High‐Performance Phosphorene‐Based Transistors Using a Novel Exfoliation‐Free Direct Crystallization on Silicon Substrates

AbstractPhosphorene is one of the most promising elemental 2D materials. So far, mechanical exfoliation is the main route toward the formation of phosphorene sheets. Although field‐effect transistors are realized on phosphorene, their arrangement and size are dictated by the randomness of the exfoliation and transfer methods. Here, the evolution of highly crystalline and large‐area phosphorene sheets with a laser‐assisted phase transition from red phosphorus directly on silicon substrates in desired locations is reported. The original red phosphorus can be patterned prior to laser‐assisted crystallization to achieve the desired shape, location, and layer thickness (either mono or few). A 1064 nm laser is employed as the source to impart energy onto the red phosphorus layer and to achieve allotrope transformation. A combination of argon–oxygen (Ar:O2) and helium–hydrogen (He:H2) gases is exploited in a sequential manner to lead to phosphorene sheets. Various techniques are used to examine the physical properties of phosphorene sheets. Field‐effect transistors are made at different phases of crystallization and a high field‐effect mobility of 1450 cm2 V−1 s−1 and on/off ratio of 103 are achieved. Moreover, the optoelectrical characteristics of the phosphorene‐based phototransistors under different illumination powers and back‐gate voltages are investigated, showing superior performance.