Optimization of postgrowth electron-beam curing for focused electron-beam-induced Pt deposits

The authors use focused electron-beam-induced Pt deposition from a gaseous (CH₃)₃CH₃C₅H₄Pt precursor for the fabrication of electrically conductive structures consisting of Pt nanocrystals embedded in a carbon containing matrix. Recently it has been demonstrated that the electrical resistivity of such deposits can be strongly improved via postgrowth electron irradiation. This study shows very strong evidence that incompletely and nondissociated precursor molecules incorporated within the deposits during deposition are the key elements for efficient e-beam curing. During the early stages of e-beam curing these fragments are further dissociated, which leads to slight growth of the Pt nanocrystals. This is further supported by variable growth regime experiments during deposition which can be used to enhance the incorporation of incompletely and nondissociated precursor molecules, resulting in higher curing efficiencies and lower electrical resistivities. The absence of a predominant graphitization of the surrounding carbon matrix during this dissociation dominated curing regime suggests strongly that the observed resistivity decrease is mainly caused by the formation of preferred tunnel percolation paths due to reduced intercrystallite distances. Furthermore, it is shown that deposit height and the electron-beam energy used for curing should be adapted to each other to achieve the fastest curing time and the lowest electrical resistivities. Such optimized procedures allow then for curing rates higher than 1.5 μm² min⁻¹ and resistivity decreased to 5 ± 0.4 × 10⁴ μΩ cm, representing an improvement of up to 3 orders of magnitude.