Tunable RF phase shifters based on Vanadium Dioxide metal insulator transition

This paper presents the design, fabrication, and electrical characterization of a reconfigurable RF capacitive shunt switch that exploits the electro-thermally triggered vanadium dioxide (VO2) insulator to metal phase transition. The RF switch is further exploited to build wide-band RF true-time delay tunable phase shifters. By triggering the VO2 switch insulator to metal transition (IMT), the total capacitance can be reconfigured from the series of two metal-insulator-metal (MIM) capacitors to a single MIM capacitor. The effect of bias voltage on losses and phase shift is investigated, explained, and compared to the state of the art in the field. We report thermal actuation of the devices by heating the devices above VO2 IMT temperature. By cascading multiple stages a maximum of 40° per dB loss close to 7 GHz were obtained

A Steep-Slope Transistor Combining Phase-Change and Band-to-Band-Tunneling to Achieve a sub-Unity Body Factor

Steep-slope transistors allow to scale down the supply voltage and the energy per computed bit of information as compared to conventional field-effect transistors (FETs), due to their sub-60 mV/decade subthreshold swing at room temperature. Currently pursued approaches to achieve such a subthermionic subthreshold swing consist in alternative carrier injection mechanisms, like quantum mechanical band-to-band tunneling (BTBT) in Tunnel FETs or abrupt phase-change in metal-insulator transition (MIT) devices. The strengths of the BTBT and MIT have been combined in a hybrid device architecture called phase-change tunnel FET (PC-TFET), in which the abrupt MIT in vanadium dioxide (VO2) lowers the subthreshold swing of strained-silicon nanowire TFETs. In this work, we demonstrate that the principle underlying the low swing in the PC-TFET relates to a sub-unity body factor achieved by an internal differential gate voltage amplification. We study the effect of temperature on the switching ratio and the swing of the PC-TFET, reporting values as low as 4.0 mV/decade at 25 °C, 7.8 mV/decade at 45 °C. We discuss how the unique characteristics of the PC-TFET open new perspectives, beyond FETs and other steep-slope transistors, for low power electronics, analog circuits and neuromorphic computing

CX3CR1 knockout aggravates Coxsackievirus B3-induced myocarditis

Studies on inflammatory disorders elucidated the pivotal role of the CX3CL1/CX3CR1 axis with respect to the pathophysiology and diseases progression. Coxsackievirus B3 (CVB3)-induced myocarditis is associated with severe cardiac inflammation, which may progress to heart failure. We therefore investigated the influence of CX3CR1 ablation in the model of acute myocarditis, which was induced by inoculation with 5x105 plaque forming units of CVB3 (Nancy strain) in either CX3CR1-/- or C57BL6/j (WT) mice. Seven days after infection, myocardial inflammation, remodeling, and titin expression and phosphorylation were examined by immunohistochemistry, real-time PCR and Pro-Q diamond stain. Cardiac function was assessed by tip catheter. Compared to WT CVB3 mice, CX3CR1-/- CVB3 mice exhibited enhanced left ventricular expression of inflammatory cytokines and chemokines, which was associated with an increase of immune cell infiltration/presence. This shift towards a pro- inflammatory immune response further resulted in increased cardiac fibrosis and cardiomyocyte apoptosis, which was reflected by an impaired cardiac function in CX3CR1-/- CVB3 compared to WT CVB3 mice. These findings demonstrate a cardioprotective role of CX3CR1 in CVB3-infected mice and indicate the relevance of the CX3CL1/CX3CR1 system in CVB3-induced myocarditis

MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

https://pos.sissa.it/395/815/pdfPublished versio

Self-Assembled Nano-Electro-Mechanical Tri-state Carbon Nanotube Switches for Reconfigurable Integrated Circuits

We report, for the first time, self-assembled cantilever and clamped-clamped tri-state carbon nanotube (T-CNT) nano-electro-mechanical (NEM) switches with sub-100 nm air-gap dual lateral gates. Unlike conventional bi-state CNT switches, the T-CNT NEM switches operate in three states: CNT in the center (OFF), CNT attracted to the left gate (ON-1) or to the right gate (ON-2). They demonstrate excellent sensing current windows (I-on/I-off similar to 10(7)), ultra-low I-off (similar to 10(-14)A), good isolation and high endurance (cycle>10(2)). The proposed hysteretic switches offer a complementary metal-oxide-semiconductor (CMOS) - compatible bottom-up approach for various potential applications: logic devices, memories, etc., with higher circuit density and novel ultra-scaled configurability functions

Polarity Control of Top Gated Black Phosphorous FETs by Workfunction Engineering of Pre-Patterned Au and Ag Embedded Electrodes

We propose and experimentally demonstrate top-gated complementary n- and p-type black phosphorous field effect devices (FETs) by engineering the workfunction of pre-patterned electrodes embedded in a SiO2 bottom layer. Pre-patterned electrodes offer the advantages of reducing the exposure time of exfoliated flakes to oxidant agents with respect to top-contacted devices and maximizing the accessible area for sensing applications. The presented devices are realized by mechanical exfoliation of multilayer black phosphorous flakes on top of pre-patterned embedded source and drain contacts. A capping layer consisting of 15-nm thick Al2O3 is deposited to prevent flakes degradation and serves as top gate dielectric. The silicon substrate can be exploited as back gate to program the FETs threshold voltage. We deposited both Au and Ag embedded contacts to investigate the impact of electrodes workfunction on BP FETs polarity. Au contacted devices show p-type conduction with ON/OFF current ratio 140 and holes mobility up to 40 cm(2)V(-1)s(-1). Devices with Ag contacts exhibit prevalent n-type conduction with ON/OFF ratio 1700 and electron mobility 2 cm(2)V(-1)s(-1). The reported results represent a substantial improvement with respect to reported alternative implementations of black phosphorous FETs with pre-patterned, non-embedded electrodes. Moreover, we demonstrate that Ag is a promising metal for electron injection in black phosphorous FETs

Graphene quantum capacitors for high-Q tunable LC-tanks for RF ICs

We propose and characterize graphene quantum capacitors, tunable with voltage by the control of their charge density, for tunable LC tanks as essential building blocks for Radio-Frequency (RF) functions in densely integrated circuits. We fabricate and investigate their performance in RF, and we demonstrate quantum capacitances, C-q, in the range of pF with a tuning range of >1.3:1 within 1.25 V, with Q-factors up to 14.5 at 0.4 GHz. Our capacitors have a high capacitance density, up to 2.65 fF/mu m(2), which is 100x higher than the one of RF MEMS capacitors. Based on calibrated models and simulations, we demonstrate the potential to replace their semiconductor counterparts and RF MEMS capacitors in LC tanks, for key RF analog application

Design and fabrication of high-k filled sub-100 nm gap resonators with embedded dielectric field effect transistor for ultra high frequency applications

A novel fabrication process for the integration of Field Effect Transistors in electrostatically actuated bulk acoustic resonators is demonstrated. ALD-deposited HfO2 is used as a high-k dielectric for the FET and as an etch-stop layer during the release of the resonator structure as well, enabling the creation of sub-100 nm air-gap resonators with FET amplification enhancement