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Stannous oxide (SnO) and stannic oxide (SnO2) are both important wide-band-gap semiconductors. To study the conductive mechanism in detail, high quality epitaxial films are essential. Here we propose a simple method to grow high quality epitaxial films of either stannous oxide or stannic oxide on an r-plane sapphire substrate by using pulsed laser deposition with a metallic tin target. The valence state of tin is controlled by tuning the oxygen pressure during the deposition procedure. Metal tin impurities and the transition phase of Sn3O4 are avoided and the growth windows from stannous oxide to stannic oxide are confirmed. For single-crystalline SnO epitaxial film, a rocking curve half-width of 0.22° is obtained, which is better than the 0.46° of that on a YSZ substrate. The minimum roughnesses achieved were 0.37 nm for the SnO2 epitaxial film and 0.84 nm for the SnO epitaxial film. The epitaxial relationship between SnO and the r-sapphire substrate was determined to be SnO [ 1 ¯ 1 0 ] //sapphire [ 1 ¯ 2 1 ¯ 0 ] and SnO [1 1 0]//sapphire [ 1 0 1 ¯ 1 ] . For SnO2, the epitaxial relation is SnO2 [0 1 0]//sapphire [ 1 ¯ 2 1 ¯ 0 ] and SnO2 [ 1 ¯ 0 1 ] //sapphire [ 1 0 1 ¯ 1 ] . The band schematics, deduced by combined XPS valence band spectroscopy and optical transmittance spectroscopy, indicated p-type bands of SnO and n-type bands of SnO2. Raman spectroscopy is suggested to be a superior fingerprint of SnO single-crystalline quality, due to its greater sensitivity than X-ray diffraction.

A novel circuit for testing sequential element setup time and hold time variation at near threshold voltage (NTV) is proposed and verified at 28nm HKMG node. A structure of two-path with configurable delay differentiation enables to cancel testing errors introduced by PVT variations and RC delay along the testing path. Pico-seconds of resolution is achieved. Simulation of setup/hold time is implemented with variable voltage, process corner, temperature and data edge. The results indicate that the scenario of data rising edge has a larger setup&hold time than the scenario of data falling edge at NTV.

We describe a controllable sliding method for fabricating millions of isolated femto- to nanoliter-sized droplets with defined volume, geometry and position and a speed of up to 375 kHz. In this work, without using a superhydrophobic or superoleophobic surface, arrays of droplets are instantly formed on the patterned substrate by sliding a strip of liquid, including water, low-surface-tension organic solvents and solution, along the substrate. To precisely control the volume of the droplets, we systemically investigate the effects of the size of the wettable pattern, the viscosity of the liquid and sliding speed, which were found to vary independently to tune the height and volume of the droplets. Through this method, we successfully fabricated an oriented single metal–organic framework crystal array with control over their XY positioning on the surface, as characterized by microscopy and X-ray diffraction (XRD) techniques.

Domain wall memory (DMW) or Racetrack memory (RM) has attracted great attention for its enormous capacity. However, the array architecture are not clear. Prior arts have very low capacity utilization (only 50 % ) as well as high shift voltage. This paper proposed a 1 transistor X cells (1TXC) array architecture based on X-bar cell structure for 3D DWM, which realizes 100 % capacity utilization, 50 % shift power reduction and attains simplified peripheral decoding circuit as well as cost efficiency. Further, a corresponding anti-disturbance read operation algorithm is put forward, which can inhibit misread problem caused by sneaking current.

In terms of the charge storage mechanism of supercapacitors, there are three types, including electrical double layer (EDL), surface redox reaction and intercalation reaction. The surface redox mechanism of transition metal-layered double hydroxides (TM-LDH) supercapacitor had been previously revealed. A dual charge storage mechanism integrated with surface redox and ion intercalation for LDH-based supercapacitors, however, is seldom reported before. For this purpose, here, we synthesized NiCo layered double hydroxide nanosheets via the intrinsic pillar effect of sodium dodecylbenzene sulfonate (NiCo-SDBS-LDH), and found that the surface redox and intercalation behaviors take effect simultaneously in NiCo-SDBS-LDH via electrochemical analysis. The NiCo-SDBS-LDH electrode having a relatively low specific surface area (15.28 m 2 g −1 ) still exhibited a remarkable specific capacitance of 1094 F g −1 at a scan rate of 5 A g −1 , and super long cycle life of 81% retention over 3000 cycles. A dual charge storage mechanism is subsequently proposed based on the analysis of our results to explain the excellent properties of NiCo-SDBS-LDH. We believe that the enhancements should mainly be ascribed to the structural feature of the SDBS stabilized NiCo-LDH and the expanded interlayer space of NiCo-SDBS-LDH. These findings open new doors to functional pillared effect to control the electrochemical behaviors of TM-LDH-based materials.

