Search

Two-dimensional materials provide opportunities for developing semiconductor applications at atomistic thickness to break the limits of silicon technology. Black phosphorus (BP), as a layered semiconductor with controllable bandgap and high carrier mobility, is one of the most promising candidates for transistor devices at atomistic thickness1–4. However, the lack of large-scale growth greatly hinders its development in devices. Here, we report the growth of ultrathin BP on the centimetre scale through pulsed laser deposition. The unique plasma-activated region induced by laser ablation provides highly desirable conditions for BP cluster formation and transportation5,6, facilitating growth. Furthermore, we fabricated large-scale field-effect transistor arrays on BP films, yielding appealing hole mobility of up to 213 and 617 cm2 V−1 s−1 at 295 and 250 K, respectively. Our results pave the way for further developing BP-based wafer-scale devices with potential applications in the information industry. Centimetre-scale growth of few-layer black phosphorous with high crystalline quality and homogeneity is realized by pulsed laser deposition.

Realizing multicolored luminescence in two-dimensional (2D) nanomaterials would afford potential for a range of next-generation nanoscale optoelectronic devices. Moreover, combining fine structured spectral line emission and detection may further enrich the studies and applications of functional nanomaterials. Herein, a lanthanide doping strategy has been utilized for the synthesis of 2D ZnSe:Er

Precise morphological control over anisotropic noble metal nanoparticles (ANPs) is one of the key issues in the nano-research field owing to their unique optoelectronic, magnetic, mechanical, and catalytic properties. Although nanostructures fabricated by the directed assembly of adsorbate have been widely demonstrated recently, facile yet universal synthesis of nanocrystal with tunable morphologies, green templates, no seeds, and high yield remains challenging. Herein, we develop a versatile method, allowing for the rapid, one-step, seedless, surfactant-free synthesis of a noble metal nanostructure with tunable anisotropy on MXene in a sequence-dependent manner through a single-DNA molecular regulator. Based on the mild reducibility of MXene and the selective affinity of the DNA to the specific facets in the crystals, oriented aggregations and the growth of ANPs (Au, Pt, Pd) can be achieved and the resulting asymmetric morphology from polyhedrons, or flowers, or nanoplates to dendrites is observed. The ability to align such ANPs on the MXene surface is expected to lead to improved photothermal effect and surface-enhanced Raman scattering. Furthermore, our work makes the fabrication of the ANPs or ANP-MXene heterostructure easier, stimulating further explorations of physical, chemical, and biological applications.

Lanthanide ions have attracted great attention due to their distinct photonic properties. The optoelectronic properties and device performance are greatly affected by the interfacial coupling between the layered van der Waals heterostructure, fabricated with two or more transition metal dichalcogenide (TMD) layers. In this work, lanthanide-doped WS2/MoS2 layered heterostructures have been constructed through two synthesis steps. The doped thin films are highly textured nanosheets on wafers. Importantly, the as-prepared heterostructure exhibits efficient near-infrared emission in the range of the telecommunication window, owing to energy transfer between lanthanide ions in the two TMD layers. The use of the layered heterostructure allows the decrease of deleterious cross-relaxation due to homogeneous doping or concentration quenching. The energy transfer process was further elaborated in this work. The results suggest that lanthanide ions can effectively extend the emission band of TMD thin films and their heterostructures. The doped TMD heterostructure is highly favourable for constructing atomically thin near-infrared photonic devices.

2D hybrid perovskites are very attractive for optoelectronic applications because of their numerous exceptional properties. The emerging 2D perovskite ferroelectrics, in which are the coupling of spontaneous polarization and piezoelectric effects, as well as photoexcitation and semiconductor behaviors, have great appeal in the field of piezo-phototronics that enable to effectively improve the performance of optoelectronic devices via modulating the electro-optical processes. However, current studies on 2D perovskite ferroelectrics focus on bulk ceramics that cannot endure irregular mechanical deformation and limit their application in flexible optoelectronics and piezo-phototronics. Herein, we synthesize ferroelectric EA4 Pb3 Br10 single-crystalline thin-films (SCFs) for integration into flexible photodetectors. The in-plane multiaxial ferroelectricity is evident within the EA4 Pb3 Br10 SCFs through systematic characterizations. Flexible photodetectors based on EA4 Pb3 Br10 SCFs are achieved with an impressive photodetection performance. More importantly, optoelectronic EA4 Pb3 Br10 SCFs incorporated with in-plane ferroelectric polarization and effective piezoelectric coefficient show great promise for the observation of piezo-phototronic effect, which is capable of greatly enhancing the photodetector performance. Under external strains, the responsivity of the flexible photodetectors can be modulated by piezo-phototronic effect with a remarkable enhancement up to 284%. Our findings shed light on the piezo-phototronic devices and offer a promising avenue to broaden functionalities of hybrid perovskite ferroelectrics.

The controllable biaxial strain is experimentally imposed on α-In2Se3 nanosheets by an electromechanical device. A redshift of Raman spectra is observed from the nanosheets under the strain. The Gruneisen parameter is calculated to analyze the strain effect on the vibrational behavior. Photoluminescence shows a blueshift, which can reach up to 215 meV per 1% strain. Such tunability of optical characteristics observed from α-In2Se3 nanosheets is much higher than that from conventional semiconductors. The physical mechanism behind the observation is investigated, which is related to the variations in the energy band and photoexcited carriers under a piezoelectric field and laser power.

The near-infrared (NIR) emission of Er3+ ions has been extensively studied owing to their significance in optical communication applications. However, studies concerning the incorporation of lanthanide ions into the two-dimensional (2D) matrix are still in the early stages. In this work, we developed an ingenious two-step vapor-phase-transfer method to synthesize Er3+ doped MoS2 single-crystalline monolayers. The NIR emission at 1530 nm was observed from the doped MoS2 nanosheets under 980 nm diode laser excitation, corresponding to the energy transition from 4I13/2 to 4I11/2 of the Er3+ dopant. The concentration quenching effect was demonstrated with an optimal Er content of around 4 mol. %. To further understand the effect of lanthanide doping on the 2D MoS2 host matrix in terms of the growth mechanism and electronic structures, theoretical analysis was performed on Er-doped monolayer MoS2 using the density functional theory calculation. The computed band structure with the superimposed Dieke diagram was in good accordance with our experimental results. Our work offers the possibility to develop doping strategies in the 2D limit and provides an in-depth understanding of the lanthanide doping in atomically thin materials.