(Invited) Emerging Ferroelectric Devices

Abstract

Ferroelectrics comprise a class of polar materials with an electrically switchable spontaneous polarization allowing their use as binary data storage media in nonvolatile ferroelectric random access memories (FeRAMs). Currently available FeRAMs utilize a destructive read process of stored information, which requires the memory cells to be re-written by a relatively high voltage, increases the read time and limits the scalability. An alternative approach to the read operation is based on the polarization-driven resistive switching, known as the tunneling electroresistance (TER) effect. If the ferroelectric film is sufficiently thin (of the order of several nanometers), conduction electrons can quantum-mechanically tunnel through the ferroelectric barrier. By flipping the polarization of the ferroelectric barrier it is possible to change an internal electronic potential profile and, hence, alter the transmission probability and produce the TER effect. Using this effect, reading of the polarization state can be performed in a non-destructive manner by measuring the resistance of the memory cell to a relatively low voltage. Since TER does not depend on the amount of the stored charge it allows a much better scalability. In addition to being highly relevant to technological applications, the TER effect concerns the fundamental issues of the critical behavior and switching dynamics in ultrathin ferroelectric films, role of structural defects and interfacial properties in the transport behavior. Maintaining a stable polarization in ultrathin ferroelectric films is essential for exploiting the functionality of these materials in nonvolatile memory applications. This talk will focus on investigation of the polarization-controlled tunneling conductance in the FTJ devices that incorporate both ferroelectric films and 2D transition metal dichalcogenides (TMD). In addition, the in-plane transport of the TMD conducting channel in the ferroelectric field effect transistor (FE-FET) devices modulated by polarization reversal will be discussed. We show that interface engineering in these hybrid TMD-FE systems provides a possibility of successfully addressing the most serious challenges relevant to ferroelectric device performance, such as ON/OFF ratio, lifetime, operation endurance and reliability.