\u00famero de feixes difratados participantes da gera\u00e7\u00e3o de imagens, s\u00e3o obtidas imagens de alta resolu\u00e7\u00e3o de nomes diferentes. Devido \u00e0s diferentes condi\u00e7\u00f5es de difra\u00e7\u00e3o e espessura da amostra, as micrografias eletr\u00f4nicas de alta resolu\u00e7\u00e3o com diferentes informa\u00e7\u00f5es estruturais podem ser divididas em cinco categorias: franjas de treli\u00e7a, imagens estruturais unidimensionais, imagens de treli\u00e7a bidimensional (imagens de c\u00e9lula \u00fanica), bidimensionais imagem da estrutura (imagem em escala at\u00f4mica: imagem da estrutura cristalina), imagem especial.<\/div>\n
Franjas de treli\u00e7a: Se um feixe de transmiss\u00e3o no plano focal traseiro for selecionado pela lente objetiva e um feixe de difra\u00e7\u00e3o interferir entre si, \u00e9 obtido um padr\u00e3o de franja unidimensional com uma mudan\u00e7a peri\u00f3dica de intensidade (como mostrado pelo tri\u00e2ngulo preto em Fig. 2 (f)) Essa \u00e9 a diferen\u00e7a entre uma franja de rede e uma imagem de rede e uma imagem estrutural, que n\u00e3o exige que o feixe de el\u00e9trons seja exatamente paralelo ao plano da rede. Na verdade, na observa\u00e7\u00e3o de cristalitos, precipitados e similares, as franjas de treli\u00e7a s\u00e3o frequentemente obtidas por interfer\u00eancia entre uma onda de proje\u00e7\u00e3o e uma onda de difra\u00e7\u00e3o. Se um padr\u00e3o de difra\u00e7\u00e3o de el\u00e9trons de uma subst\u00e2ncia como cristalitos for fotografado, um anel de adora\u00e7\u00e3o aparecer\u00e1 como mostrado na (a) da Fig. 2.<\/div>\n

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Imagem da estrutura unidimensional: se a amostra tiver uma certa inclina\u00e7\u00e3o, de modo que o feixe de el\u00e9trons seja paralelo a um determinado plano de cristal do cristal, ele pode satisfazer o padr\u00e3o de difra\u00e7\u00e3o de difra\u00e7\u00e3o unidimensional mostrado na Fig. 2 (b) ( distribui\u00e7\u00e3o sim\u00e9trica em rela\u00e7\u00e3o ao ponto de transmiss\u00e3o) Padr\u00e3o de difra\u00e7\u00e3o). Nesse padr\u00e3o de difra\u00e7\u00e3o, a imagem de alta resolu\u00e7\u00e3o obtida sob a condi\u00e7\u00e3o de foco ideal \u00e9 diferente da franja da rede e a imagem da estrutura unidimensional cont\u00e9m as informa\u00e7\u00f5es da estrutura do cristal, ou seja, a imagem da estrutura unidimensional obtida, como mostrado na Fig. 3 (uma imagem estrutural unidimensional de alta resolu\u00e7\u00e3o do \u00f3xido supercondutor de base bi-mostrada.<\/div>\n
Two-dimensional lattice image: If the electron beam is incident parallel to a certain crystal axis, a two-dimensional diffraction pattern can be obtained (two-dimensional symmetric distribution with respect to the central transmission spot, shown in Fig. 2(c)). For such an electron diffraction pattern. In the vicinity of the transmission spot, a diffraction wave reflecting the crystal unit cell appears. In the two-dimensional image generated by the interference between the diffracted wave and the transmitted wave, a two-dimensional lattice image showing the unit cell can be observed, and this image contains information on the unit cell scale. However, information that does not contain an atomic scale (into atomic arrangement), that is, a two-dimensional lattice image is a two-dimensional lattice image of single crystal silicon as shown in Fig. 3(d).<\/div>\n
Two-dimensional structure image: a diffraction pattern as shown in Fig. 2(d) is obtained. When a high-resolution electron microscope image is observed with such a diffraction pattern, the more diffraction waves involved in imaging, the information contained in the high-resolution image is also The more. A high-resolution two-dimensional structure image of the Tl2Ba2CuO6 superconducting oxide is shown in Fig. 3(e). However, the diffraction of the high-wavelength side with higher resolution limit of the electron microscope is unlikely to participate in the imaging of the correct structure information, and becomes the background. Therefore, within the range allowed by the resolution. By imaging with as many diffracted waves as possible, it is possible to obtain an image containing the correct information of the arrangement of atoms within the unit cell. The structure image can only be observed in a thin region excited by the proportional relationship between the wave participating in imaging and the thickness of the sample.<\/div>\n

