Mapping crystal shapes could fast-track 2D materials
Experts call for global effort to clear hurdles to mass production

Date:
July 27, 2020
Source:
Rice University
Summary:
Materials scientists are calling for a collective, global effort
to fast- track the mass production of 2D materials like graphene
and molybdenum disulfide.



FULL STORY ========================================================================== Materials scientists at Rice University and the University of Pennsylvania
are calling for a collective, global effort to fast-track the mass
production of 2D materials like graphene and molybdenum disulfide.


==========================================================================
In a perspective article published online in Materials Today, journal
editor- in-chief Jun Lou and colleagues make a case for a focused,
collective effort to address the research challenges that could clear
the way for large-scale mass production of 2D materials.

Lou and fellow Rice materials scientists Ming Tang, Jing Zhang and
Fan Wang joined Penn's Vivek Shenoy in describing the potential
transformation in 2D materials technology that could result from a
systematic, communitywide effort to map the shapes of the 2D crystals
that are being grown in labs worldwide via a process known as chemical
vapor deposition (CVD).

"Like snowflakes in nature, 2D crystals exhibit a rich variety of
morphologies under different growth conditions," they wrote.

Mapping these unique crystal patterns and compiling the maps in a global database, alongside the recipes for creating each pattern, could unlock
a wealth of information "for understanding, diagnosing and controlling
the CVD process and environment for 2D material growth," the researchers
wrote.

CVD is a commonly used process for creating thin films, including
commercially important materials in the semiconductor industry. In a
typical CVD reaction, a flat sheet of material called a substrate is
placed in a reaction chamber and gases are flowed through the chamber
in such a way that they react and form a solid film atop the substrate.

One goal of the field is developing computer software that can accurately predict the properties of a thin film that will result from the mixing of specific reactant gases under specific conditions. Creating such models
is complicated by both an incomplete understanding of the physical and
chemical processes that take place during CVD and by the existence of
dozens of CVD reactor formats.

Cataloging the shape of crystals produced by CVD experiments could provide materials scientists with important information about their synthesis,
in much the same way that mineralogists retrieve valuable clues about
the history of Earth based on examination of naturally occurring crystal structures, Lou and colleagues suggested.

"Take the beautiful snowflakes as an example," the authors wrote. "A
perhaps surprising fact to many is that snow crystals can exhibit many different categories of shapes, which depend on the temperature and water supersaturation of the atmosphere in which they are formed." The Japanese scientist Ukichiro Nakaya, through extensive observations of snowflakes
in both nature and the laboratory, developed a figure known as the Nakaya diagram to help decipher the information in snowflakes. By examining
the shapes in a snowflake, and seeing where those shapes lie on Nakaya's diagram, scientists can determine the exact atmospheric conditions that produced the snowflake, which Nakaya poetically referred to as "a letter
from the sky." Inspired by Nakaya's work, Lou and colleagues created a Nakaya-like diagram of 2D crystal patterns that have been produced via
CVD and demonstrated how it and other morphology diagrams could be used
to infer clues about process variables like gas flow rates and heating temperatures that produced each pattern.

Thanks to advances in real-time imaging and in automated systems that can produce large datasets of crystal structures, the authors said there is
"real potential for morphology diagram development to become a common
practice and serve as a cornerstone of crystal growth."

========================================================================== Story Source: Materials provided by Rice_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Jing Zhang, Fan Wang, Vivek B. Shenoy, Ming Tang, Jun Lou. Towards
controlled synthesis of 2D crystals by chemical vapor deposition
(CVD).

Materials Today, 2020; DOI: 10.1016/j.mattod.2020.06.012 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200727194654.htm

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