On the stochastic nature of resistive switching in Cu doped Ge0.3Se0.7 based memory devices

Currently, there is great interest in using solid electrolytes to develop resistive switching based nonvolatile memories (RRAM) and logic devices. Despite recent progress, our understanding of the microscopic origin of the switching process and its stochastic behavior is still limited. In order to understand this behavior, we present a statistical "breakdown" analysis performed on Cu doped Ge0.3Se0.7 based memory devices under elevated temperature and constant voltage stress conditions. Following the approach of electrochemical phase formation, the precursor of the "ON resistance switching" is considered to be nucleation - the emergence of small clusters of atoms carrying the basic properties of the new phase which forms the conducting filament. Within the framework of nucleation theory, the observed fluctuations in the time required for "ON resistance switching" are found to be consistent with the stochastic nature of critical nucleus formation. (C) 2011 American Institute of Physics. [doi:10.1063/1.3631013

Ferroelectricity in Lu doped HfO2 layers

Doped HfO2 has become a promising candidate for non-volatile memory devices since it can beeasily integrated into existing CMOS technology. Many dopants like Y, Gd, and Sr have beeninvestigated for the stabilization of ferroelectric HfO2. Here, we report the fabrication of capacitorscomprising ferroelectric HfO2 metal-insulator-metal structures with TiN bottom and top electrodesusing the dopant Lu. Amorphous 5% Lu doped HfO2 was deposited by pulsed laser deposition andafterwards annealed to achieve the ferroelectric, orthorhombic phase (space group Pbc21). Thepolarization of the layers was confirmed by capacitance-voltage, polarization-voltage, and currentvoltagemeasurements. Depending on the anneal temperature, the remanent polarization changesand the initial state of the oxide varies. The layer exhibits initially a pinched hysteresis up to anannealing temperature of 600 °C and an unpinched hysteresis at 700 °C. The maximum polarizationis about 11 lC/cm2 which is measured after 104 cycles and stable up to 106 cycles. The influence ofthe layer thickness on the oxide properties is investigated for 10–40 nm thick HfLuO; however, athickness dependence of the ferroelectric properties is not observed. Published by AIP Publishing

Characterization of epitaxial lanthanum lutetium oxide thin films prepared by pulsed-laser deposition as an alternative gate dielectric

Launch of the National Stroke Foundation stroke awareness campaigns has occurred annually during Stroke Week (September) since 2004. From 2006, the campaign used FAST (Face, Arm, Speech, Time) with calling an ambulance added in 2007. The aim of this study was to explore the impact of these campaigns on ambulance dispatches for stroke (Medical Priority Dispatch Card 28) in Melbourne, Australia.A cross-sectional study examining the monthly proportions of ambulance dispatches for stroke between August 1999 and 2010 was conducted. The proportions of dispatches for stroke were used due to increases in the population and in ambulance dispatches over the study period. These proportions were statistically compared for the month before Stroke Week (August) and the month after Stroke Week (October) for each year and seasonal variation was examined.Between 1999 and 2009, the annual proportion of dispatches for stroke increased from 2.1% (n=4327) to 2.95% (n=9918). When stroke dispatches in August were compared with those in October, a significant increase in October was only detected since the call an ambulance message was added to FAST: 2007 (2.62% to 3.00%, P=0.006), 2008 (2.62% to 3.05%, P=0.003), and 2009 (2.70% to 3.09%, P=0.007). From 2005, the peak season for stroke dispatches shifted from winter to spring.Ambulance dispatches for stroke significantly increased after the National Stroke Foundation campaigns began, particularly in years receiving greater funding and featuring the FAST symptoms and the message to call an ambulance. Monitoring ambulance use appears to be an effective measure of campaign penetration