| With the rapia developing ot the Big Data,the Artificial Intelligence,the Cloud Computing ana the 5th Generation mobile networks technologies in recent years,the Global Datasphere has grown at an alarming rate.The memory bears the continuation and development of human civilization.In the new era,the memory faces new challenges.Phase change memory is considered to be one of the alternatives to existing storage technology due to its ultra-fast operating speed,long life,easy size reduction and non-volatility.However,its poor thermal stability and low storage density still limit its large-scale commercial applications.Therefore,understanding the phase change material crystallization process and accurately controlling the metastable phase transition is very important for achieving multi-level data storage applications.In this thesis,the in-situ Raman laser is used to induce and study the spectrum information of Sb-based phase change materials,and the dependence of Raman laser power and irradiation time on the phase transition threshold of these films is analyzed.The specific research conclusions are as follows:1.The Ge2Sb2Te5,Sb2Te3 and ZnSb phase change materials were irradiation by in-situ Raman laser with different powers,and the in-situ Raman spectra were recorded.For Ge2Sb2Te5,the coexistence state of amorphous state and FCC state was found under 25 mW Raman laser irradiation,and the coexistence state of FCC and HEX was found at 250 mW,and it was completely converted to stable HEX state under 500 mW;For Sb2Te3,its f-ST structure was found under the laser irradiation of 5 mW,and a coexistence state of f-ST and t-ST structures was obtained at 25 mW and 50 mW,respectively,and converted into a stable t-ST structure at a high Raman laser power of 250 mW;As for ZnSb film,the large laser power of 250 mW and 500 mW irradiated and produced the phase change of metastable state,and the limited Raman laser power did not achieve the phase transition to a steady state.By characterizing the multi-state evolution,the laser power intensity reflects that ZnSb has the better thermal stability than Ge2Sb2Te5.Sb2Te3 is the worst.2.The nanocomposites with different oxides(NiO,Al2O3 and ZnO)doping contents were prepared and characterized by electrical properties,XRD,Raman and TEM.For the combination of NiO and ZnO,the thermal stability of ZnSb is improved,and it seems that the phase transition process of ZnSb metastable state is inhibited by conventional research methods,and directly changed from amorphous phase to steady state.The addition of NiO into ZnSb film formed more nucleation sites and NiO/ZnSb interfaces,which accelerated the crystallization rate,suppressed grain growth,and reduced the RMS of film to 4.855 nm.In ZnO-ZnSb film,phase separate domain formation(ZnSb-rich domains are enclosed by ZnO-rich domains)was found clearly,which limited crystal growth of ZnSb stable phase.However,the doping of Al2O3 exhibited different behaviors.It promoted the growth of ZnSb grains,and the grain size reached～100 nm.The thermal stability had no significant effect,and the intermediate state can be clearly observed.3.Further characterization of ZnSb composite films by in-situ Raman laser irradiation has been done.It was found the evolution among multi-state of ZnSb.For the(ZnSb)96.o(NiO)4.o film,the coexistence of amorphous state and metastable state was found at 250 mW,which converted into metastable state at 500 mW For Al2O3 and ZnO composite films,Raman laser lead to the phase transformation in ZnSb alloy.The compositions exhibit a partial shift of the Raman peaks because of the difference in atomic interaction between the ZnSb domain boundary and the separated oxide in the local range.As for(ZnSb)96.0(NiO)4.0 and(ZnSb)81.8(ZnO)18.2 composite films,in-situ Raman characterization captured the metastable state,which was not found by conventional characterization methods,indicating that the two dopants do not inhibit the metastable state,but accelerate the phase-change process from metastable to stable state.The in-situ Raman laser-induced phase-change process of multi-state films has the complementary effect with the traditional research methods,which makes the multi-state evolution of phase change material be more accurate.In summary,this thesis combines conventional characterization methods and in-situ Raman laser irradiation characterization to reveal the disappearance of ZnSb metastable phase and further understand the phase transition behavior of ZnSb nanocomposite films.The metastable state of all ZnSb-based films are captured by in-situ Raman laser irradiation,especially(ZnSb)89.4(Al2O3)io.6 had good multi-state storage capacity.The doping concentration is diferent,and the acceleration effect on the metastable transition to the steady state is different.The in-situ Raman laser-induced phase-change process of multi-state films has the complementary effect with the conventional research methods,which makes the multi-state evolution of phase change material be more accurate. |
