Spatially extended nature of resistive switching in perovskite oxide thin films

We report the direct observation of the electric pulse induced resistance-change (EPIR) effect at the nano scale on La1-xSrxMnO3 (LSMO) thin films by the current measurement AFM technique. After a switching voltage of one polarity is applied across the sample by the AFM tip, the conductivity in a local nanometer region around the AFM tip is increased, and after a switching voltage of the opposite polarity is applied, the local conductivity is reduced. This reversible resistance switching effect is observed under both continuous and short pulse voltage switching conditions. It is important for future nanoscale non-volatile memory device applications.Comment: 11 pages, 3 figure

Electrically Variable or Programmable Nonvolatile Capacitors

Electrically variable or programmable capacitors based on the unique properties of thin perovskite films are undergoing development. These capacitors show promise of overcoming two important deficiencies of prior electrically programmable capacitors: Unlike in the case of varactors, it is not necessary to supply power continuously to make these capacitors retain their capacitance values. Hence, these capacitors may prove useful as components of nonvolatile analog and digital electronic memories. Unlike in the case of ferroelectric capacitors, it is possible to measure the capacitance values of these capacitors without changing the values. In other words, whereas readout of ferroelectric capacitors is destructive, readout of these capacitors can be nondestructive. A capacitor of this type is a simple two terminal device. It includes a thin film of a suitable perovskite as the dielectric layer, sandwiched between two metal or metal oxide electrodes (for example, see Figure 1). The utility of this device as a variable capacitor is based on a phenomenon, known as electrical-pulse-induced capacitance (EPIC), that is observed in thin perovskite films and especially in those thin perovskite films that exhibit the colossal magnetoresistive (CMR) effect. In EPIC, the application of one or more electrical pulses that exceed a threshold magnitude (typically somewhat less than 1 V) gives rise to a nonvolatile change in capacitance. The change in capacitance depends on the magnitude duration, polarity, and number of pulses. It is not necessary to apply a magnetic field or to cool the device below (or heat it above) room temperature to obtain EPIC. Examples of suitable CMR perovskites include Pr(1-x)Ca(x)MnO3, La(1-x)S-r(x)MnO3,and Nb(1-x)Ca(x)MnO3. Figure 2 is a block diagram showing an EPIC capacitor connected to a circuit that can vary the capacitance, measure the capacitance, and/or measure the resistance of the capacitor

Buffer-Enhanced Electrical-Pulse-Induced-Resistive Memory Effect in Thin Film Perovskites

A multilayer perovskite thin film resistive memory device has been developed comprised of: a Pr0.7Ca0.3MnO3 (PCMO) perovskite oxide epitaxial layer on a YBCO bottom thin film electrode; a thin yttria stabilized zirconia (YSZ) buffer layer grown on the PCMO layer, and a gold thin film top electrode. The multi-layer thin film lattice structure has been characterized by XRD and TEM analyses showing a high quality heterostructure. I-AFM analysis indicated nano granular conductivity distributed uniformly throughout the PCMO film surface. With the addition of the YSZ buffer layer, the pulse voltage needed to switch the device is significantly reduced and the resistance-switching ratio is increased compared to a non-buffered resistance memory device, which is very important for the device fabrication. The magnetic field effect on the multilayer structure resistance at various temperatures shows CMR behavior for both high and low resistance states implying a bulk material component to the switch behavior.Comment: 16 pages, 4 figure

Implementation of the Flipped Classroom Combined with Problem-Based Learning in a Medical Nursing Course: A Quasi-Experimental Design

Background: Medical Nursing is one of the most important core courses in nursing education, and the emergence of the flipped classroom has made up for the shortcomings of traditional teaching and improved the effectiveness of teaching. However, it is worth exploring how to maximize the effect of students’ self-study before class while making full use of classroom teaching to promote the cultivation of students’ abilities, so that the flipped classroom can have a maximal teaching effect. Therefore, this study explored the effect of a flipped-classroom teaching mode based on a small private online course (SPOC) combined with problem-based learning (PBL) in a course of Medical Nursing. Methods: Nursing undergraduates from the years 2018 (control group) and 2019 (experimental group), respectively, used the traditional lecture method and the flipped-classroom teaching mode based on a SPOC combined with PBL. The teaching effect was evaluated by teaching-mode-recognition evaluation, critical thinking measurement, and academic achievement. Results: The scores of teaching-mode recognition evaluated by the students in the experimental group were higher than those in the control group in the following five aspects: “helping to improve learning interest” (p = 0.003), “helping to improve autonomous learning ability” (p = 0.002), “helping to improve communication and cooperation ability” (p p = 0.012), and “helping to promote self-perfection and sense of achievement” (p = 0.001). Compared with the control group, the score on the “analytical ability” dimension of the Critical Thinking Disposition Inventory in the experimental group was higher (p = 0.030). The excellent rates of the final theoretical examination (p = 0.046) and comprehensive case analysis (p = 0.046) in the experimental group were higher than those in the control group. Conclusions: The flipped-classroom teaching mode based on a SPOC combined with PBL can promote students’ abilities of autonomous learning, communication and cooperation, and clinical and critical thinking; improves their academic performance; and is recognized and welcomed by them. However, to extend the flipped-classroom teaching model of a SPOC combined with PBL to other nursing education courses, more optimization and evaluation are required