Monte Carlo Simulation of Structural Modifications in SnO2/Si and Pt-Doped SnO2/Si Heterostructures under 1.25 MeV Co Ion Irradiation

Abstract We conducted Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulations to investigate how 1.25 MeV cobalt (Co) ions implant into different SnO2-based thin-film structures on silicon (Si) substrates. Three basic configurations were modeled that consisted of pure Si, a bilayer SnO2/Si structure, and a Pt-doped SnO2:Pt/Si heterostructure. Each model was developed according to the unique layer thicknesses, atomic compositions, and densities that were established from experimental and literature sources. The average depth of Co ion scattering during bombardment at 1.25 MeV achieved a projected range of approximately 4667 Å, which correlated with a straggle of 1666 Å. The Co ion distribution was slightly skewed, with a skewness of approximately –0.71, indicating non-uniform scattering that had occurred due to a combination of the two oxides and Si interfaces. Inclusion of platinum into the SnO2 layer generally modified the bonding environment, increased the stability of this lattice structure, and altered the disposition of the Co ions as well. The Si substrate, in contrast, influenced both backscattering and recoil behavior which lead to significantly different defect development and energy loss characteristics for the three sample configurations. These outcomes offer evidence that the SnO2:Pt/Si heterostructure has tunable defect engineering capabilities, where platinum doping in combination with the silicon heterostructure interface allows for stable structures with controlled vacancy charge concentrations. These properties are especially important for gas sensor applications, in which dopant active sites and surface vacancy play an important role in improving sensing selectivity and sensitivity.

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