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

Abstract

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(NH 3 ) 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 , NH 3 , and HCl. Also, surface-bound NH x (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 NH 3 ligands releases atomic hydrogen, a species known to efficiently remove surface Cl via HCl formation. Furthermore, proton transfer from NH 3 to Cl − triggered by ionization is deduced from the formation of NH 4 + and proposed as a second reaction pathway producing HCl. Overall, this leads to rapid loss of the Cl ligands. We thus provide evidence that NH 3 is favorable either as a ligand in FEBID precursors or as a postdeposition purification agent for halide-contaminated FEBID deposits.

Combined Ammonia and Electron Processing of a Carbon-Rich Ruthenium Nanomaterial Fabricated by Electron-Induced Deposition

“…• radicals as intermediates in an in situ X-ray photoelectron spectroscopy (XPS) study, but not in a complementary RAIRS study that was carried out ex situ [22]. The absence of vibrational features of the NH 2…”

“…Electron-induced fragmentation of NH3 that has diffused into the deposit yields N2 (see also ESD experiments in Section 3.2.2.) and releases atomic hydrogen (AH) that can, among other reactions, recombine to form H2 [22,25,28]. These gases can be held responsible for the observed swelling and bubble formation.…”

“…Rather than removing material, processing in NH 3 leads to incorporation of the process gas into the deposit and consequent swelling, as is obvious from the occurrence of large bubble-type structures in the halo regions of the deposits (see SEM and AFM images in Figure 1, right side). Electron-induced fragmentation of NH 3 that has diffused into the deposit yields N 2 (see also ESD experiments in Section 3.2.2) and releases atomic hydrogen (AH) that can, among other reactions, recombine to form H 2 [22,25,28]. These gases can be held responsible for the observed swelling and bubble formation.…”

“…• moieties in ex situ RAIRS was explained by consumption of the reactive radicals during handling at ambient conditions [22]. The absence of NH 2…”

“…With respect to FEBID applications, we demonstrated that chlorine-contaminated ruthenium deposits produced from η 3 -allyl ruthenium tricarbonyl chloride (η 3 -C 3 H 5 )Ru(CO) 3 Cl can be purified by electron exposure in the presence of NH 3 [ 20 ]. Additionally, NH 3 enhances the rate of metal reduction when applied as a precursor ligand [ 21 , 22 ]. However, NH 3 also adds to unsaturated hydrocarbon structures in an electron-induced reaction [ 23 , 24 , 25 ].…”