The ablation of thin films by single laser pulses is a well known technique with widespread industrial applications. Ablation occurs in a well defmed power density region if a supported thin film is illuminated by a single laser pulse. In the literature there are a number of theoretical description of ablation, but a very few based on in-situ experiments. In our study we have directly visualised the ablation processes with fast photography based on application of dye laser probe pulses. The ablation of chromium and tungsten layers supported onto glass substrates with pulses of ArF excimer laser was investigated. The ablated area was illuminated by a delayed short pulse of a fluorescein dye laser or a Rhodamine6G dye laser. Snapshots of initial phase of ablation and the forthcoming material transport were recorded by an optical system and a video camera. Blowing-off mechanisms and thermo-mechanical mechanisms are considered to take place during ablation. Pressures formed during laser ablation were calculated and compared with experimental data. It was found that thermo-desorbtion of gas adsorbed on to the substrate surface, substrate material evaporation and film exfoliation by its longitudinal thermal enlargement may be acting during laser ablation of thin films.

H-6 720 eg, Dôm tér 9 . , Hungary ABSTRZCT Besults of a systematic study on Q-switched nthy laser induced rrrn2 area transfer of supported titanium and chranium thin films and Ge/Se multilayer structures are reported. The appearance of the prints is governed by film-support adhesion and source-target spacing. Best quality prints are produced by ablating well adhering ntal films in close proximity ( spacing < 15 pm) to the target to be patterned. Transfer fran stacked elenntaxy layers as a source offers a unique possibility of depositing acinpound films by mixing the constituents and transferring the material onto the target substrate in a single step. INTIOJ1JcTIONThe transfer of thin absorbing films from a transparent support onto another target substrate in close proximity with single laser pulses (Laser Induced Forward Transfer = LIFT) offers a straightforward novel approach to surface 1-5,The advantages of this technique are quite obvious : there is no need for cciplicated gas handling and/or vacuiin systems ( in fact all studies reported have been perforrrd in air1or in vacuum5 ) and the propei±ies of the target substrate surface to be patterned have essentially no influence on the process . Although it is anticipated that in the ideal case a spatial resolution approaching the pm danain can be achieved the minflnum lateral dittensions of the patterns actually deposited lie beten 30 and 120 iirn1-5.As a first systematic study of the rather diverse processes involved in thin film ablation and concctnitant deposition by single laser pulses we reporb here on imi2-area processing of supported titanium and chromium thin films . We focus /i / on the role of the glass support film interface in governing the characteristics of both ablation and printing and hi! On tI depennce of irorphology and lateral dirrensions of the transferred patterns on target-source distance . We analyse the elerrentary events by caiiparing experirrental data with calculated temperature distributions in space and tine. The results of a canparative study on Ge/Se bilayer structures allow to clarify the role of the interface in rerroving the absorbing film these also allow to verify the validity of our ablation/deposition rrocèl for fluences not far frau threshold. As a powerful extension we show that LIFT from stacked elementaxy layers on a transparent support as sources offers the unique possibility of positing aaround films by mixing the constituents and transferring the material onto the target substrate in a single step. 2.EXPE REMENTAL'I sets of titanium films the substrates of which were cleaned differently, 150

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A simple and inexpensive single-step technique for surface patterning in the jim regime is presented. As a result of a systematic study on laser-induced ablation and transfer of tungsten thin films it is shown that deposition of well adhering micrometer sized patterns of 100% coverage preserving the shape and dimensions of the laser processed area can be attained by single pulses of peak power up to 100 mW and 100 jis -1 ms duration from a diode laser pumped YAG laser.

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Laser ablation of layer structures made of optically and thermally dissimilar materials is markedly different from ablation of homogeneous bulk materials. In the case of supported thin films the ablation characteristics are influenced by the variation of the material properties at the interface. This concept is highlighted by comparing experimental and thermal calculation data on pulsed laser ablation of metal, tin oxide and indium-tin oxide films from glass support to those ofcharacterising bulk ablation.

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