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Register a new userYBCO-based non-volatile ReRAM tested in Low Earth Orbit
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An YBCO-based test structure corresponding to the family of ReRAM devices associated with the valence change mechanism is presented. We have characterized its electrical response previous to its lift-off to a Low Earth Orbit (LEO) using standard electronics and also with the dedicated LabOSat-01 controller. Similar results were obtained in both cases. After about 200 days at LEO on board a small satellite, electrical tests started on the memory device using the LabOSat-01 controller. We discuss the results of the first 150 tests, performed along a 433-day time interval in space. The memory device remained operational despite the hostile conditions that involved launching, lift-off vibrations, permanent thermal cycling and exposure to ionizing radiation, with doses 3 orders of magnitude greater than the usual ones on Earth. The device showed resistive switching and IV characteristics similar to those measured on Earth, although with changes that follow a smooth drift in time. A detailed study of the electrical transport mechanisms, based on previous models that indicate the existence of various conducting mechanisms through the metal-YBCO interface showed that the observed drift can be associated with a local temperature drift at the LabOSat controller, with no clear evidence that allows determining changes in the underlying microscopic factors. These results show the reliability of complex-oxide non-volatile ReRAM-based devices in order to operate under all the hostile conditions encountered in space-borne applications.
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In this work, we theoretically and experimentally investigate the working principle and non-volatile memory (NVM) functionality of 2D $alpha$-In$_2$Se$_3$ based ferroelectric-semiconductor-metal-junction (FeSMJ). First, we analyze the semiconducting and ferroelectric properties of $alpha$-In$_2$Se$_3$ van-der-Waals (vdW) stack via experimental characterization and first-principle simulations. Then, we develop a FeSMJ device simulation framework by self-consistently solving Landau-Ginzburg-Devonshire (LGD) equation, Poissons equation, and charge-transport equations. Based on the extracted FeS parameters, our simulation results show good agreement with the experimental characteristics of our fabricated $alpha$-In$_2$Se$_3$ based FeSMJ. Our analysis suggests that the vdW gap between the metal and FeS plays a key role to provide FeS polarization-dependent modulation of Schottky barrier heights. Further, we show that the thickness scaling of FeS leads to a reduction in read/write voltage and an increase in distinguishability. Array-level analysis of FeSMJ NVM suggests a 5.47x increase in sense margin, 18.18x reduction in area and lower read-write power with respect to Fe insulator tunnel junction (FTJ).
An optical equivalent of the field-programmable gate array (FPGA) is of great interest to large-scale photonic integrated circuits. Previous programmable photonic devices relying on the weak, volatile thermo-optic or electro-optic effect usually suffer from a large footprint and high energy consumption. Phase change materials (PCMs) offer a promising solution due to the large non-volatile change in the refractive index upon phase transition. However, the large optical loss in PCMs poses a serious problem. Here, by exploiting an asymmetric directional coupler design, we demonstrate PCM-clad silicon photonic 1 times 2 and 2 times 2 switches with a low insertion loss of ~1 dB and a compact coupling length of ~30 {mu}m while maintaining a small crosstalk less than ~10 dB over a bandwidth of 30 nm. The reported optical switches will function as the building blocks of the meshes in the optical FPGAs for applications such as optical interconnects, neuromorphic computing, quantum computing, and microwave photonics.
Non-volatile memory devices have been limited to flash architectures that are complex devices. Here, we present a unique photomemory effect in MoS$_2$ transistors. The photomemory is based on a photodoping effect - a controlled way of manipulating the density of free charges in monolayer MoS$_2$ using a combination of laser exposure and gate voltage application. The photodoping promotes changes on the conductance of MoS$_2$ leading to photomemory states with high memory on/off ratio. Such memory states are non-volatile with an expectation of retaining up to 50 % of the information for tens of years. Furthermore, we show that the photodoping is gate-tunable, enabling control of the recorded memory states. Finally, we propose a model to explain the photodoping, and we provide experimental evidence supporting such a phenomenon. In summary, our work includes the MoS$_2$ phototransistors in the non-volatile memory devices and expands the possibilities of memory application beyond conventional memory architectures.
YBCO fabrics composed of nanowires, produced by solution blow spinning (SBS) are so brittle that the Lorentz force produced by induced currents can be strong enough to damage them. On the other hand, it is known that silver addition improves the mechanical and flux pinning properties of ceramic superconductors. Thus, in this work, we show how we successfully obtained a polymeric precursor solution containing YBCO$+$Ag salts, which can be spun by the SBS route to produce ceramic samples. Yttrium, barium, copper, and silver metal acetates, and polyvinylpyrrolidone (PVP) (in a ratio of 5:1wt [PVP:acetates]) were dissolved in a solution with 61.5 wt% of methanol, 12 wt% of propionic acid, and 26.5 wt% of ammonium hydroxide, together with 6 wt% of PVP in solution. Three different amounts of silver (10 wt%, 20 wt%, and 30 wt%) were used in YBa$_2$Cu$_3$O$_{7-x}$. The TGA characterizations revealed a lowering of crystallization and partial melting temperatures by about SI{30}{celsius}. SEM images show that after burning out the polymer, a fabric composed of nanowires of diameters up to SI{380}{ ano metre} is produced. However, after the sintering process at SI{925}{celsius} for SI{1}{hour}, the nanowires shrink into a porous-like sample.
The interplay between ferromagnetism and topological properties of electronic band structures leads to a precise quantization of Hall resistance without any external magnetic field. This so-called quantum anomalous Hall effect (QAHE) is born out of topological correlations, and is oblivious of low-sample quality. It was envisioned to lead towards dissipationless and topologically protected electronics. However, no clear framework of how to design such an electronic device out of it exists. Here we construct an ultra-low power, non-volatile, cryogenic memory architecture leveraging the QAHE phenomenon. Our design promises orders of magnitude lower cell area compared with the state-of-the-art cryogenic memory technologies. We harness the fundamentally quantized Hall resistance levels in moire graphene heterostructures to store non-volatile binary bits (1, 0). We perform the memory write operation through controlled hysteretic switching between the quantized Hall states, using nano-ampere level currents with opposite polarities. The non-destructive read operation is performed by sensing the polarity of the transverse Hall voltage using a separate pair of terminals. We custom design the memory architecture with a novel sensing mechanism to avoid accidental data corruption, ensure highest memory density and minimize array leakage power. Our design is transferrable to any material platform exhibiting QAHE, and provides a pathway towards realizing topologically protected memory devices.
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