Dielectric breakdown of ferromagnetic tunnel junctions

Oepts, W.; Verhagen, HJ; Jonge, de Wjm Wim; Coehoorn, R.

doi:10.1063/1.122462

Cited by 70 publications

(41 citation statements)

References 10 publications

(10 reference statements)

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“…This is rather low compared with the MR ratio of 18% of identically fabricated Co/Al 2 O 3 /Co 50 Fe 50 junctions, within which the two magnetic layers have strongly different coercivities. 2 However, since the structure and thickness of the Al 2 O 3 layers in the Co/Al 2 O 3 /Co junctions employed in the present study are identical to those in the Co/Al 2 O 3 /Co 50 Fe 50 junctions mentioned, we regard our experimental data obtained on the breakdown effect as representative for junctions in which tunneling is strongly spin dependent.…”

Section: Resultsmentioning

confidence: 73%

“…For our tunnel junctions, we concluded in Ref. 2 that with increasing applied voltage the probability of breakdown per unit of time increases, and thus the lifetime at a fixed voltage decreases. We have been able to locate the position of the breakdown with a technique for visualizing hot spots on the junction surface that is described in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we have investigated breakdown voltages for a series of Co/Al 2 O 3 /Co tunnel junctions as a function of the voltage ramp speed. 2 The results of these measurements are given in Fig. 1 for a series of junctions with varying electrode widths.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of breakdown in ferromagnetic tunnel junctions

Oepts

Verhagen

Coehoorn

et al. 1999

Journal of Applied Physics

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Due to their very thin tunnel barrier layer, magnetic tunnel junctions show dielectric breakdown at voltages of the order of 1 V. At the moment of breakdown, a highly conductive short is formed in the barrier and is visible as a hot spot. The breakdown effect is investigated by means of voltage ramp experiments on a series of nominally identical Co/Al 2 O 3 /Co tunnel junctions. The results are described in terms of a voltage dependent breakdown probability, and are further analyzed within the framework of a general model for the breakdown probability in dielectric materials, within which it is assumed that at any time the breakdown probability is independent of the ͑possibly time-dependent͒ voltage that has been previously applied. The experimental data can be described by several specific forms of the voltage breakdown probability function. A comparison with the models commonly used for describing thin film SiO 2 breakdown is given, as well as suggestions for future experiments.

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Section: Resultsmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

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Analysis of breakdown in ferromagnetic tunnel junctions

Oepts

Verhagen

Coehoorn

et al. 1999

Journal of Applied Physics

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“…The dielectric breakdown of the junctions, which is of major importance for their reliability, has been investigated for the formerly used Alumina based [7,8,9,10] as well as the recently introduced MgO based MTJs [11] due to their possible use in electronic devices. These studies were generally done by analyzing the transport properties of the MTJs [7,8,9,11] and/ or indirect imaging of the proposed breakdown mechanism [10], generally single pinholes in the insulating barrier.…”

mentioning

confidence: 99%

“…These studies were generally done by analyzing the transport properties of the MTJs [7,8,9,11] and/ or indirect imaging of the proposed breakdown mechanism [10], generally single pinholes in the insulating barrier. Direct investigations of intact MTJs were also performed [12,13].…”

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confidence: 99%

Direct imaging of the structural change generated by dielectric breakdown in MgO based magnetic tunnel junctions

