Preparation of AlSb films by laser annealing

The preparation of AlSb thin films by the pulsed laser annealing of Al/Sb sandwiches was studied in order to resolve some past controversy about the temperature rise induced by the laser pulse. Using films 1000 Å thick supported by transmission electron microscope grids, we investigated the energy threshold for complete transformation into AlSb as a function of pulse duration from 35 ns to 100 ms and at film temperatures ranging from -100 to 350 °C. By extrapolation we obtained the temperature rise directly induced by the laser beam as about 650 °C, i.e. approximately the melting point of the two metals, whereas during anneals of comparable films in an inert gas furnace the transformation at this temperature only occurs in times exceeding 100 s. We discuss the isoenergetic nature of the system for short laser pulses and the role of the heat of transformation, and we conclude that the reaction is thermally triggered by the laser pulse but is to some extent self-sustained via the heat of transformation which is locally distributed. Further, the laser-induced crystal growth is shown to be influenced by the beam shape.