Nanofabrication of Fresnel zone plate lenses for X-ray optics

Abstract

Fresnel zone plate (FZP) lenses are, in many cases, essential elements to obtain X-ray microbeams in synchrotron light (SL) facilities. They have become a common optical device during the latest years. The increasing complexity of the relevant scientific problems is associated with an increasing demand on the optical performances of the X-ray microscopy to the point that the optical elements have to be tailored to fit the characteristics of the optical source and of the sample. This fact justifies a research effort to optimize and simplify the fabrication processes of such devices. However, FZP fabrication for X-ray wavelengths is not straightforward, since the involved dimensions are in the nanometer scale. A joint effort involving CELLS (consortium for the development of a synchrotron light source in Barcelona), the Optics Department of the Autonomous University and the Microelectronics Center in Barcelona has been recently undertaken in order to develop the processes for the fabrication of FZP lenses as X-ray focusing elements. In this paper, we present the first results using a very simple lift-off technique, which up to now allows the fabrication of FZP with sub-100 nm resolution with 110 nm metal rings.