atomic | Ed's Threads

Researchers from Intel Corporation and the University of Minnesota and the University of Wisconsin have shown that strained atom-scale films of pure ruthenium (Ru) metal exhibit ferromagnetism at room temperature, openning up the possibility of using the material to build novel magnetic random access memory (MRAM) devices. As per details recently published in Nature Communications (https://doi.org/10.1038/s41467-018-04512-1), Ru thin films with a thickness of 2.5, 6, or 12 nm, were grown on Al2O3 substrates cut along the (110) direction, that had been covered with a 20 nm Mo seed layer. The thin films were grown using a eight-target UHV sputtering system with base pressure of 8 × 10−8 Torr or lower, resulting in the controlled epitaxial growth of strained body-centered tetragonal phase Ru.

From first principles of materials engineering, there should be ways to use different templating materials for this graphoepitaxial process such that silicon-oxide could be used as the substrate instead of aluminum-oxide. If so, then this process could be run on 300mm silicon wafers in today’s leading commercial IC fabs.

The (001) tetragonal Ru plane does not lie perpendicular to the substrates which leads to a soft coercive field, however, if out-of-plane texturing can be achieved high coercivity Ru may be realized. The thickness dependence was also examined, and it was found that due to Ru relaxing into a non-ferromagnetic phase, the magnetization drops with increasing thickness. The 12 nm thick sample showed magnetization of about one-half that of the two thinner samples.

Original Article: https://www.nature.com/articles/s41467-018-04512-1

—E.K.

A team led by researchers at the University of Warwick have discovered a breakthrough in how to measure the electronic structures of stacked 2D semiconductors using the photoelectric (PE) effect. Materials scientists around the world have been investigating various heterostructures to create different 2D materials, and stacking different combinations of 2D materials creates new materials with new properties.

The new PE method measures the electronic properties of each layer in a stack, allowing researchers to establish the optimal structure for the fastest, most efficient transfer of electrical energy. “It is extremely exciting to be able to see, for the first time, how interactions between atomically thin layers change their electronic structure,” says Neil Wilson, who helped to develop the method. Wilson is from the physics department at the University of Warwick.

Wilson formulated the technique in collaboration with colleagues at the University of Warwick, University of Cambridge, University of Washington, and the Elettra Light Source in Italy. The team reported their findings in Science Advances (DOI: 10.1126/sciadv.1601832).

—E.K.

Tag Archives: atomic

Ruthenium Nanolayers are Ferromagnetic at RT

Photoelectric measure of atomically thin stacks