Growth, microstructure and thermal transformation behaviour of epitaxial Ni-Ti films

TL;DR

This study explores the growth and properties of epitaxial Ni-Ti thin films on MgO substrates, demonstrating how deposition conditions influence their microstructure and reversible martensitic transformation behavior.

Contribution

It introduces optimized sputter deposition and heat treatment protocols for producing high-quality epitaxial Ni-Ti films with controlled microstructure and transformation characteristics.

Findings

Epitaxial Ni-Ti films can be grown on MgO substrates with proper conditions.

Controlled heat treatments improve film quality and transformation behavior.

Films exhibit reversible martensitic transformations.

Abstract

Epitaxial films have the potential to be used as model systems for fundamental investigations on the martensitic transformation in binary NiTi. In this paper, we discuss growth of binary NiTi thin films on single crystalline MgO substrates. Sputter deposition is used to grow NiTi films. Films prepared by complementary preparation routes (with different deposition temperatures and subsequent heat treatments) are investigated by X-ray diffraction, electron microscopy, atomic force microscopy, and electrical resistivity measurements, with the aim of optimizing film properties, particularly to obtain a well defined orientation of the austenitic unit cell and smooth surfaces. Our results show that deposition at elevated temperatures and carefully controlled subsequent heat treatments allow to produce epitaxially grown and smooth NiTi films that exhibit reversible one- or two-step martensitic transformations.