The influence of calcination on the stability of copper particles supported on oxidized Si(100)

In this paper we investigated the influence of calcination on the stability of supported copper (oxide) particles by means of atomic force microscopy (AFM) and Auger electron spectroscopy (AES). Samples were sintered by means of vacuum annealing at 573 K. Samples were calcined in 1 atm oxygen at 573 K. Calcination had a stabilizing effect on the particles: no significant sintering was observed for samples calcined longer than three hours. Rate constants of the sintering process were obtained from in situ measurements of the Cu L3VV signal during vacuum annealing. The activation energy of the sintering process increased from Eact = 23±30 kJ/mol for uncalcined samples and Eact = 38±23 kJ/mol for samples calcined during 0.5 h to Eact = 240±78 kJ/mol for samples calcined during 3 h. AFM measurements of the sintering of a 3 h calcined sample at 423 K indicated a sintering mechanism involving crystallite coalescence instead of a ripening mechanism involving atom migration.