Impact of the precursor chemistry and process conditions on the cell-to-cell variability in 1T-1R based HfO2 RRAM devices.

The Resistive RAM (RRAM) technology is currently in a level of maturity that calls for its integration into CMOS compatible memory arrays. This CMOS integration requires a perfect understanding of the cells performance and reliability in relation to the deposition processes used for their manufacturing. In this paper, the impact of the precursor chemistries and process conditions on the performance of HfO2 based memristive cells is studied. An extensive characterization of HfO2 based 1T1R cells, a comparison of the cell-to-cell variability, and reliability study is performed. The cells' behaviors during forming, set, and reset operations are monitored in order to relate their features to conductive filament properties and process-induced variability of the switching parameters. The modeling of the high resistance state (HRS) is performed by applying the Quantum-Point Contact model to assess the link between the deposition condition and the precursor chemistry with the resulting physical cells characteristics.

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition.

With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 µm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.

The optimal treatment of severe hypertension in pregnancy: update of the role of nicardipine.

OBJECTIVE: Hypertensive disorders in pregnancy remain a major cause of maternal morbidity and mortality. Blood pressure control is essential for maternal and neonatal outcome. Therefore, we analyzed the potency and side effects of two treatment options (nicardipine compared to labetalol) in order to gain insight in improved treatment of severe hypertension during pregnancy and to evaluate the feasibility of a randomised controlled trial. STUDY DESIGN: A nested case control study in an inner city teaching hospital alongside a meta-analysis. Data from women who received nicardipine were compared with patients who received labetalol during pregnancy. Primary outcome measure was successful control of severe hypertension. Secondary outcome measures were maternal and neonatal side effects. These results were included in a meta-analysis. RESULTS: Only one previous study described nicardipine in comparison to labetalol during pregnancy. The combined results indicate a similar success-rate of treatment with nicardipine compared to labetalol during pregnancy. Women treated with nicardipine had more often tachycardia, headache and nausea compared to women treated with labetalol. Hypotension resulting in fetal distress was found more often in the labetalol group. CONCLUSION: Nicardipine is a potent drug to control hypertension during pregnancy with side effects including maternal headaches, nausea and tachycardia. Labetalol had more neonatal side effects including hypotension compared with nicardipine. These results support the justification and prove that it is safe to perform a randomized controlled trial comparing nicardipine to labetalol in the treatment of severe hypertension in pregnancy.

[Metformin, renal function and lactate: the MetClear Study]. / Metformine, nierfunctie en lactaat: het MetClear-onderzoek.

OBJECTIVE: To map the relation between metformin prescription and renal function in an outpatient setting. To investigate whether there is an association between renal function, metformin concentration and lactate concentration. DESIGN: Pilot for a prospective observational cohort study. METHOD: We included outpatients with diabetes mellitus type 2 who were treated with metformin. At inclusion, we determined the HbA1c, lactate, metformin and creatinine concentrations and the estimated glomerular filtration rate (eGFR). Information on the prescribed dosage of metformin was acquired from patient files. Our primary outcome measure was the number of patients in whom the dose was not adjusted to the renal function. Our secondary outcome measure was the difference in median lactate concentration between patients with a normal (≤ 2.5 mg/l) and an increased (> 2.5 mg/l) metformin concentration. RESULTS: Eighty-eight patients were included, 12 (14%) of whom had an eGFR ≤ 30, 31 (36%) an eGFR of 30-50 and 44 (50%) an eGFR > 51 ml/min/1.73 m2. In 27 (31%) of all patients, the daily dose of metformin exceeded the dose recommended in the practice guidelines. The 28 patients with an increased metformin concentration had a significantly higher median lactate concentration: 2.3 mmol/l compared to 1.5 mmol/l for the 60 patients with a normal metformin concentration (p < 0.0001). CONCLUSION: Our study shows that in outpatient practice, the metformin dose is not sufficiently adjusted to a reduced renal function in 31% of the patients. The accumulation of metformin appears to be associated with an increased lactate concentration and a reduced renal function. Extra attention to the dose of metformin in reduced renal clearance is therefore recommended.