Epitaxial Growth of Few-Layer Black Phosphorene Quantum Dots on Si Substrates

Elemental 2D materials, such as silicene, germanene, and stanene, are synthesized by molecular beam epitaxy (MBE). However, the epitaxial growth of black phosphorene is challenging to date. Herein, the successful MBE growth of few-layer black phosphorene quantum dots (BPQDs) directly on Si substrates at relatively low temperature using white phosphorus as the precursor is reported. The formation of black phosphorene is confirmed by atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, in combination with density functional theory (DFT) calculations. Uniform and pyramid-shaped BPQDs with an average radius of 27.5 +/- 5 nm and height of 3.1 +/- 0.6 nm are obtained at surface steps on fully deoxidized Si(111) substrates. The growth mechanism is probed by DFT at atomic level, demonstrating the crystallization of BPQDs at steps in preference to terraces on Si substrates of (111) and (100) surfaces. The results show that BPQDs follow the Frank-van der Merwe growth mode and the favored few-layer growth trend with pyramid configuration. The realization of MBE-grown BPQDs enables the synthesis of inch-sized low-dimensional black phosphorus with high purity and crystallinity, particularly promising for nanoelectronics and optoelectronics.