Combinatorial fabrication and cathodoluminescence properties of composition spread MHfO3:Tm3+(M = Ca, Sr and Ba) films

A series of MHfO3:Tm3+ (M=Ca, Sr and Ba) films were fabricated on SrTiO3 (0 0 1) substrate by using combinatorial pulsed laser deposition (PLD) technique. Their crystal structures and luminescence properties were characterized by the concurrent X-ray diffraction (CXRD) and by the cathodoluminescence (CL) using 5 kV electron beam, respectively. By monitoring the reflection high energy electron diffraction (RHEED) intensity oscillation, the growth of MHfO3:Tm3+ films were optimized to proceed in a epitaxial layer-by-layer fashion. Different from bulk powders, which had the highest CL intensity in SrHfO3:Tm3+, the composition spread film of Sr1−xCaxHfO3:Tm3+ (x=0–1) exhibited the highest CL intensity at x=0.7 rather than SrHfO3:Tm3+ (x=0). This anomalous behavior in the films is discussed in view of the stress effect from the substrate.