Optically and Electrically Controllable Light-Emitting Nonvolatile Resistive Switching Memory

Resistive switching memory (RSM) emerges as a decisive player for the future development of semiconductor industry due to its many advantages, such as high speed, cost effectiveness, excellent scalability, and compatibility with current technology. However, the electrical reading of the RSM array is usually in series sequence, which limits its maximum data storage density and processing speed. This drawback can be overcome by optically readable memory devices. Herein, we demonstrate an unprecedented optically and electrically controllable light-emitting RSM. This device uses a tandem structure which is composed of a light-emitting RSM and a perovskite solar cell. The state of the device can be encoded both electrically and optically, with high-resistive state and low-resistive state. Interestingly, the device exhibits electroluminescence in the low-resistive state, which provides the capability for reading the encoded signal optically. By integrating with a solar cell, the whole device enables to assist on the light-emitting RSM to achieve the unique feature of optical writing. Compared with conventional memory, our designed device with multiple functionalities of optical/electrical encoding and electrical/optical reading should be very useful and timely for the development of next-generation information technology

Multifunctional Controllable Two-Terminal Vertical Nonvolatile Memory Transistor

An electrically, magnetically, and temperature controllable two-terminal nonvolatile memory transistor with a vertical topology has been designed, fabricated, and demonstrated. This intriguing memory transistor is composed of a nonvolatile resistive random-access memory (RRAM) of the layered structure of indium–tin oxide/poly­(methyl methacrylate)/Ag in tandem with a micropyramid-structured magneto-electric film supported by a 150 μm thick partition. The magneto-electric film is made of FeNi (or CrO2)/polydimethylsiloxane composite covered with silver nanowires and can be brought in contact with the top Ag electrode of the RRAM, forming a magneto-electric device through applying an appropriate magnetic field strength. The output current of the proposed device can be regulated when the electric voltage and magnetic field are active simultaneously, a unique property enabling versatile functionalities. When using CrO2, the demagnetization property of CrO2 upon heating allows this device to produce an additional thermal induction and optically controllable capability. Additionally, this memory transistor has several outstanding features, including cost effectiveness, fast response time, touchless control, and mechanical flexibility. All these characteristics enable to diversify the applications of our designed nonvolatile memory transistor in several emerging technologies, including communications, touchless devices, and wearable electronics

Ultrafast and Ultrasensitive Gas Sensors Derived from a Large Fermi-Level Shift in the Schottky Junction with Sieve-Layer Modulation

Gas sensors play an important role in numerous fields, covering a wide range of applications, including intelligent systems and detection of harmful and toxic gases. Even though they have attracted much attention, the response time on the order of seconds to minutes is still very slow. To circumvent the existing problems, here, we provide a seminal attempt with the integration of graphene, semiconductor, and an addition sieve layer forming a nanocomposite gas sensor with ultrahigh sensitivity and ultrafast response. The designed sieve layer has a suitable band structure that can serve as a blocking layer to prevent transfer of the charges induced by adsorbed gas molecules into the underlying semiconductor layer. We found that the sensitivity can be reduced to the parts per million level, and the ultrafast response of around 60 ms is unprecedented compared with published graphene-based gas sensors. The achieved high performance can be interpreted well by the large change of the Fermi level of graphene due to its inherent nature of the low density of states and blocking of the sieve layer to prevent charge transfer from graphene to the underlying semiconductor layer. Accordingly, our work is very useful and timely for the development of gas sensors with high performance for practical applications

Electrically Driven White Light Emission from Intrinsic Metal–Organic Framework

Light-emitting diodes (LEDs) have drawn tremendous potential as a replacement of traditional lighting due to its low-power consumption and longer lifetime. Nowadays, the practical white LEDs (WLED) are contingent on the photon down-conversion of phosphors containing rare-earth elements, which limits its utility, energy, and cost efficiency. In order to resolve the energy crisis and to address the environmental concerns, designing a direct WLED is highly desirable and remains a challenging issue. To circumvent the existing difficulties, in this report, we have designed and demonstrated a direct WLED consisting of a strontium-based metal–organic framework (MOF), {[Sr­(ntca)­(H₂O)₂]·H₂O}_<i>n</i> (<b>1</b>), graphene, and inorganic semiconductors, which can generate a bright white light emission. In addition to the suitable design of a MOF structure, the demonstration of electrically driven white light emission based on a MOF is made possible by the combination of several factors including the unique properties of graphene and the appropriate band alignment between the MOF and semiconductor layer. Because electroluminescence using a MOF as an active material is very rare and intriguing and a direct WLED is also not commonly seen, our work here therefore represents a major discovery which should be very useful and timely for the development of solid-state lighting

