Abstract
In this work, the effects of compressive and tensile biaxial strain, applied to monolayered 1T Pd Janus PdSSe, PdSTe, and PdSeTe structures are investigated. For tensile strengths larger than 4%, the valence band maxima no longer occur at the high symmetry Γ point; this phenomenon is accompanied by the emergence of a quasi-direct bandgap, where Dirac-like cones develop for large enough strain. A semiconductor-semimetal phase transition takes place for compressive strain strengths of −8%, −4%, and −2% in PdSSe, PdSTe, and PdSeTe respectively. Phonon dispersion calculations show that the Janus structures, subject to tensile strains, are dynamically stable; yet under compressive strains, they are only stable for values not exceeding −6% in PdSSe, −4% in PdSTe, and −2% in PdSeTe. All structures are mechanically stable except for PdSTe under a 14% tensile strain, registering negative in-plane stiffness constants of −9.36 and −7.62 N/m along the x and y directions respectively. Optical absorption/emission within the infrared region is possible when the materials are exclusively subject to tensile strain. Once the Pd Janus structures are synthesized, the results presented here can serve as a guide for the fabrication of optoelectronic devices of optimal performance.
•A quasi-direct bandgap emerges for tensile strengths larger than 4%.•Semiconductor-semimetallic phase transitions occur more rapidly for compressive strains.•Optical-optical and acoustic-optical bandgaps decrease in the strained systems.•All systems are mechanically stable except PdSTe under a 14.•Under tensile strains, absorption/emission optical peaks move towards the infrared region.