Dynamics of long-pulse laser transfer of micrometer-sized metal patterns as followed by time-resolved measurements of reflectivity and transmittance

Kántor, Z.; Szörényi, T.

doi:10.1063/1.360076

Cited by 36 publications

(13 citation statements)

References 25 publications

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“…In particular, the deposition of pure-metal droplets in the liquid phase allows for deposition of conductive patterns [9,10], from which the semiconductor industry could benefit [11]. However, despite process improvements in various ways [12][13][14][15][16], the high potential of LIFT for liquid-metal deposition has not been met because the deposited features are poorly controlled. This lack of control can result in deposition of one main droplet surrounded by smaller satellite droplets, the deposition of many particles [8], or a significant uncertainty in the deposition location due to limited control of the ejection angle [17].…”

Section: Introductionmentioning

confidence: 99%

Ejection Regimes in Picosecond Laser-Induced Forward Transfer of Metals

et al. 2015

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Laser-induced forward transfer (LIFT) is a 3D direct-write method suitable for precision printing of various materials, including pure metals. To understand the ejection mechanism and thereby improve deposition, here we present visualizations of ejection events at high-spatial (submicrometer) and hightemporal resolutions, for picosecond LIFT of copper and gold films with a thickness 50 nm ≤ d ≤ 400 nm. For increasing fluences, these visualizations reveals the fluence threshold below which no ejection is observed, followed by the release of a metal cap (i.e., a hemisphere-shaped droplet), the formation of an elongated jet, and the release of a metal spray. For each ejection regime, the driving mechanisms are analyzed, aided by a two-temperature model. Cap ejection is driven by relaxation of thermal stresses induced by laser-induced heating, whereas jet and spray ejections are vapor driven (as the metal film is partly vaporized). We introduce energy balances that provide the ejection velocity in qualitative agreement with our velocity measurements. The threshold fluences separating the ejection regimes are determined. In addition, the fluence threshold below which no ejection is observed is quantitatively described using a balance between the surface energy and the inertia of the (locally melted) film. In conclusion, the ejection type can now be controlled, which allows for improved deposition of pure metal droplets and sprays.

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Section: Introductionmentioning

confidence: 99%

Ejection Regimes in Picosecond Laser-Induced Forward Transfer of Metals

et al. 2015

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“…Since its development by Bohandy et al, 3 the feasibility of LIFT for the deposition of inorganic materials in a solid state has been repeatedly demonstrated. [4][5][6] In this case, the heating caused by the laser in the precursor film leads to the vaporization of the material, which recondenses in the receptor substrate following the transfer. Under these conditions, the transfer of biomolecules is clearly not possible due to the irreversible damage to the biomaterial caused by a direct interaction with the laser radiation.…”

Section: Introductionmentioning

confidence: 99%

Laser-induced forward transfer of liquids: Study of the droplet ejection process

Colina¹,

Duocastella²,

Fernández-Pradas³

et al. 2006

Journal of Applied Physics

132

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Laser-induced forward transfer ͑LIFT͒ is a laser direct-write technique that offers the possibility of printing patterns with a high spatial resolution from a wide range of materials in a solid or liquid state, such as conductors, dielectrics, and biomolecules in solution. This versatility has made LIFT a very promising alternative to lithography-based processes for the rapid prototyping of biomolecule microarrays. Here, we study the transfer process through the LIFT of droplets of a solution suitable for microarray preparation. The laser pulse energy and beam size were systematically varied, and the effect on the transferred droplets was evaluated. Controlled transfers in which the deposited droplets displayed optimal features could be obtained by varying these parameters. In addition, the transferred droplet volume displayed a linear dependence on the laser pulse energy. This dependence allowed determining a threshold energy density value, independent of the laser focusing conditions, which acted as necessary conditions for the transfer to occur. The corresponding sufficient condition was given by a different total energy threshold for each laser beam dimension. The threshold energy density was found to be the dimensional parameter that determined the amount of the transferred liquid per laser pulse, and there was no substantial loss of material due to liquid vaporization during the transfer.

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“…This basic LIFT process has been widely used to transfer various types of materials such as metals [2][3][4][5][6] . Further improvements of the LIFT process, mainly to the type and composition of the donor, resulted in various LIFT based techniques, aiming at a more temperature sensitive and a more controllable process [7][8][9][10][11] . However, still the basic LIFT process of metals is not yet fully understood.…”

Section: Introductionmentioning

confidence: 99%

High-resolution imaging of ejection dynamics in laser-induced forward transfer

et al. 2014

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Laser-induced Forward Transfer (LIFT) is a 3D direct-write method suitable for precision printing of various materials. As the ejection mechanism of picosecond LIFT has not been visualized in detail, the governing physics are not fully understood yet. Therefore, this article presents an experimental imaging study on the ejection process of gold-based LIFT. The LIFT experiments were performed using a 6.7 picosecond Yb:YAG laser source equipped with a SHG. The beam was focused onto a 200 nm thick gold donor layer. The high magnification images were obtained using bright field illumination by a 6 ns pulsed Nd:YAG laser source and a 50× long-distance microscope objective that was combined with a 200 mm tube lens. For laser fluence levels up to two times the donor-transfer-threshold, the ejection of a single droplet was observed. The typical droplet radius was estimated to be less than 3 µm. A transition of ejection features towards higher fluence, indicates a second fluence-regime in the ejection process. For higher laser fluence, the formation of an elongated gold jet was observed. This jet fragments into multiple relatively small droplets, resulting in a spray of particles on the receiving substrate.

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Dynamics of long-pulse laser transfer of micrometer-sized metal patterns as followed by time-resolved measurements of reflectivity and transmittance

Cited by 36 publications

References 25 publications

Ejection Regimes in Picosecond Laser-Induced Forward Transfer of Metals

Ejection Regimes in Picosecond Laser-Induced Forward Transfer of Metals

Laser-induced forward transfer of liquids: Study of the droplet ejection process

High-resolution imaging of ejection dynamics in laser-induced forward transfer

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