scholarly journals Interface and surface stabilization of the polarization in ferroelectric thin films

2020 ◽  
Vol 117 (46) ◽  
pp. 28589-28595 ◽  
Author(s):  
Chiara Gattinoni ◽  
Nives Strkalj ◽  
Rea Härdi ◽  
Manfred Fiebig ◽  
Morgan Trassin ◽  
...  
Keyword(s):  
Thin Films ◽  
Density Functional ◽  
Second Harmonic ◽  
Information Storage ◽  
Digital Information ◽  
Polarization Direction ◽  
Strontium Ruthenate ◽  
Precise Control ◽  
Surface And Interface ◽  
Bottom Interface

Ferroelectric perovskites present a switchable spontaneous polarization and are promising energy-efficient device components for digital information storage. Full control of the ferroelectric polarization in ultrathin films of ferroelectric perovskites needs to be achieved in order to apply this class of materials in modern devices. However, ferroelectricity itself is not well understood in this nanoscale form, where interface and surface effects become particularly relevant and where loss of net polarization is often observed. In this work, we show that the precise control of the structure of the top surface and bottom interface of the thin film is crucial toward this aim. We explore the properties of thin films of the prototypical ferroelectric lead titanate (PbTiO3) on a metallic strontium ruthenate (SrRuO3) buffer using a combination of computational (density functional theory) and experimental (optical second harmonic generation) methods. We find that the polarization direction and strength are influenced by chemical and electronic processes occurring at the epitaxial interface and at the surface. The polarization is particularly sensitive to adsorbates and to surface and interface defects. These results point to the possibility of controlling the polarization direction and magnitude by engineering specific interface and surface chemistries.

Hrtem Study of Interface Structure Of Heteroepitaxially Grown GaAs Thin Films on GaAs(l00)

1998 ◽  
Vol 4 (S2) ◽  
pp. 624-625
Author(s):  
Z.R. Dai ◽  
S.R. Chegwidden ◽  
F.S. Ohuchi
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Mechanical Properties ◽  
Second Harmonic ◽  
Interface Structure ◽  
Thermal And Mechanical Properties ◽  
Surface And Interface ◽  
Device Structures ◽  
New Generation ◽  
Related Compounds

GaSe, a member of the III-VI compound semiconductors, and its related compounds have recently gained an considerable attention because of their high non-linear optical coefficients in the infrared ranges, making them candidates for second harmonic generation (SHG) materials[l,2]. While the optical properties of those materials in bulk form are quite promising, poor thermal and mechanical properties preclude their easy applications. In thin film devices, the thermal and mechanical properties are dominated by those of the substrate, therefore, heteroepitaxially grown thin films of GaSe and related materials on substrates such as GaAs, Si and A12O3 should enable their application in device structures. Development of such new generation of materials, however, require fundamental knowledge about the surface and interface structure that play decisive roles in the thin film crystallinity and materials properties.

scholarly journals Production of zinc oxide thin films and crystals in different deposition times and investigation of their structural, optical and electronic properties

2019 ◽  
Vol 37 (1) ◽  
pp. 90-99
Author(s):  
Haleh Kangarlou ◽  
Parisa Esmaili
Keyword(s):  
Thin Films ◽  
Zinc Oxide ◽  
Electronic Properties ◽  
Density Functional ◽  
Colloidal Solution ◽  
Second Harmonic ◽  
Nonlinear Refraction ◽  
Zno Films ◽  
Full Potential ◽  
Band Gap Structure

AbstractAn aqueous colloidal solution was prepared at 80 °C and pH = 9 from suitable chemical compounds to produce zinc oxide (ZnO) crystals and thin films. The ZnO crystals were grown in the colloidal solution under special conditions. Their micrographs showed ZnO rods with hexagonal structure. The number of the rods, increased over time. The ZnO thin films were produced on glass substrates in the same colloidal solution using the chemical bath deposition (CBD) method in different deposition times. The produced films were post-annealed for about one hour at 400 °C. Crystalline structure, phase transitions and nanostructure of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). ZnO wurtzite structure was dominant, and by increasing the deposition time, the films became more crystalline. Nanostructure of the films changed from rod to wire and transformed into pyramid-like structures. Also, morphology of the films changed and re-nucleation ocurred. Optical reflectance was measured in the wavelength of 300 nm to 800 nm with a spectrophotometer. Other optical properties and optical band gaps were calculated using Kramers-Kronig relation on reflectivity curves. Second harmonic generation was calculated by Z-scan technique. Nonlinear refraction and real part of susceptibilities were obtained. Both positive and negative nonlinear refractions appeared in the ZnO films. It is important for the use in optoelectronic devices. Electronic properties were assessed by the full potential linearized augmented plane wave (FP-LAPW) method, within density functional theory (DFT). In this approach, the generalized gradient approximation (GGA) was used for the exchange-correlation potential calculation. The band gap structure and density of states were calculated.

