X-ray diffraction study of the optimization of MgO growth conditions for magnetic tunnel junctions

We have carried out a systematic study optimizing the MgO growth via preparation and sputtering conditions and underlayer structures. It was found that to prevent water vapor which is detrimental to MgO (200) growth, the chamber pressure needs to be reduced below 10-8 Torr. Simple underlayers such as 5 nm CoFeB tend to give better MgO, but we have also succeeded in growing MgO on more complicated underlayers such as 1 Ta/20 Au/5 Co40 Fe40 B20 and 1 Ta/20 conetic (Ni77 Fe14 Cu5 Mo4) 1.5 Co40 Fe40 B20 (units in nanometers). We accomplished this by extensive baking of the deposition chamber and use of Ti-getter films. Short sputtering distance and high sputtering power were found to optimize MgO deposition. We found that both preparation and sputtering conditions have important effects on the MgO growth. X-ray diffraction analysis was used as the characterization tool for optimizing the MgO growth conditions. © 2008 American Institute of Physics.link_to_subscribed_fulltex

Evolution of free volume in ultrasoft magnetic FeZrN films during thermal annealing

The thermal stability of nanocrystalline ultra-soft magnetic (Fe98Zr2)(1-x)N-x films with x=0.10-0.25 was studied using high-resolution transmission electron microscopy (HRTEM), positron beam analysis (PBA) and thermal desorption spectrometry (TDS). The results demonstrate that grain growth during the heat treatment is accompanied by an increase of the free volume, by nitrogen reallocation and desorption. All this can drastically deteriorate the ultrasoft magnetic properties. The desorption starts already at slightly elevated temperatures, below 100 degreesC. However, most of the nitrogen leaves the sample at a temperature above 500 degreesC