Dry and steam laser cleaning, DLC and SLC, of nano-and micro-contaminant particles from UV/vis opaque and transparent critical substrates has been studied in front-side laser illumination geometry with the help of time-resolved optical techniques and broadband photoacoustic spectroscopy using a nanosecond 10.6-μm TEA CO2-laser and different absorbing energy transfer media (ETM) fluids. Corresponding basic DLC and SLC mechanisms for removal of nano- and micro-particles from opaque and transparent critical substrates as well as parameters of explosive removal of ETM fluids have been determined and discussed.
A lot of work has been done in the area of laser sterilization using UV lasers whereas this area is not much explored using an IR laser. In this study the cells were catapulted from glass or oxidized silicon substrates by a nanosecond IR CO2 laser. Removal of cells and bacteria was achieved under the micron thick liquid layer pre-deposited on the substrates and lifted off together with biological species at laser fluences exceeding the corresponding boiling thresholds for the liquids used. Catapulting with front-side laser illumination is studied
KEYWORDS: Particles, Silicon, Gas lasers, Stanford Linear Collider, Pulsed laser operation, Microscopes, Carbon monoxide, Liquids, Semiconducting wafers, Energy transfer
Selective laser removal of micro-particles of one chemical composition from their mixture with micro-particles of another chemical type pre-deposited on hydrophobic or hydrophilic surfaces have been demonstrated by means of steam laser cleaning method realized with nanosecond IR laser and various liquid energy transfer media (ETM). Microscopic imaging of particle mixture deposition, ETM dosing and final particle removal has been performed with the help of timeresolved optical microscopy. Optimal ETM/particle combinations for selective targeting and removal of specific
particles from their mixture on the surfaces have been revealed.
Dry and steam laser cleaning, DLC and SLC, of nano-and micro contaminant particles from UV/vis opaque and transparent critical substrates has been studied in front-side laser illumination geometry with the help of time-resolved optical techniques using a nanosecond IR CO2-laser and different energy transfer media (ETM) fluids. In the case of SLC, microscopic details of particle-ETM-substrate interactions in pre-deposited micron-thick ETM layers have been revealed preliminarily by means of time-resolved optical microscopy. Fundamental DLC and SLC mechanisms for removal of nano- and micro-particles from opaque and transparent critical substrates have been determined. Optimal conditions for nearly complete laser cleaning have been chosen for different combinations of contaminating nano- and micro-particles and substrates.
Pulsed laser cleaning of sub- and micron-sized (0.3-10 μm) monodispersed model spherical polystyrene particles and fused silica particles from fused silica and glass optical surfaces was performed by means of ns TEA CO2 laser. Efficient removal of these absorbing particles has been demonstrated in certain laser fluence range, which is below the threshold for ablative damage of the fused silica and glass substrate. Removal mechanisms of dry and steam laser cleaning of various critical optical surfaces are discussed.
The dynamics of explosive boiling of a 2-propanol layer of variable thickness on a Si substrate heated by a nanosecond KrF excimer laser was studied using a contact photoacoustic technique. The transition from acoustic generation at a free Si boundary to that at a rigid alcohol/Si boundary accompanied by a sharp increase of acoustic generation efficiency was found above a laser fluence threshold of 0.17 J/cm2 and a liquid layer thickness greater than 0.25 μm due to subnanosecond near-critical explosive boiling of the superheated liquid layer near the hot absorbing Si substrate. The gradual increase of the photoacoustic response of the superheated alcohol with increasing thickness of the liquid film at fluences above the explosive boiling threshold was attributed to the fluence- and time-dependent increase of the area undergoing explosive boiling.
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