J.C. Conde

Extensive Studies of the Plume Deflection Angle During Laser Ablation of Si Target

The plume deflection effect during long laser irradiation of a Si target has been extensively studied. Two different laser ablation experiments were performed to study the plume deflection angle and the ablation rate versus the number of laser pulses/site. Scanning electron microscopy (SEM) analyses and profilometry of the Si target surface were performed to examine the continuous morphological changes produced by the laser irradiation. The roughening of the target surface strongly influenced the formation and expansion of the Si plume. Plume deflection angles higher than 30° have been observed by a digital camera. Complementary mass spectrometer measurements confirmed that the ion flux distribution is strongly oriented along the laser beam direction. In addition to laser ablation experiments, two other laser deposition experiments were performed: with the conventional configuration and with a new approach, termed frontal off-axis deposition. The new pulsed-laser deposition configuration provides much better control of uniformity and film thickness than the conventional deposition configuration.

Temperature distribution in laser marking

A theoretical model describing the temperature distribution on plastic material during the laser marking process has been developed. The heat conduction differential equation was solved analytically by the Green function method, and numerically, based on the finite element method using ANSYS®(5.5). The experimental irradiation of a methacrylate piece by a CO2 laser was carried out in order to check the validity range of the model.

Temperature distribution in a material heated by laser radiation: modelling and application

Laser-based techniques are widely used for thin film deposition, crystallization of amorphous materials, surface treatment, alloying and the modification of material properties. For these purposes, the knowledge of the temperature field in a material induced by the laser beam irradiation is very helpful. In this paper, the spatial and temporal temperature distribution in a material is calculated by the Green function method for different cases of laser radiation. Two mathematical descriptions of the physical process are carried out: the first one considers an external flux impinging on the material, and in the second case it is assumed that the heat is stored on the material surface in the absence of an external heat source. The equivalence of both approaches is demonstrated. These theoretical calculations are applied to investigate the formation of SiGe epitaxial layers by pulsed laser-induced epitaxy (PLIE).

Finite element simulation for ultraviolet excimer laser processing of patterned Si/SiGe/Si(100) heterostructures

Ultraviolet (UV) Excimer laser assisted processing is an alternative strategy for producing patterned silicon germanium heterostructures. We numerically analyzed the effects caused by pulsed 193 Excimer laser radiation impinging on patterned amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bilayers deposited on a crystalline silicon substrate [Si(100)]. The proposed two dimensional axisymmetric numerical model allowed us to estimate the temperature and concentration gradients caused by the laser induced rapid melting and solidification processes. Energy density dependence of maximum melting depth and melting time evolution as well as three dimensional temperature and element distribution have been simulated and compared with experimentally obtained results.