The breakup of dislocation dipoles in plastically deformed samples of undoped and 30‐ppm‐MgO‐doped sapphire (α‐Al2O3) was monitored using conventional TEM techniques. Dislocation dipoles break up into prismatic dislocation loops in a sequential process during annealing; i.e., dislocation loops are pinched off at the end of a dislocation dipole. This pinch‐off process is primarily controlled by pipe diffusion, and pipe diffusion coefficients at temperatures between 1300° and 1500°C were estimated by monitoring the kinetics of the dipole breakup process. We determined DPU= 8.1(–4.3+9.1) × 10–3 exp [–(4.5 ± 1.3eV)/kT)] m2/s for the undoped material. The pipe diffusion kinetics for the MgO‐doped crystal was determined at 1250° and 1300°C and was about 6 times higher than for undoped sapphire. Finally, climb dissociation of the dislocations constituting the perfect dipoles in sapphire is common; annihilation of one set of partials can result in the formation of faulted dipoles, which can pinch off to form faulted dislocation loops. DPU for faulted dipoles in the undoped material was determined at 1300° and 1350°C, and was about 4–10 times higher than for perfect dipoles.

Spontaneous CuPt ordering is observed in AlxIn1−xP layers grown by metal-organic vapor-phase epitaxy in pure nitrogen ambient with tertiarybutylphosphine as phosphorus precursor. Changes of the degree of ordering of the AlxIn1−xP epilayer versus annealing temperature have been investigated by using photoluminescence and transmission electron diffraction. The degree of ordering of the AlxIn1−xP layers is reduced after annealing the sample at a temperature higher than the sample growth temperature. It becomes completely disordered when the annealing temperature reaches 900°C and above.