Effects of strain and thickness on the mechanical, electronic, and optical properties of Cu₂Te

Two-dimensional transition-metal chalcogenides (TMCs) have attracted considerable attention because of their exceptional photoelectric properties, finding applications in diverse fields such as photovoltaics, lithium-ion batteries, catalysis, and energy conversion and storage. Recently, experimentally fabricated monolayers of semiconducting Cu₂Te have emerged as intriguing materials with outstanding thermal and photoelectric characteristics. In this study, we employ first-principles calculations to investigate the mechanical, electronic, and optical properties of monolayer Cu₂Te exhibiting both λ and ζ structures, considering the effects of thickness and strain. The calculations reveal the robust mechanical stability of λ-Cu₂Te and ζ-Cu₂Te under varying thickness and strain conditions. By applying -5% to +5% strain, the band gaps can be modulated, with ζ-Cu₂Te exhibiting an indirect-to-direct transition at a biaxial strain of +5%. In addition, a semiconductor-to-metal transition is observed for both ζ-Cu₂Te and λ-Cu₂Te with increasing thickness. The absorption spectra of λ-Cu₂Te and ζ-Cu₂Te exhibit a redshift with an increase in the number of layers. These computational insights into Cu₂Te provide valuable information for potential applications in nano-electromechanical systems, optoelectronics, and photocatalytic devices and may guide subsequent experimental research efforts.