Scalable ALD Process for High-Performance MoS₂ Films on Flexible Substrates Unlocks Advanced Electronics Applications

This study by researchers from the University of Southampton (UK), LMU Munich (Germany), and VTT Technical Research Centre of Finland, presents a scalable Atomic Layer Deposition (ALD) method to grow large-area, atomically thin molybdenum disulfide (MoS₂) films with high electrical performance, addressing a key challenge for Transition Metal Dichalcogenides (TMDCs) in commercial semiconductor applications. The ALD process enables precise control over film thickness, stoichiometry, and crystallinity, starting with a MoO₃ layer grown via ALD, followed by a sulfurization process to convert it into MoS₂. This two-step approach decouples film properties, ensuring uniform growth on substrates up to six inches in size. The MoS₂ films are then transferred to flexible substrates using a chemical-free transfer process, resulting in highly uniform films with low surface roughness. Field-effect transistors (FETs) fabricated with these MoS₂ films demonstrate impressive mobility values (up to 55 cm²/Vs), subthreshold slopes as low as 80 mV/dec, and on/off ratios of 10⁷, making them suitable for advanced flexible electronics.

The process begins with 6-inch p-type silicon wafers, onto which a 285 nm layer of thermal SiO₂ is grown at 1000°C using a tube furnace. To enhance the chemical termination of the surface oxide, the wafers are treated in a UV/O₃ reactor for 10 minutes. The subsequent step involves the deposition of MoO₃ via a thermal atomic layer deposition (ALD) process using a Cambridge Nanotech Savannah S200 system. The ALD process utilizes bis(tert-butylimido)bis(dimethylamido) molybdenum as the molybdenum precursor and ozone as the oxidant. By conducting 15 ALD cycles at 250°C, a uniform MoO₃ film with a thickness of 1.31 ± 0.13 nm is achieved across the entire 6-inch wafer, ensuring excellent consistency. This initial MoO₃ layer provides precise control over the number of MoS₂ layers that are subsequently formed, making it a critical step in the overall process.

The study further highlights the integration of MoS₂ in ferroelectric field-effect transistors (FeFETs), which show a memory window of 3 V at ±5 V operation and stable multi-state switching capabilities. These FeFETs, utilizing a thin P(VDF-TrFE) layer as a ferroelectric gate dielectric, offer superior performance compared to traditional flexible memory devices. Electrical measurements confirm the devices’ scalability and uniformity over a 5 × 5 mm² area, with minimal device-to-device variation. The ALD-grown MoS₂ films also retain high stability under repeated bias stress, demonstrating their potential for use in flexible memory and neuromorphic applications. This process provides a commercially viable pathway for integrating high-quality 2D materials into next-generation electronics.

Sources:

Aspiotis, N., Morgan, K., März, B. et al. Large-area synthesis of high electrical performance MoS2 by a commercially scalable atomic layer deposition process. npj 2D Mater Appl 7, 18 (2023). https://doi.org/10.1038/s41699-023-00379-z

Intel Sets Record with 2D TMD Transistors for Next-Gen Electronics

Intel researchers have achieved record-breaking performance in transistors using ultra-thin 2D transition metal dichalcogenides (TMDs) like MoS₂ and WSe₂ as channels. These monolayer materials are ideal for scaled devices but present challenges in integration due to their lack of atomic “dangling bonds.” By developing a specialized gate oxide atomic layer deposition (ALD) process and low-temperature gate cleaning, Intel built GAA NMOS and PMOS transistors with record subthreshold slopes and high drain currents. Specifically, they achieved a subthreshold slope of <75 mV/dec and Idmax >900 µA/µm in MoS₂ NMOS transistors, and a slope of 156 mV/dec with Idmax = 132 µA/µm in WSe₂ PMOS devices. These advancements highlight the promise of 2D TMDs for next-gen electronics and the need for further research to overcome integration challenges.

The images above are TEM characterizations of the record GAA NMOS device across the gate, showing a healthy, conformal GAA architecture with 43nm-wide monolayer MoS2 channel and conformal HfO2 with a thickness of ~4.0nm.

