Laser writing and erasing on chalcogenide films

Abstract

Optical switching from the mostly crystalline to the amorphous state has been studied in TeGeAs alloy films using ∼ 5-nsec pulses from a nitrogen laser pumped dye laser. These ``reverse-mode'' written spots were switched (erased) by both optical and thermal means. Microscopic examination of the films, thermally crystallized before optical writing, indicates the existence of a two-phase system consisting of Te crystallites in a background of amorphous Ge-rich material. A similar condition is again found after a write-erase cycle has occurred. Computer calculations on the thermal history of the crystalline film resulting from a 5-nsec pulse indicate initial cooling rates of the order of 1010°C/sec.