Optimization of the buffer surface of CoFeB/MgO/CoFeB-based magnetic tunnel junctions by ion beam milling

• Type: Article in International Scientific Journal
• Date: 2017

Authors

Martins, L (Author) Other; ventura, j. (Author) FCUP; Ferreira, R (Author) Other; Freitas, PP (Author) Other

Journal

Title: Applied Surface Science

Vol. 424

Pages: 58-62

ISSN: 0169-4332

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 7 Citations

Scopus - 7 Citations

Other information

Authenticus ID: P-00N-19Y

DOI: 10.1016/j.apsusc.2017.02.112

Abstract (EN): Due to their high tunnel magnetoresistance (TMR) ratios at room temperature, magnetic tunnel junctions(MTJs) with a crystalline MgO insulating barrier and CoFeB ferromagnetic (FM) layers are the best candidates for novel magnetic memory applications. To overcome impedance matching problems in electronic circuits, the MgO barrier must have an ultra-low thickness (similar to 1 nm). Therefore, it is mandatory to optimizethe MTJ fabrication process, in order to prevent relevant defects in the MgO barrier that could affect the magnetic and electrical MTJ properties. Here, a smoothing process aiming to decrease the roughness of the buffer surface before the deposition of the full MTJ stack is proposed. An ion beam milling process was used to etch the surface of an MTJ buffer structure with a Ru top layer. The morphologic results prove an effective decrease of the Ru surface roughness with the etching time. The electrical and magnetic results obtained for MTJs with smoothed buffer structures show a direct influence of the buffer roughness and coupling field on the improvement of the TMR ratio.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5