A transmission electron microscopy investigation of sulfide nanocrystals formed by ion implantation

Ion implantation was used to form compound semiconductor nanocrystal precip itates of ZnS, CdS, and PbS in both glass and crystalline matrices. The pre cipitate microstructures and size distributions were investigated by cross- sectional transmission electron microscopy techniques. Several unusual feat ures were observed, including strongly depth-dependent size variations of t he ZnS precipitates and central void features in the CdS nanocrystals. The morphology and crystal structure of the nanocrystal precipitates could be c ontrolled by selection of the host material. The size distribution and micr ostructural complexity were significantly reduced by implanting a low conce ntration of ions into a noncrystalline host, and by using multi-energy impl ants to give a flat concentration profile of the implanted elements.