Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

http://chialvo.org/Curso/UBACurso/DIA7/Papers/Aono_NatMat_07_Ionic%20Switching%20Memory.pdf

Nanoionics-based resistive switching memories

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

A very sensitive photodector based on molybdenum disulphide with potential for integrated optoelectronic circuits, light sensing, biomedical imaging, video recording or spectroscopy is now demonstrated.

/pdf/ultrasensitive-photodetectors-based-on-monolayer-mos2-2ytu9i2qtp.pdf

Ultrasensitive photodetectors based on monolayer MoS2.

Memristive devices are electrical resistance switches that can retain a state of internal resistance based on the history of applied voltage and current. These devices can store and process information, and offer several key performance characteristics that exceed conventional integrated circuit technology. An important class of memristive devices are two-terminal resistance switches based on ionic motion, which are built from a simple conductor/insulator/conductor thin-film stack. These devices were originally conceived in the late 1960s and recent progress has led to fast, low-energy, high-endurance devices that can be scaled down to less than 10 nm and stacked in three dimensions. However, the underlying device mechanisms remain unclear, which is a significant barrier to their widespread application. Here, we review recent progress in the development and understanding of memristive devices. We also examine the performance requirements for computing with memristive devices and detail how the outstanding challenges could be met.

Memristive devices for computing

Resistive switching in transition metal oxides

We have developed monolithic white light emitting diodes (LEDs), which consist of planar planes and nano size hexagonal pyramids structure. The white spectrum is achieved by blue and yellow emissions from the InGaN multi quantum wells (MQWs) on the planar c-planes and on the nano-pyramids, respectively. The color temperature is tuned from 3600K to 6400K by controlling the relative area ratio of c-plane and nano-pyramids.

Monolithic white LED with controllable color temperature

A novel method of metal-organic chemical vapor deposition (MOCVD) Pb(Zr,Ti)O3 (PZT) has been developed for use in high-density ferroelectric memory device. Well-aligned polycrystalline PZT films were grown onto Iridium bottom electrode by the MOCVD method with tmhd-family precursors in octane-based solvent under oxygen atmosphere at 550°C. Moreover, crystallinity of the PZT films on Ir bottom electrode was improved dramatically by inserting TiAlN barrier layer. It is also investigated the Iridium bottom electrode effect on the PZT in the ways of roughness, grain size, remnant polarization, fatigue and retention properties. Resultantly, highly reliable (111)-oriented PZT capacitors were obtained with 2Pr of 45 μC/cm2 and Vc of 0.8 V through MOCVD method and the interface engineering of the Iridium bottom electrode.

The Effect of Iridium Bottom Electrode on the Characteristics of Pb(Zr,Ti)O3 Films Grown by MOCVD Method

Effects of the PbTiO 3 (PTO) seeding layer on lowering the PZT crystallization temperature and reducing the capacitor stack height, especially PZT thin film, were systematically investigated. For these purposes, PZT film was modified by using the PTO seeding layer. By using the PTO seeding layer; the crystallization temperature of the PZT film was successfully lowered to 550°C. And remanant polarization of PTO-used 100nm thick PZT capacitors measured at 3V was approximately 23 w C/cm 2 , that is 30% higher than that of the PTO-unused PZT capacitors. XRD analysis indicated that the use of the PTO seeding layer remarkably increased the relative intensity of (111) orientation. XRF studies showed that the atomic concentration ratio of Ti-to-Zr was increased by using PTO seeding layers. Necessarily, as the PZT thickness and crystallization temperature are lowered, the thickness of bottom electrode can be reduced as well. Finally, we successfully developed a capacitor stack height of below 400nm, which was comp...

Novel PZT Capacitor Technology for 32Mb and Beyond FRAM Device Using PbTiO 3 Seeding Layer

We have developed a cylindrical TiN/HfO/sub 2//TiN (TIT) capacitor for 70 nm DRAMs application. TIT capacitors with HfO/sub 2/ films deposited by ALD(Atomic Layer Deposition) using Hf(NEtMe)/sub 4/ precursor and O/sub 2/ plasma as a reactant is shown to be applicable to DRAM device below 70 nm design rule for the first time. It shows the thermal budget endurance against back-end process of DRAM device as well as the very low enough Toxeq of about 13 /spl Aring/ to provide the sufficient cell capacitance.

TiN/HfO/sub 2//TiN capacitor technology applicable to 70 nm generation DRAMs

Among various semiconductor devices, electronically active oxide thin film transistors (TFTs) have received considerable attention for a wide range of device applications Double metal-oxide thin film transistor (TFT) shows high photo current as Ilight/Idark >106, a mobility of >10cm2/Vs and high stability under LCD operation condition In this paper, the possibility of a novel application of an optical touch screen which is entirely based on the metal oxide TFT is proposed

U-In Chung

Papers

Monolithic white LED with controllable color temperature

The Effect of Iridium Bottom Electrode on the Characteristics of Pb(Zr,Ti)O3 Films Grown by MOCVD Method

Novel PZT Capacitor Technology for 32Mb and Beyond FRAM Device Using PbTiO 3 Seeding Layer

TiN/HfO/sub 2//TiN capacitor technology applicable to 70 nm generation DRAMs

Oxide based photosensor thin film transistor for interactive display