Epitaxy of iridium on SrTiO3/Si (001): A promising scalable substrate for diamond heteroepitaxy

• The thermal stability of SrTiO3 film vs. the temperature and the thickness was studied by FE-SEM, ellipsometry and XRD.
• Iridium deposition was optimized by identifying the deposition temperature and the thickness of SrTiO3 buffer layer.
• The Bias Enhanced Nucleation treatment resulted in highly homogeneous and dense domains on Ir/SrTiO3/Si.
• Crystalline quality of iridium and heteroepitaxial diamond layers are at the state of art as shown by XRD and FE-SEM.

Iridium epitaxy on SrTiO3/Si (001) was investigated using field emission scanning electron microscopy (FE-SEM), spectroscopic ellipsometry, X-ray diffraction (XRD) and atomic force microscopy (AFM). Thermal stability of SrTiO3 buffer layers (12–40 nm thick) was first investigated by annealing at different temperatures (620 °C–920 °C) under vacuum to optimize iridium epitaxy conditions. The surface morphology was monitored by FE-SEM and optical constants by spectroscopic ellipsometry. Iridium films were then deposited and their morphology and crystalline quality were evaluated by FE-SEM and XRD. It was found that iridium epitaxy is optimized at 660 °C on SrTiO3 films thicker than ~ 30 nm. The polar and azimuthal mosaicities of the iridium films on SrTiO3/Si (001) were 0.3° and 0.1°, respectively. These epitaxial iridium films were further used for diamond heteroepitaxy. The bias enhanced nucleation (BEN) treatment resulted in highly homogeneous and dense diamond domains. Heteroepitaxial diamond films were further grown by microwave plasma enhanced chemical vapor deposition (MPCVD) on 7 × 7 mm2 Ir/SrTiO3/Si (001) substrates and characterized by XRD.

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