Chemical Mechanisms of Interface Degradation Between Barium Hexaferrite Thin Films On Wide Bandgap 6H-SiC

There is a growing interest for the integration of multifunctional ferrimagnetic-ferroelectric oxides on wide bandgap semiconductors, such as silicon carbide (6H-SiC), for next generation, tunable electronic and microwave devices. Ferrimagnetic barium hexaferrite (BaM) is ideal for microwave device applications because of its high permeability (> 100) and strong uniaxial magnetocrystalline anisotropy (17 kOe). Effective integration of device quality BaM on SiC has been demonstrated using a two-step process strategy with a molecular beam epitaxy (MBE) 10 nm MgO (111) single crystal template film and 100 nm BaM seed layer followed by pulsed laser deposition (PLD) 500 micrometer thick films of BaM. In optimizing the magnetic properties of the BaM film, variations in magnetic properties were linked to BaM/SiC interface degradation. X-ray photoelectron spectroscopy (XPS), in both angle resolved and argon etch depth profiling, along with reflection high-energy electron diffraction (RHEED) and x-ray diffraction (XRD), provided detailed chemical and structural characterization of the interface layers after different post growth treatments. Chemical mechanisms of interface degradation and proposed strategies for maintaining interface chemical integrity will be discussed.