skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Mechanically reconfigurable van der Waals devices via low-friction gold sliding
Interfaces of van der Waals (vdW) materials, such as graphite and hexagonal boron nitride (hBN), exhibit low-friction sliding due to their atomically flat surfaces and weak vdW bonding. We demonstrate that microfabricated gold also slides with low friction on hBN. This enables the arbitrary post-fabrication repositioning of device features both at ambient conditions and in situ to a measurement cryostat. We demonstrate mechanically reconfigurable vdW devices where device geometry and position are continuously tunable parameters. By fabricating slidable top gates on a graphene-hBN device, we produce a mechanically tunable quantum point contact where electron confinement and edge-state coupling can be continuously modified. Moreover, we combine in situ sliding with simultaneous electronic measurements to create new types of scanning probe experiments, where gate electrodes and even entire vdW heterostructure devices can be spatially scanned by sliding across a target.  more » « less
Award ID(s):
2046849
PAR ID:
10486349
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
Sciences Advances
Date Published:
Journal Name:
Science Advances
Volume:
9
Issue:
14
ISSN:
2375-2548
Subject(s) / Keyword(s):
2d materials condensed matter physics nanodevices quantum devices MEMS van der Waal heterostructures moirés
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Journal of Applied Physics)
    Uniaxial strain has been widely used as a powerful tool for investigating and controlling the properties of quantum materials. However, existing strain techniques have so far mostly been limited to use with bulk crystals. Although recent progress has been made in extending the application of strain to two-dimensional van der Waals (vdW) heterostructures, these techniques have been limited to optical characterization and extremely simple electrical device geometries. Here, we report a piezoelectric-based in situ uniaxial strain technique enabling simultaneous electrical transport and optical spectroscopy characterization of dual-gated vdW heterostructure devices. Critically, our technique remains compatible with vdW heterostructure devices of arbitrary complexity fabricated on conventional silicon/silicon dioxide wafer substrates. We demonstrate a large and continuously tunable strain of up to −0.15% at millikelvin temperatures, with larger strain values also likely achievable. We quantify the strain transmission from the silicon wafer to the vdW heterostructure, and further demonstrate the ability of strain to modify the electronic properties of twisted bilayer graphene. Our technique provides a highly versatile new method for exploring the effect of uniaxial strain on both the electrical and optical properties of vdW heterostructures and can be easily extended to include additional characterization techniques. 
    more » « less
  2. ; ; ; ; ; ; ; ; (, Nano Letters)
    Van der Waals (vdW) moirés offer tunable superlattices that can strongly manipulate electronic properties. We demonstrate the in situ manipulation of moiré superlattices via heterostrain control in a vdW device. By straining a graphene layer relative to its hexagonal boron nitride substrate, we modify the shape and size of the moiré. Our sliding-based technique achieves uniaxial heterostrain values exceeding 1%, resulting in distorted moirés values that are larger than those achievable without strain. The stretched moiré is evident in transport measurements, resulting in shifted superlattice resistance peaks and Landau fans, consistent with an enlarged superlattice unit cell. Electronic structure calculations reveal how heterostrain shrinks and distorts the moiré Brillouin zone, resulting in a reduced electronic bandwidth as well as the appearance of highly anisotropic and quasi-one-dimensional Fermi surfaces. Our heterostrain control approach opens a wide parameter space of moiré lattices to explore beyond what is possible by twist angle control alone. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Advanced Materials Interfaces)
    Abstract While hexagonal boron nitride (hBN) has been widely used as a buffer or encapsulation layer for emerging electronic devices, interest in utilizing it for large‐area chemical barrier coating has somewhat faded. A chemical vapor deposition process is reported here for the conformal growth of hBN on large surfaces of various alloys and steels, regardless of their complex shapes. In contrast to the previously reported very limited protection by hBN against corrosion and oxidation, protection of steels against 10% HCl and oxidation resistance at 850 °C in air is demonstrated. Furthermore, an order of magnitude reduction in the friction coefficient of the hBN coated steels is shown. The growth mechanism is revealed in experiments on thin metal films, where the tunable growth of single‐crystal hBN with a selected number of layers is demonstrated. The key distinction of the process is the use of N2gas, which gets activated exclusively on the catalyst's surface and eliminates adverse gas‐phase reactions. This rate‐limiting step allowed independent control of activated nitrogen along with boron coming from a solid source (like elemental boron). Using abundant and benign precursors, this approach can be readily adopted for large‐scale hBN synthesis in applications where cost, production volume, and process safety are essential. 
    more » « less
  4. ; ; ; ; ; ; ; (, Nanomaterials)
    Polar van der Waals (vdW) crystals, composed of atomic layers held together by vdW forces, can host phonon polaritons—quasiparticles arising from the interaction between photons in free-space light and lattice vibrations in polar materials. These crystals offer advantages such as easy fabrication, low Ohmic loss, and optical confinement. Recently, hexagonal boron nitride (hBN), known for having hyperbolicity in the mid-infrared range, has been used to explore multiple modes with high optical confinement. This opens possibilities for practical polaritonic nanodevices with subdiffractional resolution. However, polariton waves still face exposure to the surrounding environment, leading to significant energy losses. In this work, we propose a simple approach to inducing a hyperbolic phonon polariton (HPhP) waveguide in hBN by incorporating a low dielectric medium, ZrS2. The low dielectric medium serves a dual purpose—it acts as a pathway for polariton propagation, while inducing high optical confinement. We establish the criteria for the HPhP waveguide in vdW heterostructures with various thicknesses of ZrS2 through scattering-type scanning near-field optical microscopy (s-SNOM) and by conducting numerical electromagnetic simulations. Our work presents a feasible and straightforward method for developing practical nanophotonic devices with low optical loss and high confinement, with potential applications such as energy transfer, nano-optical integrated circuits, light trapping, etc. 
    more » « less
  5. ; ; ; ; (, Small)
    Abstract Heat dissipation is a major limitation of high‐performance electronics. This is especially important in emerging nanoelectronic devices consisting of ultra‐thin layers, heterostructures, and interfaces, where enhancement in thermal transport is highly desired. Here, ultra‐high interfacial thermal conductance in encapsulated van der Waals (vdW) heterostructures with single‐layer transition metal dichalcogenides MX2(MoS2, WSe2, WS2) sandwiched between two hexagonal boron nitride (hBN) layers is reported. Through Raman spectroscopic measurements of suspended and substrate‐supported hBN/MX2/hBN heterostructures with varying laser power and temperature, the out‐of‐plane interfacial thermal conductance in the vertical stack is calibrated. The measured interfacial thermal conductance between MX2and hBN reaches 74 ± 25 MW m−2K−1, which is at least ten times higher than the interfacial thermal conductance of MX2in non‐encapsulation structures. Molecular dynamics (MD) calculations verify and explain the experimental results, suggesting a full encapsulation by hBN layers is accounting for the high interfacial conductance. This ultra‐high interfacial thermal conductance is attributed to the double heat transfer pathways and the clean and tight vdW interface between two crystalline 2D materials. The findings in this study reveal new thermal transport mechanisms in hBN/MX2/hBN structures and shed light on building novel hBN‐encapsulated nanoelectronic devices with enhanced thermal management. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email