Carbon Implantation into Nickel and Gold Thin Films: A Comparative Study Exploring the Experimental Limits of Metal Carbide Formation

Transition metal carbides exhibit distinctive electrical, mechanical, and physical properties that motivate their use in electrocatalysis, semiconductor devices, cutting tools, and refractory applications. Traditional synthetic approaches utilize thermal energy to overcome the kinetic barrier for carbide formation. However, thermodynamically unfavorable/metastable carbides (Ni₃C and Au₂C₂) typically decompose or rearrange into more thermodynamically favorable phases with prolonged exposure to moderate-to-high temperatures. Herein, we investigate the carburization of nickel and gold thin films using carbon ion implantation (15 kV) at a variety of fluences (1–20 × 10¹⁶ atoms·cm^–2). This fabrication approach created localized temperatures (>1000 K) which dissipated within tens to hundreds of picoseconds, i.e., thermal spikes, maximizing the chances of forming and retaining metastable carbide phases. Grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, and scanning transmission electron microscopy were used to identify the phases formed by carbon implantation into the Ni and Au thin films. For implantation into Ni thin films, a single metastable Ni₃C (trigonal crystal structure) phase was observed for a variety of carbon fluences. At high implantation doses (>1 × 10¹⁷ atoms·cm^–2), excess carbon precipitated into graphitic clusters. In contrast, the carburization of gold was not achieved even at very high carbon implantation doses, demonstrating that the thermodynamic barriers to the formation of Au–C bonds were not surpassed.