Numerical Study on Resistance Change Characteristics of Phase Change Materials

Yifang Su,Guanjun Zhao,Zuoqi Hu,Xiongfei Tao,Yihang Zhang,Qinzheng Yu,Kaifeng Lin,José António Fonseca De Oliveira Correia

doi:10.1155/2021/7934173

Abstract

Phase change materials are a type of emerging materials whose states will change under certain conditions, which then lead to changes in resistance. To study the characteristics of the phase change materials, a numerical simulation model of the resistive change unit based on the finite element method and the classic nucleation/growth theory is established, while the partial differential equations of electricity and heat conduction and the discrete formula of the finite element are also derived. According to the phase transition process of phase change materials, a crystalline-amorphous simulation model is also proposed in this paper to simulate the electrical and thermal properties and phase transition process of the resistive change unit. Simulations of the resistance change unit under single pulses with different amplitudes and widths as well as the simulations under continuous pulses are conducted in this paper. These results verify the characteristics of resistance change and can provide references for selecting the parameters of the resistance change units.

Highlights

Phase change materials (PCM) usually have two states, which are crystalline and amorphous. e structural differences between the two states result in electronic performances
GST materials have been deeply studied for their high crystallization rate (10 years). is virtue allows PCM to be widely used in nonvolatile random-access memories (PCRAM) [3, 4]
We have established a physical model and employed numerical calculations to simulate and analyze this phenomenon, and we study the resistance change characteristics of phase change materials

Summary

Introduction

Phase change materials (PCM) usually have two states, which are crystalline and amorphous. e structural differences between the two states result in electronic performances. E latter is adopted in this paper, which applies a high but narrow electric pulse on the resistive change unit, where a large amount of Joule heat is generated in a short time, and the local temperature rises rapidly above the melting point Tm of the materials. Compared with the narrow and intensive pulse mentioned above, if a relatively low but wide pulse is employed on the phase change materials, Joule heat is generated which induces a temperature increase in a range between the crystallization temperature Tg and the melting point Tm. Owing to the wider pulse, the amorphous phase change materials have sufficient time to nucleate, grow, and transform into a crystalline state. We have established a physical model and employed numerical calculations to simulate and analyze this phenomenon, and we study the resistance change characteristics of phase change materials. 2.1. e Structural Model of Resistance Change Unit. e model of the resistance change unit used in this paper is shown in Figure 2, which includes the bottom electrode (metal W), the bottom electrode contact (or heater TiN), the phase change layer (GST), the top electrode contact (TiN), and top electrode (W), where the material parameters of each layer are from literature [10, 11]

Amorphization

Application of Resistance Change Unit

Conclusions