13:30 〜 15:30
▲ [19p-P1-59] Preparation of Mg1-xTixO-based magnetic tunnel junctions with CoFeB electrodes
キーワード：magnetic tunnel junctions,barrier,tunneling magnetoresistance
The MgO-based magnetic tunnel junctions (MTJs) have been at the heart of development of spintronics application such as spin-transfer-torque magnetic random access memory (STT-MRAM), especially due to their giant tunneling magnetoresistance (TMR) ratio which is a result of coherent tunneling across the barrier[1]. Further development of gigabit-scale STT-MRAM requires MTJs with resitance-are product (RA) lower than 10 Ωμm2, which is very challenging for the MgO barrier considering its large band gap.
Substituting metallic elements for Mg sites can be used to tune the band gap of MgO barrier, hence its barrier height [2]. Here we report the study of Mg1-xTixO-based MTJs. MTJ stacks of Ta(5)/ Ru(10)/ Ta(5)/CoFeB(5)/Mg1-xTixO (0-1.8)/ CoFeB(4)/ Ta(5)/ Ru (5, in nm) were prepared by using the magnetron sputter, with x = 0, 0.1, and 0.2. The MTJ devices were fabricated by electron beam lithography, photolithography, and Argon-ion milling. The electrical measurement was performed by the four-probe method at room temperature.
The introduction of Ti was found to reduce the RA of MTJs for a given barrier thickness, as shown in Fig. 1, which is presumably caused by the reduction of barrier height. In general, the TMR ratio was found to decrease with increasing Ti concentration. The high TMR ratio of 240% and 160% were observed in Mg0.9Ti0.1O-based and Mg0.8Ti0.2O-based MTJs (Fig. 2), respectively, possibly due to the presence of coherent tunneling even in the alloyed-MgO barriers. The possibility of band gap tuning in the alloyed-MgO barrier with keeping the high TMR ratio is demonstrated in this work.
Substituting metallic elements for Mg sites can be used to tune the band gap of MgO barrier, hence its barrier height [2]. Here we report the study of Mg1-xTixO-based MTJs. MTJ stacks of Ta(5)/ Ru(10)/ Ta(5)/CoFeB(5)/Mg1-xTixO (0-1.8)/ CoFeB(4)/ Ta(5)/ Ru (5, in nm) were prepared by using the magnetron sputter, with x = 0, 0.1, and 0.2. The MTJ devices were fabricated by electron beam lithography, photolithography, and Argon-ion milling. The electrical measurement was performed by the four-probe method at room temperature.
The introduction of Ti was found to reduce the RA of MTJs for a given barrier thickness, as shown in Fig. 1, which is presumably caused by the reduction of barrier height. In general, the TMR ratio was found to decrease with increasing Ti concentration. The high TMR ratio of 240% and 160% were observed in Mg0.9Ti0.1O-based and Mg0.8Ti0.2O-based MTJs (Fig. 2), respectively, possibly due to the presence of coherent tunneling even in the alloyed-MgO barriers. The possibility of band gap tuning in the alloyed-MgO barrier with keeping the high TMR ratio is demonstrated in this work.