Surface modifications of silicon using the high intensity Nd:YAG laser

Complete test of publication follows. Surface modification of semiconductor materials such as silicon by various types of energetic beams including the laser radiation is of a great fundamental and technological importance. The interest in studies of laser beam interaction with silicon is still extremely high. Silicon exhibits very good physico-chemical characteristics like high melting/boiling point, thermodynamic and chemical stability, semi-conducting properties, etc. and hence very attractive in electronics, semi-conductors industries, etc. In the present work surface morphological effects on a crystalline silicon target due to interaction of Nd: YAG laser radiation (TEM00 mode), pulse duration of 40 picosecond at 532 nm are reported. The sample was a crystalline silicon plate (dimensions of 10 mm x 0.5 mm) with typical greyish colour. The surface roughness of the sample was about 0.1 μm. The samples were irradiated in air, at the atmospheric pressure. The p-polarized laser beam was incident normal to the target surface. Various analytical techniques were used for the characterization of the sample before and after irradiation using X-ray diffractometry, microscopy (optical, SEM, AFM), etc. Our experimental results show that laser energy flux (LEF) exceeding to 0.7 J/cm2 (i.e. peak intensity - 2 x 1010 W/cm2) was sufficient for inducing surface morphological changes on the samples. The absorbed laser energy generates a series of effects such as melting, vaporization of the molten material, cracking, etc. The morphological modifications of the silicon surface can be summarized as follows: (i) intense damage in the central zone of the irradiated area was recorded in the flux range 0.7 to 22.5 J/cm2 (with 100 accumulated laser pulses). (ii) Appearance of a wave-like microstructures (MS) across the entire irradiated spot for all the flux range (for low number of accumulated pulses). The estimated spatial wave-length of MS was about 10 microns, and (iii) creation of hydrodynamic features at the periphery, like resolidified forms, were expressed for higher laser flux. The creation of microstructures is very complex process. Preliminary consideration, among other, can include interaction of the incident wave with the surface electromagnetic waves. Further investigation and details of the work will be presented during the conference.