Three-dimensional (3D), periodic nanowriting on diamond clusters is reported in this letter. Concentric circular rings were observed on diamond microclusters, nucleated near the periphery of a laser-irradiated region, when chemical-vapor deposited diamond was processed in air, with laser pulses of 380 fs duration and at a wavelength of 248 nm. Periodic ripples also have been observed on single-crystal and polycrystalline diamond surfaces. Further, it is experimentally shown that the periodicity of these corrugated two-dimensional and 3D structures is shorter than that of the laser wavelength used (248 nm for the excimer fs laser and 825 nm for the Ti–sapphire fs laser).
Aluminum nitride (AN) is beginning to replace alumina as a substrate and heat sink for electronic circuits. The thermal conductivity of A1N, about 8 times that of alumina, is the primary reason for its selection in these applications. While beryllium oxide has even higher conductivity, concerns about that material's toxicity reduce its appeal.Alumina is easily scribed and cut with carbon dioxide lasers. The high thermal conductivity that makes AIN useful, however, makes it difficult to machine with a laser because the material can absorb considerable incident energy without melting or vaporizing. Process settings that produce good results with alumina are not suitable for AIN. It is therefore necessary to develop a new processing regime for aluminum nitride.We cut 0.7 mm thick aluminum nitride sheet with a carbon dioxide laser using a large matrix of process variables and examined the resulting edges for surface quality, microcracking, aluminum deposition and recast. With this information, we defined the volume in process space where effective processing can be accomplished.
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