Recent progress of atomic resolution holography: from point defects to defect complexes

Atomic-resolution holography, which uses X-rays or neutrons with wavelengths of about 1 Å, is a technique for visualizing three-dimensional local structures around specific elements, and its variations were demonstrated between 1990 and 2001. Subsequently, it was used to analyze the local structure of point defects such as dopants in single crystals. However, with the development of apparatuses and analytical methods, it has come to be used to elucidate more complex structures such as defect complexes or interface defects. In this review, we introduce basics and our recent activities in X-ray fluorescence holography, neutron holography, and photoelectron holography.