Investigation of finite size effects in a first order phase transition: High pressure Raman study of CdS microcrystallites

We have used Raman scattering to explore finite size effects in the phase transition of 300 Å colloidal microcrystallites of CdS. By measuring the shifts in LO phonon frequencies as a function of pressure we conclude that these small microcrystallites undergo a well-defined first order phase transition similar to the one occurring in bulk CdS. However, the phase transformation in the colloids exhibits a smaller hysteresis, which we attribute to efficient annealing of defects in the high surface area colloidal material.