ADSORPTION, DIFFUSION AND GROWTH MODE OF ZnO THIN FILM FROM FIRST PRINCIPLES

2007 ◽  
Vol 21 (11) ◽  
pp. 1891-1901 ◽  
Author(s):  
YANG CHUN ◽  
Y. R. LI ◽  
YU YI
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Density Functional ◽  
Atomic Layer ◽  
Potential Method ◽  
Growth Mode ◽  
Zno Thin Film ◽  
Heteroepitaxial Growth ◽  
Surface And Interface ◽  
Growth Modes

A heteroepitaxial growth model of the ZnO film on sapphire (0001) is calculated by using a plane wave ultrasoft pseudo-potential method based on density functional theory. It is found that interfacial atoms have different diffusivity at 400°C, 600°C and 800°C. The temperature has a decisive effect on the surface and interface structures of ZnO /α- Al 2 O 3 (0001) and on the growth mode of ZnO thin films. In the whole process of the adsorption and growth of ZnO , the diffusivity of O atoms is higher than that of Zn , and the interlayer diffusion has an important impact on the homogeneous growth of thin films. There are two growth modes of ZnO on sapphire (0001), which is further demonstrated by theoretical calculation. The growth mode at about 400°C has a character of mainly spiral-twisted growth with Zn -hexagonal symmetry structure, and it is favorable for forming the Zn -terminated surface. But in the case of 600°C, a regular in-plane growth is observed, which facilitates the O -terminated surface of the ZnO thin film. It can be observed from the calculation that the vacancies of Zn where the atomic layer is near to the α- Al 2 O 3 (0001) surface is more than that of O atoms.

scholarly journals Multiferroic and Optical Properties of La0.05Li0.85NbO3 and LiNbO3 Nanocrystals

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Carlos A. Díaz-Moreno ◽  
Jorge A. López ◽  
Yu Ding ◽  
A. Hurtado Macias ◽  
Chunqiang Li ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Lithium Niobate ◽  
Single Phase ◽  
Permanent Magnets ◽  
Second Harmonic ◽  
Information Storage ◽  
Antireflection Coatings ◽  
Magnetoelectric Properties ◽  
Magnetic Ions

The chemistry and physics of surfaces is an increasingly important subject. The study of surfaces is the key of many important nanotechnological applications due to the understanding of phase transitions, electronic structure, and chemical bonding. In later years, exotic phenomena that jointly involve the magnetic and electrical conductivity properties have been discovered in oxides that contain magnetic ions. Moreover, the uses of magnetic oxides in electronic technology have become so important due to the miniaturization of devices and magnetic materials with dielectric properties or vice versa being required for inductors, information storage, thin films for high-density computer memories, microwave antireflection coatings, and permanent magnets for automobile ignitions among others. On the contrary, nanotechnology developments over 10 years or so have provided intensive studies in trying to combine properties such as ferroelectric, ferromagnetic, and optics in one single-phase nanoparticles or in composite thin films; this last effort has been recently known as multiferroic. Because of this, the resurgence of nanomaterials with multiferroic and optical properties is presented in this work of one single phase in lanthanum lithium niobate (La0.05Li0.85NbO3) and lithium niobate (LiNbO3) with ferromagnetic, ferroelectric, relaxor ferroelectricity, second harmonic generation, high-temperature ferromagnetic, and magnetoelectric properties.

DYNAMICS OF DIFFUSION AND ADSORPTION: ZnO/α-Al2O3(0001)

2007 ◽  
Vol 21 (11) ◽  
pp. 645-654 ◽  
Author(s):  
CHUN YANG ◽  
Y. R. LI ◽  
YU YI
Keyword(s):  
Thin Films ◽  
Density Functional ◽  
Atomic Layer ◽  
Potential Method ◽  
Heteroepitaxial Growth ◽  
Surface And Interface ◽  
Whole Process ◽  
Growth Modes ◽  
Α Al2o3 ◽  
Interface Structures

A heteroepitaxial growth model of the ZnO film on sapphire(0001) is calculated by using a plane wave ultrasoft pseudo-potential method based on the density functional theory. A strong chemical adsorption on the sapphire(0001) is observed. It is found that interfacial atoms have different diffusivity at 400°C, 600°C and 800°C. The temperature has a decisive effect on the surface and interface structures of ZnO /α -Al 2 O 3(0001) and on the growth mode of ZnO thin films. In the whole process of the adsorption and growth of ZnO , the diffusivity of O atoms is higher than that of Zn , and the interlayer diffusion has an important impact on growth of the thin films. There are two growth modes of ZnO on sapphire(0001), which is further demonstrated by theoretical calculation. It can be observed from the calculation that the vacancies of Zn where the atomic layer is near to the α -Al 2 O 3(0001) surface is more than that of O atoms.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Deoxyribonucleic Acid as a Tool for Digital Information Storage: An Overview

