ARRESTED SOLID-SOLID PHASE-TRANSITION IN 4-NM-DIAMETER CDS NANOCRYSTALS

CdS crystallites of 4-nm diameter have been studied under high pressure up to 10 GPa by optical absorption and Raman scattering. The solid-solid phase transition from the zinc blende to the rock salt phase is observed at pressures far in excess of the bulk phase transition pressure of 3 GPa. The pressure of the phase transition depends on the nature of the moiety used to derivatize the surface. In addition, because the compression of the lattice with pressure is the same as in the bulk crystal, it is possible to observe the dependence of the zinc blende crystallite properties up to pressures far higher than in the bulk. The elevated phase transition pressure and its dependence on the surface stabilizer can be explained by a higher value of the surface tension for the rock salt phase nanocrystals compared to the zinc blende.