TEM构造、成像方式及变倍原理 1
1 TEM构造、成像方式及变倍原理
TEM构造、成像方式及变倍原理 ,TEM的照明、成像、观察记录、真空及电源系统 TEM的主要部件一样品台、光阑 TEM成像方式 Source-filament plus anode plates with Electron gun applied accelerating voltage. Vacuum Condenser Lenses-electromagnetic lenses column adjusted by lens currents not position. 。TEM变倍原理 Tilt rotation Specimen Stage-allows translations and tilts. Objective Lens-usually <50X. Imaging System-multiple electromagnetic lenses below the objective:set magnification, focal plane (image vs.diffraction pattern). Phosphor Detector/lmaging-fluorescent screen,plate screen:film: digital recording film,CCD camera. system Instruments often have attachments such as 1 in 1020 electrons X-ray detectors are collected 2
TEM的照明、成像、观察记录、真空及电源系统 TEM的主要部件—样品台、光阑 TEM成像方式 TEM变倍原理 2 TEM构造、成像方式及变倍原理
Structure of a TEM Example TEM schematic One of many types of TEMs Filament PHILIPS Wehnelt "Gun" Anode Gun deflectors 照明系统 Condensor aperture 1 8日 (may be adustable by user depending on TEM type) Condensor lens 1 Condensor stigmator Fixed aperture Condensor lens 2 Beam deflectors Condensor aperture 2 Sample holder Objective stigmator Objective lens upper Objective lens lower 样品室 Objective aperture Image deflectors Selected area aperture (or immediate aperture) Intermediate lens Diffraction stigmator 成像系统/ 11 Projector lens 1 Projector lens 2 图像观察 CCD camera Beam axis Viewing screen 3
3 Structure of a TEM 照明系统 成像系统/ 图像观察 样品室
照明系统 组成：电子枪、聚光镜和相应的平移对中、倾 斜调节装置组成 ·作用：提供一束高亮度、孔径半角小、平行度 好、束流稳定的电子波；通过聚光镜的控制可 以实现从平行照明到大会聚角的照明条件；为 满足中心暗场成像的需要，照明电子束可在 2~3°范围内倾斜 4
4 照明系统 • 组成：电子枪、聚光镜和相应的平移对中、倾 斜调节装置组成 • 作用：提供一束高亮度、孔径半角小、平行度 好、束流稳定的电子波；通过聚光镜的控制可 以实现从平行照明到大会聚角的照明条件；为 满足中心暗场成像的需要，照明电子束可在 2~3°范围内倾斜
照明系统 ·电子枪 1 CATHODE(negative potential) ·Thermionic(热电子) 2 WEHNELT Bias resistor ELECTRODE Tungsten (negative potential) LaB6 10-1000kV Space o Field emission(场发射) charge Electron Beam Crossover Cold FEG 3 ANODE PLATE Schottky FEG (positive potential) Ground Tungsten(W)hair-pin filament LaB.Tip Field-emission gun Tip 5
5 照明系统 Tungsten (W) hair-pin filament LaB6 Tip Field-emission gun Tip • 电子枪 • Thermionic (热电子) – Tungsten – LaB6 • Field emission (场发射) – Cold FEG – Schottky FEG
照明系统 ·电子枪 Units Tungsten LaB Schottky FEG Cold FEG Operating temperature K 2700 1700 1700 300 Work function,Φ eV 4.5 2.4 3.0 4.5 Current density A/m2 5 102 105 106 Crossover size nm >105 104 15 2~3 Brightness A/m2sr 1010 5x1011 5x1012 1013 Energy spread eV 3 1.5 0.7 0.3 Emission current stability %/hr 5000 >5000 6
Units Tungsten LaB6 Schottky FEG Cold FEG Operating temperature K 2700 1700 1700 300 Work function, Φ eV 4.5 2.4 3.0 4.5 Current density A/m2 5 102 105 106 Crossover size nm >105 104 15 2~3 Brightness A/m2sr 1010 5x1011 5x1012 1013 Energy spread eV 3 1.5 0.7 0.3 Emission current stability %/hr 5000 >5000 6 照明系统 • 电子枪
Structure of a TEM Example TEM schematic One of many types of TEMs Filament PHILIPS Wehnelt "Gun" Anode Gun deflectors 照明系统 Condensor aperture 1 (may be adustable by user depending on TEM type) C J Condensor lens 1 Condensor stigmator Fixed aperture Condensor lens 2 Beam deflectors Condensor aperture 2 Objective stigmator Sample holder Objective lens upper Objective lens lower 样品室 Objective aperture Image deflectors Selected area aperture (or immediate aperture) Intermediate lens Diffraction stigmator 成像系统/ 11 Projector lens 1 Projector lens 2 图像观察 CCD camera Beam axis Viewing screen 7
7 Structure of a TEM 照明系统 成像系统/ 图像观察 样品室
照明系统 聚光镜：会聚电子枪射出的电子束，以最小的损失照 明样品，调节照明强度、孔径角和束斑大小 第1聚光镜 第2聚光镜 光阑 会聚小透镜 (CM透镜) 物镜 前置磁场 试样 后置磁场 (a)TEM模式 (b)EDS模式(C)NBD模式(d)CBED模式 8
8 照明系统 • 聚光镜：会聚电子枪射出的电子束，以最小的损失照 明样品，调节照明强度、孔径角和束斑大小 (a) TEM模式 (b) EDS模式 (c) NBD模式 (d) CBED模式
照明系统 聚光镜：利用磁偏转器可使电子束平移、偏转 平移：上、下偏转线圈偏转角相等，但方向相反 倾斜：上线圈偏0转角，下线圈反方向偏转0+β角，则倾斜了角β 上偏转线圈 ∽ 下偏转线圈 L +B 聚光镜电子束对中系统工作原理图 9
9 照明系统 • 聚光镜：利用磁偏转器可使电子束平移、偏转 聚光镜电子束对中系统工作原理图 平移: 上、下偏转线圈偏转角相等，但方向相反 倾斜: 上线圈偏θ转角，下线圈反方向偏转 θ+β角，则倾斜了角β
Structure of a TEM Example TEM schematic One of many types of TEMs Filament PHILIPS Wehnelt "Gun" Anode 照明系统 Condensor aperture 1 8日 Gun deflectors (may be adustable by user depending on TEM type) 1 Condensor lens 1 Fixed aperture Condensor stigmator Condensor lens 2 Beam deflectors Condensor aperture 2 Obiective stiamator Sample holder Objective lens upper Objective lens lower 样品室 Objective aperture Image deflectors Selected area aperture (or immediate aperture) Intermediate lens Diffraction stigmator 成像系统/ Projector lens 1 Projector lens 2 图像观察 CCD camera Beam axis Viewing screen 10
10 Structure of a TEM 照明系统 成像系统/ 图像观察 样品室