Query: Single-layer MoS2 electronics

Candidate papers:

abstract: CONSPECTUS: Atomic crystals of two dimensional materials consisting of single sheets extracted from layered materials are gaining increasing attention. The most well known material from this group is graphene, a single layer of graphite that can be extracted from the bulk material or grown on a suitable substrate. Its discovery has given rise to intense research effort culminating in the 2010 Nobel Prize in physics awarded to Andre Geim and Konstantin Novoselov. Graphene however represents only the proverbial tip of the iceberg, and increasing attention of researchers is now turning towards the veritable zoo of so called "other 2D materials" They have properties complementary to graphene, which in its pristine form lacks a bandgap: MoS2, for example, is a semiconductor, while NbSe2 is a superconductor. They could hold the key to important practical applications and new scientific discoveries in the two dimensional limit. This family of materials has been studied since the 1960s, but most of the research focused on their tribological applications: MoS2 is best known today as a high performance dry lubricant for ultrahigh vacuum applications and in car engines. The realization that single layers of MoS2 and related materials could also be used in functional electronic devices where they could offer advantages compared with silicon or graphene created a renewed interest in these materials. MoS2 is currently gaining the most attention because the material is easily available in the form of a mineral, molybdenite, but other 2D transition metal dichalcogenide (TMD) semiconductors are expected to have qualitatively similar properties. In this Account, we describe recent progress in the area of single layer MoS2 based devices for electronic circuits. We will start with MoS2 transistors, which showed for the first time that devices based on MoS2 and related TMDs could have electrical properties on the same level as other, more established semiconducting materials. This allowed rapid progress in this area and was followed by demonstrations of basic digital circuits and transistors operating in the technologically relevant gigahertz range of frequencies, showing that the mobility of MoS2 and TMD materials is sufficiently high to allow device operation at such high frequencies. Monolayer MoS2 and other TMDs are also direct band gap semiconductors making them interesting for realizing optoelectronic devices. These range from simple phototransistors showing high sensitivity and low noise, to light emitting diodes and solar cells. All the electronic and optoelectronic properties of MoS2 and TMDs are accompanied by interesting mechanical properties with monolayer MoS2 being as stiff as steel and 30x stronger. This makes it especially interesting in the context of flexible electronics where it could combine the high degree of mechanical flexibility commonly associated with organic semiconductors with high levels of electrical performance. All these results show that MoS2 and TMDs are promising materials for electronic and optoelectronic applications.
author_names: Dominik S Lembke

Simone Bertolazzi

Andras Kis
title: Single Layer MoS 2 Electronics Published as part of the Accounts of Chemical Research special issue " 2 D Nanomaterials beyond Graphene "
year: 2015

abstract: Structuring materials with atomic precision is the ultimate goal of nanotechnology and is becoming increasingly relevant as an enabling technology for quantum electronics/spintronics and quantum photonics. Here, we create atomic defects in monolayer MoS2 by helium ion beam lithography with a spatial fidelity approaching the single atom limit in all three dimensions. Using low temperature scanning tunneling microscopy (STM) we confirm the formation of individual point defects in MoS2 upon He ion bombardment and show that defects are generated within 9 nm of the incident helium ions. Atom specific sputtering yields are determined by analyzing the type and occurrence of defects observed in high resolution STM images and compared with Monte Carlo simulations. Both theory and experiment indicate that the He ion bombardment predominantly generates sulfur vacancies.
author_names: Elmar Mitterreiter

Bruno Schuler

Katherine A Cochrane

Ursula Wurstbauer

Alexander Weber-Bargioni

Christoph Kastl

Alexander W Holleitner
title: Atomistic positioning of defects in helium ion treated single layer MoS2.
venue: Nano letters
year: 2020

abstract: Transition metal dichalcogenides (TMDs) have emerged in recent years as a special group of two dimensional materials and have attracted tremendous attention. Among these TMD materials, molybdenum disulfide (MoS2) has shown promising applications in electronics, photonics, energy, and electrochemistry. In particular, the defects in MoS2 play an essential role in altering the electronic, magnetic, optical, and catalytic properties of MoS2, presenting a useful way to engineer the performance of MoS2. The mechanisms by which lattice defects affect the MoS2 properties are unsettled. In this work, we reveal systematically how lattice defects and substrate interface affect MoS2 electronic structure. We fabricated single layer MoS2 by chemical vapor deposition and then transferred onto Au, single layer graphene, hexagonal boron nitride, and CeO2 as substrates and created defects in MoS2 by ion irradiation. We assessed how these defects and substrates affect the electronic structure of MoS2 by performing X ray photoelectron spectroscopy, Raman and photoluminescence spectroscopies, and scanning tunneling microscopy/spectroscopy measurements. Molecular dynamics and first principles based simulations allowed us to conclude the predominant lattice defects upon ion irradiation and associate those with the experimentally obtained electronic structure. We found that the substrates can tune the electronic energy levels in MoS2 due to charge transfer at the interface. Furthermore, the reduction state of CeO2 as an oxide substrate affects the interface charge transfer with MoS2. The irradiated MoS2 had a faster hydrogen evolution kinetics compared to the as prepared MoS2, demonstrating the concept of defect controlled reactivity in this phase. Our findings provide effective probes for energy band and defects in MoS2 and show the importance of defect engineering in tuning the functionalities of MoS2 and other TMDs in electronics, optoelectronics, and electrochemistry.
author_names: Yuwei Chen

