Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F57: 2D Semiconductors: Ferroelectric and Electronic PhenomenaFocus Session Live
|
Hide Abstracts |
Sponsoring Units: DMP Chair: Keji Lai, University of Texas at Austin |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F57.00001: Diffusion Quantum Monte Carlo calculations of layered In2Se3 polytypes Igor Evangelista, Anderson Janotti, Anouar Benali In2Se3 is a semiconductor that can be found in a variety of crystal structures, most of them forming two dimensional layers stacked via van der Waals interactions. The different layered crystal structures, composed of quintuple Se-In-Se-In-Se layers, show very different electrical and optical properties that can be leveraged in a variety of device applications, including solar cells, photodetectors and phase-change memory devices. Yet, the phase ordering and the transition between them remains unclear. Density functional theory calculations show large variations in total energy differences between the different phases of In2Se3, dependent of the functional and the van der Waals correction used. Here we use diffusion Monte Carlo (DMC) calculations to accurately determine the total energy and charge density differences between the three most stable layered structures of In2Se3, namely, α, α’, and β, which differ in bonding within the quintuple layer and stacking of quintuple layers. Results for single quintuple layer will also be discussed. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F57.00002: Interfacial Charge Transfer and Gate Induced Hysteresis in Monochalcogenide InSe/GaSe Heterostructures Arvind Shankar Kumar, Mingyuan Wang, Yancheng Li, Ryuji Fujita, Xuan Gao Heterostructures of 2D van der Waals semiconductor materials offer a diverse playground for exploring fundamental physics and potential device applications. In InSe/GaSe heterostructures formed by sequential mechanical exfoliation and stacking of 2D monochalcogenides InSe and GaSe, we observe charge transfer between InSe and GaSe due to the 2D van der Waals interface formation and a strong hysteresis effect in the electron transport through the InSe layer when a gate voltage is applied through the GaSe layer. A gate voltage dependent conductance decay rate is also observed. We relate these observations to the gate voltage dependent dynamical charge transfer between InSe and GaSe layers. |
Tuesday, March 16, 2021 11:54AM - 12:06PM Live |
F57.00003: Probing spin dynamics in InSe with time-resolve Kerr rotation Jovan Nelson, Teodor Stanev, Trevor LaMountain, Nathaniel Stern The layered structure of two-dimensional materials can allow for enhanced flexibility and control optical, electrical, and spin properties in devices. Currently, transition metal dichalcogenides are the canonical example of such control, but methods of spin manipulation in these materials are often limited by spin-valley locking, which couples carrier spin projection with momentum. This prevents the level of spin control possible in traditional, direct band gap, III-V semiconductors, motivaitng a search for other potential van der Waals materials for spintronics. InSe, a group-III monochalcogenide, has been predicted to have direct bandgap, spin-dependent optical selection rules, thus avoiding spin-valley locking. Here, we present measurements of optical spin orientation, relaxation, and precession in InSe using time-resolved Kerr rotation in the near infrared spectrum. These observations demonstrate the unexplored potential of a diverse set of van der Waals materials for spintronics. |
Tuesday, March 16, 2021 12:06PM - 12:18PM Live |
F57.00004: First-principles study on two-dimensional semiconductor GeSe and its heterostructure Yuliang Mao Based on first-principles calculations, we predicted that there is a direct band gap in two-dimensional (2D) GeSe under three layers[1]. The stability and electronic structure of double-layer GeSe were studied through different stacking orders[2]. The heterojunction composed of single-layer GeSe and graphene was proposed to form Schottky contact[3]. Moreover, our calculated results showed that GeSe/SnSe 2D heterojunction has type-II band alignment and a direct band gap. Theoretical calculation showed that the photoelectric conversion efficiency of the 2D GeSe/SnSe heterojunction can reach 21.47%[4]. We also found 2D GeSe has broad prospect in the enhancement of photoluminescence efficiency[5], spin-electronics[6], detecting of toxic gas molecules[7] and hydrogen storage[8]. |
Tuesday, March 16, 2021 12:18PM - 12:30PM Live |
F57.00005: Thermoelectric Enhancement in Lateral Transition-Metal Dichalcogenide Heterostructures Sathwik Bharadwaj, Ashwin Ramasubramaniam, L Ramdas Ram-Mohan Increasing demands for renewable sources of energy has been a major driving force for developing efficient thermoelectric materials. Two-dimensional (2D) transition-metal dichalcogenides (TMDC) have emerged as promising candidates for thermoelectricity due to their large effective masses and low thermal conductivity. Here, we study the thermoelectric performance of lateral TMDC heterostructures within a multiscale quantum transport framework. Both n-type and p-type lateral heterostructures are considered for all possible combinations of semiconducting TMDCs: MoS2, MoSe2, WS2, and WSe2. The band alignment between the materials is found to play a crucial in enhancing the thermoelectric figure-of-merit (ZT) and power factor far beyond the pristine TMDCs. In particular, we show that the room-temperature ZT value of n-type WS2 with WSe2 triangular inclusions is five times larger than the pristine WS2 monolayer. p-type MoSe2 with WSe2 inclusions is also shown to have a room-temperature ZT value about two times larger than the pristine MoSe2 monolayer. The peak power factor values calculated here, are the highest amongst the gapped 2D monolayers at room temperature. Hence, 2D lateral TMDC heterostructures opens new avenues to construct ultra-efficient in-plane thermoelectric devices. |
