Metal contacts play a fundamental role in nanoscale devices. In this work, Schottky metal contacts in monolayer molybdenum disulfide (MoS 2 ) field-effect transistors are investigated under electron beam irradiation. It is shown that the exposure of Ti/Au source/drain electrodes to an electron beam reduces the contact resistance and improves the transistor performance. The electron beam conditioning of contacts is permanent, while the irradiation of the channel can produce transient effects. It is demonstrated that irradiation lowers the Schottky barrier at the contacts because of thermally induced atom diffusion and interfacial reactions. The simulation of electron paths in the device reveals that most of the beam energy is absorbed in the metal contacts. The study demonstrates that electron beam irradiation can be effectively used for contact improvement through local annealing.

We report the fabrication and the electrical characterization of back-gated field effect transistors with black phosphorus channel. We show that the hysteresis of the transfer characteristic, due to intrinsic defects, can be exploited to realize non-volatile memories. We demonstrate that gate voltage pulses allow to trap and store charge inside the defect states, which enable memory devices with endurance over 200 cycles and retention longer than 30 minutes. We show that the use of a protective poly (methyl methacrylate) layer, positioned on top of the black phosphorus channel, does not affect the electrical properties of the device but avoids the degradation caused by the exposure to air.

We studied the temperature dependent transport properties and memory behaviour of ultrathin black phosphorus field-effect transistors. The devices show electrical conductance and field-effect mobility that decreases with the rising temperature. The field effect mobility, which depends also on the gate voltage sweep range, is 283 cm2V-1s-1 at 150 K and reduces to 33 cm2V-1s-1 at 340 K, when the voltage gate sweep range is ± 50 V. The transfer characteristics show a hysteresis width that increases with the temperature and is exploited to enable non-volatile memories with a wider programming window at higher temperatures.

We report the fabrication, electrical, and optical characterizations of few-layered black phosphorus (BP)-based field-effect transistor (FET). The fabricated device exhibits a p-type transport with hole mobility up to 175 cm2 V−1 s−1 at Vds = 1 mV. The transfer characteristics show a large hysteresis width that depends linearly on the gate voltage and decreases with the increasing drain bias. The fabricated device also ensures a non-volatile charge-trap memory behaviour, with a stable and long retention time. The material’s photodetection capabilities enhance the functionality of the device making it controllable by light. The photocurrent was observed to be linearly increasing with the light incident power and exposure time. As a photodetector, the transistor reaches a responsivity and detectivity up to 340 mA W−1 and 6.52 × 1011 Jones under white light at 80 $$\mathrm{mW}$$ mW , respectively. Time-resolved measurements provide evidence of a long single exponential decay process through deep intra-gap states. Our results highlight the potential of a few layers BP as a nanomaterial for field-effect, memory, and optoelectronic devices. Graphical Abstract

Herein, the fabrication and electrical characterization of multilayer black phosphorus (BP)‐based field effect transistors with Ni or NiCr alloy contacts are reported. The devices show p‐type conduction and hysteresis in the transfer characteristics that enable their use as nonvolatile memories. The differences between Ni and NiCr contacts are investigated and the Y‐function method is applied to extract the channel mobility up to 112 cm2 V−1 s−1 and the contact resistances. Ni contacts present specific contact resistance of 6.3 k Ω μm that increases to 18.1 k Ω μm for NiCr. These findings are important for the technological exploitation of multilayer BP in a new class of electronic and optoelectronic devices.