Femtosecond laser ablation technique has been used to process Si and Au targets in vacuum, air and water environment. The threshold of ablation was found to be much lower for Si compared to Au and that was related to much better radiation absorption of Si. The values of the threshold were almost identical for vacuum, air and water in the case of Si (0.4 J/cm2 0.2 J/cm2 in the single and multi-pulse irradiation regime, respectively) and Au (0.9 J/cm2 and 0.3 J/cm2). Craters on the surface of Si and Au were essentially similar for low fluences, suggesting an involvement of the same radiation-related mechanism of material removal, whereas for high fluences significant differences could take place. In particular, quite different crater morphologies were observed during the laser ablation in water, including ones with nanoporous layers for Si and ones with concentric spheres for Au. The differences of morphologies for high laser fluences were explained by the involvement of plasma-related effects under the processing in relatively dense media.
Highly accurate resistances can be made by iterative laser-induced local diffusion of dopants from the drain and source of a gateless field effect transistor into its channel, thereby forming an electrical link between two adjacent p-n junction diodes. In this paper we present a complete modeling, which permits to obtain the device characteristics from process parameters. Three-dimensional (3D) temperature calculations are performed from heat diffusion equation using an apparent heat capacity formulation. Melted region determinations are satisfactory compared with in-situ real-time optical measurements of the melted region behavior. Then 3D dopant diffusion profiles are calculated using Fick’s diffusion equation. Finally electronic characteristics are obtained from the new tube multiplexing algorithm for computing the I-V characteristic and the device differential resistance. Numerical simulations using our software are satisfactory compared with experimental I-V measurements.
Highly accurate resistances can be made by iteratively laser inducing local diffusion of dopants from the drain and source of a gateless field effect transistor into the channel, thereby forming an electrical link between two adjacent p-n junction diodes. Using transmission electron microscopy, we showed that the laser induced diffusible resistance can be performed without any structural modification to the microdevices. Current-voltage (I-V) characteristics of these new microdevices are shown to be linear at low voltages and sublinear at higher voltages where carrier mobility is affected by the presence of high fields. A process model involving an approximate calculation of the laser melted region in which the dopant diffusion occurs has been developed. Experimental results are well described by the proposed model.
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