Hybrid memory comprised of a big SCM and a little DRAM (BSLD) is widely studied to address the growing power consumption challenge of pure DRAM. However, the performance degradation, limited endurance and immature mass production of ultra-high-density SCM are still the painful points of BSLD. Here we propose a Retention-Aware Hybrid Main Memory (RAHMM) architecture with a big DRAM and a little SCM (BDLS) for the first time. DRAM is refreshed at a much longer interval by using SCM to store the small quantity of leaky tail bits in DRAM. A two-step search technology combined with outcome forecasting is put forward to get ultra-fast read access, as well as to diminish the power and performance overheads. A hidden buffer strategy (HBS) is proposed to optimize write performance and endurance hurt. The experimental results show 45 percent reduction of power consumption and 30 percent performance optimization, which are significantly improved compared to that of both serial and parallel BSLD with a counterpart capacity

Magnetoresistive random access memory (MRAM) suffers from low magnetoresistance ratio and serious variations in both low-resistance state (R P ) and high-resistance state (R AP ). The resulting narrow resistance window between R P and R AP makes it difficult to acquire a sufficient sense margin for accurate read operation. In this brief, a novel read circuit for MRAM is proposed with dynamic data-dependent reference current to improve the sense margin. Instead of using the average of read currents of a pair of dummy R P and R AP cells as reference, our reference current is generated in a data-dependent manner by subtracting the read current of the selected cell from the sum of read currents of a pair of dummy R P and R AP cells. Thus, a larger or smaller reference current can be obtained for the read of R AP or R P cell, respectively, helping in expanding the sense margins. The larger sense margin can further improve the sense speed and the read yield. Evaluation shows that 2× increase in typical sense margin, 60% reduction in sense time, and remarkable reduction in bit error rate are achieved compared with the conventional averaging reference scheme. The accompanying cost in power consumption is acceptable.

To understand the insightful mechanics of the effects of the trivalent metal ions on the electrochemical performance of ternary-component layered double hydroxides (LDH), the ternary LDH composed by NiCoAl-LDH, NiCoAl 0.5 Fe 0.5 -LDH and NiCoFe-LDH are designed, synthesized and characterized. Despite bivalent metal ions (Ni 2+ , Co 2+ ) having been demonstrated to play a highly specialized role in surface redox chemistry, the role of the trivalent metal ions within the metal hydroxide layer has not been elucidated yet in supercapacitor applications. Here we demonstrated that Al 3+ has a positive effect on the stabilization of host layers of LDH, which leads to the improvement of the electrochemical performance. It was also found that Al 3+ could regulate the crystallinity, hydrophilicity and nanosheets stacking of LDH. Further, comparative studies show that NiCoAl-LDH exhibited superior specific capacitance of 1153 F g −1 at 6 A g −1 , and excellent cycling stability (ca. 92.97% capacitance retention after 3000 cycles). We attribute such remarkable enhancement in cyclic performance to the framework stability of Al 3+ in the multi-metal LDH matrix layer. These results highlight the importance of trivalent metal ions in ternary-component LDH for high-performance supercapacitors and may guide future design and synthesis of LDH.

