Prediction of first-order martensitic transitions in strained epitaxial films

M Richter,K Koepernik,S Schönecker,H Eschrig

doi:10.1088/1367-2630/17/2/023005

Abstract

Coherent epitaxial growth allows us to produce strained crystalline films with structures that are unstable in the bulk. Thereby, the overlayer lattice parameters in the interface plane, (a, b), determine the minimum-energy out-of-plane lattice parameter, . We show by means of density-functional total energy calculations that this dependence can be discontinuous and predict related first-order phase transitions in strained tetragonal films of the elements V, Nb, Ru, La, Os, and Ir. The abrupt change of can be exploited to switch properties specific to the overlayer material. This is demonstrated for the example of the superconducting critical temperature of a vanadium film which we predict to jump by 20% at a discontinuity of .

Highlights

Epitaxy is an important concept for the fabrication of films with good crystalline quality like overlayers, multilayers, compound materials, and ordered alloys
The face-centered cubic (FCC) structure was found at a saddle point of E(a, c) and assigned to a maximum of EEBP [11, 15, 28, 29]
We have shown that coherently grown epitaxial films can exhibit a discontinuous relation between in-plane and out-of-plane lattice parameters in a strain-driven first-order phase transition

Summary

Introduction

Epitaxy is an important concept for the fabrication of films with good crystalline quality like overlayers, multilayers, compound materials, and ordered alloys. Such films are technologically important materials with adjustable electronic, magnetic, and optical properties [1]. In coherent or pseudomorphic film growth, the in-plane film lattice parameters are determined by the substrate-in-plane lattice parameters. This allows to expose a material to static, non-isotropic but homogeneous strain which is a valuable mean to influence its intrinsic properties [4]. Even a continuous variation of the lattice parameters and of the related film properties was achieved [7, 8]

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Conclusion