Ballistic electron microscopy study of ultrathin oxidized aluminum barriers for magnetic tunnel junctions

Abstract

Ballistic electron emission microscopy has been used to study thin aluminum oxide tunnel junction barriers formed both by magnetron sputter deposition and thermal evaporation. We have found that the barriers made by oxidation of evaporated Al become fully formed at a significantly thinner mean deposited thickness (∼6 Å) than junctions made by sputter deposition. The effective barrier height of the aluminum oxide has been determined to be 1.22±0.05 eV and is independent of the method of deposition, thickness, and oxidation conditions.

STM-induced reversible switching of local conductivity in thinAl2O3films

“…For realistic parameters one thus obtains an estimate V B ϳ1 -2 V. This can be compared to the value around 1 eV we obtained from a rough estimate based on the measured low-bias resistance of our 0.7 nm oxide film and V B ϭ1.2 eV as obtained from ballistic electron emission microscopy ͑BEEM͒. 12 Thus, we believe that 1 -1.5 eV is a reasonable estimate of the barrier height of our oxide film.…”

Excitation and spin-transport of hot holes in ballistic hole magnetic microscopy

“…͓DOI: 10.1063/1.2212066͔ Ballistic electron emission microscopy 1 ͑BEEM͒ is widely used to study nanoscale properties of metalsemiconductor interfaces, ultrathin gate and tunnel oxides, and metallic and silicide thin films. [2][3][4][5][6] Its spin-sensitive counterpart, ballistic electron magnetic microscopy 7 ͑BEMM͒, can be used for nanoscale magnetic imaging employing spin-dependent transmission of hot electrons in ferromagnetic thin films. Recently, spin-dependent transmission of hot holes, rather than electrons, was also demonstrated 8 in ballistic hole magnetic microscopy ͑BHMM͒.…”

Ballistic hole magnetic microscopy

“…These include buried metal-semiconductor interfaces, semiconductor heterostructures and quantum dots, ultrathin gate as well as tunnel oxides, and metallic and silicide thin films. [2][3][4][5][6] The high spatial resolution makes it an attractive technique for the study of magnetic nano-and heterostructures which form the basis of spintronics and magnetic data storage. The extension of BEEM to its spinsensitive counterpart, ballistic electron magnetic microscopy, was demonstrated to allow magnetic imaging with nanoscale resolution.…”