Shanthini.

This is a quit difficult question taking into account a complexity of your substrate. Moreover, additional information about your implantation regime is necessary to suggest anything. I mean the ion energy, fluence, the sample temperature, etc.

First of all, anybody should separate two different results of ion irradiation: 1) surface patterning and 2) ion implantation.

There are different surface nano-structures: waves, pyramids, nano-dots, caused by ion irradiation. Formation of a defined relief depends on many factors, and a complete theory is absent yet.

Implanted ions have a close to Gaussian distribution. If you implant element with the fluence, which offershigh enough concentration of implanted element to exceed the dilute maximum for this element in this matrix, the sample annealing results formation of nano-incorporations (nano-crystals). This is the so-called ostwald ripening mechanism. I do not remember publications when nano-incorporations are formed without annealing for the low energy implantation.

But! There is so-called “thermal spike regime”. There are many publications about crystallization and nano-crystal formation under the thermal spikes regime.

A coalescence process occurs during ion irradiation "automatically" due to ion mixing process. But the atomic mixing parameter is in the range of 1-10nm, approx. So you can estimate yourself is it enough for coalescence in your case.

Thank you sir. I have used N ions of 3+ charge state with energy 24 keV in the fluence range 1e15 to 1e16. Also after completing implantation process I didn't thermally anneal the samples, as they are made of polymer

Ok. You can make a quick simulation with a Monte Carlo program TRIM (www.srim.org) of projected range of you ions and distribution of defects generated. 24keV N+ ions is not "low energy", really speaking, low energy means few keV and sub-keV energy range. Nitrogen ions with 24keV could penetrate up to 100 Angstroms, o so. So, the primary ions and generated defects will be accumulated UNDER the surface in your case. But a surface modification is possible already with such fluences.

Ion implantation with such energy and fluence results many additional effects in polymers, for example, graphitization of implanted zone with emission of O and H from the polymer. But I have no idea about your composite. There is one more parameter (additionally to composition), which complicates the situation. I mean triple charge of you ions. This can be important for ion irradiation dielectric, but I have no experience in this area.  

Hi guys, with so little detail any response can only be speculative. Bearing that in mind here are a few things I would suggest.

Unless your material is really dense, and you really are having triple charged monoatomic nitrogen ion with 24 keV, the implantation range will be >30 nm. The advice above to simulate what you should get is definitely one to follow.

Nucleation of a precipitate and growth during ion implantation can happen. There is quite a lot of publications on ion beam synthesis of nanoparticles. A good place to start: Stepanov, A. L., and I. B. Khaibullin. "Fabrication of metal nanoparticles in sapphire by low-energy ion implantation." Rev. Adv. Mater. Sci 9, no. 2 (2005): 109-129. In first approximation, direct ion beam synthesis is mostly balisticIt works (Yuan, C.W., Yi, D.O., Sharp, I.D., Shin, S.J., Liao, C.Y., Guzman, J., Ager III, J.W., Haller, E.E. and Chrzan, D.C., 2009. Size-distribution evolution of ion-beam-synthesized nanoclusters in silica. Physical Review B, 80(13), p.134121.) so it can also work on polymer (advertisement to my own profile).

Then you have the issue of the polymer in your matrix. The chemistry can change dramatically under ion implantation (the displaced atoms will lead to polymer chain breaking, cross-linking, formation of an hydrogen rich amorphous carbon precipitate-> search these key words with ion beam and you will find plenty). This can lead to changes in the material and on the surface depending of the damage profile and how the changes affect the materials (density changes, stress distribution).

I would rate the chances of having structuring from sputtering as quite low. But that is an open guess, you really need that simulation.  

As for "structuring" I assume it is an increase in roughness. Is it following the pattern from the pristine materials roughness, or is it an altogether different looking surface?

There is also the chances of formation of gas bubles, and blisters. Again quite a lot of publication on the domain. Here is an oldie: Shrinet, V., Chaturvedi, U.K., Agrawal, S.K. and Nigam, A.K., 1984. A simple set-up for in-situ observation of the critical dose of blistering during ion implantation in polymers. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1(2), pp.617-620. Yes it is not the same range of energy etc. but it gives an idea, lots of key words and open up towards more recent publications.

I would not separate patterning and ion implantation, especially when speculating around possible outcome of an ion beam process. I would consider patterning alongside ion implantation, damage, atomic displacement precipitation, precipitate growth, ...

I'd love to see the SEM pictures before/after.

Cheers.