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MICROSCOPIC TECHNIQUES LIKE SEM,TEM,AFM,EDAX,STM.pptx
- 1. MICROSCOPIC TECHNIQUES (SEM,TEM,AFM,STM,EDAX) KARTHIKKUMAR R RESEARCH SCHLOAR SAS-CHEMISTRY VIT CHENNAI Dr. Ritu Mamgain Assistant Professor SCHOOL OF ADVANCED SCIENCES VIT UNIVERSITY , CHENNAI APPLICATION OF ADVANCED INSTRUMENTATION
- 2. ELECTRON MICROSCOPE What are electron microscopy? Microscope that attains extremely high resolution using an electron beam of light to illuminate the object of the study.
- 3. INFORMATION • TOPOGRAPHY The internal surface future of an object ( hardness, reflectivity,etc..,) • MORPHOLOGY The shape and size of the particles • COMPOSITION The elements and compounds that the object is composed of and the relative amount of them. • CRYSTALLOGRAPHIC INFORMATION How the atoms are arranged in the objects
- 4. TYPES OF ELECTRON MICROSCOPY There are two types of microscopes, namely, 1. Scanning electron microscopy (SEM) – Used to visualize the surface of objects 2. Transmission electron microscopy (TEM) – Used to visualize the inner surface of the objects
- 5. INNER STRUCTURE OF MICROSCOPES
- 6. SCANNING ELECTRON MICROSCOPE • Directly visualise the surface topography of solid unsectioned specimens. • Probe scan the specimen in square pattern. • The first scanning electron microscope (SEM) debuted in 1938 (Van Ardenne ) with commercial instruments around 1965 • SEM can achieve resolution better than 1 nm • Acceleration voltage : 5 KV – 30 KV • Resolution ≥ 0.7 nm • Larger specimen chamber
- 7. PRINCIPLE • The basic principle is that a beam of electrons is generated by a suitable source, typically tungsten filament or a filled emission gun. • The electron beam is accelerated through a high voltage (eg-20kv) and pass through a system of apertures and electromagnetic lenses to produce a thin beam of electron. • Then the beam of electron scan the surface of the specimen. Electrons are emitted from the specimen by the action of the scanning beam and collected by a suitablyc-positioned detectors
- 8. HOW THE SEM WORKS
- 10. COMPONENTS OF SEM • Electron gun - Tungsten filament or field emission gun • Condenser lens – Just like optical microscope and its used to focus and control the electron beam. • Specimen chamber – maintained at high vacuum • Detectors – secondary electron ,backscattered electron and X-RAY • Amplifier – magnifies the image • Vacuum tube – The vacuum pressure of 10-7 to 10-9 pa is applied .
- 14. SECONDARY ELECTRONS • Generated from collision between the incoming electrons the loosely bonded outer electrons • Low energy electrons (῀10 – 50 eV) • Only SE generated close to surface escape ( topographic information is obtained )
- 15. BACKSCATTERED ELECTRONS • Backscattered electrons (BSEs) are generated by elastic scattering events. When the electrons in the primary beam travel close to the atom’s nuclei in the specimen, their trajectory is deviated due to the force they feel with the positive charges in the nuclei. Depending on the size of the atom nuclei, the number of backscattered electrons differs. • High energy electrons • fewer BSE than SE Elastic scattering occurs when there is no loss of energy of the incident primary electron
- 18. ADVANTAGES
- 19. DISADVANTAGES
- 20. APPLICATIONS
- 21. SOFTWARES TO ANALYSIS SEM IMAGES • ImageJ / FIJI • Gwyddion • SPIP™ (Scanning Probe Image Processor) • Avizo • MATLAB Image Processing Toolbox • NanoScope Analysis (Bruker) • Photoshop / Adobe Photoshop Elements
- 23. WORKING CONCEPT OF TEM
- 25. using this image we find lattice points and crystal structure
- 26. Selected area electron diffraction (SAED) is a crystallographic experimental techniqu
- 27. COMPONENTS OF TEM • Electron gun – V-shaped filament and whenelt clinder and anode plate • Condenser lens – Just like optical microscope and its used to focus and control the electron beam. • Specimen chamber – maintained at high vacuum • Objective lens – placed below the specimen stage • Projector lens – its collects the magnified image and focus onto fluorescent screen • Amplifier – magnifies the image • Vacuum tube – The vacuum pressure of 10-7 to 10-9 pa is applied .