Bismuth ferrite/graphene (N-doped graphene) photocatalysts are successfully prepared by a facile and effective two-step hydrothermal method. Bismuth ferrite/graphene shows superior photocatalytic activity compared with bismuth ferrite/N-doped graphene and pure BiFeO 3 . X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy analyses indicate that Bi 25 FeO 40 crystalline phase is obtained with the addition of graphene, while BiFeO 3 is formed under the same hydrothermal conditions in the presence of N-doped graphene. Core-level and valence-band X-ray photoelectron spectroscopy analyses reveal a downward band bending of bismuth ferrite (∼0.5 eV) at the interface of the bismuth ferrite/(N-doped) graphene composites, which facilitates the electron transfer from bismuth ferrite to (N-doped) graphene and suppresses the recombination of photo-generated electron–hole pairs. This downward bending band alignment at the interface supposes to be the main mechanism underlying the enhanced photocatalytic activity of the bismuth ferrite/graphene composites that are currently of great interest in the photocatalysis field.

Emerging nonvolatile memories (NVMs), such as MRAM, PRAM, and RRAM, have been widely investigated to replace SRAM as the configuration bits in field-programmable gate arrays (FPGAs) for high security and instant power ON. However, the variations inherent in NVMs and advanced logic process bring reliability issue to FPGAs. This brief introduces a low-power variation-tolerant nonvolatile lookup table (nvLUT) circuit to overcome the reliability issue. Because of large $R_{\mathrm{{\scriptscriptstyle OFF}}}$ / $R_{\mathrm{{\scriptscriptstyle ON}}}$ , 1T1R RRAM cell provides sufficient sense margin as a configuration bit and a reference resistor. A single-stage sense amplifier with voltage clamp is employed to reduce the power and area without impairing the reliability. Matched reference path is proposed to reduce the parasitic $RC$ mismatch for reliable sensing. Evaluation shows that 22% reduction in delay, 38% reduction in power, and the tolerance of variations of $2.5\times $ typical $R_{\mathrm{{\scriptscriptstyle ON}}}$ or $R_{\mathrm{{\scriptscriptstyle OFF}}}$ in reliability are achieved for proposed nvLUT with six inputs.

Layered double hydroxide (LDH) was in situ grown on the disordered platelets of montmorillonite (Mt), and a self-assembled sheet-on-sheet nanohybrid was obtained. To obtain a nanohybrid of cationic/anionic clay with exfoliated Mt platelets, NaMt (sodium-montmorillonite) was fractionated and subsequently treated by ultrasonication in a solution of aluminum nitrate and magnesium nitrate to ensure good dispersion of the NaMt and cation adsorption. Subsequently, the precursors were reacted with ammonia under hydrothermal conditions. The phase compositions of the as-prepared samples were analyzed by X-ray diffraction and Fourier transform infrared spectroscopy. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy investigations revealed the typical sheet-on-sheet and exfoliated Mt structures. The results demonstrated that the LDH grown on the disordered platelets of montmorillonite was successfully synthesized by a simple in situ growth route. A possible formation mechanism for the sheet-on-sheet architecture has been suggested. Using ultrasonically pre-exfoliated disordered Mt platelets as matrixes provided an essential substrate for the nucleation and in situ growth of LDH crystallites. The ammonia solution provided hydroxyl moieties for LDH growth and split the Mt platelets via a breaker effect. It is suggested that the in situ-grown LDH crystals, as spacers, played a crucial role in preventing the reaggregation of the disordered Mt platelets. This study can offer some new insights into developing a nanohybrid of cationic/anionic clay with a unique sheet-on-sheet structure.

Self-assembly 3D layered double hydroxide (LDH) nanosheets were synthesized using nano-SiO2 as self-sacrificial templates via a facile bottom-up strategy. It is an environmentally friendly and economic strategy to prepare LDH nanosheets in comparison with the conventional method by exfoliation of bulk LDHs.

Metal–organic frameworks (MOFs), produced by metal ions coordinated to organic linkers, have attracted increasing attention in recent years. For the utilization in MOFs in numerous applications, achieving positioned MOF growth on surfaces is essential to fabricate multiple-functional devices. We develop a novel miniaturized method to realize surface-tension-confined assembly of HKUST-1 in femtoliter droplet arrays. HKUST-1 crystal arrays grown by evaporation-induced crystallization are observed, and five typical crystal morphologies (i.e., hexagonal, irregular hexagonal, triangular, arc-like and ribbon-like crystals) are found in the large area on the patterned substrate during crystallization. Our research provides a better understanding of the formation mechanism of MOF crystals in confined sessile droplets. The key factors determining HKUST-1 single-crystal growth are the internal flows in an evaporating droplet and consequently aggregation induced by the combination of metallic Cu(II) and BTC ions. Understanding the formation of different morphologies of HKUST-1 crystals is useful to guide the production of crystals with desired shapes for various applications.

