Reflection high-energy electron diffraction (RHEED)
Reflection high-energy electron diffraction (RHEED)
Reflection high-energy electron diffraction (RHEED)
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4.5.1 InstrumentationElectrons 5-100 keV directed towards sample at very near θ i 90° - keeps evenlong-pathlength (<strong>high</strong>-<strong>energy</strong>) <strong>electron</strong>s in near-surface regionForward-diffracted <strong>electron</strong>s strike phosphor screenGrid used to repel secondary and inelastically scattered <strong>electron</strong>s4.5.2 Basic Theory of <strong>RHEED</strong>Theory very similar to LEED (Ewald sphere) but incident wavevector rk nowvery large:Example: 50 keV <strong>electron</strong> incident in [110] direction of Cu (a 0 =3.56 Å)λ =2m(eV)= 5.5x10 −12 m= 0.055 Årk = 2π λ= 114 Å −1and reciprocal lattice spacing isCEM 924 7.2 Spring 2001
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