Forums
Bruker Media
Community Media
Bruker AFM Probes
SPM Digest
Application Notes
NanoTheater
Website
中文
Brochures & Datasheets
Publications
Probes Catalog
Events
Manuals & Documentation
Presentations
Guide to AFM Modes
News
Journal Club
Webinars & Video
Nanovations
Other
Hi, I'm looking for some AFM tips which I hope to coat with silver nanoparticles to be used in tip-enhanced Raman spectroscopy (TERS). I was wondering if there are any suggestions as to the kind of tips that would be best suited for this?
Thanks,
Faris Sinjab
University of Nottingham
Hi Faris,
You should use tips that support the feedback mode you are using and that have the chemistry necessary for your coating process. Bruker AFM Probes has a great selection of these probes : http://www.brukerafmprobes.com/. For Tapping Mode I would suggest TESP(A) or OTESP(A) probes if you want to work at around 300 kHz and FESP(A) if you would like to work at lower frequencies.
You also want to check out Markus Raschke's group at: http://nano-optics.colorado.edu/ They are very succesful in using their Bruker Innova AFM for a variety of nano-optical experiments which of course includes TERS.
Best,
Stefan
Hi,
Further addition to Stephens reply.
If your excitation wavelength is very small (<600), usually SiN tips are preferred over Si tips as the enhancement factor of Si tips is too low at lower excitation.
Conventional Si tips are heavily doped and have much lower resistivities than undoped Si. If ohmic junctions are formed between Ag nanoparticles and the tip, the conduction electron density of Ag would be reduced which in turn would reduce the ability to excite surface plasmon.
Another factor in favor of SiN tips is its refractive index (n). Si has higher n 4.4 compared to SiN 2.05 which will reduce surface plasmon and thus TERS enhancement. For higher excitation wavelength Si tips are adequate and are preferred because of its sharpness.
Bruker has a selection of nitride probes which can be suitable for TERS application. OTR8 andORC8. Each probe has 4 cantilevers with varying stiffness. Depending on the sample and the scan mode right cantilever can be selected.
Rakesh
Rakesh,
One probably wants to coat the tips before depositing the Ag or Au layer anyhow. AlF(3) for SiN e.g. Tip sharpness should really not be an issue if you plan on placing metal particles of ~30nm diameter or so onto the tip itself.
Stefan,
You are right. If he deposits a thin layer of AlF3 or any low n dielectric between tip and Ag, it should enhance the TERS signal. For some reason most of the research articles use SiN probes but I guess with the said approach any tip will be good.
Thanks