Record Performance with 2D Channels: Ultra-thin transition metal dichalcogenides (TMDs), such as MoS2 and WSe2, are called monolayer, or 2D, materials because they’re one just atomic layer thick. They are being extensively studied for use as the channel in extremely scaled devices because of their excellent electrical performance. However, interfacing them with other materials in a device structure is difficult because at the atomic level there are no available “dangling bonds” to use. Thus, 2D channels have been a challenge to optimize.

Intel researchers will describe how they used 1) a unique gate oxide atomic layer deposition (ALD) process and 2) a low-temperature gate cleaning process to build GAA devices that demonstrated breakthrough performance for MoS2- and WSe2-based GAA NMOS and PMOS transistors, respectively. This includes record subthreshold slope (<75mv/dec) and drain current (Idmax>900 µA/µm at <50nm gate length) in sub-1nm-thick monolayer MoS2 GAA NMOS transistors. Also, using ruthenium (Ru) source and drain (S/D) contacts, they achieved record subthreshold slope (156mV/dec) and drain current (Idmax = 132µA/µm) in a ~30nm gate-length WSe2 PMOS device. The researchers say these results both underscore the potential of 2D TMDs for use in next-generation electronics, and highlight the critical need for continued research to address the remaining scientific and technological challenges.

Sources:

https://www.ieee-iedm.org/press-kit

(Paper #24.3, “Gate Oxide Module Development for Scaled GAA 2D FETs Enabling SS<75mV/d and Record Idmax>900µA/µm at Lg<50nm,” W. Mortelmans et al, Intel)

Linköping University Researchers Pioneer the Synthesis of 'Goldene - a Monolayer Gold Material

Researchers form Linköping University, Sweden, publish a novel method for synthesizing "goldene," a monolayer of gold, achieved by etching away Ti3C2 from a nanolaminated Ti3AuC2 structure using a hydrofluoric acid-free process. The Ti3AuC2 was initially formed by substituting Si in Ti3SiC2 with Au, utilizing a unique aspect of MAX phases—materials characterized by their layered structures and the ability to etch away specific layers. This process not only highlights a new avenue in the synthesis of 2D materials but also overcomes the limitations of previous methods that often required more complex and less environmentally friendly chemicals. The resulting goldene exhibits a lattice contraction of about 9% compared to bulk gold, confirmed via electron microscopy, with further characterization showing an increase in the Au 4f binding energy by 0.88 eV, suggesting altered electronic properties.

Graphical abstract. (From: Synthesis of goldene comprising single-atom layer gold)

The practical implications of goldene extend to various advanced technological applications. Its high surface-area-to-volume ratio, a characteristic of two-dimensional materials, could significantly enhance its catalytic and electronic properties. Applications in fields such as electronics, catalysis, and medicine are discussed, with potential uses ranging from improved catalytic converters to novel approaches in cancer treatment through photothermal therapies. The intrinsic stability of goldene, supported by ab initio molecular dynamics simulations, suggests that despite some physical challenges like curling and agglomeration, the material holds substantial promise for the development of next-generation devices and systems.

The production of atomically thin gold layers in the past typically involved methods that produce few atoms in thickness rather than true monolayers and often required complex supporting substrates or matrices to stabilize the gold layer. The method of exfoliating gold from a nanolaminated MAX phase as described in the publication is a novel approach, potentially opening new pathways for the production and application of gold in nanotechnology and materials science.

 

Schematic illustration of the preparation of goldene. (From: Synthesis of goldene comprising single-atom layer gold),

The production process of goldene is scalable and could potentially be adapted for the synthesis of other non-van der Waals 2D materials. The study outlines further research avenues, including the exploration of different etching schemes and surfactants to enhance the stability and yield of the synthesized layers. The success in manipulating the atomic structure of gold at such a fundamental level not only paves the way for innovative applications but also deepens our understanding of material science at the atomic scale, opening doors to new research in 2D material science.

Source: Synthesis of goldene comprising single-atom layer gold | Nature Synthesis

DOE Invests $4M in Argonne's ALD Tech to Develop Energy-Efficient Semiconductor Devices

The US Department of Energy (DOE) has awarded Argonne National Laboratory a $4 million grant to pioneer research in microchip energy efficiency using Atomic Layer Deposition (ALD). This innovative project, part of the DOE's Energy Efficient Scaling for Two Decades (EES2) initiative, aims to harness the potential of 2D materials, specifically molybdenum disulfide (MoS2), to create microchips that could consume up to 50 times less energy than current models. 

