No abstract

Ever since discovery of graphene, two‐dimensional (2D) materials become a new tool box for information technology. Among the 2D family, ultrathin bismuth (Bi) has attracted a great deal of attention in recent years due to its unique topological insulating properties and large magnetoresistance. However, the scalable synthesis of layered Bi ultrathin films is rarely been reported, which would greatly restrict further fundamental investigation and practical device development. Here, we demonstrate the direct growth of homogeneous and centimeter‐scale layered Bi films by pulsed laser deposition (PLD) technique. The as‐grown Bi film exhibits high‐purity phase and good crystallinity. In addition, both (111) and (110)‐oriented Bi films can be synthesized by precisely controlling the processing temperature. The characterization of optical properties shows a thickness dependent band gaps (0.075‐0.2 eV). Moreover, Bi thin‐film‐based field‐effect transistors have been demonstrated, exhibiting a large carrier mobility of 220 cm2 V−1 s−1. Our work suggests that the PLD‐grown Bi films would hold the potential to develop spintronic applications, electronic and optoelectronic devices used for information science and technology.

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 EA4Pb3Br10 single‐crystalline thin‐films (SCFs) for integration into flexible photodetectors. The in‐plane multiaxial ferroelectricity is evident within the EA4Pb3Br10 SCFs through systematic characterizations. Flexible photodetectors based on EA4Pb3Br10 SCFs are achieved with an impressive photodetection performance. More importantly, optoelectronic EA4Pb3Br10 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.