Hey there, I would say, that they have different mechanical stabilites and conductivities. Pt/Ir was used strengthen gold tips of pens (now rhodium is used), however it's conductivity is (I have to guess) weaker than that of gold. Gold on the other hand is very ductile. It's likely that you will loose your coating if you press to hard. TiN is i guess not conductive at all or very poor conductor.

Au coatings are made for better reflectivity. TiN, PtIr or Au probes may be used for conductivity studies. Please, see more information here

http://www.ntmdt-tips.com/products/group/cond

Au coated tips usually use for conductive AFM while PtIr and TiN coated tips mostly use for contact and noncontact modes depending on their frequencies.

Good day!

All the three types of materials listed can be coated from tip-side to make cantilevers to be conductive.

Au coating mechanically weak and it can be easily damaged during a scan in the contact mode. So we don't recommend such probes for usage in Spreading resistance technique. I've heard that Au coated probes are good for the new microwave mode, but I have no exact information about it.

Pt coating is stronger but it's not recommended to use Pt coated probes for measuring high currents. They are being heated and the conductive layer may destroy. Conductivity of such layer is still very good.

TiN layer are much more mechanically stronger. I tried some experiments with these probes several years ago and I didn't succeeded killing them even with currents of several mkA. They conduct well - not so great as Pt, but good enough. The only possible shortcoming - they looked to degrade slightly with time. We decided that the reason was high humidity. Just recently we started to use a new type of conductive probes with TiN cover, I didn't test their degradation yet.

By the way, recently we started to sell new cantilevers with W2C conductive cover. Also very nice for Spreading Resistance in my opinion.