Effective modulation of the exotic properties of two-dimensional multifunctional TM2@g-C4N3 monolayers via transition metal permutation and biaxial strain

The exotic physicochemical properties of TM atom (3d, 4d, and 5d) embedded g-C4N3 as a novel class of 2D monolayers were systematically investigated through hierarchical high-throughput screening combined with spin-polarized first-principles calculations. After several rounds of efficient screening, 18 types of TM2@g-C4N3 monolayers with a TM atom embedded g-C4N3 substrate in large cavities on both sides in asymmetrical mode have been obtained. The effects of transition metal permutation and biaxial strain on the magnetic, electronic, and optical properties of TM2@g-C4N3 monolayers were comprehensively and deeply analyzed. By anchoring different TM atoms, various magnetic states including ferromagnetism (FM), antiferromagnetism (AFM), and nonmagnetism (NM) can be obtained. The Curie temperatures of Co2@ and Zr2@g-C4N3 are substantially improved up to 305 K and 245 K by applying −8% and −12% compression strains, respectively. This makes them promising candidates for low-dimensional spintronic device applications at or close to room temperature. Additionally, rich electronic states (metal, semiconductor, and half-metal) can be realized through biaxial strains or diverse metal permutations. Interestingly, the Zr2@g-C4N3 monolayer undergoes a transition of FM semiconductor → FM half-metal → AFM metal under biaxial strains from −12% to 10%. Notably, the embedding of TM atoms dramatically enhances visible light absorption compared to bare g-C4N3. Excitingly, the power conversion efficiency of the Pt2@g-C4N3/BN heterojunction can be as high as 20.20%, which has great potential in solar cell applications. This large class of 2D multifunctional materials provides a candidate platform to develop promising applications under different circumstances and is expected to be prepared in the future.