Growth of ultimate high-density scintillating films for high-resolution X-ray imaging at synchrotrons

Abstract

Scintillators are X-ray to visible light converters applied in X-ray imaging detectors used at synchrotrons. Drastically improved performances of the 4${}^{th}$ generation synchrotron sources enable us to perform X-ray imaging experiments at higher energies. For high spatial resolution X-ray imaging (micrometer to submicrometer), thin scintillating films are required. Consequently, especially for high X-ray energies (30 keV to 100 keV), the detection efficiency is limited due to the low X-ray absorption efficiency of the thin films. We have used Liquid Phase Epitaxy (LPE) to grow thin films of one of the ultimate high-density materials, Lu${}_2$Hf${}_2$O${}_7$:Eu${}^{3+}$, which demonstrate scintillating properties and thus combine high spatial resolution and maximized absorption efficiency. X-ray imaging experiments demonstrate that the Modulation Transfer Function (MTF) reaches 10% at 900 lp/mm, and radiographs visually confirm the promising imaging properties. We present structural, luminescent, and scintillation characterization of Lu${}_2$Hf${}_2$O${}_7$:Eu thin films grown on ZrO${}_2$:Y substrates, showing that the films crystallize in the disordered fluorite structure and the europium ions incorporate into the structure and enhance the luminescence intensity. This contribution is a first step toward developing promising ultra-dense, hafnate-based scintillating screens for high spatial resolution X-ray imaging.