- 30. ADVANTAGES • Has the highest magnification abilities (up to 1,000,000x or higher) • Offers detailed information on compound and element structures • Produces high-quality images with accurate details • Easy to learn and operate • Compatible with various applications in various fields
- 31. DISADVANTAGES • Takes a lot of time to prepare • Requires special training to operate and analyze specimens • Only specimens that are electron transparent can be used • Specimen has to be very small • Images only come in black and white
- 33. EDAX – Energy Dispersive Analysis X-ray Spectroscopy 5/9/2024 33
- 34. 5/9/2024 34 EDX stands for Energy Dispersive X-ray analysis, Sometimes referred to also EDS or EDAX analysis. This tool is available in Scanning and Transmission Electron Microscope (SEM/TEM) machine. Change the mode form SEM/TEM to EDX. SEM-EDAX Instrument (EDX,EDS,EDXS,XEDS,EDXA,EDAX)
- 35. What we need to get from EDAX? EDAX is an analytical method used for determine the chemical elements present in the sample. Measure the multilayer coating thickness and analysis of various alloys. Used for identifying the element composition and quantitative analysis of the specimen. The EDX/EDS results are in weight percentage or Atomic percentage. 5/9/2024 35
- 36. Principle • The incident beam may excite an electron in an inner shell while creating a vacancy. • An electron from outer, higher energy shell fill the vacancy, the difference in energy between the higher energy shell and lower energy shell may be release in the X-ray. • The number and energy of the X-ray emitted form the specimen can be measure by Energy–Dispersive Spectrometer. 5/9/2024 36
- 37. 5/9/2024 37 The detector generated a charge pulse proportional to the X-ray energy. Pulse converted to voltage. The signal is amplified electronically as resulting from an X-ray of specific energy. Collected data it displays its intensity ie., (Number of counts) vs (voltage)
- 40. 5/9/2024 40
- 42. ATOMIC FORCE MICROSCOPY (AFM) • The atomic force microscope (AFM) is a type of scanning probe microscope whose • primary roles include measuring properties such as magnetism, height, friction. • The resolution is measured in a nanometer • Invented in 1982 and commercialized in 1989
- 43. PRINCIPLE The Atomic Force Microscope works on the principle measuring intermolecular forces and sees atoms by using probed surfaces of the specimen in nanoscale. Its functioning is enabled by three of its major working principles that include Surface sensing, Detection, and Imaging. SURFACE SENSING The Atomic Force Microscope (AFM) performs surface sensing by using a cantilever (an element that is made of a rigid block like a beam or plate, that attaches to the end of support, from which it protrudes making a perpendicularly flat connection that is vertical like a wall). The cantilever has a sharp tip that scans over the sample surface, by forming an attractive force between the surface and the tip when it draws closer to the sample surface. When it draws very close making contact with the surface of the sample, a repulsive force gradually takes control making the cantilever avert from the surface.
- 44. DETECTION • During the deflection of the cantilever away from the sample surface, there is a change in direction of reflection of the beam, and a laser beam detects the aversion, by reflecting off a beam from the flat surface of the cantilever. Using a positive-sensitive photo-diode (PSPD- a component that is based on silicon PIN diode technology and is used to measure the position of the integral focus of an incoming light signal), it tracks these changes of deflection and change in direction of the reflected beam and records them.
- 45. IMAGING • The Atomic Force Microscope (AFM) takes the image of the surface topography of the sample by force by scanning the cantilever over a section of interest. Depending on how raised or how low the surface of the sample is, it determines the deflection of the beam, which is monitored by the Positive-sensitive photo-diode (PSDP). The microscope has a feedback loop that controls the length of the cantilever tip just above the sample surface, therefore, it will maintain the laser position thus generating an accurate imaging map of the surface of the image.
- 46. HOW ARE FORCE MEASURED • The probe is placed on the end of the cantilever ( which one can think of as a spring ) • The amount of force between the probe and surface is dependant on the spring constant (stiffness of the cantilever and the distance between the probe and the sample surface). • This force can be described using Hookes law F = -k.x • Suppose you have an AFM cantilever with spring constant of K=0.1N/m when you approach the AFM tip to the sample surface, the cantilever bends, and lets say the deflection is d = 10nm Using Hookes law : F = -K.x = -(0.1N/m)*(10nm) = -(0.1N/m)*(10*109) F = -(1*10-10 N)
- 47. APPLICATIONS Some of these applications include: • Identifying atoms from samples • Evaluating force interactions between atoms • Studying the physical changing properties of atoms • Studying the structural and mechanical properties of protein complexes and assembly, such as microtubules. • used to differentiate cancer cells and normal cells. • Evaluating and differentiating neighboring cells and their shape and cell wall rigidity.
- 48. ADVANTAGES • Easy to prepare samples for observation • It can be used in vacuums, air, and liquids. • Measurement of sample sizes is accurate • It has a 3D imaging • It can be used to study living and nonliving elements • It can be used to quantify the roughness of surfaces • It is used in dynamic environments.
- 49. DISADVANTAGES • It can only scan a single nanosized image at a time of about 150x150nm. • They have a low scanning time which might cause thermal drift on the sample. • The tip and the sample can be damaged during detection. • It has a limited magnification and vertical range.