清华大学2007年电子显微分析期末考试试题.doc

清华大学2007年电子显微分析期末考试试题考试科目：电子显微分析考试时间：2007年试卷类型： 本科期末Examination of Electron Microscopy and Analysis (Jan. 2007)Question sheet ADepartment:Name (in Chinese):Student ID No.:Section ISection IISection IIITotalScoreSectionI.(20 marks. The answers should be written in English onthisquestion sheet)1.There are two diffraction spotsG1and G2inan electron diffraction pattern. Theexcitation error (s)ofG1is m and theexcitation errorofG2is2m(m0). Which diffraction spot looks brighter,G1orG2? ()(2 marks)2. The thickness of a TEM specimen is usually thinner than 100nm. Write out two TEM specimen preparation methods that can make TEM specimen of ceramic samples with the required thickness. ()(2 marks)3. You want to take an atomic resolution image of a specimen, but you do not want the image contrast to alter with a change in defocusing. Which technique should you use? (HRTEM,HAADF, EF-TEM)(2 marks)4. O Kaline is at 520eV and Cr Lais at 590eV. If you want to separate them using an X-ray analysis technique in SEM, which technique should you use?(). If you want to distinguish diamond from graphite using microanalysis technique in TEM, which technique should you use ? () If you want to determine if a materials is polycrystalline or amorphous using TEM, which technique should you use?()(3 marks)5. The side length of the CRT of a SEM is100mmand the scanning distance of the electron beam on an object in a specimen is0.02mm. What is the real length of this object if the image of the object displayed on the CRT has a length of5mm?()(3 marks)6. The Kikuchi lines can be used for measuring a small tilting angle. If you tilt a sample holder by a small angle and the corresponding movement of the Kikuchi lines is7mm, how many degree have you tilted (assume the camera length L is800mm) ?()(4 marks)7. The TEM of aPhilips CM-120 has an accelerating voltage of 120kV. What is the wavelength of the electron beam (Relativistic effects should be taken into account)?()Assume n=1 and sina=0.95, what is the theoretical resolution of this TEM. ()(4 marks)Section II. (30 marks. The answers should be written in English or Chinese on the answer book)1. Explain briefly what is a bright field (BF) image and what is a centered dark field (CDF) image. (The optical ray diagram of BF and CDF images should be drawn).(10marks)2. What is the principle of observing defects in crystalline material using diffraction contrast imaging? Are the shape and size of the real defect the same as those of its diffraction contrast image? (Give an example to support your answer)(10 marks)3. The size of the selected area in selected area diffraction (SAD) of TEM depends on the size of the SAD aperture. Is it possible to obtain a SAD from an area of0.05mm in diameter if the size of the SAD aperture is0.05mm? (The reason should be given). Are there any other methods that can be used to obtain a electron diffraction pattern from an area of0.05mm in size? (If yes, give the names of the techniques.)(10 marks)Section III. (50 marks. The answers should be written in English on the answer book)1(1) Find the corresponding twin reflection of the matrix reflection (420) in an fcc material if HKL=111, and determine if the diffraction spots of the twin reflection superimpose with the diffraction spots of the matrix reflection?(2) Find the corresponding twin reflections of the matrix reflection (110) in a bcc material if HKL= 11, and determine if the diffraction spots of the twin reflection superimpose with the diffraction spots of the matrix reflection?(10 marks)2. The electron diffraction pattern of an fcc material is shown in the figure, whereR1R2=10mm, R3=16.3mm, the angle between R1and R2isq170, and the angle between R2and R3isq235.The camera constantLlis2.05mmnm.Index the diffraction pattern anddete