Enthalpy of Formation for Cu–Zn–Sn–S (CZTS) Calculated from Surface Binding Energies Experimentally Measured by Ion Sputtering

Herein, we report an analytical procedure to calculate the enthalpy of formation for thin film multinary compounds from sputtering rates measured during ion bombardment. The method is based on Sigmund’s sputtering theory and the Born–Haber cycle. Using this procedure, an enthalpy of formation for a CZTS film of the composition Cu 1.9 Zn 1.5 Sn 0.8 S 4 was measured as −930 ± 98 kJ mol –1 . This value is much more negative than the sum of the enthalpies of formation for the constituent binary compounds, meaning the multinary formation reaction is predicted to be exothermic. The measured enthalpy of formation was used to estimate the temperature dependence of the Gibb’s free energy of reaction, which appears consistent with many experimental reports in the CZTS processing literature.