Led by Argonne's Distinguished Fellow Jeffrey Elam, the research team will collaborate with Stanford, Northwestern, and Boise State Universities to develop ALD techniques for fabricating atomically precise MoS2 films. This breakthrough could lead to microchips with integrated memory and logic functions, significantly reducing energy waste and addressing the critical "von Neumann bottleneck" in computing. The project is a step forward in the global effort to enhance computational efficiency and sustainability.

Source: Argonne National Lab gets $4M to develop MoS2 chips - News (compoundsemiconductor.net)

TSMC To Report Breakthrough in NMOS Nanosheets Using Ultra-Thin MoS2 Channels at IEDM 2023

A TSMC-led research team, in collaboration with National Yang Ming Chiao Tung University and National Applied Research Laboratories, has unveiled promising results for using ultra-thin transition metal dichalcogenides (TMDs), specifically MoS2, as the channel material in NMOS nanosheets. Their innovative approach deviates from the conventional method of thinning Si channels. The team's devices exhibited impressive performance metrics: a positive threshold voltage (VTH) of ~1.0 V, a high on-current of ~370 µA/µm at VDS = 1 V, a large on/off ratio of 1E8, and a low contact resistance ranging between 0.37-0.58 kΩ-µm. These outcomes were primarily attributed to the introduction of a novel C-shaped wrap-around contact, which enhances contact area, and an optimized gate stack. While the devices demonstrated satisfactory mechanical stability, a challenge remains in addressing defect creation within the MoS2 channels. This groundbreaking study, titled "Monolayer-MoS2 Stacked Nanosheet Channel with C-type Metal Contact" by Y-Y Chung et al., is a pivotal step forward in nanosheet scaling using TMDs.

ALD is a the technique for the precise and uniform synthesis of MoS₂, especially for semiconductor applications on large-scale wafers. The choice of precursors plays a crucial role in achieving optimal deposition characteristics. Mo (CO) 6 and H2S have been identified as the primary precursors for depositing molybdenum and sulfur components, respectively. These precursors have demonstrated the capacity for self-limiting growth behavior within a specific ALD temperature window, leading to uniform MoS₂ layers. Notably, this process has been successfully scaled up to achieve highly uniform film growth on large 300 mm SiO2/Si wafers, marking its potential for industry-level manufacturing. The ability to maintain uniformity and thickness control on such wafers emphasizes the potential of ALD in integrating MoS₂ into next-generation electronic devices and further underscores the significance of selecting appropriate precursors for optimal deposition outcomes. Other precursors have been investigated. MoCl₅ and MoF₆ serve as alternative molybdenum sources. For the sulfur component, H₂S is commonly paired with molybdenum precursors, but (CH₃)₂S has also been explored. The choice of these precursors directly impacts the properties of the resulting MoS₂ film in the ALD process and therefore precursor development for 2D MoS2 is a hot field of ongoing research.

While deposition methods are abundant, etching processes are comparatively scarce. Recent research by Elton Graugnard et al also introduces a thermal Atomic Layer Etching (ALE) technique for MoS2, leveraging MoF6 for fluorination, alternated with H2O exposures, to etch both crystalline and amorphous MoS2 films. This process has been characterized using various analytical techniques like QCM, FTIR, and QMS. The etching is temperature-dependent, with a significant increase in mass change per cycle as temperature rises. The mechanism involves two-stage oxidation of Mo, producing volatile byproducts. The resultant etch rates were established for different films, and post-etch annealing rendered crystalline MoS2 films. The thermal MoS2 ALE introduces a promising low-temperature method for embedding MoS2 films in large-scale device manufacturing.

Chem. Mater. 2023, 35, 3, 927-936

Sources:

 https://www.ieee-iedm.org/press-kit

https://pubs.acs.org/doi/10.1021/acs.chemmater.2c02549

AIXTRON's MOCVD Machine Advancing 2D-Materials at imec

AIXTRON, a German semiconductor equipment manufacturer, has successfully installed the CCS 2D Metal-Organic Chemical Vapour Deposition (MOCVD) reactor at the Interuniversitair Micro-Electronica Centrum (imec) in Belgium. Part of the 2D Experimental Pilot Line initiative, this reactor facilitates large-scale epitaxial deposition of 2D-materials on 200/300 mm wafers, marking a significant milestone in the transition of these materials from lab to fab.

