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We present a process for sculpting Bi2Se3nanoflakes into application-relevant geometries using a high-resolution transmission electron microscope. This process takes several minutes to sculpt small areas and can be used to cut the Bi2Se3into wires and rings, to thin areas of the Bi2Se3, and to drill circular holes and lines. We determined that this method allows for sub 10 nm features and results in clean edges along the drilled regions. Using in situhigh-resolution imaging, selected area diffraction, and atomic force microscopy, we found that this lithography process preserves the crystal structure of Bi2Se3. TEM sculpting is more precise and potentially results in cleaner edges than does ion-beam modification; therefore, the promise of this method for thermoelectric and topological devices calls for further study into the transport properties of such structures.

Heterostructures of transition metal dichalcogenides (TMDs) offer the attractive prospect of combining distinct physical properties derived from different TMD structures. Here, we report direct chemical vapor deposition of in-plane monolayer heterostructures based on 1H-MoS2and 1T′-MoTe2. The large lattice mismatch between these materials led to intriguing phenomena at their interface. Atomic force microscopy indicated buckling in the 1H region. Tip-enhanced Raman spectroscopy showed mode structure consistent with Te substitution in the 1H region during 1T′-MoTe2growth. This was confirmed by atomic resolution transmission electron microscopy, which also revealed an atomically stitched, dislocation-free 1H/1T′ interface. Theoretical modeling revealed that both the buckling and absence of interfacial misfit dislocations were explained by lateral gradients in Te substitution levels within the 1H region and elastic coupling between 1H and 1T′ domains. Phase field simulations predicted 1T′ morphologies with spike-shaped islands at specific orientations consistent with experiments. Electrical measurements across the heterostructure confirmed its electrical continuity. This work demonstrates the feasibility of dislocation-free stitching of two different atomic configurations and a pathway toward direct synthesis of monolayer TMD heterostructures of different phases.

Two-dimensional materials are promising for a range of applications, as well as testbeds for probing the physics of low-dimensional systems. Tungsten disulfide (WS2) monolayers exhibit a direct band gap and strong photoluminescence (PL) in the visible range, opening possibilities for advanced optoelectronic applications. Here, we report the realization of two-dimensional nanometer-size pores in suspended monolayer WS2membranes, allowing for electrical and optical response in ionic current measurements. A focused electron beam was used to fabricate nanopores in WS2membranes suspended on silicon-based chips and characterized using PL spectroscopy and aberration-corrected high-resolution scanning transmission electron microscopy. It was observed that the PL intensity of suspended WS2monolayers is ∼10–15 times stronger when compared to that of substrate-supported monolayers, and low-dose scanning transmission electron microscope viewing and drilling preserves the PL signal of WS2around the pore. We establish that such nanopores allow ionic conductance and DNA translocations. We also demonstrate that under low-power laser illumination in solution, WS2nanopores grow slowly in size at an effective rate of ∼0.2–0.4 nm/s, thus allowing for atomically controlled nanopore size using short light pulses.

Black phosphorus (BP) is a highly anisotropic allotrope of phosphorus with great promise for fast functional electronics and optoelectronics. We demonstrate the controlled structural modification of few-layer BP along arbitrary crystal directions with sub-nanometer precision for the formation of few-nanometer-wide armchair and zigzag BP nanoribbons. Nanoribbons are fabricated, along with nanopores and nanogaps, using a combination of mechanical–liquid exfoliation and in situtransmission electron microscopy (TEM) and scanning TEM nanosculpting. We predict that the few-nanometer-wide BP nanoribbons realized experimentally possess clear one-dimensional quantum confinement, even when the systems are made up of a few layers. The demonstration of this procedure is key for the development of BP-based electronics, optoelectronics, thermoelectrics, and other applications in reduced dimensions.

We report how the presence of electron-beam-induced sulfur vacancies affects first-order Raman modes and correlate the effects with the evolution of the in situtransmission-electron microscopy two-terminal conductivity of monolayer MoS2under electron irradiation. We observe a red-shift in the E′ Raman peak and a less pronounced blue-shift in the A′1peak with increasing electron dose. Using energy-dispersive X-ray spectroscopy and selected-area electron diffraction, we show that irradiation causes partial removal of sulfur and correlate the dependence of the Raman peak shifts with S vacancy density (a few %). This allows us to quantitatively correlate the frequency shifts with vacancy concentration, as rationalized by first-principles density functional theory calculations. In situdevice current measurements show an exponential decrease in channel current upon irradiation. Our analysis demonstrates that the observed frequency shifts are intrinsic properties of the defective systems and that Raman spectroscopy can be used as a quantitative diagnostic tool to characterize MoS2-based transport channels.