tailieunhanh - ENCYCLOPEDIA OF MATERIALS CHARACTERIZATIONC phần 2

Bốn kỹ thuật bao gồm trong chương này đều có kính hiển vi trong tên của họ. Vai trò của họ (nhưng chắc chắn không phải chỉ duy nhất của họ) để cung cấp một hình ảnh phóng đại. Mục tiêu, đơn giản nhất, là quan sát các tính năng vượt quá độ phân giải của mắt người (khoảng 100). Kể từ khi mắt sử dụng ánh sáng bước sóng có thể nhìn thấy, | 2 IMAGING TECHNIQUES MICROSCOPY Light Microscopy 60 Scanning Electton Microscopy SEM 70 Scanning Tunneling Scanning Force Microscopy STM and SFM 85 Transmission Electron Microscopy TEM 99 INTRODUCTION The four techniques included in this chapter all have microscopy in their names. Their role but certainly not only their only one is to provide a magnified image. The objective at its simplest is to observe features that are beyond the resolution of the human eye about 100 pm . Since the eye uses visible wavelength light only a Light Microscope can do this direcdy. Reflected or transmitted light from the sample enters the eye after passing through a magnification column. All other microscopy imaging techniques use some other interaction probe and response signal usually electrons to provide the contrast that produces an image. The response signal image or map is then processed in some way to provide an optical equivalent picture for US to see. We usually think of images as three dimensional with the object as solid. The microscopies have different capabilities not only in terms of magnification and lateral resolution but also in their ability to represent depth. In the light microscope topological contrast is provided largely by shadowing in reflection. In Scanning Electron Microscopy SEM the topological contrast is there because the efficiency of generating secondary electrons the signal which originate from the several top tens of nanometers of material strongly depends on the angle at which the probe beam strikes the surface. In Scanning Tunneling Microscopy Scanning Force Microscopy STM SFM the surface is directly profiled by scanning a tip capable of following topology at atomic-scale resolution 57 across the surface. In Transmission Electron Microscopy TEM which can also achieve atomic-scale lateral resolution no depth information is obtained because the technique works by having the probe electron beam transmined through a sample that is up