Retrieving the displacement of strained nanoobjects: the impact of bounds for the scattering magnitude in direct space

• Published in: Optics express Vol. 21; no. 23; pp. 27734 - 27749
• Main Authors: Köhl, Martin, Schroth, Philipp, Minkevich, A A, Baumbach, Tilo
• Format: Journal Article
• Language: English
• Published: United States 18-11-2013
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.21.027734

Coherent X-ray diffraction imaging (CXDI) of the displacement field and strain distribution of nanostructures in kinematic far-field conditions requires solving a set of non-linear and non-local equations. One approach to solving these equations, which utilizes only the object's geometry and the intensity distribution in the vicinity of a Bragg peak as a priori knowledge, is the HIO+ER-algorithm. Despite its success for a number of applications, reconstruction in the case of highly strained nanostructures is likely to fail. To overcome the algorithm's current limitations, we propose the HIO(O(R))(M)+ER(M)-algorithm which allows taking advantage of additional a priori knowledge of the local scattering magnitude and remedies HIO+ER's stagnation by incorporation of randomized overrelaxation at the same time. This approach achieves significant improvements in CXDI data analysis at high strains and greatly reduces sensitivity to the reconstruction's initial guess. These benefits are demonstrated in a systematic numerical study for a periodic array of strained silicon nanowires. Finally, appropriate treatment of reciprocal space points below noise level is investigated.