Combination Of Low Voltage Research Articles

ULTRARAM: A Low‐Energy, High‐Endurance, Compound‐Semiconductor Memory on Silicon

AbstractULTRARAM is a nonvolatile memory with the potential to achieve fast, ultralow‐energy electron storage in a floating gate accessed through a triple‐barrier resonant tunneling heterostructure. Here its implementation is reported on a Si substrate; a vital step toward cost‐effective mass production. Sample growth using molecular beam epitaxy commences with deposition of an AlSb nucleation layer to seed the growth of a GaSb buffer layer, followed by the III–V memory epilayers. Fabricated single‐cell memories show clear 0/1 logic‐state contrast after ≤10 ms duration program/erase pulses of ≈2.5 V, a remarkably fast switching speed for 10 and 20 µm devices. Furthermore, the combination of low voltage and small device capacitance per unit area results in a switching energy that is orders of magnitude lower than dynamic random access memory and flash, for a given cell size. Extended testing of devices reveals retention in excess of 1000 years and degradation‐free endurance of over 107 program/erase cycles, surpassing very recent results for similar devices on GaAs substrates.

Effect of Processing Parameters on the Diameter and Morphology of Electrospun Iron-Modified Montmorillonite (Fe-MMT)/Polycaprolactone Nanofibers

Iron-modified montmorillonite-filled polycaprolactone nanofiber mats were produced via electrospinning with varying applied voltage, flow rate, needle-tip-to-collector distance, and needle diameter. Scanning electron microscopy (SEM) was used to observe fiber morphology and characteristics. The effects of varying process parameters on various fiber characteristics were evaluated using a two-level fractional factorial experimental design. The effect of voltage on fiber diameter differed with varying flow rate. At 32 ml/hr, the average fiber diameter decreased from 518.38 nm ± 289.37 nm to 466.43 nm ± 312.36 nm when the voltage is increased. At 42 ml/hr the effect of voltage on fiber diameter was reversed. The average fiber diameter was also found to decrease from 516.03 nm ± 283.48 nm to 467.96 nm ± 318.07 nm with decreasing tip-to-collector distance at 32 mL/hr flow rate. The variation of the effect of the factors on fiber diameter was mainly due to a significant loss of material observed at 12 kV and 15 cm tip-to-collector distance. Bead formation was observed for all runs with more beads being formed at 12 kV applied voltage and 15 cm tip-to-collector distance. Spherical beads were observed at 12 kV and 15 cm tip-to-collector distance while spindle-like beads were present in nanofiber membranes spun at high voltage and at the combination of low voltage and low tip-to-collector distance. The parameter setting combination of 19 kV, 32 ml/hr flow rate, 10 cm tip-to-collector distance, and 0.514 mm needle diameter yielded the lowest fiber diameter with the least amount of beading and small bead size. Small fiber diameters and less beading provide larger surface area and more exposure of the Fe-MMT particles for more efficient adsorption.

The Findings of Electrocardiography in Patients with Cardiac Amyloidosis

The electrocardiography (ECG) was the simplest and common adjunctive diagnostic tool for cardiac amyloidosis (CA). We sought to clarify the findings of ECG in patients with CA in order to early identification of CA according to the findings of ECG. A total of 276 patients with diagnosis of systemic amyloidosis admitted to Peking Union Medical College Hospital from January 2000 to December 2011, were enrolled. Two groups were classified according to the cardiac involvement or not, namely CA (n = 189) and control (n = 87) groups. The low voltage on limb leads defined by the amplitude of the QRS complex in each limb leads ≤0.5 mV. The pseudo-infarct pattern defined by the presence of pathologic Q waves on at least two contiguous leads on ECG without obstructive coronary artery disease. The mean age was 55± 12 (15-88) years, 168 patients (61%) were male. Atrial arrhythmia (15.9% vs 3.4%, P = 0.003), low voltage on limb leads (54.5% vs 20.7%, P<0.001), atrioventricular block (14.8% vs 1.1%, P = 0.001) and pseudo-infarct pattern (40.2% vs 4.6%, P<0.001) were more prevalent in CA than control groups. The combination of low voltage on limb leads and pseudo-infarct pattern was more common (28.0% vs 2.3%, P<0.001) in CA than control groups. The sensitivity, specificity, positive and negative predictive values of the presence of low voltage on limb leads and pseudo-infarct pattern for the diagnosis of CA were 28%, 98%, 96%, and 39%, respectively. In CA patients, low voltage on limb leads and pseudo-infarct pattern were the most common ECG findings. Atrial arrhythmia and atrioventricular block were the most common arrhythmias in CA patients. The combination of low voltage on limb leads and pseudo-infarct pattern had high specificity and positive predictive value for the diagnosis of CA.

On Detection of Resistive Bridging Defects by Low-Temperature and Low-Voltage Testing

Test application at reduced power supply voltage (low-voltage testing) or reduced temperature (low-temperature testing) can improve the defect coverage of a test set, particularly of resistive short defects. Using a probabilistic model of two-line nonfeedback short defects, we quantify the coverage impact of low-voltage and low-temperature testing for different voltages and temperatures. Effects of statistical process variations are not considered in the model. When quantifying the coverage increase, we differentiate between defects missed by the test set at nominal conditions and undetectable defects (flaws) detected at non nominal conditions. In our analysis, the performance degradation of the device caused by lower power supply voltage is accounted for. Furthermore, we describe a situation in which defects detected by conventional testing are missed by low-voltage testing and quantify the resulting coverage loss. Experimental results suggest that test quality is improved even if no cost increase is allowed. If multiple test applications are acceptable, a combination of low voltage and low temperature turns out to provide the best coverage of both hard defects and flaws.