Upcoming Events

Quantitative Phase Nanotomography from Ptychography Projections

July 31, 2012 2:00PM to 3:00PM
Presenter 
Ana Diaz, Paul Scherrer Institut
Location 
Building 223, Room S105
Type 
Seminar
Series 
Materials Science Seminar
Abstract:
Imaging objects of several tens of microns in thickness with high resolution in three dimensions (3D) is a challenging task. It has recently been shown that ptychographic diffractive imaging is a promising approach to image such objects in 3D with a resolution in the 100 nm range [1]. In ptychography, a finite coherent illumination is used to record diffraction patterns in the far field from overlapping areas of the sample, and iterative phase retrieval algorithms are used to retrieve the complex wave field past the specimen. Tomographic reconstruction of projections at different angles allows the 3D imaging of samples, yielding a quantitative measurement of the electron density.

Here we present our last results about the evaluation of the quantitativeness and sensitivity of ptychographic tomography with a test object of known structure and density. We show that this technique provides the expected density values in (42 nm)3 voxels with a relative error of 5%, while this can be reduced below 1% in a volume of (1.6 mm)3 of a homogeneous region of the sample [2]. We also show the application of this technique for the imaging of hardened cement paste, for which ptychographic tomography has enabled segmentation of several hydrated and non-hydrated cement components while finding accurate density values for each component [3].

References:
[1] M. Dierolf, A. Menzel, P. Thibault, P. Schneider, C. M. Kewish, R. Wepf, O. Bunk, and F. Pfeiffer, Nature (2010) 467, 436.
[2] A. Diaz, P. Trtik, M. Guizar-Sicairos, A. Menzel, P. Thibault, and O. Bunk, Phys. Rev. B (2012) 85, 020104(R).
[3] P. Trtik, A. Diaz, M. Guizar-Sicairos, A. Menzel, and O. Bunk, accepted in Cement Concrete Comp. (2012), DOI: 10.1016/j.cemconcomp.2012.06.001