PZT铁电栅MoS2场效应晶体管的电输运特性研究

As a two-dimensional(2D) semiconductor with large bandgap of 1-2 eV, MoS2 has potential applications in low-power, high-on/off ratio ultrathin channel transistors. Understanding and controlling the transport properties of carriers is the key and fundamental issue in the research of MoS2 transistors. Due to the high dielectric constant and spontaneous polarization of ferroelectrics, it is very interesting to use ferroelectric thin films as gate dielectric to tune the transport process of MoS2 carriers, which is expected to increase the mobility of MoS2 transistors and add nonvolatile functionality to it. In this project, lead zirconate titanate(PZT) ferroelectric thin films will be used as the back gate of MoS2 transistors, tuning the transport properties of carriers by ferroelectric polarization. The interface state of PZT and MoS2 will be controlled by varying the microstructure of PZT thin films, and the effect of interface characteristics on the transport properties of MoS2 transistors will be investigated. In order to understand the relationship of polarization characteristics of PZT and transport properties of MoS2, the evolution of transport properties of MoS2 transistors with electric field and temperature will be studied. By quantitatively analyzing the relation between the ferroelectricity of PZT and nonvolatility of MoS2 transistors, combined with the effect of PZT/MoS2 interface, the mechanism of coupling effect between the ferroelectric polarization and channel carriers will be revealed. This study can increase the knowledge about the mechanism of ferroelectric polarization tuning the transport properties of 2D materials, and will provide reference for practical application of 2D materials in developing nonvolatile ferroelectric filed effect devices.

MoS2具有类石墨烯的二维平面结构，且存在1-2eV的能隙，在低静态功耗、高开关比的超薄沟道晶体管有着重要的应用前景。调控MoS2沟道载流子的输运并揭示其物理机制，是MoS2晶体管研究中的关键性基础问题。铁电薄膜具有高的介电常数和自发极化特性，将其作为栅介质调控MoS2沟道载流子的输运，有望提高晶体管的迁移率并使其具有非挥发性。本项目拟采用锆钛酸铅（PZT）作为背栅，通过制备具有不同微结构的PZT薄膜，研究PZT/MoS2的界面特性对晶体管输运特性的影响。研究晶体管的输运特性随电场和温度的演变规律，阐明PZT的极化特性与MoS2晶体管输运特性的内在联系。深入分析PZT的铁电性与MoS2晶体管非挥发性之间的内在联系，揭示PZT铁电极化与MoS2沟道载流子之间的耦合机制。该项研究可深化对铁电极化调控二维材料输运特性物理机制的认识，同时为发展基于二维材料的非挥发性铁电场效应器件提供参考。

Pb(Zrx,Ti1-x)O3(PZT)铁电薄膜兼具高的介电常数和自发极化特性，将其作为栅介质调控MoS2沟道电子的输运，有望降低器件的操作电压并使其具有非挥发特性。本项目首先采用传统的SiO2作为栅介质，研究了MoS2 FET的非挥发特性，首次提出回滞面积(<A>)及记忆窗口(△V)与背栅电压范围(Vbg,max)之间存在幂次定律；然后采用高介电常数的 Al2O3作为栅介质调控MoS2载流子输运，降低了器件操作电压，并通过介电屏蔽效应提高其迁移率；最后采用兼具高介电常数和自发极化特性PZT铁电薄膜作为背栅介质调控MoS2沟道载流子的输运。分别采用化学溶液沉积法和溅射法制备了具有不同取向和微结构的PZT薄膜，发现具有细小晶粒且表面平整的CSD-PZT可以直接用来调控MoS2沟道电子的输运，相应的器件的操作电压仅为±2 V，亚阈值摆幅低至87 mV/dec，电流开关比接近10E6，并观察到完全由铁电极化定义的逆时针本征回滞。通过研究不同环境中MoS2 FET的输运特性随电场的演变规律，发现了回滞面积与Vbg,max之间的幂次定律，以及PZT铁电极化定义的转变电压；另外，观察到回滞的方向随Vbg,max增加而发生反转。通过深入分析PZT的铁电性与MoS2晶体管非挥发性之间的内在联系，结合PZT/MoS2界面的影响因素，阐述了PZT铁电极化与MoS2沟道电子之间的耦合机制。该项研究深化了对铁电极化调控二维材料输运特性物理机制的认识，同时为发展基于二维材料的非挥发性铁电场效应器件提供了参考。