Laser Ablation of 6H-SiC Single Crystals and Spectral Characterization.

Laser micromachining has proven to be a useful tool for precision processing of semiconductors. For Silicon Carbide (SiC) single crystals, ablation with ultraviolet wavelength laser could lead to the maximum absorption efficiency of incident energy. In this paper, laser ablations were performed on 6H-SiC single crystals through a 355 nm solid state laser. Different confining media were also employed to find the optimal processing condition. The surface of SiC after laser ablation was characterized by Raman spectroscopy. Amorphous silicon and nanocrystalline graphite were found to be the main compositions left. For SiC wafers ablation in air, the amorphous silicon exhibited mainly around rather than inside the ablated crater. However, the amorphous silicon showed opposite spatial distribution features for samples processing under liquid. Through analysis of the compositions left on the ablated surface, the ablation mechanism was investigated from another point of view. For liquid confined laser processing,previous studies mainly concentrate on the thickness and viscosity of the liquids, little information has been done on the reducibility of liquids. To investigate the influence of liquid reducibility, the surface morphology and oxygen content of ablation under different confining media were checked by confocal laser scanning microscopy and energy dispersive spectroscopy. Results showed that the reducibility of confining liquid also played a vital role in the ablation process under liquid. Utilizing liquids with deoxidizing ability as confining media will result in a remarkable reduction of surface oxygen content and a more regular morphology.

Optical planar waveguide fabricated in Nd:LuVO4 crystal by MeV oxygen implantation.

We report the first time optical planar waveguide fabricated in vanadate laser crystal Nd:LuVO4 by 3.0 MeV oxygen ion implantation with the dose of 6x1014 ions/cm2 at room temperature. After the implantation, an enhanced ordinary refractive index region was formed with a width of about 2.1 microm beneath the sample surface to act as a waveguide structure. The modes were observed at 633 nm, while only one mode was observed at 1539 nm after annealing at 300 degrees C for 60 min in air. The changes of ordinary refractive index in the guiding region were about 4.42% and 4.07% before and after annealing.

Synthesis of stable ACC using mesoporous silica gel as a support.

Stable amorphous calcium carbonate supported by mesoporous silica gel was successfully synthesized. The silica gel support is prepared through the hydrolytic polycondensation of ethyl silicate under suitable conditions. Laser scanning confocal microscopy (LSCM) observations reveal that the morphology of the products is branched with cruciform-like and flower-like structure. Raman spectroscopic analysis and scanning electron microscopy (SEM) observation of the products confirm the combination of stable amorphous calcium carbonate (ACC) nanoparticles and mesoporous silica gel. A possible growth mechanism for the branched structure has been proposed. Results indicate potential application of this work to ACC storage, crystal engineering, biomimetic synthesis, etc.