Experimental Realization of Semiconducting Monolayer Si₂Te₂ Films

The experimental realization of large-scale, homogeneous semiconducting films with a single-layer thickness is of major importance for next-generation devices. Especially in view of the compatibility with state-of-the-art semiconductor technology, Si-based monolayer crystals are of particular interest. Here, the successful epitaxial growth of monolayer Si₂Te₂ (ML-Si₂Te₂) films on semiconducting Sb₂Te₃ thin film substrates is reported. High-quality (1 × 1) ML-Si₂Te₂ films with a coverage as high as 95% are obtained as revealed by scanning tunneling microscopy. X-ray photoelectron spectroscopy confirms the existence of the Si-Te bonds in the obtained films. By combining scanning tunneling spectroscopy with density functional theory calculations, the existence of a semiconducting bandgap is demonstrated on the order of 370 meV for the ML-Si₂Te₂ films which reside in an important mid-infrared spectral range. The results pave the way for practical applications of this novel artificial two-dimensional material.