2019 ◽  
Vol 15 (01) ◽  
pp. 1-8
Author(s):  
Ashish C Patel ◽  
C G Joshi
Keyword(s):  
Data Storage ◽  
Dna Sequences ◽  
Consensus Sequence ◽  
Random Access ◽  
Information Storage ◽  
Digital Data ◽  
Digital Information ◽  
Multiple Sequence ◽  
Digital World ◽  
Digital File

Current data storage technologies cannot keep pace longer with exponentially growing amounts of data through the extensive use of social networking photos and media, etc. The "digital world” with 4.4 zettabytes in 2013 has predicted it to reach 44 zettabytes by 2020. From the past 30 years, scientists and researchers have been trying to develop a robust way of storing data on a medium which is dense and ever-lasting and found DNA as the most promising storage medium. Unlike existing storage devices, DNA requires no maintenance, except the need to store at a cool and dark place. DNA has a small size with high density; just 1 gram of dry DNA can store about 455 exabytes of data. DNA stores the informations using four bases, viz., A, T, G, and C, while CDs, hard disks and other devices stores the information using 0’s and 1’s on the spiral tracks. In the DNA based storage, after binarization of digital file into the binary codes, encoding and decoding are important steps in DNA based storage system. Once the digital file is encoded, the next step is to synthesize arbitrary single-strand DNA sequences and that can be stored in the deep freeze until use.When there is a need for information to be recovered, it can be done using DNA sequencing. New generation sequencing (NGS) capable of producing sequences with very high throughput at a much lower cost about less than 0.1 USD for one MB of data than the first sequencing technologies. Post-sequencing processing includes alignment of all reads using multiple sequence alignment (MSA) algorithms to obtain different consensus sequences. The consensus sequence is decoded as the reversal of the encoding process. Most prior DNA data storage efforts sequenced and decoded the entire amount of stored digital information with no random access, but nowadays it has become possible to extract selective files (e.g., retrieving only required image from a collection) from a DNA pool using PCR-based random access. Various scientists successfully stored up to 110 zettabytes data in one gram of DNA. In the future, with an efficient encoding, error corrections, cheaper DNA synthesis,and sequencing, DNA based storage will become a practical solution for storage of exponentially growing digital data.

scholarly journals Precise control of Jeff=12 magnetic properties in Sr2IrO4 epitaxial thin films by variation of strain and thin film thickness

2020 ◽  
Vol 102 (21) ◽  
Author(s):  
Stephan Geprägs ◽  
Björn Erik Skovdal ◽  
Monika Scheufele ◽  
Matthias Opel ◽  
Didier Wermeille ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Magnetic Properties ◽  
Film Thickness ◽  
Epitaxial Thin Films ◽  
Thin Film Thickness ◽  
Precise Control

Nomadic life archiving across platforms: Hyperlinked storage and compartmentalized sharing

2021 ◽  
Vol 23 (4) ◽  
pp. 796-815
Author(s):  
Yang Wang ◽  
Sun Sun Lim
Keyword(s):  
Everyday Life ◽  
Collective Memory ◽  
Life Experiences ◽  
Information Storage ◽  
Digital Data ◽  
Digital Content ◽  
Digital Information ◽  
Host Countries ◽  
Multi Media ◽  
Nomadic Life

People are today located in media ecosystems in which a variety of ICT devices and platforms coexist and complement each other to fulfil users’ heterogeneous requirements. These multi-media affordances promote a highly hyperlinked and nomadic habit of digital data management which blurs the long-standing boundaries between information storage, sharing and exchange. Specifically, during the pervasive sharing and browsing of fragmentary digital information (e.g. photos, videos, online diaries, news articles) across various platforms, life experiences and knowledge involved are meanwhile classified and stored for future retrieval and collective memory construction. For international migrants who straddle different geographical and cultural contexts, management of various digital materials is particularly complicated as they have to be familiar with and appropriately navigate technological infrastructures of both home and host countries. Drawing on ethnographic observations of 40 Chinese migrant mothers in Singapore, this article delves into their quotidian routines of acquiring, storing, sharing and exchanging digital information across a range of ICT devices and platforms, as well as cultural and emotional implications of these mediated behaviours for their everyday life experiences. A multi-layer and multi-sited repertoire of ‘life archiving’ was identified among these migrant mothers in which they leave footprints of everyday life through a tactical combination of interactive sharing, pervasive tagging and backup storage of diverse digital content.

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