Nanosecond laser-induced phase transitions and metastable phases quenching

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Abstract
Pulsed-laser treatment of solid surfaces has two major features: fast heating, up to the melting point, on the nanosecond time scale, and subsequent rapid solidification and cooling. Metastable phases are often quenched in. The way in which one can control experimentally the solidification velocity, which is the main parameter in selecting between the different solid phases that can solidify, is discussed. As a reverse process, a metastable phase retained at room temperature can be heated to its melting point and melted, by-passing any solid-phase transformation or decomposition due to the fast heating rate. Examples are shown, throughout this paper, which relate mainly to the semiconductor field. This is because historically the technique has been developed as a tool to remove damage in ion-implanted semiconductors. Amorphous Si, amorphous Si–As solutions, supersaturated Si-dopant solutions and metastable silicides are sequentially presented both as examples of rapid melting and as examples of liquid-quenched metastable phases.