Methane adsorption and hydrogen isothermal desorption kinetics on a C(001)–(1×1) surface

Methane (CH₄) adsorption and isothermal hydrogen (H₂) desorption kinetics on a C(001)–(1×1) surface have been investigated by observing the surface hydrogen coverage θ_H which is estimated from the electron‐stimulated desorption yield of H⁺ ions. The time evolution of θ_H under CH₄ exposure, in pressure and temperature ranges of 1×10⁻⁸–5×10⁻⁷ Torr and 600–800 °C, reveals that the CH₄ adsorption is a first‐order reaction. The isothermal H₂ desorption is conducted in a temperature range of 1095–1270 °C. The time evolution of θ_H shows that the isothermal H₂ desorption is also a first‐order reaction. From Arrhenius plots of the reaction coefficients, the activation energies of CH₄ adsorption and H₂ desorption are evaluated to be 7.3±1.7 and 21±4.9 kcal/mol, respectively. Atomistic kinetics model for CH₄ adsorption and H₂ desorption are discussed, especially in connection with a recent finding of gas source molecular beam epitaxy of diamond (001) with pure CH₄ without any hydrogen or oxygen radicals.