Monolayer MoS₂ is an emergent 2D semiconductor for next‐generation miniaturized and flexible electronics. Although the high‐quality monolayer MoS₂ is already available at wafer scale, doping of it uniformly remains an unsolved problem. Such doping is of great importance in view of not only tailoring its properties but also facilitating many potential large‐scale applications. In this work, the uniform oxygen doping of 2 in wafer‐scale monolayer MoS₂ (MoS_2−xO_x) with tunable doping levels is realized through an in situ chemical vapor deposition process. Interestingly, ultrafast infrared spectroscopy measurements and first‐principles calculations reveal a reduction of bandgaps of monolayer MoS_2−xO_x with increased oxygen‐doping levels. Field‐effect transistors and logic devices are also fabricated based on these wafer‐scale MoS_2−xO_x monolayers, and excellent electronic performances are achieved, exhibiting promise of such doped MoS₂ monolayers.

Monolayer MoS₂ is an emerging two-dimensional (2D) semiconductor with promise on novel electronics and optoelectronics. Standard micro-fabrication techniques such as lithography and etching are usually involved to pattern such materials for devices but usually face great challenges on yielding clean structures without edge, surface and interface contaminations induced during the fabrication process. Here a direct writing patterning approach for wafer-scale MoS₂ monolayers is reported. By controllable scratching by a tip, wafer-scale monolayer MoS₂ films on various substrates are patterned in an ultra-clean manner. MoS₂ field effect transistors fabricated from this scratching lithography show excellent performances, evidenced from a room-temperature on–off ratio exceeding 10¹⁰ and a high field-effect mobility of 50.7 cm² V⁻¹ s⁻¹, due to the cleanness of as-fabricated devices. Such scratching approach can be also applied to other 2D materials, thus providing an alternate patterning strategy to 2D-materials based devices.

In recent years, two-dimensional (2D) type-II van der Waals (vdW) heterojunctions have emerged as promising candidates for high-performance photodetectors. However, direct experimental evidence confirming the enhancement of photoelectric properties by the heterojunction’s type and structure remains scarce. In this work, we present flexible photodetectors based on individual GaSe and MoS₂, as well as a vertically stacked type-II GaSe/MoS₂ vdW heterojunction on polyethylene terephthalate (PET) substrate. These devices demonstrate outstanding responsivities and rapid response speeds, ensuring stable and repeatable light detection. It is notable that the GaSe/MoS₂ heterojunction photodetector exhibits the highest on-off ratio and fastest response speed, attributed to the formation of type-II band alignment. Furthermore, the GaSe/MoS₂ heterojunction photodetector maintains robust stability even in a bent state, highlighting remarkable flexibility. This work exemplifies the type-II vdW heterojunctions in enhancing photoelectric properties through direct in-situ experimentation, laying the groundwork for practical applications of 2D flexible photodetectors.

Lithium iron phosphate (LiFePO4) with an olivine-type structure has garnered great interest due to its electrochemical activity. It is considered one of the most promising cathode materials for lithium-ion batteries because of its high discharge platform, large theoretical capacity, and excellent cycling performance and stability. However, the typical crystal structure of LiFePO4 restricts the formation of efficient electron conduction pathways and hampers the embedding and removal motion of lithium ions, resulting in low electron conductivity and a low ion diffusion rate. The experimental results show that element doping can reduce the activation energy of diffusion, increase the diffusion rate of lithium ions, improve the rate capability of lithium-ion batteries, and contribute to the improvement of its conductivity. In this work, the electronic structure and diffusion mechanism of a S/Co/Mn co-doped LiFePO4 system are systematically studied. The introduction of S, Co, and Mn atoms leads to the formation of impurity bands, resulting in a significant reduction in the bandgap from 3.593 eV to 0.190 eV, which is beneficial for improving the conductivity of LiFePO4. Moreover, the diffusion activation energy of lithium ions decreases from 0.73 eV to 0.34 eV, and the diffusion rate of lithium ions increases from 2.7 × 109 cm/s to 1.0 × 1016 cm/s. These results demonstrate that co-doping of S, Co, and Mn can effectively enhance the conductivity and diffusion rate of lithium ions in LiFePO4, providing a reliable reference for improving the electrochemical performance of lithium iron phosphate.

Quantum confinement has remarkable effects on the band structures and optoelectronic performance of semiconducting materials. The confinement of electronic states developed along van der Waals (vdW) gaps in transition metal dichalcogenides (TMDs) has unique advantages compared with those of artificial quantum wells. Here, we detected the quantized electronic states of few-layered ${\mathrm{MoS}}_2$ in real space using scanning tunneling microscope/spectroscopy. Combined with density-functional theory calculations, the quantized states were attributed to quantum-well states (QWSs), and the number of the states was strictly determined by the ${\mathrm{MoS}}_2$ layer thickness. We further regulated the QWSs of few-layered ${\mathrm{MoS}}_2$ by tuning the strength of interlayer hybridization through directly adjusting the interlayer distance. More importantly, substitutional defects in few-layered ${\mathrm{MoS}}_2$ were introduced to control the energy eigenvalues of the QWSs. Our work proves the existence of the interlayer electronic hybridization in conventional weakly coupled vdW interfaces, and provides a way to manipulate the electronic states of few-layered TMD through controlling interlayer hybridization. It also suggests potential applications of quantum-well materials in subband transitions, spin splitting, photoexcitation, and electronic devices.