Giant second harmonic generation in two-dimensional tellurene with synthesis and thickness engineering

Second harmonic generation (SHG) is a prominent branch of non-linear optics (NLO) heavily reliant on conventional bulk NLO crystals. However, the difficulty in downsizing these crystals imposes technical limitations on the future of miniaturized NLO devices. Tellurene emerges as a promising candidate to overcome these restrictions, excelling in electrical applications and believed to possess a giant second-order optical susceptibility comparable to conventional NLO crystals. In this study, a face-to-face substrate configuration is employed for the synthesis of ultrathin tellurene via PVD. Our findings reveal that tellurene's SHG performance surpasses that of monolayer transition metal dichalcogenides by two orders of magnitude, with maximum efficiency when the flake thickness is between 16 and 20 nm under various wavelengths. High sensitivity to thickness variation encourages post-growth thinning through hydrogen plasma etching, enabling precise engineering of the flake thickness for optimal SHG. This establishes a foundation for controlled tellurene thickness, further broadening its potential in diverse applications.