Search query: Single crystal functional

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abstract: Single crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single crystal functional oxides on demand on silicon.
author_names: Saidur Rahman Bakaul

Claudy Rayan Serrao

Michelle J Lee

Chun Wing Yeung

A Sarker

Shang-Lin Hsu

Ajay K Yadav

Liv R Dedon

Long You

Asif Islam Khan

James David Clarkson

Chenming Calvin Hu

Ramamoorthy Ramesh

Sayeef S Salahuddin
title: Single crystal functional oxides on silicon
venue: Nature communications
year: 2016

abstract: Abstract In this work the functional behavior of the new Ni 51.2 Ti 23.4 Hf 25.4 high temperature shape memory alloy is investigated along three crystal orientations in compression and compared with the polycrystal behavior. Transformation temperatures were measured following specific aging treatments with the aim to optimize the shape memory and pseudoelastic behaviors. Two aging treatments were then selected in order to fulfill the optimum pseudoelastic behavior (500degC/4 h) and the maximum transformation temperatures (550degC/10 h) without compromising the alloy functionality. High temperature X ray diffraction was utilized to determine the crystal orientations in the austenite phase for the single crystal specimens. The martensite structure was found to be the B19 orthorhombic, in contrast with monoclinic structure for lower Hf contents. Digital image correlation was successively used during isobaric strain temperature experiments on the single crystal and polycrystal specimens. Large strain heterogeneities were found for the single crystals which pair with X ray diffraction data that show un transformed austenite below the martensite finish temperature. This reveals the heterogeneity of the austenite to martensite transformation for the present NiTiHf alloy which explains the divergence between the theoretical and experimental transformation strains. In addition, using digital image correlation it is possible to capture the local strain fields associated with fully transformed specimen regions. The transformation strains calculated locally are in close agreement with the theoretical transformation strains calculated with lattice deformation theory for the cubic austenite to the orthorhombic martensite phase transformation.
author_names: Luca Patriarca

Huseyin Sehitoglu

Elena Panchenko

Yuriy I Chumlyakov
title: High temperature functional behavior of single crystal Ni51.2Ti23.4Hf25.4 shape memory alloy
year: 2016

abstract: Developing an understanding of structure activity relationships and reaction mechanisms of catalytic processes is critical to the successful design of highly efficient catalysts. As a fundamental reaction in fuel cells, elucidation of the oxygen reduction reaction (ORR) mechanism at Pt(hkl) surfaces has remained a significant challenge for researchers. Here, we employ in situ electrochemical surface enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculation techniques to examine the ORR process at Pt(hkl) surfaces. Direct spectroscopic evidence for ORR intermediates indicates that, under acidic conditions, the pathway of ORR at Pt(111) occurs through the formation of HO2* whereas at Pt(110) and Pt(100) it occurs via the generation of OH* However, we propose that the pathway of the ORR under alkaline conditions at Pt(hkl) surfaces mainly occurs through the formation of O2 Notably, these results demonstrate that the SERS technique offers an effective and reliable way for real time investigation of catalytic processes at atomically flat surfaces not normally amenable to study with Raman spectroscopy.The oxygen reduction reaction, catalysed by platinum, is a crucial process in the operation of fuel cells, but the mechanistic pathways through which it occurs remain a matter for debate. Here, the authors use in situ Raman spectroscopy to identify key intermediates for this reaction at different atomically flat platinum surfaces, shedding light on the mechanism.
author_names: Jin-chao Dong

Xia-Guang Zhang

Valentin Briega-Martos

Xi Jin

Ji Yang

Shu Chen

Zhi-Lin Yang

De-Yin Wu

Juan M Feliu

Christopher T Williams

Zhongqun Tian

Jian-feng Li
title: In situ Raman spectroscopic evidence for oxygen reduction reaction intermediates at platinum single crystal surfaces
year: 2019

abstract: Design of active and stable Pt based nanoscale electrocatalysts for the oxygen reduction reaction (ORR) will be the key to improving the efficiency of fuel cells that are needed to deliver reliable, affordable and environmentally friendly energy. Here, by exploring the ORR on Pt single crystals, cubo octahedral (polyhedral) Pt NPs with different sizes (ranging from 2 to 7 nm) and 7 8 nm Pt NPs with different shapes (cubo octahedral vs. cube vs. octahedral) we presented a surface science approach capable of rationalizing, and ultimately understanding, fundamental relationships between stability of Pt NPs and activity of the ORR in acidic media. By exploring the potential induced dissolution/re deposition of Pt between 0.05 and 1.3 V, we found that concomitant variations in morphology of Pt(111) and Pt(100) lead to narrowing differences in activity between Pt single crystal surfaces. We also found that regardless of an initial size or shape, NPs are metastable and easily evolve to thermodynamically equilibrated shape and size with very similar activity for the ORR. We concluded that while initially clearly observed, the particle size and shape effects diminish as the particles age to the point that it may appear that the ORR depends neither on the particle size nor particle shape.
author_names: Dongguo Li

