Post annealing x-ray photoemission spectroscopy depth profiling investigating B-concentration in B:Cr₂O₃ thin films

Chromium Oxide (Cr₂O₃) is a magnetoelectric antiferromagnetic material with a Néel temperature i.e., T_N ~ 307 K. Doping Cr₂O₃ with Boron (B) increases the antiferromagnetic transition temperature (T_N). The enhancement of T_N from B-doping facilitates the operation of B:Cr₂O₃ based devices in CMOS environments. In addition, B-doping turns Cr₂O₃ into a multifunctional single-phase material which enables the Néel vector rotation in the absence of applied magnetic field. In context of antiferromagnetic spintronics, this peculiar nonvolatile voltage driven Néel vector rotation makes B:Cr₂O₃ an extremely good candidate for ultra-low power, ultra-fast, nonvolatile memory and logic device applications. In our work we prepare 200 nm thick B:Cr₂O₃ films grown epitaxially on Al₂O₃ (0001) substrates by using pulsed laser deposition. We utilize x-ray photoemission spectroscopy depth profiling to independently confirm data from cold neutron depth profiling which reveal thermally activated B-accumulation at the B:Cr₂O₃/ vacuum interface within a layer of about 50 nm thickness. We attributed the stable B-enrichment to surface segregation.