Search query: Ferroelectric tunneling junction

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abstract: Ferroelectric tunnel junctions, in which ferroelectric polarization and quantum tunneling are closely coupled to induce the tunneling electroresistance (TER) effect, have attracted considerable interest due to their potential in non volatile and low power consumption memory devices. The ferroelectric size effect, however, has hindered ferroelectric tunnel junctions from exhibiting robust TER effect. Here, our study proposes doping engineering in a two dimensional in plane ferroelectric semiconductor as an effective strategy to design a two dimensional ferroelectric tunnel junction composed of homostructural $p$ type semiconductor/ferroelectric/$n$ type semiconductor. Since the in plane polarization persists in the monolayer ferroelectric barrier, the vertical thickness of two dimensional ferroelectric tunnel junction can be as thin as monolayer. We show that the monolayer In:SnSe/SnSe/Sb:SnSe junction provides an embodiment of this strategy. Combining density functional theory calculations with non equilibrium Green's function formalism, we investigate the electron transport properties of In:SnSe/SnSe/Sb:SnSe and reveal a giant TER effect of 1460$ The dynamical modulation of both barrier width and barrier height during the ferroelectric switching are responsible for this giant TER effect. These findings provide an important insight towards the understanding of the quantum behaviors of electrons in materials at the two dimensional limit, and enable new possibilities for next generation non volatile memory devices based on flexible two dimensional lateral ferroelectric tunnel junctions.
author_names: Xin-Wei Shen

Yue-Wen Fang

Bobo Tian

Chungang Duan
title: Two Dimensional Ferroelectric Tunnel Junction: The Case of Monolayer In:SnSe/SnSe/Sb:SnSe Homostructure
venue: ACS Applied Electronic Materials
year: 2019

abstract: Abstract The ferroelectric tunnel junction represents a memory concept that allows a nondestructive readout by utilizing a very thin ferroelectric film between two metal electrodes. Application of an electric field across the thin ferroelectric changes the polarization orientation and an accompanying modulation of the barrier height of the stack, which alters the tunneling current. For a long time, this concept was neglected due to the expected difficulties using common perovskite ferroelectrics and epitaxy for depositing such a thin layer while maintaining high ferroelectric properties. The discovery of ferroelectricity in the hafnium oxide system represents a game changer. In this chapter, the crucial design parameters are discussed that have to be considered for controlling the current transport, reducing the depolarization field, and finally optimizing the tunneling electroresistance effect.
author_names: Shosuke Fujii

Masumi Saitoh
title: Ferroelectric Tunnel Junction
year: 2019

abstract: We have developed a numerical simulation framework for HfO2 based Ferroelectric Tunnel Junction (FTJ) memory using Non Equilibrium Green Function (NEGF) and self consistent potential method which is calibrated by our experimental FTJ results. Scalability and design guideline of Metal Ferroelectric Insulator Semiconductor (MFIS) structure FTJ is investigated in this work. Due to the large asymmetry of dielectric screening length of MFIS structure FTJ electrodes, MFIS structure FTJ shows a higher tunneling electroresistance (TER) ratio than Metal Ferroelectric Insulator Metal (MFIM) structure FTJ, while it has almost the same read current as MFIM structure FTJ. High read current and high TER ratio can be obtained by adjusting property of semiconductor bottom electrodes. A guideline of designing MFIS structure FTJ has been proposed for high read current and high TER ratio. MFIS type FTJ shows a potential for scaling down to sub 20 nm diameter.
author_names: Fei Mo

Yusaku Tagawa

Takuya Saraya

Toshiro Hiramoto

Masaharu Kobayashi
title: Scalability Study on Ferroelectric HfO2 Tunnel Junction Memory Based on Non equilibrium Green Function Method
venue: 2019 19th Non Volatile Memory Technology Symposium (NVMTS)
year: 2019

abstract: Abstract This paper proposes a device incorporating ferroelectric tunnel junction which analyzes the concept of tunneling across a silicon doped hafnium oxide ferroelectric. Variation of electrical parameters with ferroelectric thickness has been examined. Subthreshold swing (SS) of 40 mV/dec has been achieved with ferroelectric thickness of 2 nm. An increasing trend in the ION/IOFF ratio is observed with the increase in ferroelectric thickness. Moreover, the impact of temperature (300 K 500 K) on drain current as well as various RF parameter performance such as gate capacitance (CGG) transconductance (gm) output conductance (gd) intrinsic delay, intrinsic gain (gm/gd) cut off frequency (ft) and transconductance frequency product (TFP) has been studied.
author_names: Pujarini Ghosh

Rupam Goswami

Brinda Bhowmick
title: Optimization of ferroelectric tunnel junction TFET in presence of temperature and its RF analysis
venue: Microelectron. J.
year: 2019

abstract: Abstract The electroresistance in silicene based normal/ferroelectric gated/normal junction is investigated. The energy gap in silicene can be tuned by electric field. The spontaneous electric polarization in ferroelectric (FE) can be switched by external electric field. Due to the combination of these properties, we find that the studied junction may generate tunneling electroresistance (TER) exceeding 109% The conductance ratio of ON to OFF state, GON/GOFF, is found to be larger than 107, enhanced by increasing the thickness of the barrier or increasing the magnitude of electric polarization in the FE layer. The giant TER effect is directly related to the buckled lattice and the presence of spin orbit interaction in silicene. This work reveals the potential of silicene as a good material for application of ferroelectric random access memory.
author_names: Assanai Suwanvarangkoon