Chao Wang

Dusan Strmcnik

Dusan V Tripkovic

Xiaolian Sun

Yijin Kang

Miaofang Chi

Joshua D Snyder

Dennis van der Vliet

Yifen Tsai

Vojislav R Stamenkovic

Shouheng Sun

Nenad M Markovic
title: Functional links between Pt single crystal morphology and nanoparticles with different size and shape: the oxygen reduction reaction case
year: 2014

abstract: We report on the anisotropic optical properties of single crystal tin monosulfide (SnS) The components ea, eb, and ec of the pseudodielectric function tensor <e> <e1> i<e2> spectra are taken from 0.73 to 6.45 eV by spectroscopic ellipsometry. The measured <e> spectra are in a good agreement with the results of the calculated dielectric response from hybrid density functional theory. The <e> spectra show the direct band gap onset and a total of eight above band gap optical structures that are associated with the interband transition critical points (CPs) We obtain accurate CP energies by fitting analytic CP expressions to second energy derivatives of the <e> data. Their probable electronic origins and implications for photovoltaic applications are discussed.
author_names: Rona E Banai

Lee A Burton

Sukgeun Choi

Florian Hofherr

Tina Sorgenfrei

Aron Walsh

Bobby To

A Croll

Jeffrey Brownson
title: Ellipsometric characterization and density functional theory analysis of anisotropic optical properties of single crystal a SnS
year: 2014

abstract: Single crystal to single crystal (SCSC) transformations represent some of the most fascinating phenomena in chemistry. They are not only intriguing from a basic science point of view but also provide a means to modify or tune the properties of the materials via the postsynthetic introduction of suitable guest molecules or organic functional groups into their structures. Here, we describe UCY 2, a new flexible Nd(3+ metal organic framework (MOF) which exhibits a unique capability to undergo a plethora of SCSC transformations with some of them being very uncommon. These structural alterations involve the replacement of coordinating solvent molecules of UCY 2 by terminally ligating solvents and organic ligands with multiple functional groups including OH, SH, NH and NH(2) or their combinations, chelating ligands, anions, and two different organic compounds. The SCSC coordinating solvent exchange is thus demonstrated as a powerful method for the functionalization of MOFs.
author_names: Manolis J Manos

Eleni J Kyprianidou

Giannis S Papaefstathiou

Anastasios J Tasiopoulos
title: Insertion of functional groups into a Nd3+ metal organic framework via single crystal to single crystal coordinating solvent exchange.
venue: Inorganic chemistry
year: 2012

abstract: Luminescence alterations in solid state materials upon external stimulations have attracted much attention due to their potential for the development of highly functional devices or sensors. We have previously reported the first examples of mechano induced single crystal to single crystal (SCSC) phase transitions of gold(I) isocyanide complexes under concomitant emission color changes. However, the reverse phase transitions of the crystals obtained after mechanical stimulation have not yet been achieved. Herein, a reversible change of the luminescence based on two SCSC phase transitions via mechanical cutting and solvent vapor adsorption is described. Crystallization of a gold(I) complex that bears CF3 and biaryl moieties from CH2Cl2/MeOH afforded a green emitting single crystal packed in a polar space group (Pna21) The green emitting single crystals included MeOH molecules. Upon cutting the crystal under MeOH vapor at 22 degC, the green emitting single crystal spontaneously changed into a centrosymmetric orange emitting single crystal (P1) under concomitant release of MeOH. Remarkably, the initial green emitting crystal could be recovered from the orange emitting crystal by a solvent induced SCSC transition under saturated MeOH vapor. The combination of two different types of SCSC phase transitions enables the reversible structural and photoluminescent alternations.
author_names: Mingoo Jin

