We compare two types of laser ablation for ARC removal on polished and textured surfaces. Selective ablation with limited impact on the underlying substrate is performed with short wavelength picosecond sources working at relatively low repetition rate (<200 kHz). By adapting wavelength and fluence, the SiNx could be removed efficiently with slight change initial topography. Crystal damage is detected whatever the laser parameters but could be reduced using low fluence in UV regime. The second ablation process uses ultra-high repetition rate picosecond laser (80 MHz) and targets both SiNx ablation and over-doping of the initial n+ emitter. The thermal effect induced by the short duration between pulses performs simultaneously SiNx removal and selective emitter structure with with deep dopant profiles and low surface concentration. We investigate the correlation between the post-ablation properties and a nickel silicidation process using Excimer Laser Annealing of a thin layer of Ni. A reference process is first described on pyramid topography without pre-ablation of SiNx. It is demonstrated efficient formation of SixNiy compounds on the silicon substrate depending and laser fluence. The similar silicidation process is transferred on sample after the SiNx ablation step. A continuous nickel silicide layer is observed but its thickness distribution reveals non-uniformity over the pyramids due to post ablation roughness.
The mechanisms involved in respiratory rhythm and in its persistence along lifetime have not been completely elucidated yet. The debate if they rely on pacemaker units or on the emerging properties of neural networks is still on. We propose a simple model taking advantage of the synaptic noise and allowing to bridge network and pacemaker theories. The pBC (reticular preBotzinger Complex) and PC (pneumotaxic center) are two randomly and sparsely connected excitatory networks. pBC excites PC that in turn, strongly inhibits pBC. As a part of the reticular formation, the pBC, receives many uncorrelated inputs (noise). The model reproduces most of the experimental observations. Once started, the pBC, whose activity is started by synaptic noise, increase of activity is an emerging property of the excitatory network. This activates the PC that in turn inhibits the pBC and starts the expiration. If, for any reason, noise becomes too low, the network becomes silent, and pacemakers become the only active units able to restart a new inspiration. Safety measures of this kind are very much expected in the operation of a system as vital as respiration. Simulations using an enhanced biologically plausible model of neurons fully support the proposed model.
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