Imaging of quantum array structures with coherent and partially coherent diffraction

J. Synchrotron Rad. (2003), 10, 409–415

A 2D array of quantum dots (a), shape of individual island (b) and corresponding coherent diffraction patterns (c, d).

Quantum structures on the nanometer scale are important elements of modern technology. Their electronic properties directly depend on the structure of these devices. We propose to use the technique of coherent X-ray diffraction in combination with phase retrieval methods based on the Gerchberg–Saxton–Fienup algorithm to image quantum dots in a model-independent way. An image of a quantum dot array and its diffraction pattern is shown to the right. We have shown that the correct shape and orientation of the individual island can be obtained in the case of coherent illumination. We also demonstrated the possibility of imaging individual islands with partially coherent illumination when the coherence length of the incoming beam is reduced to match the size of the island.