Comparison of strain field in cleaved XSTM specimen with un-cleaved InAs/GaAs quantum dot nanostructure

A three-dimensional finite element analysis has been carried out to investigate the strain field at the surface of cleaved cross-sectional scanning tunnelling microscopy (XSTM) specimen of InAs quantum dots embedded in GaAs matrix. As a comparison standard, the strain field in un-cleaved state has also been analysed. As compared with the bulk state, the tensile εzz strain component increases significantly at the cleaved surface, especially at the central region of the dot, where the experimental determination of the strain is usually performed. On the other hand, magnitudes of the compressive εxx and εyy components decrease with the cleavage of specimen. Development of shear strain, εzx, with the specimen cleavage is most apparent at the base and top surface of the truncated dot. Therefore, care has to be taken when referring to experimentally determined strain information based on XSTM specimen, since the artefact due to the cleavage of the specimen is involved in the experimental data.