Tuesday, March 16, 2021 12:30PM - 12:42PM Live |
F57.00006: Geometry, electronic properties, and optical characteristics of monolayer GeSe monochalcogenides from parameter-free Quantum Monte Carlo simulation Hyeondeok Shin, Jaron Krogel, Kevin Gasperich, Paul Kent, Anouar Benali, Olle Heinonen The GeSe monochalcogenide has received a great deal of attention due to its unique thermoelectric and electronic properties that can be exploited in wide range of industrial devices. While bulk GeSe has been known as a semiconductor with a 1.2 ~ 1.5 eV band gap, the optical characteristics of the GeSe monolayer form are not well known experimentally. Theoretical studies based on density functional theory (DFT) have been predicting slightly larger band gap energy for monolayer than bulk; however, DFT cannot conclusively determine detailed optical characteristics because the DFT-optimized geometry and computed band gap energy vary strongly with the choice of exchange-correlation functional. Using fixed-node diffusion Monte Carlo (DMC), we fully optimize atomic coordinates and lattice parameters for the monolayer by minimizing DMC energy based on the DFT energy Hessian. In the optimized geometry, we find band structure and band gap energies that differ from the DFT results. Based on our DMC band gap energies, we conclude that GeSe optical properties are sensitive to strain and can therefore be manipulated, and furthermore that DFT underestimates gap energies for the monolayer. |
Tuesday, March 16, 2021 12:42PM - 12:54PM Live |
F57.00007: Effect of Copper Doping on the Polymorphic Chalcogenide As2Te3 Jeremy Dion, Maureen Reedyk The chalcogenides are a family of layered compounds that have been exploited in a wide range of applications such as phase change memory, photodetectors, and thermoelectric cooling. As2Te3 is a layered semiconducting material with three different allotropic phases, α, β and β′[1]. β-As2Te3 is of interest as it is isostructural to Bi2Te3, a superconducting, topological insulator, that has been a topic of much research over the past decade[2]. β-As2Te3 is predicted to be a topological insulator at high pressure[3]. |
Tuesday, March 16, 2021 12:54PM - 1:06PM Live |
F57.00008: Tuning flexoelectricity and electronic properties of graphene nanoribbons Tribhuwan Pandey, Lucian Covaci, Francois Peeters Flexoelectricity — the coupling between polarization and strain gradients is an electro-mechanical phenomenon, which is observed by bending a material. Flexoelectricity is present in a variety of materials including soft matter, liquid crystals, and crystalline materials, but is only significant at small length-scales, where high strain-gradients develop. Here, the flexoelectric and electronic properties of zig-zag graphene nanoribbons are explored under mechanical bending using state of the art first-principles calculations. We predict that the inferior flexoelectric properties of graphene nanoribbons can be improved by more than two orders of magnitude by hydrogen and fluorine functionalization. We also find that bending can control the charge localization of valence band maxima and therefore enables the tuning of the hole effective masses and band gaps. Our results are an important advance towards the understanding of flexoelectric and electronic properties of low dimensional materials, which will be useful for potential flexible electronic applications. |
Tuesday, March 16, 2021 1:06PM - 1:18PM Live |
F57.00009: Photoconductivity of 2D Tin-doped Indium Selenide (In1-xSnxSe) Prasanna Patil, Robinson Karunanithy, Hansika I Sirikumara, Olli Pitkanen, Poopalasingam Sivakumar, Krisztian Kordas, Sidong Lei, Thushari Jayasekera, Saikat Talapatra Selenide based binary- and ternary-layered compounds show exotic physical properties and could aid in developing future electronic & opto-electronics based applications.1 It has been demonstrated that proper alloying of ternary alloys [e.g. Copper Indium Selenide (CuIn7Se11)] can lead to layered structure with to enhanced electronic and opto-electronic properties. In this talk, we will report on the investigations of photoconductive properties of few-layered Tin-doped Indium Selenide (In1-xSnxSe). Specifically, our investigation will focus on Tin doping with x = 0, 0.05, 0.1 and 1. We will also present and discuss the evolution of electronic band structure of these compounds under increased tin concentration through first principle density functional theory (DFT) and its effect on the photo responsive behaviour of the compounds. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Live |
