Direct nuclear spectroscopic evidence against lithium incorporation in aqueous chemical bath deposition-grown ZnO nanorods

Achieving reliable p-type conductivity in zinc oxide (ZnO) remains a long-standing challenge, with lithium frequently proposed as a candidate acceptor dopant in solution-grown ZnO. Despite numerous reports of Li-related electrical and optical effects, direct and element-specific verification of lithium incorporation in aqueous chemical bath deposited (CBD) ZnO has remained elusive. Here, complementary nuclear ion-beam techniques, Particle-Induced Gamma-ray Emission (PIGE) and Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA), were employed to directly probe lithium incorporation in aqueous CBD-grown ZnO nanorods synthesized over a wide range of precursor concentrations. In all samples, no lithium was detected within the experimental sensitivity of either technique, establishing an upper bound for Li incorporation below 0.01 at%. This unambiguous absence of lithium demonstrates that Li⁺ does not act as a substitutional or interstitial dopant under aqueous CBD conditions. The results are consistent with lithium influencing the growth chemistry and defect landscape of ZnO without lattice incorporation, offering a rational explanation for Li-related effects reported in solution-grown systems. More broadly, this work clarifies the role of lithium in aqueous CBD-grown ZnO nanostructures and underscores the value of nuclear spectroscopic methods for validating light-element incorporation in oxide semiconductors.