Thomas

Drewello

Schaefers

et al. 2008

Applied Physics Letters

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MgO based magnetic tunnel junctions are prepared to investigate the dielectric breakdown of the tunnel barrier. The breakdown is directly visualized by transmission electron microscopy measurements. The broken tunnel junctions are prepared for the microscopy measurements by focussed ion beam out of the junctions characterized by transport investigations. Consequently, a direct comparison of transport behavior and structure of the intact and broken junctions is obtained. Compared to earlier findings in Alumina based junctions, the MgO barrier shows much more microscopic pinholes after breakdown. This can be explained within a simple model assuming a relationship between the current density at the breakdown and the rate of pinhole formation.PACS numbers: 68.37. Lp, 85.30.Mn, In 1975 the tunnel magnetoresistance effect (TMR) in ferromagnet/ insulator/ ferromagnet systems was discovered by Jullière [1]. In 1995 significant TMR was found at room temperature [2,3]. Since then, magnetic tunnel junctions (MTJ) became potential candidates for magnetic random access memory (MRAM) [4] and have already replaced the giant magnetoresistance [5,6] read heads in hard discs.The dielectric breakdown of the junctions, which is of major importance for their reliability, has been investigated for the formerly used Alumina based [7,8,9, 10] as well as the recently introduced MgO based MTJs [11] due to their possible use in electronic devices. These studies were generally done by analyzing the transport properties of the MTJs [7,8,9,11] and/ or indirect imaging of the proposed breakdown mechanism [10], generally single pinholes in the insulating barrier. Direct investigations of intact MTJs were also performed [12,13].Here, we try to directly image the broken barriers of the tunnel junctions. In order to do this, we prepared MTJs and performed standard transport measurements. Then, one half of the junctions was stressed by high voltages to induce the dielectric breakdown. Finally, slices were cut out of the broken and intact junctions by focussed ion beam (FIB) and investigated with transmission electron microscopy (TEM). This allows to directly compare structure and transport properties of the intact and broken samples and to compare the findings with those of alumina based MTJs. A simple model is presented to explain the behavior. The magnetic tunnel junctions are prepared in a magnetron sputter system with a base pressure of 1 × 10 −7 mbar. The layer stack is * Electronic address: athomas@physik.uni-bielefeld.de; URL: http: //www.spinelectronics.de (100) wafer. To activate the exchange biasing and for the crystallization of the MgO barrier, the layer stack is annealed after sputtering at 623 K for 60 minutes in a magnetic field of 6500 Oe. The stack is patterned by optical lithography and ion beam etching. The junction sizes are between 7 × 7 and 22.5 × 22.5 µm 2 . All measurements are done by conventional two probe technique.The transmission electron microscopy samples were prepared by FIB with a FEI NOVA NANOLAB 600, which allow...

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Fabrication of tunnel junction-based molecular electronics and spintronics devices

Tyagi

2012

J Nanopart Res

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Scope of molecule based devices may govern the advancement of the next generation's logic and memory devices. Molecules have the potential to be unmatched device elements as chemists can mass produce an endless variety of molecules with novel optical, magnetic, and charge transport characteristics. However, the biggest challenge is to connect two metal leads to a target molecule(s) and develop a robust and versatile device fabrication technology that can be adopted for commercial scale mass production. This paper discusses distinct advantages of utilizing commercially successful tunnel junctions as a vehicle for developing molecular electronics and molecular spintronics devices. We describe the use of a tunnel junction with the exposed sides as a testbed for molecular devices. On the exposed sides of a tunnel junction molecules are bridged across an insulator by chemically bonding with the two metal electrodes; sequential growth of metalinsulator-metal layers ensures that separation between two metal electrodes is controlled by the insulator thickness to the molecular device length scale. This paper critically analyzes and discusses various attributes of tunnel junction based molecular devices with ferromagnetic electrodes for making molecular spintronics devices. Here we also strongly emphasize a need for close collaboration between chemists and magnetic tunnel junction researchers. Such partnerships will have a strong potential to develop tunnel junction based molecular devices for the futuristic areas such as memory devices, magnetic metamaterials, and high sensitivity multi-chemical biosensors etc.

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Dielectric breakdown of ferromagnetic tunnel junctions

Cited by 70 publications

References 10 publications

Analysis of breakdown in ferromagnetic tunnel junctions

Analysis of breakdown in ferromagnetic tunnel junctions

Direct imaging of the structural change generated by dielectric breakdown in MgO based magnetic tunnel junctions

Fabrication of tunnel junction-based molecular electronics and spintronics devices

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