Experimental Observation of Surface Modes of Quasifree Clusters

Raman measurements have been carried out on Si clusters embedded in porous Si (PS). Conspicuous new Raman peaks are observed, and are identified as surface modes of Si clusters and their combination with TA modes. Good agreement is achieved between the observed Raman peaks and calculated results. The Si clusters drop into pores and softly land on the mother skeleton of the PS; thus quasifree clusters are formed.