Application-driven synthesis and characterization of hexagonal boron nitride deposited on metals and carbon nanotubes

Abstract

Hexagonal boron nitride (h-BN) is unique among two-dimensional materials, with a large band gap (~6 eV) and high thermal conductivity (>400 Wm -1 K -1 ), second only to diamond among electrical insulators. Most electronic studies to date have relied on h-BN exfoliated from bulk crystals; however, for scalable applications the material must be synthesized by methods such as chemical vapor deposition (CVD). Here, we demonstrate single-and few-layer h-BN synthesized by CVD on single crystal platinum and on carbon nanotube (CNT) substrates, also comparing these films with h-BN deposited on the more commonly used polycrystalline Pt and Cu growth substrates. The h-BN film grown on single crystal Pt has a lower surface roughness and is more spatially homogeneous than the film from a polycrystalline Pt foil, and our electrochemical transfer process allows for these expensive foils to be reused with no measurable degradation. In addition, we demonstrate monolayer h-BN as an ultrathin, 3.33 Å barrier protecting MoS2 from damage at high temperatures and discuss other applications that take advantage of the conformal h-BN deposition on various substrates demonstrated in this work.

Fractional Factorial Design to Evaluate the Synthesis and Electrochemical Transfer Parameters of h-BN Coatings

“…The samples S 3 , S 5 , and S 7 , which show some granular areas, present the highest RMS values and dispersion (see Supplementary Material for complementary optical microscopy images). However, it is worth noting that these roughness characteristics are consistent with h-BN samples approaching few-layer thickness, as reported in previous studies [81,82].…”

Horizontal Arrays of One-Dimensional van der Waals Heterostructures as Transistor Channels

“…Whether or not the coaxial van der Waals heterostructures can offer superior switching behavior in terms of interface state density and gate geometry (i.e., gate-all-around FETs) remains an open question. The comparison should be made with 2D hBN as interfacial layers, ,, as well as conventional bulk metal oxides (i.e., HfO 2 and Y 2 O 3 ) before further attempts to prepare the high-density horizontal arrays of 1D van der Waals heterostructures. Another challenge toward the realization of FETs with CNT@BNNT heterostructures would be the development of tools to evaluate the crystalline quality of BNNTs in devices (e.g., on oxide substrates).…”

Ultrathin Three-Monolayer Tunneling Memory Selectors

“…The complete H-shaped device with CVD-grown monolayer MoS 2 sandwiched by CVD-grown monolayer h -BN and graphene/​graphite as the BE/TE, respectively, is shown in Figure a. We were able to characterize the effect of the tunnel barrier on the out-of-plane current transport by controlling the band alignment with a back-gate, whose electric field penetrates through the graphene BE, modulating the heterostructure band alignment.…”

“…Figure is the cross-sectional schematic of the H-shaped device, a stack of graphene/​ h -BN/MoS 2 /​ h -BN/​graphite heterojunction fabricated on a 90 nm SiO 2 /p ++ Si substrate (0.001–0.005 Ω·cm) by transferring the 2D materials layer by layer in air . All monolayer materials are grown by large-area chemical vapor deposition (CVD), , except the top-electrode (TE) graphite flakes are exfoliated from bulk crystals. We used MoS 2 as the middle material in the H-shaped heterojunction due to its availability as high quality grown films in our laboratories .…”