Influence of thickness and band structure of insulating barriers on resistance and tunneling magnetoresistance properties of magnetic tunnel junctions with Al-oxide and Ti-alloyed Al-oxide barriers

Jin Oh Song; Seong Rae Lee; Hyun Joon Shin

doi:10.1016/j.cap.2005.06.007

Influence of thickness and band structure of insulating barriers on resistance and tunneling magnetoresistance properties of magnetic tunnel junctions with Al-oxide and Ti-alloyed Al-oxide barriers

Jin Oh Song, Seong Rae Lee, Hyun Joon Shin

Department of Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

5 Citations (Scopus)

Abstract

We investigated the influence of insulating barrier thickness and the Ti composition dependence of the band structure of Al-oxide on the resistance and tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junction (MTJ). Low resistance × area (RA) value (1.1 MΩ μm²) was achieved by decreasing the Al-oxide thickness down to 1.0 nm. However, this led to the partial oxidation of the bottom ferromagnetic (FM) electrode of the junction and non-continuous thin barriers by the occurrence of pinholes, with low TMR ratio of 8.3%. For an alternative for low RA value, we developed a new Ti-alloyed Al-oxide (TiAlO_x) that had lower band gap than Al-oxide as an insulating barrier of MTJ. As the Ti concentration increased up to 5.33 at.% Ti in Al, the RA value of the MTJs was reduced from 9.5 to 0.69 MΩ μm², owing to the band-gap reduction of TiAlO_x caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlO_x has localized d states in the band gap below the conduction band. In addition, the TMR ratio increased with the Ti concentration and reached a maximum of 49% at 5.33 at.% Ti owing to the microstructural evolution of Ti-Al alloy film in the pre-oxidation state.

Original language	English
Pages (from-to)	18-20
Number of pages	3
Journal	Current Applied Physics
Volume	7
Issue number	1
DOIs	https://doi.org/10.1016/j.cap.2005.06.007
Publication status	Published - 2007 Jan

Bibliographical note

Funding Information:
This work was supported by the Korea Ministry of Science and Technology under contract National Research Laboratory program and the Korea research Foundation Grant (KRF-2004-005-C00068) and the Basic Research Program of the Korea Science and Engineering Foundation Grant (R-01-2005-000-11188-0). The authors also gratefully acknowledge the Korea University’s support for the Korea University’s 100th Anniversary Symposium on the State of the Art and the Prospect of the Interdisciplinary Nano Sciences.

Keywords

Barrier thickness
Low resistance MTJ
Magnetic tunnel junction
TiAlO barrier

ASJC Scopus subject areas

General Materials Science
General Physics and Astronomy

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10.1016/j.cap.2005.06.007

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Influence of thickness and band structure of insulating barriers on resistance and tunneling magnetoresistance properties of magnetic tunnel junctions with Al-oxide and Ti-alloyed Al-oxide barriers. / Song, Jin Oh; Lee, Seong Rae; Shin, Hyun Joon.
In: Current Applied Physics, Vol. 7, No. 1, 01.2007, p. 18-20.

Research output: Contribution to journal › Article › peer-review

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title = "Influence of thickness and band structure of insulating barriers on resistance and tunneling magnetoresistance properties of magnetic tunnel junctions with Al-oxide and Ti-alloyed Al-oxide barriers",

abstract = "We investigated the influence of insulating barrier thickness and the Ti composition dependence of the band structure of Al-oxide on the resistance and tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junction (MTJ). Low resistance × area (RA) value (1.1 MΩ μm2) was achieved by decreasing the Al-oxide thickness down to 1.0 nm. However, this led to the partial oxidation of the bottom ferromagnetic (FM) electrode of the junction and non-continuous thin barriers by the occurrence of pinholes, with low TMR ratio of 8.3%. For an alternative for low RA value, we developed a new Ti-alloyed Al-oxide (TiAlOx) that had lower band gap than Al-oxide as an insulating barrier of MTJ. As the Ti concentration increased up to 5.33 at.% Ti in Al, the RA value of the MTJs was reduced from 9.5 to 0.69 MΩ μm2, owing to the band-gap reduction of TiAlOx caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlOx has localized d states in the band gap below the conduction band. In addition, the TMR ratio increased with the Ti concentration and reached a maximum of 49% at 5.33 at.% Ti owing to the microstructural evolution of Ti-Al alloy film in the pre-oxidation state.",

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N1 - Funding Information: This work was supported by the Korea Ministry of Science and Technology under contract National Research Laboratory program and the Korea research Foundation Grant (KRF-2004-005-C00068) and the Basic Research Program of the Korea Science and Engineering Foundation Grant (R-01-2005-000-11188-0). The authors also gratefully acknowledge the Korea University’s support for the Korea University’s 100th Anniversary Symposium on the State of the Art and the Prospect of the Interdisciplinary Nano Sciences.

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N2 - We investigated the influence of insulating barrier thickness and the Ti composition dependence of the band structure of Al-oxide on the resistance and tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junction (MTJ). Low resistance × area (RA) value (1.1 MΩ μm2) was achieved by decreasing the Al-oxide thickness down to 1.0 nm. However, this led to the partial oxidation of the bottom ferromagnetic (FM) electrode of the junction and non-continuous thin barriers by the occurrence of pinholes, with low TMR ratio of 8.3%. For an alternative for low RA value, we developed a new Ti-alloyed Al-oxide (TiAlOx) that had lower band gap than Al-oxide as an insulating barrier of MTJ. As the Ti concentration increased up to 5.33 at.% Ti in Al, the RA value of the MTJs was reduced from 9.5 to 0.69 MΩ μm2, owing to the band-gap reduction of TiAlOx caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlOx has localized d states in the band gap below the conduction band. In addition, the TMR ratio increased with the Ti concentration and reached a maximum of 49% at 5.33 at.% Ti owing to the microstructural evolution of Ti-Al alloy film in the pre-oxidation state.

AB - We investigated the influence of insulating barrier thickness and the Ti composition dependence of the band structure of Al-oxide on the resistance and tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junction (MTJ). Low resistance × area (RA) value (1.1 MΩ μm2) was achieved by decreasing the Al-oxide thickness down to 1.0 nm. However, this led to the partial oxidation of the bottom ferromagnetic (FM) electrode of the junction and non-continuous thin barriers by the occurrence of pinholes, with low TMR ratio of 8.3%. For an alternative for low RA value, we developed a new Ti-alloyed Al-oxide (TiAlOx) that had lower band gap than Al-oxide as an insulating barrier of MTJ. As the Ti concentration increased up to 5.33 at.% Ti in Al, the RA value of the MTJs was reduced from 9.5 to 0.69 MΩ μm2, owing to the band-gap reduction of TiAlOx caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlOx has localized d states in the band gap below the conduction band. In addition, the TMR ratio increased with the Ti concentration and reached a maximum of 49% at 5.33 at.% Ti owing to the microstructural evolution of Ti-Al alloy film in the pre-oxidation state.

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Influence of thickness and band structure of insulating barriers on resistance and tunneling magnetoresistance properties of magnetic tunnel junctions with Al-oxide and Ti-alloyed Al-oxide barriers

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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