The atomic distribution in the monolayer of two different Mn-doped US quantum dots (QDs) was studied first time with ToF-SIMS. The model Cd:Mn QDs were immobilized on Au substrate by use of a self-assembled monolayer via 1,10-decanedithiol. Morphological analysis by SPM and TEM indicates larger particle size of in situ synthesizing CdS:Mn. ToF-SIMS depth profile and 3D-images reveal that Mn atoms reside on the surface of in situ synthesizing CdS:Mn and are uniformly embedded in capped CdS:Mn. The results obtained by SPM, TEM, and ToF-SIMS are comparable, indicating that ToF-SIMS might find potential applications in surface and interface study of semiconductor nanocrystals. (c) 2006 Elsevier B.V. All rights reserved.