F57.00010: Probing anisotropic transport in atomically thin ReS2 via ferroelectric domain controlled nanowire patterning Dawei Li, Shuo Suo, Zhiyong Xiao, Jingfeng Song, Ding-Fu Shao, Evgeny Y Tsymbal, Stephen P Ducharme, Xia Hong The layered van der Waals material ReS2 exhibits highly anisotropic band structure in the 1T' phase. In this work, we probe the effect of the band anisotropy on the transport properties of single- and few-layer ReS2 via ferroelectric field effect combined with ferroelectric domain patterning. We fabricated mechanically exfoliated ReS2 flakes into two-point transistor devices sandwiched between a SiO2/Si back gate and a ferroelectric polymer P(VDF-TrFE) thin film top layer. The polarization of P(VDF-TrFE) was then controlled at the nanoscale using conductive atomic force microscopy. By uniformly polarizing the ferroelectric top layer into the up (Pup) and down (Pdown) directions, we induced up to 105 current switching in a bilayer ReS2 channel at 300 K. We then polarized the entire channel into the insulating state, and created a line-shape domain across the channel, leading to a conductive nanowire. By creating nanowires at different orientations, we mapped out the angular dependence of ReS2 conductivity, which reveals more than one order of magnitude difference between the directions along and perpendicular to the b-axis. We compared the results with DFT calculated band structure of ReS2. |
Tuesday, March 16, 2021 1:30PM - 2:06PM Live |
F57.00011: Van der Waals In2Se3: from phase transitions and phase-defined heterostructures to ferroelectrics Invited Speaker: Yi Gu Due to its structural polymorphism, In2Se3 can take the form of multiple crystalline phases, a few of which (α and β phases, in particular) have layered structures. Recent studies of crystalline In2Se3 in the two-dimensional (2D) form have revealed interesting structural phase transitions, phase-specific physical properties, and room-temperature ferroelectricity down to the monolayer limit with uniquely interlocked in-plane and out-of-plane polarizations. In this talk, we will discuss distinct electrical and thermal properties of 2D α- and β-In2Se3, and how this large contrast in phase-specific properties leads to unique characteristics in phase-defined vertical and in-plane heterostructures, the latter of which can be realized by a scalable laser direct-writing technique. We will also discuss the recent discovery of 2D ferroelectricity sustained by covalent bonding in α-In2Se3. Particularly, the interlocked in-plane (IP) and out-of-plane (OOP) ferroelectricity allows the switching of the IP (OOP) polarization using an OOP (IP) external electric field. This unique aspect enables novel device concepts such as van der Waals ferroelectric memristors with multidirectional switching capabilities. Our recent studies have revealed new switching mechanisms in these devices, and the obtained mechanistic insights are critical to further development of ultrathin and novel memory devices for information storage and processing applications. |
Tuesday, March 16, 2021 2:06PM - 2:18PM Live |
F57.00012: Nonvolatile ReS2 transistors gated by highly ordered ferroelectric polymer nanowires Kun Wang, Dawei Li, Shuo Suo, Stephen P Ducharme, Xia Hong In this work, we report the fabrication and characterization of high performance of ReS2 field effect transistors gated by highly ordered ferroelectric polymer nanowires. We deposited 2 - 20 nm poly(vinylidene-fluoride-trifluorethylene) (P(VDF-TrFE)) thin films on mechanically exfoliated ReS2 layers using the Langmuir-Blodgett technique. After thermal annealing, the P(VDF-TrFE) films recrystallize into highly ordered nanowire structures with a radius of 10 or 25 nm. The nanowires are closely packed and well aligned along the direction perpendicular to the b-axis of ReS2. TEM studies showed that the molecular chains’ orientation is highly ordered within the nanowire, and revealed an epitaxial relation between ReS2 and nanowires. We then characterized the polarization of the nanowires using vertical and lateral piezo-response force microscopy (PFM), which shows a predominately out-of-plane polarization. Switching the polarization of the nanowires can lead to the change of conductivity in underlying few-layer ReS2, with a switching on-off ratio of up to 108. Our study provides a novel approach to fabricating high-quality ferroelectric-gated nonvolatile 2D field effect transistors. |
Tuesday, March 16, 2021 2:18PM - 2:30PM Live |
F57.00013: Ferroelectric domain studies of CuInP2S6 on PbZr0.2Ti0.8O3 Jia Wang, Kun Wang, Dawei Li, Yifei Hao, Xia Hong Van der Waals CuInP2S6 (CIPS) exhibits ferroelectricity at room temperature. Above a critical thickness (90-100 nm), it possesses both out-of-plane and in-plane polarization. Here, we study the effect of a ferroelectric base layer on thick and few-layer CIPS using piezoresponse force microscopy (PFM). We mechanically exfoliated 10-150 nm CIPS flakes, and transferred them on top of 50 nm epitaxial (001) PbZr0.2Ti0.8O3 (PZT) films, which were deposited on 10 nm (La,Sr)MnO3-buffered SrTiO3 substrates. Using conductive atomic force microscopy, we created stable and switchable ferroelectric domains on PZT in the regions with and without CIPS, and imaged the domain structures using vertical and lateral PFM. The domains written on bare PZT show well-defined sharp domain walls (DWs). In contrast, the domains on CIPS/PZT show crooked DWs, and the switched area extends well beyond the region where the bias voltage was applied. We attribute this observation to the mobile charge carrier diffusion. Our study provides important insight into the role of mobile charges in the ferroelectric semiconductors during polarization switching. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700