posted on 2019-12-26, 18:36authored byMomoko Onodera, Takashi Taniguchi, Kenji Watanabe, Miyako Isayama, Satoru Masubuchi, Rai Moriya, Tomoki Machida
Hexagonal boron nitride (h-BN) synthesized under high
pressure
and high temperature (HPHT) has been used worldwide in two-dimensional
(2D) materials research as an essential material for constructing
van der Waals heterostructures. Here, we study h-BN synthesized with
another method, i.e., via synthesis at atmospheric pressure and high temperature (APHT) using a metal alloy solvent.
First, we examine the APHT h-BN in a bulk crystal form using cathodoluminescence
and find that it does not have carbon-rich domains that inevitably
exist in a core region of all the HPHT h-BN crystals. Next, we statistically
compare the size of the crystal flakes exfoliated on a SiO2/Si substrate from APHT and HPHT h-BN crystals by employing our automated
2D material searching system. Finally, we provide direct evidence
that APHT h-BN can serve as a high-quality substrate for 2D materials
by demonstrating high carrier mobility, ballistic transport, and Hofstadter
butterfly in graphene and photoluminescence in WS2.