High-Speed and Low-Energy Nitride Memristors Choi, Byung Joon; Torrezan, Antonio C.; Strachan, John Paul ...
Advanced functional materials,
August 2, 2016, Letnik:
26, Številka:
29
Journal Article
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High‐performance memristors based on AlN films have been demonstrated, which exhibit ultrafast ON/OFF switching times (≈85 ps for microdevices with waveguide) and relatively low switching current ...(≈15 μA for 50 nm devices). Physical characterizations are carried out to understand the device switching mechanism, and rationalize speed and energy performance. The formation of an Al‐rich conduction channel through the AlN layer is revealed. The motion of positively charged nitrogen vacancies is likely responsible for the observed switching.
Ultrafast switching of an AlN memristor: ON switching is acheived using an 85 ps positive voltage pulse, and OFF switching using an 85 ps negative voltage pulse on the Al electrode of a Pt/AlN/Al memristor stack. A relatively low switching current (≈15 μA for 50 nm devices) has also been demonstrated in these memristors based on AlN films. The formation of an Al‐rich conduction channel through the AlN layer is revealed.
We report the growth of erbium monoantimonide (ErSb) thin films on indium antimonide (100) substrates by low-pressure metalorganic chemical vapor deposition. The growth rate of ErSb thin films shows ...strong dependency on the growth temperature and the Sb/Er precursor molar flow rate ratio. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffractometry (XRD) were employed to study the ErSb thin films grown under the growth conditions that gave the maximum growth rate in the range we investigated. We also report the growth of two types of nanocomposites in which ErSb nanocolumns or nanoslabs with lengths ~500 nm and diameters 20 nm to 30 nm are embedded in Zn-doped InGaSb (ErSb/InGaSb:Zn) and ErSb nanoparticles with diameters of ~30 nm are embedded in Zn-doped InSbAs (ErSb/InSbAs:Zn). These nanocomposites were intended to increase phonon scattering in a mid-to-long phonon wavelength range to reduce lattice thermal conductivity. We used time-domain thermoreflectance to measure total thermal conductivity for the two types of nanocomposites, obtaining 4.0 ± 0.6 W/mK and 6.7 ± 0.8 W/mK for the ErSb/InAsSb:Zn and ErSb/InGaSb:Zn nanocomposites, respectively, which suggests that the thermal conductivity was close to or slightly smaller than the alloy limit of the two ternary alloy hosts. The two nanocomposites were further studied by transmission electron microscopy (TEM) to reveal their microscopic features and by XRD to assess their crystalline structures.
Caveolae are plasma membrane invaginations that may play an important role in numerous cellular processes including transport, signaling, and tumor suppression. By targeted disruption of caveolin-1, ...the main protein component of caveolae, we generated mice that lacked caveolae. The absence of this organelle impaired nitric oxide and calcium signaling in the cardiovascular system, causing aberrations in endothelium-dependent relaxation, contractility, and maintenance of myogenic tone. In addition, the lungs of knockout animals displayed thickening of alveolar septa caused by uncontrolled endothelial cell proliferation and fibrosis, resulting in severe physical limitations in caveolin-1-disrupted mice. Thus, caveolin-1 and caveolae play a fundamental role in organizing multiple signaling pathways in the cell.
The steady‐state solution of filamentary memristive switching may be derived directly from the heat equation, modelling vertical and radial heat flow. This solution is shown to provide a continuous ...and accurate description of the evolution of the filament radius, composition, heat flow, and temperature during switching, and is shown to apply to a large range of switching materials and experimental time‐scales.
Previous computational models of self-replication using cellular automata (CA) have been manually designed, a difficult and time-consuming process. We show here how genetic algorithms can be applied ...to automatically discover rules governing self-replicating structures. The main difficulty in this problem lies in the choice of the fitness evaluation technique. The solution we present is based on a multiobjective fitness function consisting of three independent measures: growth in number of components, relative positioning of components, and the multiplicity of replicants. We introduce a new paradigm for CA models with weak rotational symmetry, called orientation-insensitive input, and hypothesize that it facilitates discovery of self-replicating structures by reducing search-space sizes. Experimental yields of self-replicating structures discovered using our technique are shown to be statistically significant. The discovered self-replicating structures compare favorably in terms of simplicity with those generated manually in the past, but differ in unexpected ways. These results suggest that further exploration in the space of possible self-replicating structures will yield additional new structures. Furthermore, this research sheds light on the process of creating self-replicating structures, opening the door to future studies on the discovery of novel self-replicating molecules and self-replicating assemblers in nanotechnology.
The evaluation of palpebral laxity can be performed by the distraction test (DT). Although widely used in ophthalmologic practice, there is no consensus about the results considered normal by the ...test. The objectives of this study are to obtain the value of DT in a group of individuals with healthy eyelids and to compare with the measurements in subjects with senile ectropion.
Lower eyelid DT was performed in 200 individuals without any eyelid pathology and in 30 individuals with lower lid ectropion. The results were analyzed by age and sex in the control group and compared with the results of the ectropion group.
The mean value of DT in the control group was 6.96 mm, lower than in the ectropion group (9.48 mm) (p < 0.001). In the control group, the mean female DT was 6.70 mm, while the male was 7.22 mm. There were differences in the DT values in the subgroups of 20-39 and 40-59-year old according to gender, with men presenting higher measurements than women. In the other age subgroups, both genders presented similar DT values. Even when considering only individuals in the control group with the same range of age as in the ectropion group, the DT value was higher in individuals with ectropion (7.23 and 9.48 mm, respectively, p < 0.001).
The mean DT value is 6.96 mm; however, the measurement varies according to age and sex in people without palpebral pathology. Individuals with senile eyelid ectropion present higher measurements than healthy ones.In this study, the authors performed the eyelid distraction test in 200 healthy individuals, bringing to the literature the new information that there is a variability of the normal test's value regarding age and gender.
Recent advancements in molecular genetics raise the possibility that therapeutics or a ‘cure’ for Down syndrome (DS) may become available. However, there are no data regarding how parents of children ...with DS perceive the possibility of mitigating specific manifestations such as the intellectual disability (ID) associated with DS, or curing the condition entirely. To explore these issues, we distributed a questionnaire to members of the Lower Mainland Down Syndrome Society in British Columbia, Canada. Questionnaires were completed by 101 parents (response rate = 41%). A majority (61%) viewed the possibility of reversing ID in DS positively, but only 41% said that they would ‘cure’ their child of DS if it were possible. Twenty‐seven percent of respondents said they would not ‘cure’ their child, and 32% were unsure if they would ‘cure’ their child. The most commonly cited motivation for opting for a ‘cure’ was to increase their child's independence. However, parental attitudes' towards a ‘cure’ for DS were complex, affected by ethical issues, perceived societal values, and pragmatic factors such as the age of the individual and long‐term care‐giving burden. These findings could be used by healthcare professionals supporting families who include a member with DS and to direct future research.
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