Formation enthalpies of Sn clusters: a calorimetric investigation

The formation of a bulk Sn layer from a molecular beam of SnN clusters has been directly investigated with a picojoule-sensitive calorimeter. The calorimeter is based on a microfabricated composite cantilever, and it makes use of the bimetallic effect. The formation enthalpy ΔHf,298 for Sn(s)→(1/N) SnN(g) has been determined from the released heat during the deposition of a distribution of SnN clusters with a mean cluster size of 〈N〉=150 atoms. For this Sn cluster size distribution one obtains a formation enthalpy per atom of ΔHf,298=0.45±0.19 eV.