Tianru Wu

As a prototypical van der Waals layered monochalcogenide semiconductor, tin monosulfide (SnS) holds considerable promise for a wide range of applications owing to its distinctive physical properties. Conventional defect engineering strategies are predominantly confined to the material growth stage, which hinders localized, iterative post-fabrication modulation of electrical performance. Herein, we employ electron beam irradiation as a defect engineering strategy to systematically investigate the evolution of defect structures and electrical properties in multilayer SnS nanoflakes. Comprehensive spectroscopic and structural characterizations, along with density functional theory calculations, confirm that electron beam irradiation introduces abundant sulfur vacancies into the SnS lattice, with the vacancy concentration exhibiting a dose-dependent increase, as evidenced by Raman and X-ray photoelectron spectroscopy analyses. Electrical measurements demonstrate that the irradiated devices exhibit a current increase of two to five orders of magnitude and the pronounced suppression of gate dependence. This irradiation-induced electrical behavior is consistent with a hopping transport mechanism mediated by a percolation network of chalcogen vacancies. This study underscores the advantages of dose-controllable electron beam irradiation for defect engineering in layered SnS, providing critical guidance for rationally tailoring electrical properties in SnS and other layered chalcogenide semiconductors.

Accurate temperature measurement with a high spatial resolution is essential for understanding thermal behavior in integrated nanoscale devices and especially at heterogeneous interfaces. However, existing techniques are often limited by insufficient spatial resolution. Here, we showcase the direct and noncontact temperature measurement with a nanometer spatial resolution using transmission electron microscopy. The experimental probe is the combination of a scanning nanobeam with precession electron diffraction, which offers the collection of kinematic diffraction intensity from a local area at the nanometer scale. With a precalculated, sample- and geometry-specific structure factor–based correction, the linear fitting of diffraction intensities allows the determination of the Debye-Waller factor and, thus, temperature with a precision of 10 ⁻⁴ square angstrom per °C. Using graphene as a model material, this work reveals the influence of sample tilt, lattice thermal expansion, and sample thickness on Debye-Waller factor and offers a route to improving the measurement precision along with spatial resolution. The approach establishes a broadly applicable strategy for nanoscale thermometry in low-dimensional and heterogeneous materials.

Two-dimensional (2D) In₂Se₃ represents a uniquely versatile platform for novel electronics, hosting the rare coexistence of paraelectric (β), antiferroelectric (β'), and ferroelectric (α) phases. However, synthesizing phase-pure In₂Se₃ films, particularly the critical ferroelectric semiconducting α-phase, is fundamentally hindered by the subtle structural distinctions and minimal energetic differences among its polymorphs. Here, we directly reveal phase-selective growth of In₂Se₃ on mica using cross-sectional transmission electron microscopy (TEM). It is found that both chemical vapor deposition (CVD) and physical vapor deposition (PVD) techniques yield exclusively either the pure β′ phase or coexisting monolayer α and β′ phases, with the cooling rate playing a critical role in phase selection. Crucially, in situ stress release within the epitaxial film on mica generates wrinkles propagating along the <> direction, triggering an immediate β' to α phase transformation. The resulting phase-pure α-In₂Se₃ films enable ferroelectric transistors exhibiting a high electron mobility of 259 cm² V^-1 s^-1. This precise control over polymorph synthesis unlocks promising opportunities for 2D ferroelectric devices and nanoelectronics, offering a pathway to harness phase-specific functionalities.

In recent years, flexible pressure sensors have been seen widespread adoption in various fields such as electronic skin, smart wearables, and human–computer interaction systems. Owing to the electrical conductivity and adaptability to flexible substrates, vertical graphene nanowalls (VGNs) have recently been recognized as promising materials for pressure-sensing applications. Our study presented the synthesis of high-quality VGNs via plasma enhanced chemical vapor deposition and the incorporation of a metal layer by electron beam evaporation, forming a stacked structure of VGNs/Metal/VGNs. Metal nanoparticles attached to the edges and surfaces of graphene nanosheets can alter the charge transport paths within the material to enhance the responsiveness of the sensor. This layered structure effectively fulfilled the requirements of flexible pressure sensors, exhibiting high sensitivity (40.15 kPa⁻¹), low response time (88 ms), and short recovery time (97 ms). The pressure sensitivity remained intact even after 1000 bending cycles. Additionally, the factors contributing to the impressive pressure-sensing performance of this composite were found and its capability to detect human pulse and finger flexion signals was demonstrated, making it a promising candidate for applications of wearable electronics devices.