Diffusion-Controlled Epitaxy of Large Area Coalesced WSe 2 Monolayers on Sapphire

Xiaotian Zhang, Tanushree Holme Choudhury, Mikhail Chubarov, Yu Xiang, Bhakti Jariwala, Fu Zhang, Nasim Alem, Gwo Ching Wang, Joshua Alexander Robinson, Joan Marie Redwing

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

A multistep diffusion-mediated process was developed to control the nucleation density, size, and lateral growth rate of WSe 2 domains on c-plane sapphire for the epitaxial growth of large area monolayer films by gas source chemical vapor deposition (CVD). The process consists of an initial nucleation step followed by an annealing period in H 2 Se to promote surface diffusion of tungsten-containing species to form oriented WSe 2 islands with uniform size and controlled density. The growth conditions were then adjusted to suppress further nucleation and laterally grow the WSe 2 islands to form a fully coalesced monolayer film in less than 1 h. Postgrowth structural characterization demonstrates that the WSe 2 monolayers are single crystal and epitaxially oriented with respect to the sapphire and contain antiphase grain boundaries due to coalescence of 0° and 60° oriented WSe 2 domains. The process also provides fundamental insights into the two-dimensional (2D) growth mechanism. For example, the evolution of domain size and cluster density with annealing time follows a 2D ripening process, enabling an estimate of the tungsten-species surface diffusivity. The lateral growth rate of domains was found to be relatively independent of substrate temperature over the range of 700-900 °C suggesting a mass transport limited process, however, the domain shape (triangular versus truncated triangular) varied with temperature over this same range due to local variations in the Se/W adatom ratio. The results provide an important step toward atomic level control of the epitaxial growth of WSe 2 monolayers in a scalable process that is suitable for large area device fabrication.

Original languageEnglish (US)
Pages (from-to)1049-1056
Number of pages8
JournalNano letters
Volume18
Issue number2
DOIs
StatePublished - Feb 14 2018

Fingerprint

Aluminum Oxide
Epitaxial growth
Sapphire
epitaxy
Monolayers
sapphire
Tungsten
Nucleation
nucleation
Annealing
Adatoms
Surface diffusion
Level control
tungsten
Coalescence
Chemical vapor deposition
Grain boundaries
annealing
Mass transfer
antiphase boundaries

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

Cite this

Zhang, Xiaotian ; Choudhury, Tanushree Holme ; Chubarov, Mikhail ; Xiang, Yu ; Jariwala, Bhakti ; Zhang, Fu ; Alem, Nasim ; Wang, Gwo Ching ; Robinson, Joshua Alexander ; Redwing, Joan Marie. / Diffusion-Controlled Epitaxy of Large Area Coalesced WSe 2 Monolayers on Sapphire In: Nano letters. 2018 ; Vol. 18, No. 2. pp. 1049-1056.
@article{3779b8bf075547bdaba46397c1f2ee95,
title = "Diffusion-Controlled Epitaxy of Large Area Coalesced WSe 2 Monolayers on Sapphire",
abstract = "A multistep diffusion-mediated process was developed to control the nucleation density, size, and lateral growth rate of WSe 2 domains on c-plane sapphire for the epitaxial growth of large area monolayer films by gas source chemical vapor deposition (CVD). The process consists of an initial nucleation step followed by an annealing period in H 2 Se to promote surface diffusion of tungsten-containing species to form oriented WSe 2 islands with uniform size and controlled density. The growth conditions were then adjusted to suppress further nucleation and laterally grow the WSe 2 islands to form a fully coalesced monolayer film in less than 1 h. Postgrowth structural characterization demonstrates that the WSe 2 monolayers are single crystal and epitaxially oriented with respect to the sapphire and contain antiphase grain boundaries due to coalescence of 0° and 60° oriented WSe 2 domains. The process also provides fundamental insights into the two-dimensional (2D) growth mechanism. For example, the evolution of domain size and cluster density with annealing time follows a 2D ripening process, enabling an estimate of the tungsten-species surface diffusivity. The lateral growth rate of domains was found to be relatively independent of substrate temperature over the range of 700-900 °C suggesting a mass transport limited process, however, the domain shape (triangular versus truncated triangular) varied with temperature over this same range due to local variations in the Se/W adatom ratio. The results provide an important step toward atomic level control of the epitaxial growth of WSe 2 monolayers in a scalable process that is suitable for large area device fabrication.",
author = "Xiaotian Zhang and Choudhury, {Tanushree Holme} and Mikhail Chubarov and Yu Xiang and Bhakti Jariwala and Fu Zhang and Nasim Alem and Wang, {Gwo Ching} and Robinson, {Joshua Alexander} and Redwing, {Joan Marie}",
year = "2018",
month = "2",
day = "14",
doi = "10.1021/acs.nanolett.7b04521",
language = "English (US)",
volume = "18",
pages = "1049--1056",
journal = "Nano Letters",
issn = "1530-6984",
publisher = "American Chemical Society",
number = "2",