Bumned Soodchomshom
title: Giant tunneling electroresistance in ferroelectric gated silicene junction
year: 2015

abstract: Abstract We report successful synthesis of superconducting Bi Sr Ca Cu2 OX (BSCCO) target for fabrication of heterostructure thin films. For the first time, we have grown LSMO (50 nm)/PZT (5 nm)/BSCCO (100 nm)/LAO (100) heterostructure by pulsed laser deposition technique to understand the tunneling effect and role of the superconducting electrode on transport and magnetic properties. The bulk superconductor Bi Sr Ca Cu2 OX (BSCCO) and heterostructure shows superconducting phase transition near 92 K and 110 K, respectively. Magnetic susceptibility data indicate large negative susceptibility below 110 K which confirms the superconducting nature of heterostructure bottom electrode. A large hysteresis in current voltage data has been obtained at 78 K below the superconducting state of bottom electrode. These results suggest that the ferromagnetic/ferroelectric/superconductor tunnel structure may provide four distinct resistance states depending on the direction of ferroelectric polarization.
author_names: V N Ojha

Ashok Kumar
title: Fabrication of ferroelectric tunnel junction using superconducting and magnetic electrodes
year: 2019

abstract: Brain inspired neuromorphic computing has shown great promise beyond the conventional Boolean logic. Nanoscale electronic synapses, which have stringent demands for integration density, dynamic range, energy consumption, etc. are key computational elements of the brain inspired neuromorphic system. Ferroelectric tunneling junctions have been shown to be ideal candidates to realize the functions of electronic synapses due to their ultra low energy consumption and the nature of ferroelectric tunneling. Here, we report a new electronic synapse based on a three dimensional vertical Hf0.5Zr0.5O2 based ferroelectric tunneling junction that meets the full functions of biological synapses. The fabricated three dimensional vertical ferroelectric tunneling junction synapse (FTJS) exhibits high integration density and excellent performances, such as analog like conductance transition under a training scheme, low energy consumption of synaptic weight update (1.8 pJ per spike) and good repeatability >103 cycles) In addition, the implementation of pattern training in hardware with strong tolerance to input faults and variations is also illustrated in the 3D vertical FTJS array. Furthermore, pattern classification and recognition are achieved, and these results demonstrate that the Hf0.5Zr0.5O2 based FTJS has high potential to be an ideal electronic component for neuromorphic system applications.
author_names: Lin Chen

Tian-Yu Wang

Ya-Wei Dai

Ming-Yang Cha

Hao Zhu

Qingqing Sun

S J Ding

Peng Zhou

Leon Ong Chua

David-Wei Zhang
title: Ultra low power Hf0.5Zr0.5O2 based ferroelectric tunnel junction synapses for hardware neural network applications.
venue: Nanoscale
year: 2018

abstract: Theoretical investigations of ferroelectric tunneling in a SrRuO3/BaTiO3/Pt junction were conducted, and critical expressions for the surface charge density in the electrodes and the potential distribution across the tunnel junction were derived. It was found that the screening charges associated with the ferroelectric polarization and the charging effect of the capacitor jointly contribute to the charges in the electrodes. A current voltage study simulating the 'read' operation indicated that the tunneling electroresistance effect increases with the ferroelectric thickness, and the tunneling electroresistance values agree well with experimental results.
author_names: Zhijun Ma

G Chen

Peng Zhou

Zhiheng Mei

Tianjin Zhang
title: Ferroelectric tunneling under bias voltages
year: 2017

abstract: The ferroelectric material is one of the important platforms to realize non volatile memories. So far, existing ferroelectric memory devices utilize out of plane polarization in ferroelectric thin films. In this paper, we propose a new type of random access memory (RAM) based on ferroelectric thin films with the in plane polarization called "in plane ferroelectric tunneling junction" Apart from non volatility, lower power usage and faster writing operation compared with traditional dynamic RAMs, our proposal has the advantage of non destructive reading process, thus overcomes the write after read problem that widely exists in current ferroelectric RAMs, and faster reading operation. The recent discovered room temperature ferroelectric IV VI semiconductor thin films is a promising material platform to realize our proposal.
author_names: Huitao Shen

Junwei Liu

Kai Chang

Liang Fu
title: In Plane Ferroelectric Tunnel Junction
venue: Physical Review Applied
year: 2019

abstract: Abstract The effect of bias voltage on electron tunneling across a junction with a ferroelectric ferromagnetic composite barrier is investigated theoretically. Because of the inversion symmetry breaking of the spontaneous ferroelectric polarization, bias voltage dependence of the electron tunneling shows significant differences between the positive bias and the negative one. The differences of spin filtering or tunnel magnetoresistance increase with the increasing absolute value of bias voltage. Such direction preferred electron tunneling is found intimately related with the unusual asymmetry of the electrical potential profile in two phase composite barrier and provides a unique change to realize rectifying functions in spintronics.
author_names: Jian Wang

Sheng Ju

Zongyao Li
title: Bias voltage effect on electron tunneling across a junction with a ferroelectric ferromagnetic two phase composite barrier
year: 2012