Wide-band-gap oxides such as SrTiO3 are shown to be critical tests of theories of Schottky barrier heights based on metal-induced gap states and charge neutrality levels. This theory is reviewed and used to calculate the Schottky barrier heights and band offsets for many important high dielectric constant oxides on Pt and Si. Good agreement with experiment is found for barrier heights. The band offsets for electrons on Si are found to be small for many key oxides such as SrTiO3 and Ta2O5 which limit their utility as gate oxides in future silicon field effect transistors. The calculations are extended to screen other proposed oxides such as BaZrO3. ZrO2, HfO2, La2O3, Y2O3, HfSiO4, and ZrSiO4. Predictions are also given for barrier heights of the ferroelectric oxides Pb1−xZrxTiO3 and SrBi2Ta2O9 which are used in nonvolatile memories.

Band offsets of wide-band-gap oxides and implications for future electronic devices

This review covers important advances in recent years in the physics of thin-film ferroelectric oxides, the strongest emphasis being on those aspects particular to ferroelectrics in thin-film form. The authors introduce the current state of development in the application of ferroelectric thin films for electronic devices and discuss the physics relevant for the performance and failure of these devices. Following this the review covers the enormous progress that has been made in the first-principles computational approach to understanding ferroelectrics. The authors then discuss in detail the important role that strain plays in determining the properties of epitaxial thin ferroelectric films. Finally, this review ends with a look at the emerging possibilities for nanoscale ferroelectrics, with particular emphasis on ferroelectrics in nonconventional nanoscale geometries.

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Physics of thin-film ferroelectric oxides

Two-dimensional (2D) materials, such as molybdenum disulfide (MoS2), have been shown to exhibit excellent electrical and optical properties. The semiconducting nature of MoS2 allows it to overcome the shortcomings of zero-bandgap graphene, while still sharing many of graphene’s advantages for electronic and optoelectronic applications. Discrete electronic and optoelectronic components, such as field-effect transistors, sensors, and photodetectors made from few-layer MoS2 show promising performance as potential substitute of Si in conventional electronics and of organic and amorphous Si semiconductors in ubiquitous systems and display applications. An important next step is the fabrication of fully integrated multistage circuits and logic building blocks on MoS2 to demonstrate its capability for complex digital logic and high-frequency ac applications. This paper demonstrates an inverter, a NAND gate, a static random access memory, and a five-stage ring oscillator based on a direct-coupled transistor logic...

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Integrated Circuits Based on Bilayer MoS2 Transistors

Nanomedicine in cancer therapy: challenges, opportunities, and clinical applications.

Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review, we outline some of the progressive milestones in this stimulating field, especially for those single-phase multiferroics where magnetism and ferroelectricity coexist. First, we highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we summarize various strategies used to combine the two types of order. Special attention is paid to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry; (2) the ferroelectricity originating from the charge-ordered states; and (3) the ferrotoroidic system. Then, we address the elementary excitations such as electromagnons, and the application potentials of multiferroics. Finally, open questions and future research opportunities are proposed.

Multiferroicity: the coupling between magnetic and polarization orders

Inorganic nanoparticles for cancer imaging and therapy.

Properties of integrated sol-gel PZT thin-films of various Zr/Ti ratios, evaluated as a function of processing parameters, are presented and discussed. The substrate materials for the PZT depositions encompassed Pt, Si, and GaAs. The design, fabrication, and operation of a single PZT element combined with the GaAs JFET planar integrated circuit technology to produce non-volatile programmable random access memories (NVPRAM) are presented.

Integrated sol-gel PZT thin-films on Pt, Si, and GaAs for non-volatile memory applications

Precursors for layer-structured perovskite thin films of SrBi 2 Ta 2 O 9 (SBT) and SrBi 2 Nb 2 O 9 (SBN) were prepared by the reactions of a strontium-bismuth double methoxyethoxide and tantalum or niobium methoxyethoxide in methoxyethanol, followed by partial hydrolysis. Several spectroscopic techniques, such as 1 H-, 13 C-, and 93 Nb-NMR (nuclear magnetic resonance), and Fourier-transform infrared spectroscopy were used to analyze the arrangement of the metals and oxygen in the precursor molecules. The precursors contained Sr-O-M (where M is Ta or Nb) bonds (i.e., a strontium is connected to two MO 6 octahedra) and Sr-O-Bi bonds with a bismuth atom bonded to the oxygens of the MO 6 octahedron. The arrangement of metals and oxygens was considered to be similar to the layer-structured perovskite crystal sublattice. As a result, the sol-gel-derived SBT thin films crystallized, by rapid thermal annealing in an oxygen atmosphere below 550°C, and they exhibited preferred (115) orientation. The crystallinity improved and the crystallite size increased with temperature up to 700°C. In the case of SBN thin films, a low heating rate (2°C/min) was necessary for the control of the crystallographic (115) orientation, whereas a rate of 200°C/s (rapid thermal annealing) produced films that exhibited c-axis orientation. The (115) SBT thin film, heated to 700°C, exhibited improved ferroelectric properties.

Sol‐Gel Route to Ferroelectric Layer‐Structured Perovskite SrBi2Ta2O9 and SrBi2Nb2O9 Thin Films

Platinum and Pd show a significant difference in work function on SiO2 and high-K materials (HfO2). The effective metal work functions for Pd, Pt, and Re on atomic layer deposited HfO2, which are different from the vacuum work function and important for device threshold voltage control, are measured by the C-V method. The difference is attributed to the dipoles at the metal/HfO2 interface, which is a result of charge transfer across the interface. Moreover, the extracted charge neutrality level and screening parameter are correlated with the phase development, film stoichiometry, and density of interface states at the metal/high-K interface.

Effective work function of Pt, Pd, and Re on atomic layer deposited HfO2

Polymeric sol-gel processing represents an IC technology compatible route to fabricate defect-free and compositionally adjustable inorganic non-metallic thin-films at relatively low temperatures.The critical physico-chemical issues which affect the reproducible fabrication of PZT thin-films are outlined. The low field behavior and the high field switching and stability characteristics of PZT thin-films were studied for radiation hard and nonvolatile memory applications. Performance data of integrated PZT thin-films on solid Pt and sputtered Pt layer on silicon-nitrided GaAs substrates are presented and discussed. A compositionally adjustable low field permittivity of 1200, a dielectric break-down strength exceeding 100 V/μm, ∼1012 polarization reversal cycles, and tm ∼ 100 ns were observed. Compatibility of non-linear PZT thin-film element processing with GaAs JFET planar VLSI technology is addressed.

Sandwip Dey

Papers

Inorganic nanoparticles for cancer imaging and therapy.

Integrated sol-gel PZT thin-films on Pt, Si, and GaAs for non-volatile memory applications

Sol‐Gel Route to Ferroelectric Layer‐Structured Perovskite SrBi2Ta2O9 and SrBi2Nb2O9 Thin Films

Effective work function of Pt, Pd, and Re on atomic layer deposited HfO2

Processing and parameters of sol-gel PZT thin-films for GaAs memory applications