Coherent x-ray diffraction imaging in the reflection geometry is desirable since it offers many advantages, including (1) lensless technique without need of object lenses, (2) few restrictions on sample size, chambers or environments, (3) suitable for studies of thin films grown on any substrates, (4) no need of pin holes near samples as in holography-based techniques, and (5) easily expandable to resonant coherent x-ray imaging.

We demonstrate by numerical simulation that atomic structures on single crystal surface can be reconstructed using the ptychography coherent x-ray diffraction imaging in the reflection geometry. Our approach is based on the concept of crystal truncation rod. We can obtain the highest surface sensitivity at anti-Bragg condition, and achieve a phase contrast up to from a single atomic step. Ptychograhy scanning scheme allows us to overcome the stringent requirement for isolated samples in typical CDI experiments. We will show experimental results from real platinum (001) surfaces and their ptychography reconstructions. This technique can be readily applied to buried interfaces under catalytic and electrochemical conditions and to nanoscience applications, such as nanowire with stacking faults.
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