1. X-ray Diffraction What are X-rays?  E-M waves : Characterized by high frequency, high energy  Wavelength: 0.01 – 10 nm  Invisible to Human Eye (Visible Spectrum: 390 -750 nm)

2. X-ray Diffraction Applications:  Medical  Material Science Engineering/ Crystallography  Geologists many more… Our Interest !!  Studying crystal structure of different semiconductor materials  Is it crystalline, amorphous, polycrystalline..  Crystal parameters: lattice constants, Miller Planes

3. X-ray Diffraction How are X-rays produced ?  Tungsten: Electron Beam (same as ordinary light bulb)  Electron beam is accelerated – Electric Field  Impinge on target material – Usually Copper or Molybdenum  Target: Absorbs high energy electron --- Emit photons (high energy X-rays)

4. X-ray Diffraction Diffraction  Bending of propagating light waves --- around the obstacles  Same as Interference concept !!  Effects of diffractions are more pronounced : Wavelength of light -- - comparable to the size of the obstacles

5. Diffraction Contd..  What happens if the # of slits is high and continuous ?? X-ray Diffraction Classroom Demo !!

6. X-ray Diffraction Bragg’s Law:  Replace slits – series of atoms..  “d” Interplanar distance  http://www.eserc.stonybrook.edu/projectjava/bragg/ http://www.eserc.stonybrook.edu/projectjava/bragg/ Derivation: nλ= AB +BC AB = dsinθ But, AB = BC nλ= 2AB nλ = 2dsinθ

7. X-ray Diffraction XRD Schematic

8. X-ray Diffraction

9. Single Crystal Ex: Si (100), (110), (111) planes Polycrystalline (Powder XRD)Amorphous: Glass X-ray Diffraction