Inge Asselberghs, Director of the 2D Experimental Pilot Line at imec, emphasizes the unique position of imec as a bridge between academia and industry, offering access to both fundamental research laboratories and industrial infrastructure.

Salim El Kazzi, 2D Product Manager at AIXTRON, outlines the challenges of the lab-to-fab transition, including miscommunication and the technical intricacies of 2D-materials. AIXTRON addresses these challenges by fostering collaboration among top researchers and providing FAB-compatible reactors like the CCS 2D.

To bridge the gap effectively, Asselberghs highlights the importance of versatile tools for rapid material and process screening, crucial for seamless information exchange between industry and academia.

The CCS 2D MOCVD machine from AIXTRON offers precise control over deposition parameters and features like closed-coupled shower heads and a transfer module for 2D-material growth on 300 mm wafers.

This installation promises exciting prospects for imec's research on transition metal dichalcogenides (TMDCs) and advances in pilot-line processes for 2D-material growth and layer transfer. Both AIXTRON and imec actively participate in Graphene Week 2023, contributing to the advancement of 2D-materials in industrial applications and strengthening the link between academia and industry.

Source: AIXTRON installs a MOCVD machine CCS 2D in IMEC’s fab | Graphene Flagship (graphene-flagship.eu)

Atomic Layer Deposition of 2D Metal Dichalcogenides for Electronics, Catalysis, Energy Storage, and Beyond

Here is an interesting Review from the leading ALD Laboratory at Helsinki University in Finland on 2D dichalcogenides. We are all looking forward to get to know the ALD:ed Dichalcogenides better in the future in exciting new  devices and daily life. (Thanks for sharing - Dr. King)

Atomic Layer Deposition of 2D Metal Dichalcogenides for Electronics, Catalysis, Energy Storage, and Beyond

Miika Mattinen, Markku Leskelä, Mikko Ritala

First published: 18 January 2021 in Advanced Materials Interfaces

https://doi.org/10.1002/admi.202001677

Figure from Google cache (originally in https://doi.org/10.1002/admi.202001677)

Abstract: 2D transition metal dichalcogenides (TMDCs) are among the most exciting materials of today. Their layered crystal structures result in unique and useful electronic, optical, catalytic, and quantum properties. To realize the technological potential of TMDCs, methods depositing uniform films of controlled thickness at low temperatures in a highly controllable, scalable, and repeatable manner are needed. Atomic layer deposition (ALD) is a chemical gas‐phase thin film deposition method capable of meeting these challenges. In this review, the applications evaluated for ALD TMDCs are systematically examined, including electronics and optoelectonics, electrocatalysis and photocatalysis, energy storage, lubrication, plasmonics, solar cells, and photonics. This review focuses on understanding the interplay between ALD precursors and deposition conditions, the resulting film characteristics such as thickness, crystallinity, and morphology, and ultimately device performance. Through rational choice of precursors and conditions, ALD is observed to exhibit potential to meet the varying requirements of widely different applications. Beyond the current state of ALD TMDCs, the future prospects, opportunities, and challenges in different applications are discussed. The authors hope that the review aids in bringing together experts in the fields of ALD, TMDCs, and various applications to eventually realize industrial applications of ALD TMDCs

How ALD can be used to stack 2D materials on one another at a nanometer scale

TU Eindhoven latest publication to see how the toolbox of ALD can be used to stack various layered 2D materials on one another at a nanometer scale.

Imec introduces 2D materials in the logic device scaling roadmap

[IEDM 2020 Virtual, Imec Belgium LINK] At the 2020 IEDM conference, imec proposes that 2D semiconductors like tungsten disulfide (WS2) can further extend the logic transistor scaling roadmap. The team laid the groundwork for integrating 2D semiconductors in a 300mm CMOS fab, and worked towards improved device performance. These findings are presented in four IEDM papers, one of which was selected as IEDM highlight.

