MRS Meetings and Events


EL07.09.01 2023 MRS Fall Meeting

Large-Area, Pulsed Laser Deposition of MoS2/a-BN Heterostructures for Back-Gate Field Effect Transistors Applications

When and Where

Nov 29, 2023
8:00pm - 10:00pm

Hynes, Level 1, Hall A



Manisha Gupta1,Andres Forero Pico1,Jyoti Yadav1,Junsen Gao1,Dipanjan Nandi1

University of Alberta1


Manisha Gupta1,Andres Forero Pico1,Jyoti Yadav1,Junsen Gao1,Dipanjan Nandi1

University of Alberta1
Transition metal dichalcogenides (TMDCs) have emerged as alternative 2D materials for field effect transistor fabrication. Molybdenum disulfide (MoS<sub>2</sub>) is a TMDC with semiconducting properties with monolayer (1ML) MoS<sub>2</sub> having a 1.8 eV direct bandgap and multilayer (&gt;2ML) MoS<sub>2</sub> a 1.2 eV indirect bandgap [1]. Sulphur vacancies tend to form on the top sulphur layer which gives MoS<sub>2</sub> a natural n-type doping. However, exposure to ambient oxygen and humidity oxidizes the surface of MoS<sub>2</sub> and, along with increased number of defects from the sulphur vacancies, MoS<sub>2</sub>-based devices can lose performance. Therefore, encapsulation with different materials has been suggested as a solution for improving the device performance [2]. Hexagonal boron nitride (h-BN) is a 2D material with a 6.1 eV band gap [3] which can be utilised as an encapsulation material and also an insulator. The weak basal plane van der Waals forces of h-BN will not modify the surface of MoS<sub>2</sub> and hence improve the device performance.<br/><br/>One of challenges of 2D materials is the lack of scalable and reproducible large area 2D material growth. We propose to utilise pulsed laser deposition (PLD) as an alternative to high-quality, large-area growth of 2D materials capable of depositing uniform, large-area, thin-films with good control of the deposition parameters. High quality MoS<sub>2</sub> thin films can be grown with PLD [4], on the other hand, h-BN is difficult to grow with PLD because it needs temperatures above 1000°C. Therefore, amorphous boron nitride (a-BN) is grown as encapsulation, featuring large dielectric strength and low refractive index [5].<br/><br/>In this work, PLD was used to deposit a-BN thin-films on SiO<sub>2</sub>/Si substrates. Subsequently, PLD was used to deposit the MoS<sub>2</sub>/a-BN heterostructure on SiO<sub>2</sub>/n++ Si substrates with optimized deposition parameters for MoS<sub>2</sub> [4] and a-BN, varying the thickness of MoS<sub>2</sub> (1ML, 2ML, 4ML, 10ML, 15 ML). Back-gated field effect transistors (FETs) were fabricated on the MoS<sub>2</sub>/a-BN heterostructure samples using standard lithography techniques, followed by e-beam evaporation of Ti/Au contacts and rapid thermal annealing to reduce the contact resistance. The MoS<sub>2</sub>/a-BN back-gated FETs were electrically characterized, resulting in mobilities increasing one order of magnitude when compared to back-gated MoS<sub>2</sub> FETs without encapsulation. The devices can turn on and off, although their leakage current is still significant (~10<sup>2</sup> - 10<sup>3</sup> nA), which can be attributed to the large voltages needed to control the gate (&gt;50 V). Density functional theory (DFT) studies to understand the material interface will also be conducted and the results will be presented. DFT simulations of MoS<sub>2</sub>-based back-to-back Schottky devices will be shown to compare the measured output characteristics with the calculated ones. The effect of h-BN encapsulation on the back-to-back Schottky devices was also calculated.<br/>References<br/>[1] J. Gao, D. Nandi, and M. Gupta, “Density functional theory—projected local density of states—based estimation of Schottky barrier for monolayer MoS2,” <i>J. Appl. Phys.</i>, vol. 124, no. 1, p. 14502, Jul. 2018.<br/>[2] S. Roy <i>et al.</i>, “Structure, Properties and Applications of Two-Dimensional Hexagonal Boron Nitride,” <i>Adv. Mater.</i>, vol. 33, no. 44, p. 2101589, Nov. 2021.<br/>[3] M. J. Molaei, M. Younas, and M. Rezakazemi, “A Comprehensive Review on Recent Advances in Two-Dimensional (2D) Hexagonal Boron Nitride,” <i>ACS Appl. Electron. Mater.</i>, vol. 3, no. 12, pp. 5165–5187, Dec. 2021.<br/>[4] D. Gudi, P. Sen, A. A. Forero Pico, D. Nandi, and M. Gupta, “Optimization of growth parameters to obtain epitaxial large area growth of molybdenum disulfide using pulsed laser deposition,” <i>AIP Adv.</i>, vol. 12, no. 6, p. 065027, 2022.<br/>[5] S. Hong <i>et al.</i>, “Ultralow-dielectric-constant amorphous boron nitride,” <i>Nature</i>, vol. 582, no. 7813, pp. 511–514, 2020.


2D materials | thin film

Symposium Organizers

Gabriela Borin Barin, Empa
Shengxi Huang, Rice University
Yuxuan Cosmi Lin, TSMC Technology Inc
Lain-Jong Li, The University of Hong Kong

Symposium Support

Montana Instruments

Oxford Instruments WITec
Raith America, Inc.

Session Chairs

Gabriela Borin Barin
Yuxuan Cosmi Lin

In this Session

Large-Area, Pulsed Laser Deposition of MoS2/a-BN Heterostructures for Back-Gate Field Effect Transistors Applications

A Study of Transport and Optical Properties of Liquid Nitrogen-Assisted Deposition of Titanium Oxynitride Thin Films

High-Performance Electromechanical Power Generation of Lithography-Free Large-Scale MoS2 Monolayer Film Harvesters

An Investigation of Lithium and Cobalt Intercalation Method in 2D Transition Metal Dichalcogenides

Effect of Hot-Wire Oxidization and Sulfur Annealing on Layered p-MoS2 for TFT Application

Photoelectrochemical Polymerization (PEP) of EDOT for Formation of Pattered PEDOT at Specific Arbitrary Regions on Hematite (α-Fe2O3)

Spatially Resolved and In Situ Electrochemical Imaging on Two-Dimensional Materials using Scanning ElectroChemical Cell Microscopy (SECCM)

Nanowire-Based Sensor Platform for Breath Analysis

Sensitive Microwave Spectroscopy of Van der Waals Materials with Coplanar Waveguides

Ultratrace PFAS Detection using Amplifying Fluorescent Polymers

View More »

Publishing Alliance

MRS publishes with Springer Nature