Two-dimensional (2D) molybdenum disulfide (MoS₂) has shown considerable potential for photodetection, yet existing MoS₂-based photodetectors require either external voltage bias or complex heterojunctions. In this work, we present a new device concept based on flexoelectric engineering of bulk photovoltaic effect (BPVE) of 2H—MoS₂, simplifying the device configuration considerably while enhancing its self-powered photodetection performance. By introducing a strain gradient in the suspended 2H—MoS₂, we break its inversion symmetry, resulting in BPVE in the otherwise centrosymmetric system. The significant flexoelectric polarization induced also facilitates efficient photocarrier separation, leading to a 41-fold enhancement in short-circuit photocurrent under a strain gradient of 0.95. Furthermore, the flexoelectric-engineered photodetector can be dynamically tuned via air pressure, enabling multilevel photoconductance and achieving a responsivity of 191 mA/W. This performance surpasses existing self-powered MoS₂-based photodetectors reported in literature, offering a strategy for enhanced photodetection.

Transparent conducting oxides are increasingly important for optoelectronic and thin film transistor applications. La doped BaSnO₃ is a strong candidate for its high transparency, high carrier concentration, high mobility and abundancy. However, due to the lack of lattice-matched substrates, the mobility of La:BaSnO₃ remains inferior to single crystals. Here, by constructing a novel approach via delta doping La:BaSnO₃ in a BaSnO₃/La:BaSnO₃/BaSnO₃ (BSO/LBSO/BSO) heterostructure, we achieved room temperature mobility enhancement up to 110 cm²⸱V⁻¹⸱s⁻¹ while keeping the high carrier concentration at 5 × 10²⁰ cm⁻³, reaching to the highest electrical conductivity in BaSnO₃ based systems. The mobility is enhanced more than 100% compared to our La:BaSnO₃ films, which is among the highest mobility in BaSnO₃ based films and heterostructures. From atomic structural investigations, we found that both (1) the carrier confinement due to delta doping and (2) dislocation-free La:BaSnO₃ conducting channel, revealed by atomic resolution scanning transmission electron microscopy (STEM) studies, are responsible for mobility enhancement. The enhanced mobility from heterostructure approach is widely applicable for transparent electrodes and high current thin film transistor applications.

Negative capacitance (NC) has the potential to enable low power microelectronics beyond the fundamental thermionic limit, and it has been theorized that the thermodynamically unstable NC of ferroelectrics can be stabilized by linear dielectric, making negative capacitance ferroelectric field effect transistors (NC-FeFET) possible. Nevertheless, the validity of NC as a physical concept for ferroelectrics remain contentious despite numerous theoretical and experimental investigations, and the intrinsic ferroelectric NC with suppressed polarization has not been demonstrated except locally at vortex core. While NC-FeFET with subthreshold swing (SS) lower than 60 mV/dec limit has been reported, such device characteristics has not been directly connected to suppressed polarization at materials' level, and alternative mechanisms other than NC have also been proposed. Here we demonstrate stable sub-60 mV/dec SS with hysteresis free I—V in NC-FeFET based on SrTiO₃/Pb(Zr_0.1Ti_0.9)O₃/SrTiO₃ heterostructure, and observe its suppressed polarization at both macroscopic and microscopic scales. The intrinsic ferroelectric NC thus is experimentally confirmed and directly connected to NC-FeFET performance, and the mica-based device is also highly flexible and robust under cyclic bending as well as extended heating.

Surface-Enhanced Raman Spectroscopy attracts great interests for its ability to detect a variety of molecules at trace level. However, the commonly used noble metal substrates suffer from high cost, poor biocompatibility and inferior stability. Some oxides have the potential to substitute for noble metal and much effort has been made to improve their performance. In this paper, MoO₂ nanocones were prepared and self-assembled into hollow spheres. The structure exhibits an enhancement factor (EF) of 3 × 10⁷ and a limit of detection (LOD) of 10⁻⁹ M for Rhodamine 6G (R6G). This performance is among the best of all the oxides and is comparable to that of Au and Ag. The morphology control of hollow MoO₂ sphere was also discussed.