Microstructure of annealed magnetic tunnel junction by electron microscopy

Abstract

Transmission Electron Microscopy evidence of the growth of a magnetite layer acting as a spin filter in CoFe ∕ Al 2 O 3 ∕ CoFe magnetic tunnel junctions Transmission electron microscopy, high-resolution electron microscopy, and electron holography were used to study the microstructure of CoFe/AlO x /Co magnetic tunnel junctions ͑MTJs͒ isochronally annealed up to 400°C. A potential barrier across the metal/oxide interfaces was observed for the as-deposited MTJ sample, and was changed into a well for the MTJ samples annealed at 200 and 400°C, respectively. A shallow potential well was found when the MTJ was annealed at 200°C and the well became deeper as the annealing temperature increased to 400°C. The potential change may attribute to the formation of nonmagnetic metallic Al atoms or clusters when the MTJ sample was annealed at 200°C and the rest content of the barrier layer was more close to Al 2 O 3 , which results in the enhancement of tunneling magnetoresistance ͑TMR͒. When the MTJ sample was annealed at 400°C, more Co and Fe atoms or clusters might diffuse from the ferromagnetic layers into the barrier layer, resulting in the deeper well, and thus significantly decrease the TMR value due to the severe spin-flip scattering.

I−V Characteristics of Metal−Oxide−ZnSe Nanowire Structure

“…The most technologically important examples are metal−silicon dioxide−silicon and metal−nitride−silicon structures. Alumina oxide has exhibited a number of other interesting properties and been extensively studied because of its close connection to modern electronic device components such as the giant magnetoresistance read and writing heads made of spin valve junction and magnetic tunneling junction for magnetic data storage. , One of the most important properties is that both amorphous and crystalline alumina oxide solids belong to a particular class of materials known as Mott insulators, whose electronic structures can be simply described by using conventional band theory. In fact, insulators may be considered as semiconductors with large band gaps.…”

Microstructure investigation on barrier shapes of double barrier magnetic tunnel junctions

“…Since the conventional TEM and HRTEM are difficult to resolve due to the delocalization effects, 11 EH has been applied to study the shape of barrier in single barrier MTJs by several researchers. [10][11][12] However, the shape of barrier in their reconstructed phase profile is found to be inconsistent. The AlO x layer in phase profile shows a "potential well" in Ref.…”

“…In some previous reports, electron holography ͑EH͒ has been used to study the structure and barrier shape of single barrier MTJs in which the AlO x barrier layers are relatively broad ͑Ͼ2 nm͒. [10][11][12] Since DBMTJs are complicated and more interfaces are involved, EH is considered to be very useful for the investigation of the microstructures of DBMTJs. On the other hand, two barriers in the DBMTJs are not similar to that in the single barrier MTJs and also different from each other in the same DBMTJ due to the specific deposition sequence; thus the double barriers with equal height are hard to be obtained.…”