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Imagem especial: No padr\u00e3o de difra\u00e7\u00e3o do plano focal traseiro, a inser\u00e7\u00e3o da abertura seleciona apenas a imagem de onda espec\u00edfica para poder observar a imagem do contraste da informa\u00e7\u00e3o estrutural espec\u00edfica. Um exemplo t\u00edpico disso \u00e9 uma estrutura ordenada como. O padr\u00e3o de difra\u00e7\u00e3o de el\u00e9trons correspondente \u00e9 mostrado na Fig. 2 (e) como o padr\u00e3o de difra\u00e7\u00e3o de el\u00e9trons da liga ordenada por Au, Cd. A estrutura ordenada \u00e9 baseada em uma estrutura c\u00fabica centrada na face na qual os \u00e1tomos de Cd s\u00e3o organizados em ordem. Fig. 2 (e) os padr\u00f5es de difra\u00e7\u00e3o de el\u00e9trons s\u00e3o fracos, exceto pelas reflex\u00f5es b\u00e1sicas da rede dos \u00edndices (020) e (008). Reflex\u00e3o ordenada da estrutura, usando a lente objetiva para extrair a reflex\u00e3o b\u00e1sica da estrutura, usando ondas de transmiss\u00e3o e imagens ordenadas da reflex\u00e3o da estrutura, apenas \u00e1tomos de Cd com pontos brilhantes ou pontos escuros, como alta resolu\u00e7\u00e3o, como mostrado na Fig. 4.<\/div>\n

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Conforme mostrado na Fig. 4, a imagem de alta resolu\u00e7\u00e3o mostrada varia com a espessura da amostra perto do foco desfocado de alta resolu\u00e7\u00e3o ideal. Portanto, quando obtemos uma imagem de alta resolu\u00e7\u00e3o, n\u00e3o podemos simplesmente dizer qual \u00e9 a imagem de alta resolu\u00e7\u00e3o. Primeiro, precisamos fazer uma simula\u00e7\u00e3o por computador para calcular a estrutura do material sob diferentes espessuras. Uma imagem de alta resolu\u00e7\u00e3o da subst\u00e2ncia. Uma s\u00e9rie de imagens de alta resolu\u00e7\u00e3o calculadas pelo computador s\u00e3o comparadas com as imagens de alta resolu\u00e7\u00e3o obtidas pelo experimento para determinar as imagens de alta resolu\u00e7\u00e3o obtidas pelo experimento. A imagem de simula\u00e7\u00e3o por computador mostrada na Fig. 5 \u00e9 comparada com a imagem de alta resolu\u00e7\u00e3o obtida pelo experimento.<\/div>\n

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High resolution transmission electron microscopy (HRTEM or HREM) is the phase contrast (the contrast of high-resolution electron microscopy images is formed by the phase difference between the synthesized projected wave and the diffracted wave, It is called phase contrast.) Microscopy, which gives an atomic arrangement of most crystalline materials. High-resolution transmission electron microscopy began in…<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[79],"tags":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/posts\/1669"}],"collection":[{"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/comments?post=1669"}],"version-history":[{"count":0,"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/posts\/1669\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/media?parent=1669"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/categories?post=1669"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/pt\/wp-json\/wp\/v2\/tags?post=1669"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}