Leader: Mikhail Avdeev
Work phone number: +7 (496) 216-26-74
Work E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Scientific problem:
Aperiodic neutron supermirrors are currently in use at most neutron scattering experimental facilities. These are multilayer systems consisting of two materials with high (e.g., Ni) and low (e.g., Ti) optical potentials. Supermirrors increase the angular or wavelength range of total reflection as compared to mirrors consisting of a single material with high optical potential. The thicknesses of sublayers in bilayers vary depending on the bilayer number in accordance with a certain algorithm. According to this algorithm, the change of thicknesses of neighboring bilayers is very small. It results in unavoidable roughness at layer interfaces that is a subject of special consideration when developing mass production of supermirrors on extended substrates using magnetron deposition. As a result, there is a common problem how to characterize and control the roughness modulation in a multiparameter system with a large number of inner interfaces varying in practice from several hundreds to several thousands of bilayers. In order to avoid this problem, alternative algorithms are considered, according to which the supermirror is produced as a set of periodic stacks with a certian number of identical bilayers.As compared to the aperiodic algorithm, it allows to improve the quality of interfaces and consequently, the quality of a supermirror as a whole. The detailed investigations of various approaches to roughness control in multilayer structures are required.
Objective:
Investigation of prototype supermirror structures imitating aperiodic and periodic structures at different deposition stages using specular XRR and neutron reflectometry. Obtaining and analysis of experimental reflectivity curves for the samples prepared with different algorithms of multilayer deposition.
Tasks:
1. Investigation of periodic multilayers for imitating roughness simulation in neutron supermirrors.
2. Investigation of special structures for improving characteristics of neutron optical coatings.
Research facilities: