Critical temperature enhancement by biaxial compressive strain in FeSe0.5Te0.5 thin films

High-purity epitaxial FeSe(0.5)Te (0.5) thin films with different thicknesses were grown by pulsed laser ablation on different substrates. By varying the film thickness, T (c) values of up to 21 K were observed, significantly larger than the bulk value. Structural analyses indicated that the a axis changes significantly with the film thickness and is linearly related to T (c). The latter result indicates the important role of the compressive strain in enhancing T (c): the compressive strain derives from the Volmer-Weber growth of the films. The critical temperature is also related to both the Fe-(Se,Te) bond length and angle, suggesting the possibility of further enhancement.