}

Diffusion-Controlled Epitaxy of Large Area Coalesced WSe 2 Monolayers on Sapphire . / Zhang, Xiaotian; Choudhury, Tanushree Holme; Chubarov, Mikhail; Xiang, Yu; Jariwala, Bhakti; Zhang, Fu; Alem, Nasim; Wang, Gwo Ching; Robinson, Joshua Alexander; Redwing, Joan Marie.

In: Nano letters, Vol. 18, No. 2, 14.02.2018, p. 1049-1056.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Diffusion-Controlled Epitaxy of Large Area Coalesced WSe 2 Monolayers on Sapphire

AU - Zhang, Xiaotian

AU - Choudhury, Tanushree Holme

AU - Chubarov, Mikhail

AU - Xiang, Yu

AU - Jariwala, Bhakti

AU - Zhang, Fu

AU - Alem, Nasim

AU - Wang, Gwo Ching

AU - Robinson, Joshua Alexander

AU - Redwing, Joan Marie

PY - 2018/2/14

Y1 - 2018/2/14

N2 - A multistep diffusion-mediated process was developed to control the nucleation density, size, and lateral growth rate of WSe 2 domains on c-plane sapphire for the epitaxial growth of large area monolayer films by gas source chemical vapor deposition (CVD). The process consists of an initial nucleation step followed by an annealing period in H 2 Se to promote surface diffusion of tungsten-containing species to form oriented WSe 2 islands with uniform size and controlled density. The growth conditions were then adjusted to suppress further nucleation and laterally grow the WSe 2 islands to form a fully coalesced monolayer film in less than 1 h. Postgrowth structural characterization demonstrates that the WSe 2 monolayers are single crystal and epitaxially oriented with respect to the sapphire and contain antiphase grain boundaries due to coalescence of 0° and 60° oriented WSe 2 domains. The process also provides fundamental insights into the two-dimensional (2D) growth mechanism. For example, the evolution of domain size and cluster density with annealing time follows a 2D ripening process, enabling an estimate of the tungsten-species surface diffusivity. The lateral growth rate of domains was found to be relatively independent of substrate temperature over the range of 700-900 °C suggesting a mass transport limited process, however, the domain shape (triangular versus truncated triangular) varied with temperature over this same range due to local variations in the Se/W adatom ratio. The results provide an important step toward atomic level control of the epitaxial growth of WSe 2 monolayers in a scalable process that is suitable for large area device fabrication.

AB - A multistep diffusion-mediated process was developed to control the nucleation density, size, and lateral growth rate of WSe 2 domains on c-plane sapphire for the epitaxial growth of large area monolayer films by gas source chemical vapor deposition (CVD). The process consists of an initial nucleation step followed by an annealing period in H 2 Se to promote surface diffusion of tungsten-containing species to form oriented WSe 2 islands with uniform size and controlled density. The growth conditions were then adjusted to suppress further nucleation and laterally grow the WSe 2 islands to form a fully coalesced monolayer film in less than 1 h. Postgrowth structural characterization demonstrates that the WSe 2 monolayers are single crystal and epitaxially oriented with respect to the sapphire and contain antiphase grain boundaries due to coalescence of 0° and 60° oriented WSe 2 domains. The process also provides fundamental insights into the two-dimensional (2D) growth mechanism. For example, the evolution of domain size and cluster density with annealing time follows a 2D ripening process, enabling an estimate of the tungsten-species surface diffusivity. The lateral growth rate of domains was found to be relatively independent of substrate temperature over the range of 700-900 °C suggesting a mass transport limited process, however, the domain shape (triangular versus truncated triangular) varied with temperature over this same range due to local variations in the Se/W adatom ratio. The results provide an important step toward atomic level control of the epitaxial growth of WSe 2 monolayers in a scalable process that is suitable for large area device fabrication.

UR - http://www.scopus.com/inward/record.url?scp=85042140931&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85042140931&partnerID=8YFLogxK

U2 - 10.1021/acs.nanolett.7b04521

DO - 10.1021/acs.nanolett.7b04521

M3 - Article

C2 - 29342357

AN - SCOPUS:85042140931

VL - 18

SP - 1049

EP - 1056

JO - Nano Letters

JF - Nano Letters

SN - 1530-6984

IS - 2

ER -