Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices

Abstract

Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view toward high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations. The electron mobility of black phosphorus is significantly enhanced to 262 (377) cm V s by over 1 order of magnitude after potassium modification for two-terminal (four-terminal) measurements. Using lithography technique, a spatially controlled potassium doping technique is developed to establish high-performance complementary devices on a single black phosphorus nanosheet, for example, the p-n homojunction-based diode achieves a near-unity ideality factor of 1.007 with an on/off ratio of ∼10. Our findings coupled with the tunable nature of in situ modification scheme enable black phosphorus as a promising candidate for further complementary electronics.

Direct observation of a surface resonance state and surface band inversion control in black phosphorus

“…A gate-tunable Stark effect, i.e., the electronic control of the band gap by electric field, has been demonstrated and is directly relevant for optoelectronic applications of BP [12]. An in situ electric transport study of the conductivity of the surface of BP showed a huge increase in the conductance and a reduction of the gap upon potassium deposition [13]. This work also hinted at the existence of surface resonant states [13].…”

“…An in situ electric transport study of the conductivity of the surface of BP showed a huge increase in the conductance and a reduction of the gap upon potassium deposition [13]. This work also hinted at the existence of surface resonant states [13]. The underlying mechanism for understanding these experiments is a charge accumulation on the surface of BP or few-layer phosphorene which can be controlled by an external gate voltage.…”

Chemistry of Layered Pnictogens: Phosphorus, Arsenic, Antimony, and Bismuth

“…Ther eaction has to be well-controlled since alkali phosphide formation can take place,especially at elevated temperatures.T he interaction of few-layer black phosphorus with potassium was investigated in detail, and as trong electron-doping effect was observed on such ah eterostructure. [39] This may indicate also the possible formation of covalent or ionic bonds since potassium is highly electropositive and can form on surface phosphides.The main question is also the stability of such structure especially owing to the extreme reactivity of potassium and possible formation of phosphide at elevated temperature.Recently was reported the modification of black phosphorus by lithium hydride formed in situ by intercalation of lithium followed by subsequent hydrogenation. Theo btained material was not only more stable but also showed photoluminescence.…”

Exploring the Formation of Black Phosphorus Intercalation Compounds with Alkali Metals

“…It has recently been predicted that the electronic properties of BP can be modulated by strain or electric field 17, 18. Moreover, surface doping with K atoms leads to a tunable band gap in single‐crystal BP, leading a metallic state yielding with a significant improvement of its electronic transport 19, 20. In this regard, the intercalation of BP with donor‐type alkali metals could be envisioned as a promising strategy to electronically dope BP under atmospheric pressure.…”