More details can be found in 4 papers presented at the 2020 IEDM conference:

[1] ‘Introducing 2D-FETs in device scaling roadmap using DTCO’, Z. Ahmed et al.
[2] ‘Wafer-scale integration of double gated WS2-transistors in 300mm Si CMOS fab’, I. Asselberghs et al.
[3] ‘Dual gate synthetic WS2 MOSFETs with 120µS/µm Gm 2.7µF/cm2 capacitance and ambipolar channel’, D. Lin et al.
[4] ‘Sources of variability in scaled MoS2 FETs’, Q. Smets et al. (IEDM highlight paper)

TEM image of a 2D device fabricated with 300mm processes. (Source: Imec)

High-quality HfS2 2D-material by ALD at 100°C

A high-quality 2D-material by #ALDep at 100°C! Yuanyuan's very systematic and complete study of the well-behaved surface chemistry performed in collaboration with 7 other groups @FAU_Germany is published in Adv. Mater. Interfaces:https://t.co/Y9g1RPsdTx pic.twitter.com/dW8bG0BHAD

— CTFM lab (@CtfmLab) December 6, 2020

Russian researchers obtain atomically thin molybdenum disulfide (2D) films on large-area substrates by ALD

[Press release: LINK] Researchers from the Moscow Institute of Physics and Technology have managed to grow atomically thin films of molybdenum disulfide spanning up to several tens of square centimeters. It was demonstrated that the material’s structure can be modified by varying the synthesis temperature. The films, which are of interest to electronics and optoelectronics, were obtained at 900-1,000 degrees Celsius. The findings were published in the journal ACS Applied Nano Materials.

An atomic layer deposition reactor from Picosun used for obtaining ultrathin molybdenum oxide films, which were subsequently sulfurized to 2D molybdenum disulfide. Image courtesy of the Atomic Layer Deposition Lab, MIPT

Two-dimensional materials are attracting considerable interest due to their unique properties stemming from their structure and quantum mechanical restrictions. The family of 2D materials includes metals, semimetals, semiconductors, and insulators. Graphene, which is perhaps the most famous 2D material, is a monolayer of carbon atoms. It has the highest charge-carrier mobility recorded to date. However, graphene has no band gap under standard conditions, and that limits its applications.

Imec shows excellent performance in ultra-scaled FETs with 2D-material channel

[Press release, imec, LINK] SAN FRANCISCO (USA), December 8, 2019 — At this year’s IEEE International Electron Devices Meeting (Dec 7-11 2019), imec, a world-leading research and innovation hub in nanoelectronics and digital technologies, reports an in-depth study of scaled transistors with MoS2 and demonstrates best device performance to date for such materials. 

TEM pictures showing (a) 3 monolayers MoS2 channel, with contact length 13nm and channel length 29nm Transfer characteristics have improved sub-threshold swing (SS) with thinner HfO2. (www.imec.be)

MoS2 is a 2D material, meaning that it can be grown in stable form with nearly atomic thickness and atomic precision. Imec synthesized the material down to monolayer (0.6nm thickness) and fabricated devices with scaled contact and channel length, as small as 13nm and 30nm respectively. These very scaled dimensions, combined with scaled gate oxide thickness and high K dielectric, have enabled the demonstration of some of the best device performances so far. Most importantly, these transistors enable a comprehensive study of fundamental device properties and calibration of TCAD models. The calibrated TCAD model is used to propose a realistic path for performance improvement. The results presented here confirm the potential of 2D-materials for extreme transistor scaling – benefiting both high-performance logic and memory applications.

Atomic Layer Deposition of Emerging 2D Semiconductors, HfS2 and ZrS2, for Optoelectronics

Miika Mattinen from Prof. Mikko Ritala's group, University of Helsinki, reports the ALD growth of 2D HfS2 and ZrS2—the potential rivals of the hot favorite 2D semiconductors MoS2 and WSe2. 

Abstract: Semiconducting 2D materials are studied intensively because of their promising performance in diverse applications from electronics to energy storage and catalysis. Recently, HfS2 and ZrS2 have emerged as potential rivals for the commonly studied 2D semiconductors such as MoS2 and WSe2, but their use is hindered by the difficulty of producing continuous films. 

Herein, we report the first atomic layer deposition (ALD) processes for HfS2 and ZrS2 using HfCl4 and ZrCl4 with H2S as the precursors. We demonstrate the deposition of uniform and continuous films on a range of substrates with accurately controlled thicknesses ranging from a few monolayers to tens of nanometers. The use of semiconductor industry-compatible precursors and temperatures (approximately 400 °C) enables facile upscaling of the process. The deposited HfS2 and ZrS2 films are crystalline, smooth, and stoichiometric with oxygen as the main impurity. 

