How to grow single-crystalline and epitaxial NiTi films in (100)- and (111)-orientation

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Klara Lünser - , Chair of Metallic Materials and Metal Physics, Helmholtz-Zentrum Dresden-Rossendorf, Leibniz Institute for Solid State and Materials Research Dresden, TUD Dresden University of Technology (Author)
  • Andreas Undisz - , Chemnitz University of Technology, Friedrich Schiller University Jena (Author)
  • Kornelius Nielsch - , Chair of Metallic Materials and Metal Physics, Leibniz Institute for Solid State and Materials Research Dresden, TUD Dresden University of Technology (Author)
  • Sebastian Fähler - , Helmholtz-Zentrum Dresden-Rossendorf (Author)

Abstract

Understanding the martensitic microstructure in nickel-titanium (NiTi) thin films helps to optimize their properties for applications in microsystems. Epitaxial and single-crystalline films can serve as model systems to understand the microstructure, as well as to exploit the anisotropic mechanical properties of NiTi. Here, we analyze the growth of NiTi on single-crystalline MgO(100) and Al2O3(0001) substrates and optimize film and buffer deposition conditions to achieve epitaxial films in (100)- and (111)-orientation. On MgO(100), we compare the transformation behavior and crystal quality of (100)-oriented NiTi films on different buffer layers. We demonstrate that a vanadium buffer layer helps to decrease the low-angle grain boundary density in the NiTi film, which inhibits undesired growth twins and leads to higher transformation temperatures. On Al2O3(0001), we analyze the orientation of a chromium buffer layer and find that it grows (111)-oriented only in a narrow temperature range around 500 C. By depositing the Cr buffer below the NiTi film, we can prepare (111)-oriented, epitaxial films with transformation temperatures above room temperature. Transmission electron microscopy confirms a martensitic microstructure with Guinier Preston-zone precipitates at room temperature. We identify the deposition conditions to approach the ideal single crystalline state, which is beneficial for the analysis of the martensitic microstructure and anisotropic mechanical properties in different film orientations.

Details

Original languageEnglish
Article number035002
JournalJPhys materials
Volume6
Issue number3
Publication statusPublished - 1 Jul 2023
Peer-reviewedYes

Keywords

Keywords

  • epitaxial film growth, NiTi films, nitinol, shape memory alloys