In phase change recording, higher linear densities can be achieved with materials in which crystallization is dominated by growth. This is due to the fact that marks can be written with sharper edges, which give rise to lower jitter. Therefore AgInSbTe alloy based thin films appear to be one of the latest promising materials for optical data storage that has drawn worldwide attention. In the present paper (AgSbTe) x (In1-ySby) 1-x quaternary alloy based films for x = 0.2, 0.3, 0.4 and y = 0.7, were deposited using thermal evaporation technique under a high vacuum of 10-6 torr. The potentiality of the above mentioned films for a phase change optical memory was confirmed using Differential Thermal Analysis (DTA). The results show that this material has good glass forming ability. Further the micro-structural details of the films were studied using SEM (Scanning Electron Microscopic) technique. We also investigated the effect of 1hour thermal annealing on grain size of the films. Thermal annealing of the prepared films was done at different temperatures ranging between 200°c-400°c through radiant heating in vacuum at a pressure of ~10-5 torr. The micro-structural analyses of the as-deposited and annealed films are presented here. This also explains the effect of change in composition as well as change in annealing temperature on the crystalline phases formed on the film.
Over recent years the demand for mass storage devices with high speed has become increasingly more evident. Phase change optical recording is based on the rapid crystalline to amorphous (and vice versa) transition in a thin phase change layer enabled by laser induced heating. Among some of the potential candidates, AgInSbTe alloy appears to be one of the latest promising materials that has drawn world wide attention. The optical disk of this material with overwrites cyclability of more than 105 times, and data rate 22Mbps has been reported for DVD 4.7GB. Using this material as the active layer has other advantages such as the problem of material flow is reduced to a great extent. Moreover the marks written in AgInSbTe based media have a well defined shape with sharp edges, leading to intrinsically lower jitter values than observed for GeSbTe based media. In the present work [(AgSbTe)x(In1-y Sby)1-x] alloy and films are developed for different values of x and y. The crystallization process of Ag-In-Sb-Te films with above composition is systematically reported and compared for the first time. Thermal properties of the alloy and film are studied using X-Ray Diffraction (XRD) technique. The analysis of the film is done before annealing and also after 1hr. isothermal annealing at temperature between 200 degree(s)C and 500 degree(s)C. The structural analysis of the film is also done under same conditions (before and after annealing) using Scanning Electron Microscope (SEM) respectively. The experimental results of the analysis are presented here for compositions close to the eutectic Sb69Te31, in which some of the Te is replaced by Ag and In.
Recently the demand of high speed and high-density optical recording media using direct overwrite scheme is very high. Among some of the potential candidates, AgInSbTe alloy appears to be one of the latest promising materials that has drawn world wide attention. The optical disks of this material with overwrite cyclability of more than 105 times and data rate 22Mbps have been reported for DVD 4.5GB. Results of X-ray diffraction analysis of amorphous and
crystalline (AgSbTe)x(In1-ySby)1-x films (x = 0.2, 0.4 and y = 0.7) deposited by thermal
evaporation technique are presented here. The difference in
crystallization behavior of the crystalline phases formed
after 1hr. of thermal annealing at temperature between 200-400°c are studied through X-ray diffraction analysis. The optical band gap of above mentioned amorphous and crystalline films were also calculated from transmittance spectra. It is observed that transmittivity increase by about 20% to give significant contrast between amorphous and crystalline marks. This relative change in transmittivity varies with chemical composition also. The results show that as the annealing temperature is incresed, film becomes more
crystalline and with lower value of x, i.e. with x = 0.2 better results are obtained. These results were also confirmed through microstructural analysis of the films, involving surface detail using SEM. It has been observed that grain size depends of the annealing temperature as well as on the composition.