Black phosphorus (BP) has attracted rapidly growing attention for high speed and low power nanoelectronics owing to its compelling combination of tunable bandgap (0.3 to 2 eV) and high carrier mobility (up to ∼1000 cm(2)/V·s) at room temperature. In this work, we report the first radio frequency (RF) flexible top-gated (TG) BP thin-film transistors on highly bendable polyimide substrate for GHz nanoelectronic applications. Enhanced p-type charge transport with low-field mobility ∼233 cm(2)/V·s and current density of ∼100 μA/μm at VDS = -2 V were obtained from flexible BP transistor at a channel length L = 0.5 μm. Importantly, with optimized dielectric coating for air-stability during microfabrication, flexible BP RF transistors afforded intrinsic maximum oscillation frequency fMAX ∼ 14.5 GHz and unity current gain cutoff frequency fT ∼ 17.5 GHz at a channel length of 0.5 μm. Notably, the experimental fT achieved here is at least 45% higher than prior results on rigid substrate, which is attributed to the improved air-stability of fabricated BP devices. In addition, the high-frequency performance was investigated through mechanical bending test up to ∼1.5% tensile strain, which is ultimately limited by the inorganic dielectric film rather than the 2D material. Comparison of BP RF devices to other 2D semiconductors clearly indicates that BP offers the highest saturation velocity, an important metric for high-speed and RF flexible nanosystems.

The largest applications of high-performance graphene will likely be realized when combined with ubiquitous Si very large scale integrated (VLSI) technology, affording a new portfolio of "back end of the line" devices including graphene radio frequency transistors, heat and transparent conductors, interconnects, mechanical actuators, sensors, and optical devices. To this end, we investigate the scalable growth of polycrystalline graphene through chemical vapor deposition (CVD) and its integration with Si VLSI technology. The large-area Raman mapping on CVD polycrystalline graphene on 150 and 300 mm wafers reveals >95% monolayer uniformity with negligible defects. About 26,000 graphene field-effect transistors were realized, and statistical evaluation indicates a device yield of ∼ 74% is achieved, 20% higher than previous reports. About 18% of devices show mobility of >3000 cm(2)/(V s), more than 3 times higher than prior results obtained over the same range from CVD polycrystalline graphene. The peak mobility observed here is ∼ 40% higher than the peak mobility values reported for single-crystalline graphene, a major advancement for polycrystalline graphene that can be readily manufactured. Intrinsic graphene features such as soft current saturation and three-region output characteristics at high field have also been observed on wafer-scale CVD graphene on which frequency doubler and amplifiers are demonstrated as well. Our growth and transport results on scalable CVD graphene have enabled 300 mm synthesis instrumentation that is now commercially available.

This paper reports a 100% inkjet printed transistor with a short channel of approximately 1 µm with an operating speed up to 18.21 GHz. Printed electronics are a burgeoning area in electronics development, but are often stymied by the large minimum feature size. To combat this, techniques were developed to allow for the printings of much shorter transistor channels. The small gap size is achieved through the use of silver inks with different chemical properties to prevent mixing. The combination of the short channel and semiconducting carbon nanotubes (CNT) allows for an exceptional experimentally measured on/off ratio of 106. This all inkjet printed transistor allows for the fabrication of devices using roll-to-roll methodologies with no additional overhead compared to current state of the art production methods.

In the past decade, two-dimensional (2D) atomic crystals have stimulated great interest in the electronic device community for their interesting physics and diverse applications. With the rapid growing market of wearable electronics and the internet of things, flexible nanoelectronics with high operation speed and low power consumption has become one of the most researched topics. In this regard, 2D atomic van der Waals crystals have emerged as promising candidates for such applications owing to their compelling capabilities including ultimate thickness scalability, superior mechanical flexibility and highly tunable electronic performance. In this review, state-of-the-art advancements in 2D flextronics based on chemical vapor deposition (CVD) monolayer graphene, CVD monolayer molybdenum disulphide (MoS 2 ) and exfoliated few layer black phosphorus are presented with specific emphasis on radio frequency applications.

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