Phase changeable material

Claim 1

In a method of forming an optical data storage device having a state changeable chalcogenide phase change layer reversibly switchable between at least two detectable states, which method comprises co-depositing a chalcogen and a cross linking agent on to a substrate, the improvement comprising: (a) co-depositing the chalcogen, the cross linking agent, and an encapsulant on to the substrate and forming a substantially uniform deposit thereof; and (b) crystallizing and vitrifying the deposit to substantially irreversibly separate the deposit into a substantially continuous, non-switchable encapsulant phase and discrete cells of state changeable phase disposed through the encapsulant phase, wherein said dispersed, discrete cells of the state changeable phase are reversibly switchable between: (i) an anorphous, first chalcogen-cross linking agent composition; and (ii) crystalline chalcogen, and an amorphous, second, chalcogen-cross linking agent composition, said second chalcogen-cross linking agent composition having a lower chalcogen content then said first chalcogen-cross linking agent composition, said amorphous, first chalcogen-cross linking agent composition separating into said crystalline chalcogen and said amorphous, second chalcogen-cross linking agent composition.