Sequential adjacent Si dimer dechlorination mechanism of perchloroethylene adsorption on Si(1Â 0Â 0) with temperature evolution

► PCE/Si(1 0 0) undergoes sequential di-dechlorination with temperature evolution. ► Three tetra-σ adspecies coexist at room temperature after the first di-dechlorination. ► Two hexa-σ states are produced by further di-dechlorination at high temperature. ► The calculated IEs of C-1s and vibrational frequencies well interpret XPS and EELS.