Composition spread analysis of phase change dynamics in Ge/sub x/Sb/sub y/Te/sub 1-x-y/ films embedded in an optical multilayer stack
Composition spread analysis of ternary GexSbyTe1� xy films embedded in an optical multilayer stack close to optical storage application is presented. GexSbyTe1� xy films with two- dimensional graded composition were deposited in a combinatorial sputter process and analysed with electron-probe microanalysis. Detailed static tester analysis of the crystallisation dynamics are performed in a wide composition range around the pseudobinary line (GeTe - Sb2Te3). Both the as-deposited and the written amorphous phase show a fast crystallisation behaviour within 70-150 and 30-100 ns in a compositional range near the pseudobinary line, respectively. Interrelationship of composition and crystallisation time can directly be imaged from the presented analysis. Composition spread analysis of functional materials has gained substantial interest in the past to shorten the laborious search for optimum material compositions. In the present paper we report on the composition spread deposition of ternary phase-change materials in combina- tion with a careful study of the dynamics of phase changes relevant for optical data storage. This approach applied for a wide material composition range on a single sample significantly reduces the effort in finding optimum data storage material composition, compared with previous experiments where a vast amount of individual single- compound samples had to be manufactured and analysed (1, 2). In addition, as phase-change dynamics critically depend on the precise layer deposition conditions, having a wide composition range in one common sample drastically improves the intercomparability of the results. Until now, however, composition spread techniques have only been applied for the deposition of open phase-change material layers deposited on substrates (3-5). It is however, well known that the phase-change dynamics of optical storage materials depend critically on the layer environment (6). Here we present for the first time the fabrication and analysis of composition spread phase-change films em- bedded within an actual optical disc multilayer stack.