Cation Substitution-Induced Partial Inversion to Pervade Short-Wave Infrared Light for Improving the Accuracy of Artificial Intelligence Image Recognition System

Short-wave infrared (SWIR) light is suitable for image recognition and biomedical applications due to the ability to perform unique absorption of material components. In this study, the partial inversion of a spinel structure was modified through cation substitution to induce an inverse behavior and charge variation. For MgGa₂O₄, the substitution of Ga³⁺ with Sn⁴⁺ expanded lattice parameters (a, b, c, and V), and Mg²⁺ was used to achieve charge balance. When the concentration of Sn increased, the T_2g vibrational mode exhibited a significant decline at 638 cm^-1, which was ascribed to GaO₄, and another retentive T_2g vibrational mode at 542 cm^-1 was ascribed to MgO₄. This demonstrated that MgGa₂O₄ was a local structure with partial inversion. The clusters of (Ga/MgO₄-MgO₄) from y = 0.5 to 0.7 revealed a disordered broadband signal in the same Raman shift, and octahedral sites retained their ordering structure. The local structure induced Ni^2+/3+ to coexist and transform into pure Ni²⁺ at octahedral sites through increasing Sn concentration. The time-resolved photoluminescence and emission spectrum revealed high energy transfer efficiency (>90%). The long SWIR emission achieved through Sn substitution enabled the fabrication of an SWIR light-emitting diode device; this device, along with a two-dimensional convolutional neural network, increased the accuracy of an artificial intelligence-based image recognition system from 72.2% to 94.4%. This study promotes research on sequences for inverse tetrahedral sites such as Mg, Al, Ga, In, and other transition metals in spinel structures. In addition, the applicability of artificial intelligence to complete everyday tasks was demonstrated.