Xray Diffraction What are Xrays EM waves Characterized

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)

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

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)

X-ray 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

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

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

X-ray Diffraction XRD Schematic

X-ray Diffraction

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