Using the fourth harmonic, 266 nm laser beam of Nd:YAG, linear- and point-form structures References 
have been produced in an Aluminium hydride (HAIO) film on the substrate of copper, as 7 
imaged by AFM and Optical Microscope respectively, in figure 11 and 12. The sample is [Mei95] H 
prepared through MOCVD by M. Veith and coworkers!”!, 
From the AFM image in figure 11 it can be seen that in the laser irradiated area, where [Fra01] P. 
the intensity has a maximum, phase transformation is occurred. Detailed studies by FT- 2001 
IR-Reflection Spectra and X-ray diffraction have proved that the bond between Al and H 
is broken by laser photon energy, and these Al atoms form Al clusters in the ALO; [1] H. Glei 
matrix. A similar process is induced by three laser beam interference, to form a two microstru 
dimensional structure, as shown with optical microscopy in figure 12. [2] K.J: Ii 
4. Discussion [3] HM. P 
For the laser nano-microstructuring , there are mainly two kinds of mechanisins that are polyimide 
behind the process - photo-thermal and photo-chemical reactions. [4] H. Fuk 
For the photo-thermal process the thermalization of the excitation is faster than other initial 
processing steps, i.e., desorption of species from the surface, or structural rearrangements of [5] Stutzm 
atoms or molecules, or initial steps in a chemical reaction. Thus, the detailed excitation Stat. Sol.( 
mechanisms become irrelevant, and the laser can be considered simply as a heating source. [6] CEN 
This is the case for silicon and copper structuring, which is shown in our experiment by h S ’ ¢ 
observation of the melting-re-solidification feature of the structure. One can produce different Phys. Stat. 
structures simply by choosing different laser wave length and different laser beam ZT. Li 
configuration(two-, three-, or multi-beam interference). On the other hand, one can control the laser a . 
phase change i.e., crystallization, and in certain degree of the morphology by choosing 7. 1018(1 
suitable energy density level of the laser. Combined with the optical and thermal parameters > ; 
of the material, this determines the highest temperature of the fast heated material surface. [8] Satoru 
. . . laser inter 
In the case of photo-chemical processes, one must pay attention to the interaction between the 19(2000) 
individual photon and the molecule or atom. First of all, the energy carried by individual ’ 
photons must be larger in order to break the chemical bond among atoms, as in the case of [9] M. Veit 
HAIO, the bond among Al, H, and O, in order to induce the phase change, or to initiate j Material 
chemical modification. ‘ 
From the experiments on various structuring with different materials, we can [19] Gt 
conclude that laser interference nano-microstructuring is a feasible method for material ppl.>urt 
surface modification, through photo-thermal or photo-chemical mechanisms; the period and [11] T. Re 
the feature size can be easily controlled with micro- or nanometer resolution by laser Sur faces 
parameters and by geometrical configuration. The feature size is related also to the threshold 
of the structuring mechanism, such as crystallization, melting with or without evaporation, or 
chemical modification. Therefore it may find important applications for the functionalization 
of material surfaces including the composite effect of material surfaces. 
6