Cisplatin as a Potential Platinum Focused Electron Beam Induced Deposition Precursor: NH3 Ligands Enhance the Electron-Induced Removal of Chlorine

摘要

Nanostructures fabricated by focused electron beam induced deposition (FEBID) often have low deposit purities that can be traced back to incomplete precursor decomposition. Among others, removal of halide ligands is particularly slow under electron irradiation. Herein, we report on the electron-induced decomposition of cisplatin (cis-Pt(NH3)(2)Cl-2), a potential precursor for Pt deposition. Cisplatin samples were irradiated with electrons, and the resulting compositional and chemical changes were monitored by surface analysis tools. The results reveal that electron exposure yields nearly pure Pt deposits, and the ligands are transformed into the gas-phase species N-2, NH3, and HCl. Also, surface-bound NHx (x < 3) species were identified that can act as reducing agents. Production of such reactive intermediates and N-2 implies that the electron-induced decomposition of the NH3 ligands releases atomic hydrogen, a species known to efficiently remove surface Cl via HCl formation. Furthermore, proton transfer from NH3 to Cl- triggered by ionization is deduced from the formation of NH4+ and proposed as a second reaction pathway producing HCl. Overall, this leads to rapid loss of the Cl ligands. We thus provide evidence that NH3 is favorable either as a ligand in FEBID precursors or as a postdeposition purification agent for halide-contaminated FEBID deposits.