Structural Characterization And Photoelectric Properties Of Chalcogenide Phase-change Material And Its Phase Transition

In recent years,information and data are growing rapidly as people use a variety of intelligent devices.Information and data storage requires the memory with larger capacity,faster speed and lower power consumption.In the current new storage technology,phase change memory for its high-speed,high density,low power consumption and other aspects of the obvious advantages,is regarded as one of the next generation of mainstream non-volatile memory.However,the performance of the phase-change film,which is a key component of the phase change memory,needs to be further improved.GeSbTe phase change alloy material has excellent performance and has been widely concerned.The doping modification of GeSbTe phase change alloy material is one of the effective ways to obtain high performance phase change storage film.In addition,the search for a new phase change alloy material system in addition to the GeSbTe phase change alloy material is another effective way to obtain a high performance phase change memory film.Based on the above two methods,this paper attempts to obtain high performance phase change storage material film.The main research work and the results of the thesis are as follows:1.The Zn-GST and GST films with different Zn doping concentrations were prepared by electron beam evaporation.The relationship between the resistance of the film and the temperature was measured by the in-situ temperature resistance test.According to the results of variable temperature resistance measurement,the crystallization activation energy of Zn-GST and GST films are calculated and the results show that the crystallization activation energy increased with the decrease of Zn doping concentration,and the crystallization activation energy decreased from 2.99eV to 2.30eV,indicating that Zn doping GST film can convert from amorphous to crystalline state more easily.The I-V test of the device shows that the Zn-doped GST thin film has better switching performance than the pure GST film in the set and reset characteristics.By adding a certain amount of zinc component,the threshold voltage has been greatly improved,which can weaken the intermodulation effect in phase change memory's read and write operations.In addition,the phase transition process of Zn-GST thin films was fitted by phase transition kinetics.2.The pure GST thin films and ZnxSbyTez(ZST)films with different Zn contents were prepared by electron beam evaporation.The relationship between the film resistance and the temperature was measured by the in-situ temperature resistance test.Crystallization activation energy,the crystallization model of the film and the JMAK curve of the crystallization process were analyzed.By means of in-situ thermostatic resistance test,it was found that ZST films required longer annealing time to complete the crystallization process at the same annealing temperature,indicating that ZST had better amorphous stability.Zn5.i8Sb3.75Tei.io(ZST531)film has a crystallization temperature of up to 300 ? and a 10-year data retention temperature of 191 ?.The ZST thin film was used to fabricate a phase change memory prototype device.The device's I-V test showed that the ZST device had a threshold voltage of 2.4V and was close to the threshold voltage of the GST thin film.In the role of pulse voltage excitation,the use of very simple sandwich structure of the ZST device can possess several erase and write operations,the ratio of on/off was close to 10 times.3.The crystallization of two phase-change materials Ge2Sb2Te5 and Zn5Sb3Tei films induced by KrF Laser is investigated.The surface morphologies of the two phase change materials,Ge2Sb2Te5 and Zn5Sb3Tei films,are obtained by using atomic force microscopy(AFM).The results show that the surface roughness of Ge2Sb2Te5 film increases with the increase of laser intensity firstly.Then,the surface roughness decreases with the increasing of laser intensity.So in the Ge2Sb2Tes thin film nano-processing,the laser intensity should be chosen within a certain range.However,the surface roughness of Zn5Sb3Tei thin films increases with the increase of laser intensity and requires higher laser energy.Therefore,the higher the laser intensity is,the better the performance of Zn5Sb3Te1 thin films is.It was found that the laser energy required for nano-processing of ZnsSb3Tei thin films needed to be higher,indicating that the amorphous stability of the ZnsSb3Tei thin films are better than that of the pure Ge2Sb2Te5 films.4.The characterization and structural analysis of Ge2Sb2Te5 films were carried out by TEM and Raman spectroscopy.The size of the GST film grains crystallized from the TEM picture is approximately 8 nm in size.Using GST as the functional layer,the upper and lower surfaces of the GST are vacuum-coated with transparent conductive thin film electrodes.The electrodes on the upper and lower surfaces cross each other and add different voltages to the upper and lower electrodes.Compared with the GST films with different thicknesses,the transmittance and reflectivity of the GST films with different thicknesses changed with different voltages.After the films with different thicknesses were applied with different voltages,the transmittance and reflectance were changed relatively large.The voltage is not the bigger the better,but there is a proper voltage,in this voltage,the transmittance and reflectivity changes the largest.