Source : Atomic Layer Deposition of Emerging 2D Semiconductors, HfS2 and ZrS2, for Optoelectronics

----------------------
By Abhishekkumar Thakur

ALD yields large crystalline 2D MoS2 thin films

MRS Bulletin reports: Sheets of molybdenum disulfide (MoS2) just a few atoms thick hold promise for high-performance, flexible electronics as well as optical applications. But one obstacle the two-dimensional (2D) material faces is the lack of an efficient method to make it in large quantities. Researchers at Argonne National Laboratory have now demonstrated that the atomic layer deposition method could be used to make uniform, crystalline MoS2 thin films as large as a standard 300 mm silicon wafer. 

Full article : LINK 

JVSTA Journal article : LINK

ALD Process: molybdenum hexafluoride (MoF₆) and hydrogen sulfide at 200 °C

The atomic layer deposition method could be used to make large crystalline 2D MoS2 thin films. https://t.co/6dLel1kYwM #materialsscience

— MRS Bulletin (@MRSBulletin) March 24, 2018

New ALD High-k / 2D MoS2 light-erasable memory suitable for large area manufacturing technology

Phys.Org reports that researchers at the Institute of Microelectronics Chinese Academy of Sciences (IMECAS), and Fudan University have used 2D MoS₂ to design a new light-erasable memory.

According to the article in Applied Physics Letter, the memory stack is based on an high-k dielectric stack (Al₂O₃/HfO₂/Al₂O₃) and an atomically thin MoS₂ channel, where he HfO₂ act as the charge trapping layer. The holes in the HfO₂ charge-trapping layer will tunnel to the MoS₂ channel through the 4 nm Al₂O₃ tunnel layer. 

 

 

Schematic band diagrams of the MoS₂/Al₂O₃/HfO₂/Al₂O₃/Gate structure at (a) flat-band condition, (b) programming operation, and (c) erasing operation. (Supplementary information, Applied Physics Letters. DOI: 10.1063/1.5000552)

"In general, system-on-panel (SOP) describes a new display technology in which both active and passive components are integrated in one panel package, typically on the same glass substrate (sometimes system-on-panel is also named system-on-glass)," coauthor Hao Zhu at Fudan University told Phys.org. "This is different from traditional display technologies such as cathode ray tube (CRT) displays. One major characteristic of SOP is the application of thin-film technology, such as low-temperature poly-silicon (LTPS) thin-film transistor (TFT) arrays on the glass substrate. However, silicon-based thin-film transistors are being replaced by TFTs with new materials with improved properties. The indium gallium zinc oxide (IGZO) or zinc tin oxide (ZTO) thin film mentioned in our paper is also a good example. [Phys.org]

"Currently, we are working on the large-scale integration of such light-erasable 2-D memory devices using programmable light pulses with controllable wavelength and pulse duration," he said. "We are using new material synthesis methods such as atomic layer deposition to grow large-area MoS2 and other 2-D ultra-thin films for circuit-level applications."  [Phys.org]

The future prospects for large scale manufacturing are there. Except for the MoS₂ channel, both Al₂O₃ and HfO₂ are standard ALD processing technologies since more than 10 years in the semiconductor industry and recent developments for flexible OLED Display manufacturing  has made the ALD technology also available for large panel processing and roll to roll technology is just looking for an excuse high volume manufacturing.

 
Article: Long-Fei He et al. "Light-erasable embedded charge-trapping memory based on MoS2 for system-on-panel applications." Applied Physics Letters. DOI: 10.1063/1.5000552

Full story: LINK

AIXTRON provides novel deposition system to EPFL for 2D materials research

Leading Swiss university focuses on the development of next-generation semiconductors based on AIXTRON BM system

 
AIXTRON SE (FSE: AIXA), a worldwide leading provider of deposition equipment to the semiconductor industry, today announced that the École Polytechnique Fédérale de Lausanne (EPFL) in Lausanne (Switzerland) has purchased a BM NOVO system. This versatile tool which can produce virtually all variations of 2-dimensional materials (2D) required for emerging optoelectronic applications is dedicated to support the University’s research projects coordinated by Prof. Andras Kis and Prof. Aleksandra Radenovic.

