National Synchrotron Light Source Symposia

There is a growing interest for the integration of complex magnetic or ferroelectric oxides on wide bandgap semiconductors for robust multifunctional devices. However, difficulties arise at the interface of the complex oxide film and semiconductor substrate due to lattice mismatch, thermal mismatch, and interdiffusion. To address these challenges, it is proposed to use the quasi-hexagonal structure of the alternating layers of magnesium and oxygen in MgO (111) to facilitate, through O-O bonding, the effective integration of more complex oxides with SiC.

Epitaxial films of 10 to 300 Å thick MgO (111) were grown under Mg adsorption controlled conditions on 6H-SiC (0001) by molecular beam epitaxy (MBE). Reflection high energy electron diffraction (RHEED) was used real time to monitor the growth rate, crystal structure, and crystallographic orientation. In-situ x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) provided composition and chemical bonding information. Both 38 nm and 20Å MgO films on 6H-SiC tested for thermal stability at 790oC in vacuum (<10-9 Torr) and in air. Films showed no evidence of instability at the interface, as measured by XPS or x-ray diffraction (XRD). However, the RHEED pattern transitioned from a twinned structure to an improved, ordered structure believed to be a result of atom mobility within the MgO lattice.

Complex oxides, including barium titanate (BTO) and barium hexaferrite (BaM) were then deposited on the MgO thin films by means of pulsed laser deposition (PLD) and MBE in order to evaluate the potential for crystalline MgO to be used as an epitaxy template. Characterization by both the in-situ techniques and ex-situ atomic force microscopy (AFM), XRD, and general area diffraction (GADDS) of the subsequent complex oxide integration revealed a preferred crystal orientation in the (111) direction. This supports the hypothesis that high-quality, single crystalline MgO (111) deposited on 6H-SiC (0001) has