Toshiki Sumitani

Hiroyasu Sato

Tomohiro Seki

Hajime Ito
title: Mechanical Stimulation Triggered and Solvent Vapor Induced Reverse Single Crystal to Single Crystal Phase Transitions with Alterations of the Luminescence Color.
venue: Journal of the American Chemical Society
year: 2018

abstract: Abstract Good quality single crystals of 2 amino 4,6 dimethylpyrimidine 4 nitrophenol (AMP4N) were successfully grown by slow evaporation solution technique (SEST) at room temperature using methanol as solvent. The grown crystal was subjected to single crystal XRD (SXRD) and its structure was solved by the direct method using SHELXS program and refined using SHELXL program. The Hirshfeld surfaces analysis was carried out to define theoretically electron density boundary surfaces between the molecules in a grown crystal, which are useful to analyze and view the intermolecular interactions. The powder XRD (PXRD) was carried out to identify the crystalline planes and its strain was also calculated by the Williamson Hall equation. 13C and 1H NMR were recorded to interpret the environment of the molecular structure of the AMP4N crystal. Functional groups of AMP4N crystal were confirmed by Fourier transform infrared (FTIR) spectral analysis. The optical quality of the grown crystal was analyzed by UV Vis NIR spectral analysis. The grown crystal has good optical transparency in the range 410 1100 nm. The thermal behaviour of the crystal has been investigated by thermogravimetric and differential thermal analysis (TG DTA) Chemical etching study was carried out and the etch pit density (EPD) was calculated. The laser damage threshold (LDT) was measured under single shot mode using an Nd: YAG laser at 532 nm. The third order nonlinear optical properties such as refractive index (n2) absorption coefficient (b) and susceptibility (kh(3) were studied using the Z scan technique at 532 nm with a continuous wave (CW) solid state laser.
author_names: P Karuppasamy

T Kamalesh

K Anitha

Shaik Abdul Kalam

Muthu Senthil Pandian

P Ramasamy

Sunil Verma

S Venugopal Rao
title: Synthesis, crystal growth, structure and characterization of a novel third order nonlinear optical organic single crystal: 2 Amino 4,6 Dimethyl Pyrimidine 4 nitrophenol
year: 2018

abstract: Summary Metal organic frameworks (MOFs) have intriguing and tunable photophysical properties owing to predesignable structures from well defined metal and/or organic chromophores. We propose a one pot two step assembly strategy for engineering dual functional coordination interspace where two kinds of organic linkers are segregated in predefined positions. This design endows the three dimensional coordination framework with unidirectional deformation character, leading to an orientation dependent and pressure responsive photoluminescence color change. For the first time, unique piezofluorochromic anisotropism is achieved and can be accumulated stepwise and visualized by a metal organic framework single crystal, providing a basic model for application in stimuli responsive photoluminescence sensing, barcoding, signal switching, harvesting, and magnifying micro devices.
author_names: Cheng-Xia Chen

Zhangwen Wei

Ya-Nan Fan

Peiyang Su

Yeye Ai

Qian-Feng Qiu

Kai Wu

Shaoyun Yin

Mei Pan

Chengyong Su
title: Visualization of Anisotropic and Stepwise Piezofluorochromism in an MOF Single Crystal
year: 2018

abstract: The design and synthesis of functional materials with desired properties is the ultimate goal for chemical pursuers. Single crystal to single crystal (SCSC) transformations are an important component of solid state reactions. These transformations not only create new materials but also provide an opportunity to explore the process of forming a chemical bond, which is conducive to making function oriented crystal synthesis a reality. In this review, we provide a broad overview of SCSC transformations that take place in polymers or metal organic frameworks, and classify them into several groups based on their various inducing stimuli, such as UV light, loss/uptake of solvent vapor, temperature change, mechanical force and their synergic impact. Unlike other reviews, the SCSC transformations discussed in this paper are confined to transformations via an absolutely liquid free mode (both the reactant and product are in the solid phase) while those involving liquids, in which the transformation occurs in a recrystallization manner, are strictly excluded. These dynamic processes all involve the breakage and formation of covalent or non covalent bonds, accompanied by drastic structural rearrangement in the crystalline phase. Changes in the physical properties of these complexes resulting from SCSC transformations are also illustrated. Thanks to the regular characteristics of crystal structures before and after the reactions, the transformation processes may provide deep insights into the rational design of crystalline materials.
author_names: Wenwen He

Shun-li Li

Ya-Qian Lan
title: Liquid free single crystal to single crystal transformations in coordination polymers
year: 2018