Reflection high-energy electron diffraction (RHEED)

4.8 SummaryRHEED provides similar information to LEEDSurface sensitivity can be varied somewhat by changing incidence angle (20->500 Å)Very simple, inexpensive instrumentation amenable to MBE, MOCVD andfilm growth situationsRapid for simple analysisRocking curves can be used with theory to measure atomic positions butdifficultBUTRHEED theory not fully developed (many body multiple scattering theory)Only information in 1-D without azimuthal crystal rotationSensitive to surface roughness - not intrinsically surface sensitiveX-ray scattering techniques sensitive to short range order - accurate nearestneighbor distancesWorks for disordered materials unlike diffractionInformation about chemical environmentIntrinsically bulk sensitive - can be made surface sensitive by- grazing incidence- using core edge of adsorbate- collecting low energy electronsSimple instrumentation (in principle)NEXAFS resonances useful for determining orientation of adsorbateCEM 924 7.18 Spring 2001