By Wolfgang Braun
The publication describes RHEED (reflection high-energy electron diffraction) used as a device for crystal development. New tools utilizing RHEED to symbolize surfaces and interfaces in the course of crystal progress via MBE (molecular beam epitaxy) are provided. precise emphasis is wear RHEED depth oscillations, segregation phenomena, electron energy-loss spectroscopy and RHEED with rotating substrates.
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Additional resources for Applied RHEED: Reflection High-Energy Electron Diffraction During Crystal Growth
The calculation time therefore depends linearly on the number of scatterers and allows the treatment of large unit cells. In this way, even surface superstructures of complicated subunits can be simulated with relatively little effort. From the experimentalist's viewpoint, a rough and quick estimate of a diffraction pattern is often more useful than a comprehensive, but involved treatment. Kinematical theory is ideal for this purpose. The typical problems associated with RHEED comprise the determination of material parameters such as atomic spacing, surface roughness and crystal potential, or the test of proposed surface structures.
In favorable cases, a study of these parameters as a function of either growth or diffraction parameters allows the analysis of growth mechanisms as well as the nature of the diffraction. We briefly review some important results. During layer-by-layer growth in MBE, the surface periodically changes its morphology because of the nucleation and coalescence of islands in the growing layers. The damping of the oscillations and the recovery after growth both happen on a timescale considerably longer than the oscillation period.
4. 5) grown on GaAs at about 20 ~ below the optimum for GaAs ~(2 x 4). After 720 oscillations, the amplitude is still about 1/6 of the starting value Whereas the results presented so far suggest a correlation between surface roughness and R H E E D intensity, this notion is no longer supported when we look at the phase of the oscillations. For repeated measurements with the same growth conditions, the phase of the oscillations depends strongly on incidence angle and azimuth [167,168]. We cannot, therefore, generally identify any feature in the R H E E D oscillation cycle with a particular position 1 o 0 -- A 9 [ll0] / [0101 ,7 [1101 / f\.