TY - JOUR
T1 - 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
AU - Song, Jin Oh
AU - Lee, Seong Rae
AU - Shin, Hyun Joon
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.
PY - 2007/1
Y1 - 2007/1
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.
KW - Barrier thickness
KW - Low resistance MTJ
KW - Magnetic tunnel junction
KW - TiAlO barrier
UR - http://www.scopus.com/inward/record.url?scp=33749265475&partnerID=8YFLogxK
U2 - 10.1016/j.cap.2005.06.007
DO - 10.1016/j.cap.2005.06.007
M3 - Article
AN - SCOPUS:33749265475
VL - 7
SP - 18
EP - 20
JO - Current Applied Physics
JF - Current Applied Physics
SN - 1567-1739
IS - 1
ER -