I always get nucleation of metals onto the facets or on the defect sites or they just form separate islands. Any suggestions to achieve homogeneous nucleation?
The adsorption energy at semiconductor surfaces largely depends on the charge transfer mechanisms between the surface and adsorbed species, which is dictated by the electron affinities of the atoms involved. If the processes do not involve charge transfer, as in adsorption of closed shell systems, the adsorption energy depends only on the bonding. If charge transfer occurs, such as in your metal atoms, which are open shell systems, then the Fermi level is pinned differently, leading to vastly differing energy levels. One therefore needs to consider the atom types and surface energetics.
You need to consider the atomic level surface modification to safeguard from nucleation. Use octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) for secondary deposition which will effectively block the nucleation.
What I need is an epitaxial growth of metal on semiconductor nanocrystals and not the preferential deposition of metals. Ligand exchange does help but still it's not a homogeneous nucleation.
I think you need to treat your semiconductor surface by using a few attacks with HF (1% in EDI), this process helps to reduce the surface energy and increase the atomic growth of metal on semiconductor nanocrystals.
Treating with HF could change the morphology of semiconductor nanocrystals as it will damage the ligands attached to it.
They are synthesized in organics with Oleyalmine as the only ligand.
Ok, in this case I think you should change the ligands for example you can use the ligand-based a thiolate as (R-(SH)) which have a good affinity with metal space and more attached on semiconductor nanocrystals than Oleyalmine ligand.
I have tried DDT (Dodecanethiol) but it didn't work, I realized that it binds quite strongly to metals. The solution goes colloidally unstable when DDT was used. So, I tried DDA (Dodecylamine) which gave me the results shown in the picture.
What I have understood so far that the rate of charge transfer at semiconductor surface is slower than the metal surfaces due to the lower surface electron density which could be a potential reason for metal deposition in the form of 3D island on semiconductor surfaces or self-nucleating island.
Feel free to add, I am keen to know more about the interaction of two different class of materials.
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