Shengxi Huang

Xiang Ji

Kiran Kumar Adepalli

Kedi Yin

Xi Ling

Xinwei Wang

Jianming Xue

Mildred S Dresselhaus

Jing Kong

Bilge Yildiz
title: Tuning Electronic Structure of Single Layer MoS2 through Defect and Interface Engineering.
venue: ACS nano
year: 2018

abstract: Abstract The buckling behavior of a single layer MoS2 (SLMoS2) sheet with defects under uniaxial compression is investigated with molecular simulation in the present paper. Five typical defects are introduced to estimate the instability characteristics of defective MoS2 sheet. The buckling responses, including the critical strain and geometric morphology, influenced by defect type, stain rate, defect density and so on, are comprehensively explored. It is found that different type of defects results in reduction of the bending modulus to some different extent. Compared with the other three post buckling morphologies, the first typical geometric morphology show the biggest difference between the defect free and defective SLMoS2 sheets. It seems possible to realize our desired morphology in flexible electronics by proper preparing different kinds of defects. The finding in the present paper should be useful for the promising design of flexible optoelectronic devices and soft bioelectronics.
author_names: Yao Li

Peijian Chen

Cun Zhang

Juan Peng

Feng Gao

Hao Liu
title: Molecular dynamics simulation on the buckling of single layer MoS2 sheet with defects under uniaxial compression
venue: Computational Materials Science
year: 2019

abstract: Heterojunctions of semiconductors and metals are the fundamental building blocks of modern electronics. Coherent heterostructures between dissimilar materials can be achieved by composition, doping, or heteroepitaxy of chemically different elements. Here, we report the formation of coherent single layer 1H 1T MoS2 heterostructures by mechanical exfoliation on Au(111) which are chemically homogeneous with matched lattices but show electronically distinct semiconducting (1H phase) and metallic (1T phase) character, with the formation of these heterojunctions attributed to a combination of lattice strain and charge transfer. The exfoliation approach employed is free of tape residues usually found in many exfoliation methods and yields single layer MoS2 with millimeter (mm) size on the Au surface. Raman spectroscopy, X ray photoelectron spectroscopy (XPS) atomic force microscopy (AFM) scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have collectively been employed to elucidate the structural and electronic properties of MoS2 monolayers on Au substrates. Bubbles in the MoS2 formed by the trapping of ambient adsorbates beneath the single layer during deposition, have also been observed and characterized. Our work here provides a basis to produce two dimensional heterostructures which represent potential candidates for future electronic devices.
author_names: Fanglue Wu

Zhuotong Liu

Nathaniel Hawthorne

Michael Chandross

Quentarius Moore

Nicolas Argibay

John F Curry

James D Batteas
title: Formation of Coherent 1H 1T Heterostructures in Single Layer MoS2 on Au(111)
venue: ACS nano
year: 2020

abstract: While two dimensional (2D) van der Waals (vdW) layered materials are promising channel materials for wearable electronics and energy efficient field effect transistors (FETs) large hysteresis and large subthreshold swing induced by either dangling bonds at gate oxide dielectrics and/or trap molecules in bubbles at vdW interface are a serious drawback, hampering implementation of the 2D material based FETs in real electronics. Here, we report a monolayer MoS2 FET with near zero hysteresis reaching 0.15% of the sweeping range of the gate bias, a record value observed so far in 2D FETs. This was realized by squeezing the MoS2 channel between top h BN layer and bottom h BN gate dielectrics and further removing the trap molecules in bubbles at the vdW interfaces via post annealing. By segregating the bubbles out to the edge of the channel, we also obtain excellent switching characteristics with a minimum subthreshold swing of 63 mV/dec, an average subthreshold slope of 69 mV/dec for a current range of four orders of magnitude at room temperature, and a high on/off current ratio of 108 at a small operating voltage <1 V) Such a near zero hysteresis and a near ideal subthreshold limit originate from the reduced trap density of ~5.2 x 109 cm 2 eV 1, a thousand times smaller than previously reported values.
author_names: Quoc An Vu