Resistive random access memory (ReRAM) is very attractive for dense storage in embedded applications because of its good scalability and logic-process compatibility. However, ReRAM suffers from severe variations in R off /R on , endurance and retention, which greatly impair its yield and limit its application. Besides the variation sources from material defects, device non-uniformity and manufacturing deviations, circuit inability to provide an ideal write condition also plays an important role in causing above-mentioned variations. Especially, the requirement for a uniform and small overshoot compliance current during set (forming) is critical for narrowing the low-resistance state (LRS), i.e. R on distribution, while the prior works fail to satisfy. This paper proposed a write driver with dynamic uniform and small overshoot compliance current under different set/forming voltages. The benefits of self-adaptive write mode (SAWM) are also reserved for both set and reset operations. Simulation shows that the compliance current with 5% variation for PVT variations and 3% overshoot is achieved.

The Al doping effects on retention of HfOx based resistive switching memory were studied in detail using density functional theory. Al doping has many merits such as reducing forming voltage, improving uniformity and enhancing the ON state retention, but it was found to deteriorate the OFF state retention. This study finds that the migration barriers of oxygen vacancies in and out of the filament in the presence of Al are severely altered as compared to those far from Al. When the filament is electron-depleted, the oxygen diffusion into the filament, which corresponds to the OFF state, becomes thermodynamically unstable near Al, indicating strong implications on the OFF state retention. On the other hand, oxygen vacancies far away from Al showed similar characteristics as in undoped HfOx, with gradually decreasing barriers by the electron depletion process under the electric field. Therefore, a potential solution to address both ON and OFF state retention improvement is to consider using Al partial doping only near the inert electrode device region. This will facilitate the filament growing process at lower forming voltages and help with the ON state retention. At the same time, it will prohibit the influence of Al on the active switching area and therefore eliminate the OFF state retention degradation issue.

A true random number generator using write speed variation of oxide-based RRAM is proposed for the first time. The signal of this physical unclonable function (PUF) is strong with long duration to be easily and accurately captured by simple circuit, of which the advantage is attributed to the mechanism that the speed variation amplifies the fluctuation of oxygen vacancy trap and de-trap. Some function parts of normal RRAM IP can be reused as entropy source cells and implementation circuit. The variation of write end point is monitored by a self-adaptive write drive circuit to trig a counter, and then serialized into a bit stream. The test chips, which are AlOx/WOx bilayer back-end RRAM fabricated in 0.18 Um logic process, passed all NIST tests with advantages of small area, low power, and not using post-processor corrector. Enough bits can be generated within the endurance limitation to ensure usual Internet of Things (IoT) security application.

The area, temperature (160–300 K), and bias polarity dependences of the I – V curves of the self-rectifying n+Si-HfO2–Ni resistance random access memory (RRAM) have been measured systematically. The complementary nonrectifying p+Si-HfO2–Ni RRAM I – V data are also provided for reference. To explain all experimental data, three resistances in series in the RRAM device: 1) the Si-HfO2 contact resistance R \(_{\mathrm {Si-HfO}}\) ; 2) the HfO2 dielectric resistance R HfO; and 3) the HfO2– \(Ni\) contact resistance R HfO-Ni must be considered on an equal footing. Previously reported first principle calculation results for the density of states of the monoclinic HfO2 grain boundary with high and low densities of oxygen vacancy V \(_{O}^{0}\) are adopted for describing the conductive filament resistance R HfO of the dielectric at low- and high-resistance states. The temperature dependence of I – V is controlled by three different energy barriers: Schottky-like barrier, multiphonon trap assisted tunneling barrier, and multiphonon deep trap capture barrier ( E CAPTURE). It is demonstrated that all experimental data can be explained in a natural and unified way. This model is valuable not only for understanding the conduction mechanism, but also for guiding the future self-rectifying RRAM technology development.