A ferromagnetic spin source grown by atomic layer deposition

Abstract

We report on the growth of a ferromagnetic cobalt electrode by atomic layer deposition (ALD) and demonstrate it as a functional spin source in complete magnetic tunnel junctions (MTJs). Using an in situ protocol, we integrate a reference tunnel barrier on top of the ALD cobalt spin source stabilizing its metallic nature and allowing further characterization. The cobalt layer, grown in mbar conditions with chemical precursors, is assessed to be metallic and ferromagnetic using both x-ray photoelectron spectroscopy and superconducting quantum interference device magnetometry measurements. Atomic force microscopy tapping and conductive tip mode analyses reveal a very flat film with low roughness (0.2 nm RMS) with a high homogeneity of surface conductivity matching the best reference samples grown by sputtering. We finally evaluate its behavior in full MTJ spin valves, using a reference spin analyzer to highlight that the ALD grown layer is, indeed, spin polarized and can act as a functional spintronics electrode. This result opens the perspective of exploiting the benefits of ALD (such as the wide area low-cost process, extreme conformality, layer by layer growth of heterostructures, area selectivity, etc.) for spintronics applications.