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PROCESS SOLUTIONS FOR
2D MATERIALS

What are 2D Materials?

2D materials are at the very limit of thin-film dimensions with thicknesses down to a single atom. These materials exhibit superlative electronic and optoelectronic properties which researchers today are trying to harness for next-generation devices for electronics, optoelectronics and energy applications.

While graphene kick-started exploration and application of these ultra-thin materials, it has created a vast field of exploration and application of several other 2D materials like nitrides (hBN) and transition metal dichalcogenides (MoS2, WSe2 etc.). While these materials can be found in nature and can be exfoliated from the bulk crystals, chemical vapour-based techniques are employed to allow easy scale-up for future devices.

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2D Materials Fabrication: Graphene EO Modulators Process

Orange processes show solutions covered by Oxford Instruments' technology.

2D Materials Applications

2D materials exhibit superlative electronic and optoelectronic properties which researchers today are working on harnessing for next-generation devices for electronics, optoelectronics and flexible devices.

Various aspects of 2D materials can be beneficial for applications and depending on the application people might aim for single layers with high mobility for transistors or multiple layers in many orientations for catalysis applications, such as water splitting.

2D Materials Solutions

2D materials such as graphene, MoS2 or hBN can be used to enhance current devices and build new device architectures. FETs, batteries and filters with unique properties can now be realised.

A Proven Process

At Oxford Instruments Plasma Technology we have excellent experience with a wide range of processes, from high-temperature CVD to low-temperature ALD.

Graphene

This specification is issued for Graphene obtained through Chemical Vapour Deposition (CVD) processes.

  • Load-locked system offers higher throughput, as no cooling of the growth chamber is required to exchange samples
  • He purge gas is required for the process
  • The presence of Graphene layer(s) will be tested by Raman Spectroscopy peak 2D analysis
  • 1 layer Graphene will be confirmed by Raman Spectroscopy
Characteristic Raman peaks for graphene
Graphene EO Modulators for Datacom diagram

Graphene EO modulator for datacom.


2D hBN

This specification is issued for Boron Nitride obtained through Chemical Vapour Deposition (CVD) processes. For the purpose of process demonstration, B2H6 is used as Boron source and NH3 as the Nitrogen sources on Cu/Ni foils as catalyst substrates.

  • Temperature > 900 °C
2D hBN Raman shift 2D hBN

2D MoS2 and  TMDs

We offer PECVD systems equipped with precursor vapour delivery modules for the growth of two-dimensional layers of materials like MoS2, WS2 etc.

Excellent thickness control with low defects and strong  photoluminescence  

High-quality MoS2:

  • AFM shows defined step height and smooth uniform film
  • Raman indicates one mono-layer is deposited with characteristic peaks spaced 21.1cm-1 apart
Characteristic Raman peaks for 2D MoS2

PECVD Graphene

Direct growth of nanocrystalline Graphene on dielectric substrates using plasma-enhanced chemical vapour deposition.

  • Temperature > 900 °C

2D Heterostructures

In situ growth of 2D Molybdenum Disulphide (MoS2) Graphene heterostructures

We offer CVD/PECVD/Remote plasma (ICP) CVD systems equipped with precursor vapour delivery modules for the growth of two-dimensional layers and heterostructures of materials like Graphene, MoS2, WS2 etc. 

This is a three-step process:

  • Step 1: Grow Graphene on Cu
  • Step 2: Transfer Graphene from Cu on to SiO2
  • Step 3: Grow MoS2 on Graphene transferred on SiO2

Process features:

  • Temperature > 900 °C
  • Formation of a single layer of MoS2 confirmed by Raman Spectroscopy
  • Deposition time is critical to ensure that a complete monolayer of MoS2 is formed
  • Temperature of MoS2 deposition on Graphene and its quality is critical for the stability of the Graphene during MoS2 process
Raman shift of MoS<sub>2</sub> Raman shift of WS<sub>2</sub>

Vertical Graphene

  • Temperature 600°C - 900°C
  • Load-locked system offers higher throughput, as no cooling of the growth chamber is required to exchange samples
  • He purge gas is required for the process
  • Nucleation depends on the underlying substrate and C-source combination (Carbon, 2013, Vol. 58, 59–65)
Structure of PECVD vertical Graphene

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Plasma Processing Solutions for 2D Materials

For atomic layer deposition approaches to 2D materials, our FlexAL system can be specifically configured to allow growth of 2D transition metal dichalcogenides, such as MoS2. The FlexAL is ideal for growing metal oxide seed layers for sulfurization, deposition of high-k dielectrics, surface pretreatments and 2D materials encapsulation.

  • Remote plasma & thermal ALD in one flexible tool
  • Low damage maintained by the use of remote plasma
  • Controllable, repeatable processes via recipe-driven software interface
  • Maximum flexibility in the choice of materials & precursors

Find out more about FlexAL.

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FlexAL ALD system

FlexAL ALD system for 2D materials beyond graphene.

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