Real-time monitoring of strain accumulation and relief during epitaxy of ultrathin Co ferrite films with varied Co content

DOI: 10.3390/ma16237287

Authors: Jannis Thien (Osnabrück University) , Jari Rodewald (Osnabrück University) , Tobias Pohlmann (Osnabrück University; Deutsches Elektronen-Synchrotron (DESY)) , Kevin Ruwisch (Osnabrück University) , Florian Bertram (Deutsches Elektronen-Synchrotron (DESY)) , Karsten Kuepper (Osnabrück University) , Joachim Wollschlager (Osnabrück University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Materials , VOL 16

State: Published (Approved)
Published: November 2023
Diamond Proposal Number(s): 20857

Abstract: Ultrathin Co𝑥 Fe3−𝑥 O4 films of high structural quality and with different Co content (x = 0.6–1.2) were prepared by reactive molecular beam epitaxy on MgO(001) substrates. Epitaxy of these ferrite films is extensively monitored by means of time-resolved (operando) X-ray diffraction recorded in out-of-plane geometry to characterize the temporal evolution of the film structure. The Co ferrite films show high crystalline ordering and smooth film interfaces independent of their Co content. All Co𝑥 Fe3−𝑥 O4 films exhibit enhanced compressive out-of-plane strain during the early stages of growth, which partly releases with increasing film thickness. When the Co content of the ferrite films increases, the vertical-layer distances increase, accompanied by slightly increasing film roughnesses. The latter result is supported by surface-sensitive low-energy electron diffraction as well as X-ray reflectivity measurements on the final films. In contrast, the substrate–film interface roughness decreases with increasing Co content, which is confirmed with X-ray reflectivity measurements. In addition, the composition and electronic structure of the ferrite films is characterized by means of hard X-ray photoelectron spectroscopy performed after film growth. The experiments reveal the expected increasing Fe3+ /Fe2+ cation ratios for a higher Co content.

Journal Keywords: cobalt ferrite; ultrathin films; strain; X-ray diffraction

Diamond Keywords: Spintronics

Subject Areas: Materials, Physics


Instruments: I07-Surface & interface diffraction

Other Facilities: P22 at PETRA III at DESY

Added On: 29/11/2023 11:32

Documents:
materials-16-07287.pdf

Discipline Tags:

Surfaces Quantum Materials Physics Hard condensed matter - structures Electronics Materials Science interfaces and thin films

Technical Tags:

Diffraction Low Energy Electron Diffraction (LEED)