Band gap of nanoparticle determines which wavelength can be absorbed. The wavelength of a laser should be larger than band gap of the nanoparticle. Before experiment, you can calculate a penetration depth using refractive indice of the nanoparticle at certain wavelength.

As far as I know people are generally using continuous wave 520 nm for gold nanoparticle sintering. A few hundred mW power was enough so you can get it with many laser systems but they were using Argon lasers for it.

First of all, you need to know the optical absorption coefficient of your material. Then you could choose the appropriate laser wavelength. For example, for annealing of metal you could use infrared laser, but for Si you need UV or visible laser.

Band gap of nanoparticle determines which wavelength can be absorbed. The wavelength of a laser should be larger than band gap of the nanoparticle. Before experiment, you can calculate a penetration depth using refractive indice of the nanoparticle at certain wavelength.

In general, it depends on the materials to be treated. However, Nd:YAG is the most used laser in such application in addition to some interest in CO2 and Excimer lasers.

The question is first what kind of annealing has to be produced.

A thermal annealing which is in favor of atomic diffusion , or an electronic activation which can cause atomic rearrangement of metastable species. Of course, the optical absorption of the used laser wavelength has to be considered,=in all cases. however, considering for instance carbon materials, two different kinds of atomic rearrangement in competition to each others have to be considered.

This is not always the case for metals and for silicon when recrystallization can be achieved also with heating and temperature after the material has been molten..

The other points are if the Laser irradiation can produce laser desorbtion based on quantum electronic activation or if it can cause a thermal evaporation. Effects which are also clearly shown in producing hole on a surface with laser impact of high enough power.

Therefore, after the absorption of the laser wave length, has also to be considered the actually achieved substrate temperature and the heat conduction of the substrate/substrate holder system and the laser pulse frequency and duty cycle.

Dear All,

Thanks a lot for your answers, helped a lot to understand basics :)

I have Si and Ge nanoparticles, and so far furnace annealing, hot plate annealing and raman laser annealing tried.

i can observe some morphological changes but not enough for me!

I want to have layer which has particle-particle contact and good conduction through particle layer.

so next step would be Laser annealing with defined wavelenght.

Pulsed laser or continuous laser , I have not decided yet...

again thank you very much !!!