Morphology of various single faced sapphire surfaces prepared by rapid thermal annealing

• Atomically smooth surfaces for all commonly used sapphire planes. • Well-defined steps for all commonly used sapphire planes. • Capability to achieve these in-situ within minutes. • Report of previously not observed reconstructions. Sapphire is important as a substrate for both industry and science. However, the identification of preparation methods for its commonly used surface planes has been hindered by the high temperatures required to induce the necessary morphological changes of the sapphire surfaces. These temperatures have been difficult to attain in suitable processes, which made the in-situ preparation of the surfaces unfeasible. However, it has been shown that ≈ 10 μm light is well absorbed by sapphire; thus, the use of CO 2 laser beams for substrate heating allows access to much higher temperatures than previously available. This work demonstrates how, at elevated annealing temperatures ⪅ 2000 °C and within a few minutes of annealing time, all commonly used surface planes of sapphire can be prepared to atomical smoothness with well-defined steps.