Understanding Anisotropy of photoconductance in In₄Se₃: insights from DFT

Although In₄Se₃ has a layered structure with the ionic character of the interlayer interactions.¹ In the crystal structure of In₄Se₃, [(In₃)⁵⁺(Se^2-)₃]^- clusters are interconnected along both c and b axes forming a quasi-2D layer intermitted with chains of ionized In⁺.  Cleaving along bc plane results in a surface with 1D chain of Se and In atoms thus the electronic structure and photoconductance of the surface are expected to be anisotropic. Density functional theory calculations for the bc surface of In₄Se₃ show that the frontier orbitals are dominated by s, p_z and p_y character, not p_x, suggesting that s to p_z transitions are allowed with the light vector potential aligned along the surface normal, s to p_y transitions are allowed with the light vector potential aligned in-plane but orthogonal to the chains, but there is little opportunity for p_x to d and s to p_x transitions. Experimental investigations of the optical photoconductance anisotropy performed on devices based on In₄Se₃ flakes with signatures of quasi-1D chains confirm the above findings.¹ These open new pathways for application of In₄Se₃ in efficient integration of logic and sensing.

[1]       N. S. Vorobeva et al., Adv. Funct. Mater., 2106459 (2021).