Sidi Fan

Sang Hyup Lee

Min-Kyu Joo

Woo Jong Yu

Young Hee Lee
title: Near zero hysteresis and near ideal subthreshold swing in h BN encapsulated single layer MoS2 field effect transistors
year: 2018

abstract: Phase transitions in 2D materials, such as MoS2, result in drastic changes in the physical properties of the material. A change in the phase of MoS2 from 2H to 1T transforms it from a semiconductor to conductor, thus broadening its potential applications in electronics. The structural transformation associated with the phase change may significantly affect the mechanical properties. Here we statistically characterized the elastic modulus and fracture strength of phase changed single layer MoS2 sheets using the atomic force microscopy (AFM) nanoindentation technique. MoS2 sheets were subjected to lithium intercalation, which transformed them from the 2H phase to the 1T phase. The transformed sheets were again annealed to make a partially phase changed sample. The elastic modulus and fracture strength of 1T phase MoS2 were about 50% lower than those of 2H phase MoS2. Annealing of the 1T phase MoS2 sheet resulted in a good recovery of the mechanical properties, up to 90% of those of the original 2H phase MoS2. This result was attributed to a mixture of phases in the annealed product, and the ratio of the phases was evaluated spectroscopically. Interestingly, while the fracture strengths differed for the three phases, their average fracture strains were quite similar, suggesting that the overall structure of the material maintained its integrity during the phase transition process.
author_names: Jaehyuck Jung

Hunyoung Bark

Doyoung Byun

Changgu Lee

Dae-Hyun Cho
title: Mechanical characterization of phase changed single layer MoS 2 sheets
venue: 2D Materials
year: 2019

abstract: Atomically thin Transition metal dichalcogenides (TMDs) have come into the spotlight in optoelectronics thanks to their outstanding physical properties [1,2] In single layer (1L) TMDs strong quantum confinement effects cause a weak screening of Coulomb, so that the excitons created by photo excitation have large binding energy, up to several hundred meVs [3] While the steady state properties of TMDCs have been studied in detail by linear optical techniques, the recent application of time resolved nonlinear spectroscopy (mainly ultrafast pump probe) has enabled the study of excited state dynamics on femtosecond timescales [4] opening up questions about the mechanisms of exciton relaxations and exciton exciton interactions.
author_names: Margherita Maiuri

Stefano Dal Conte

Mattia Russo

Junjia Wang

Giancarlo Soavi

Dumitru Dumcenco

Andras Kis

Malte Selig

Sandra Khun

Marten Richter

Andreas Knorr

Andrea C Ferrari

Giulio Cerullo
title: Excitonic Effects in Single Layer MoS2 Probed by Broadband Two Dimensional Electronic Spectroscopy
venue: 2019 Conference on Lasers and Electro Optics Europe European Quantum Electronics Conference (CLEO/Europe EQEC)
year: 2019

abstract: Logic circuits and the ability to amplify electrical signals form the functional backbone of electronics along with the possibility to integrate multiple elements on the same chip. The miniaturization of electronic circuits is expected to reach fundamental limits in the near future. Two dimensional materials such as single layer MoS(2) represent the ultimate limit of miniaturization in the vertical dimension, are interesting as building blocks of low power nanoelectronic devices, and are suitable for integration due to their planar geometry. Because they are less than 1 nm thin, 2D materials in transistors could also lead to reduced short channel effects and result in fabrication of smaller and more power efficient transistors. Here, we report on the first integrated circuit based on a two dimensional semiconductor MoS(2) Our integrated circuits are capable of operating as inverters, converting logical "1" into logical "0" with room temperature voltage gain higher than 1, making them suitable for incorporation into digital circuits. We also show that electrical circuits composed of single layer MoS(2) transistors are capable of performing the NOR logic operation, the basis from which all logical operations and full digital functionality can be deduced.
author_names: Branimir Radisavljevic

Michael Brian Whitwick

Andras Kis
title: Integrated circuits and logic operations based on single layer MoS2.
venue: ACS nano
year: 2011

abstract: Field effect transistors using ultrathin molybdenum disulfide (MoS(2) have recently been experimentally demonstrated, which show promising potential for advanced electronics. However, large variations like hysteresis, presumably due to extrinsic/environmental effects, are often observed in MoS(2) devices measured under ambient environment. Here, we report the origin of their hysteretic and transient behaviors and suggest that hysteresis of MoS(2) field effect transistors is largely due to absorption of moisture on the surface and intensified by high photosensitivity of MoS(2) Uniform encapsulation of MoS(2) transistor structures with silicon nitride grown by plasma enhanced chemical vapor deposition is effective in minimizing the hysteresis, while the device mobility is improved by over 1 order of magnitude.
author_names: Dattatray J Late

Bin Liu

H S S Ramakrishna Matte

Vinayak P Dravid

C N R Rao
title: Hysteresis in single layer MoS2 field effect transistors.
venue: ACS nano
year: 2012