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Flexible and rapid preparation of FeSi2 microdots and indium tin oxide (ITO) microstructure patterns was performed using laser-induced forward transfer with a nanosecond high-frequency di-ode-pumped solid-state laser/galvanometer-based point-scanning system. Different types of source materials, i.e., FeSi2 and ITO, were used to explore the materials dependence of transfer. FeSi2 spheres with a lateral diameter of 5.5 µm were successfully arrayed on a micrometer scale. Sub-spot transfer was achieved, and we refer to this as laser-induced dot transfer (LIDT). In the case of ITO, although the transferred shape is flower-like rather than spherical, site-controlled transfer was achieved. The LIDT technique is useful for integrating functional micro-patterns with sub-spot reso-lution under room-temperature atmospheric conditions.
DOI:10.2961/jlnm.2012.01.0015
Keywords: laser-induced dot transfer, on-demand preparation, microdot pattern, FeSi2, ITO
1. Introduction
Laser-induced forward transfer (LIFT) has been studied extensively as a method for additive micro-patterning be-cause it has the advantage of being a simple atmospheric low-temperature process [1-3]. Recent LIFT works have focused on two main features: deposition that is less dam-aging to target materials, and sub-spot transfer resulting in typical droplet volumes of from a tenth to several femtoli-ters [4-8]. The former feature is favorable for patterning biomaterials [9-12] and integrating functional materials on soft substrates such as organic semiconductors and metal electrodes for organic thin-film transistors (OTFTs) [13, 14]. In the latter feature, i.e., sub-spot transfer, one-to-one dot deposition with a laser-illuminated area is used; we refer to this as laser-induced dot transfer (LIDT) [6] to distinguish it from conventional LIFT. The LIDT process provides a new way of micro-patterning a variety of mate-rials, with higher resolutions than those obtained using commercially available inkjet techniques.
We had already developed an LIDT technique using a nanosecond excimer laser/mask-projection system [6, 7]. The main advantage of this system is size-controlled depo-sition of submicron- and micro-dots in numbers of more than ten thousand by single-pulse irradiation. FeSi2 submi-cron- and micro-dots were prepared in association with room-temperature (RT) precipitation of β-FeSi2 semicon-ducting crystallites. Near-infrared (NIR) photolumines-cence was successfully detected from these dots [7]. The semiconductor β-FeSi2 is one of the potential candidates for Si-based light emitters and detectors at 1.5-1.6 µm in the NIR suitable for optical networking, solar cells, and thermoelectric devices [15, 16]. β-FeSi2 has other excellent features such as...