AIXTRON’s BM NOVO system uses a unique combination of plasma-enhanced chemical vapor deposition (PECVD) technology and metal organic chemical vapor deposition (MOCVD) technology to enable the growth of high quality 2D materials such as transition metal dichalcogenides (TMDCs) e.g. molybdenum disulfide (MoS2) or tungsten diselenide (WSe2).

Source: Aixtron LINK

Webinar - ALD for 2D materials

Oxford Instruments is running a webinar on ALD for 2D materials & devices on 14 September, 3:30pm (UK time). The webinar will comprise of two talks, with a Q&A session at the end:

• Atomic Layer Deposition for Graphene devices by Dr Daniel Neumaier, AMO GmbH
• Atomic Layer Deposition on and of 2D materials by Dr Harm Knoops, Oxford Instruments

If you would like to register please visit www.oxinst.com/ALD2D

Woah - Hafnium oxide as gate dielectric scales also in the 2D world

Hafnium oxide high-k dielectrics deposited by atomic layer deposition have been used in DRAM since 2004 (Samsung 90 nm) and 2007 in high performance CMOS logic (Intel 45 nm). Later the DRAM high-k dielectric was replaced by a zirconium oxide based material but for logic hafnium oxide has remained the material of choice for the high-k metal gate stack by toping off the native oxide of silicon with its higher k-value. Hafnium oxide even survived the transition to narrow 3D FinFET devices and is also the main contender for silicon based Nano Wire FETs. However, recent research in alternative 2D channel materials such as graphene, molybdenum disulfide and others has created a totally new situation where hafnium oxide finds it difficult to compete as the material of choice for the gate stack dielectric. 

Until now that is, because just recently some clever researchers at Stanford has presented an new all hafnium channel and dielectric combo using hafnium diselenide and the natural native oxide of that - ta da - hafnium oxide. Apparently the zirconium version is also brought into play but let us see about that...

You can read all about it in this online article published by Stanford, which also leads you to the original scientific references and journal publications.

New ultrathin semiconductor materials exceed some of silicon’s ‘secret’ powers, Stanford engineers find

The next generation of feature-filled and energy-efficient electronics will require computer chips just a few atoms thick. For all its positive attributes, trusty silicon can’t take us to these ultrathin extremes.

Now, electrical engineers at Stanford have identified two semiconductors – hafnium diselenide and zirconium diselenide – that share or even exceed some of silicon’s desirable traits, starting with the fact that all three materials can “rust.”

Continue reading: http://news.stanford.edu/2017/08/11/new-ultrathin-semiconductor-materials-exceed-silicons-secret-powers/

TEM cross-section of an experimental chip, the bands of black and white reveal alternating layers of hafnium diselenide – an ultrathin semiconductor material – and the hafnium dioxide insulator. (Image credit: Michal Mleczko)

New process for 2D MoS2 from Oxford Instruments

Scientists at Plasma Technology have developed a new process to deposit 2D MoS2 layers directly on Graphene, creating atomic layer heterostructures. This graphene-semiconductor film is a functional layer with applications in photodetection and sensing.

Source: Oxford Instruments LINK 

MoS2 grown on Grephene (Oxford Instruments)

Atomic Layer Deposition on 2D Materials by Incheon National University

Here is my new favorite ALD Research Group - The HBRL Group of Prof. Han-Bo-Ram Lee at Incheon National University in South Korea. Please do visit their web and get inspired. Just recently they published an article on ALD on 2D Materials: 

Atomic Layer Deposition on 2D Materials
Hyun Gu Kim and Han-Bo-Ram Lee*
Department of Materials Science and Engineering, Incheon National University, Incheon 22012, Korea
Chem. Mater., Article ASAP
DOI: 10.1021/acs.chemmater.6b05103
Publication Date (Web): April 25, 2017

New up&coming perspective: Atomic Layer Deposition on 2D Materials, by Han-Bo-Ram Lee #ALDep https://t.co/M7FzYUnSXp pic.twitter.com/lBoCdyo2lf

— Chem of Materials (@ChemMater) April 25, 2017

Screen dump from The HBRL Group of Prof. Han-Bo-Ram Lee at Incheon National University in South Korea (LINK)