”Får jag också fråga en varför-fråga?” En studie om elevers upplevelse av ett skolprojekt

Syftet med detta arbete är att få syn på och försöka förstå elevers perspektiv gällande ett skolprojekt som de varit delaktiga i under höstterminen 2011. Skolprojektets tema var ”Människan och samhället” och dess syfte var att ge eleverna möjlighet att uttrycka sig med hjälp av och prova på olika estetiska gestaltningsformer. Skolprojektet avslutades i en hybridutställning. Vår emperi består av material insamlat under skolprojektets gång, så som filmade klassrumssituationer, elevers loggboksanteckningar och elevutvärderingar. Dessutom genomförde vi efteråt fem kvalitativa semi-strukturerade intervjuer med elevinformanter som deltagit i skolprojektet. Det empiriska materialet kommer vi sätta i relation till begrepp som estetik, kreativitet och deltagar- och åskådarkultur. I vårt arbete kan vi se att de flesta eleverna upplever det som något lustfullt och roligt att jobba med estetiska uttrycksformer – så länge det inte betyder att de behöver reflektera eller diskutera sina produktioner. Detta ser vi som en direkt konsekvens av den skolkontext de är vana vid, där ett prövande och ifrågassättande arbetssätt inte präglar elevernas uppfattning om vad skolan kräver av dem. I vårt arbete analyserar vi också denna uppfattning och hur den kan tyckas vara ett resultat av ”de rätta svarens pedagogik”. Det vi kommer fram till är att det är komplext att kartlägga elevers upplevelser; begreppen räcker kanske inte till för att få syn på elevers perspektiv

Biomimetic Synthesis of Nacrelike Faceted Mesocrystals of ZnO−Gelatin Composite

A fabrication of ZnO hierarchical mesocrystal was achieved by a biomimetic method using gelatin as structure-directing agent. It was found that the ZnO−gelatin microcrystal with well-defined hexagonal twin plate shape is built by the stacking of nanoplates. The irregularly edged nanoplates can adjust themselves to each other throughout the microcrystal, resulting in a roughly hexagonal edge. Selected area electron diffraction (SAED) analysis of the ZnO−gelatin microcrystal demonstrates that all the stacked nanoplates are aligned and oriented to form a single-crystal structure with hexagonal symmetry. The hierarchical structure of ZnO was found to resemble that of naturally occurring nacre. Similar to nacreous architecture, the nanoplate of ZnO was constructed from the oriented attachment of ZnO nanoparticles. More importantly, the lattices of the stacked nanoplates are aligned through mineral bridges between neighboring plates. A mechanism scheme is proposed for the formation of the gelatin−ZnO hybrid hierarchical structure. The preserved hexagonal shape of the mesocrystal structure consequently results in a whispering gallery mode (WGM) of optical emission where light was confined in the hexagons by total internal reflection. The observation of WGM mode emission in the ZnO hexagon structure shows promises for nanoscale fabrication of optoelectronic devices

Electrically Driven White Light Emission from Intrinsic Metal–Organic Framework

Light-emitting diodes (LEDs) have drawn tremendous potential as a replacement of traditional lighting due to its low-power consumption and longer lifetime. Nowadays, the practical white LEDs (WLED) are contingent on the photon down-conversion of phosphors containing rare-earth elements, which limits its utility, energy, and cost efficiency. In order to resolve the energy crisis and to address the environmental concerns, designing a direct WLED is highly desirable and remains a challenging issue. To circumvent the existing difficulties, in this report, we have designed and demonstrated a direct WLED consisting of a strontium-based metal–organic framework (MOF), {[Sr­(ntca)­(H₂O)₂]·H₂O}_<i>n</i> (<b>1</b>), graphene, and inorganic semiconductors, which can generate a bright white light emission. In addition to the suitable design of a MOF structure, the demonstration of electrically driven white light emission based on a MOF is made possible by the combination of several factors including the unique properties of graphene and the appropriate band alignment between the MOF and semiconductor layer. Because electroluminescence using a MOF as an active material is very rare and intriguing and a direct WLED is also not commonly seen, our work here therefore represents a major discovery which should be very useful and timely for the development of solid-state lighting

Media 4: Optically tunable and detectable magnetoelectric effects in the composite consisting of magnetic thin films and InGaN/GaN multiple quantum wells

Originally published in Optics Express on 26 August 2013 (oe-21-17-19934

Media 1: Optically tunable and detectable magnetoelectric effects in the composite consisting of magnetic thin films and InGaN/GaN multiple quantum wells

Originally published in Optics Express on 26 August 2013 (oe-21-17-19934