scholarly journals Interface-Driven Structural Distortions and Composition Segregation in Two-Dimensional Heterostructures

2017 ◽  
Vol 56 (46) ◽  
pp. 14448-14452 ◽  
Author(s):  
Jeffrey Ditto ◽  
Devin R. Merrill ◽  
Gavin Mitchson ◽  
Joshua J. Gabriel ◽  
Kiran Mathew ◽  
...  
Keyword(s):  
Two Dimensional ◽  
Structural Distortions ◽  
Composition Segregation

scholarly journals Interface-Driven Structural Distortions and Composition Segregation in Two-Dimensional Heterostructures

2017 ◽  
Vol 129 (46) ◽  
pp. 14640-14644
Author(s):  
Jeffrey Ditto ◽  
Devin R. Merrill ◽  
Gavin Mitchson ◽  
Joshua J. Gabriel ◽  
Kiran Mathew ◽  
...  
Keyword(s):  
Two Dimensional ◽  
Structural Distortions ◽  
Composition Segregation

scholarly journals Synthetic Variation and Structural Trends in Layered Two-Dimensional Alkylammonium Lead Halide Perovskites

2019 ◽  
Author(s):  
Watcharaphol Paritmongkol ◽  
Nabeel Dahod ◽  
Nannan Mao ◽  
Shao-Liang Zheng ◽  
William Tisdale
Keyword(s):  
Crystal Structures ◽  
Periodic Variation ◽  
Two Dimensional ◽  
Halide Anion ◽  
Structural Distortions ◽  
Spacer Layer ◽  
Halide Perovskites ◽  
Spacer Chain Length ◽  
A Site ◽  
Lead Halide

We report the cooling-induced crystallization of layered two-dimensional lead halide perovskites with controllable inorganic quantum-well thickness (<i>n</i> = 1, 2, 3, 4)<i>,</i> organic spacer chain length (butyl-, pentyl-, hexylammonium), A-site cation (methylammonium, formamidinium), and halide anion (iodide, bromide). We report crystal structures for the iodide family as a function of these compositional parameters, and across their temperature dependent phase transitions. In general, lower symmetry crystal structures, increasing extents of organic-spacer interdigitation, and increasing organic-spacer corrugation tilts are observed at low temperature. In addition, greater structural distortions are seen in lead halide octahedra closest to the organic spacer layer, and larger-<i>n­ </i>structures exhibit periodic variation in Pb-I bond lengths. We also provide detailed guidance regarding the combination of synthetic parameters needed to achieve phase-pure crystals of each composition, and discuss difficulties encountered when trying to synthesize particular members of the 2D perovskite family containing formamidinium or cesium as the A-site cation. These results provide a foundation for understanding structural trends in 2D lead halide perovskites and the effect these trends have on their thermal, electrical, and optical properties.

Role of Spacer Cations and Structural Distortion in Two-Dimensional Germanium Halide Perovskites

2021 ◽  
Author(s):  
Lorenzo Malavasi ◽  
Luca Bindi ◽  
Mauro Coduri ◽  
Filippo De Angelis ◽  
Francesco Fracassi ◽  
...  
Keyword(s):  
Optical Properties ◽  
Metal Halide ◽  
Structural Distortion ◽  
Two Dimensional ◽  
Structure Property ◽  
Structural Distortions ◽  
Metal Halide Perovskite ◽  
Halide Perovskites ◽  
Halide Perovskite

The elucidation of the structure-property correlation in 2D metal halide perovskite is a key issue to understand the dependence of optical properties on structural distortions and to design novel tailored...

scholarly journals Synthetic Variation and Structural Trends in Layered Two-Dimensional Alkylammonium Lead Halide Perovskites

2019 ◽  
Author(s):  
Watcharaphol Paritmongkol ◽  
Nabeel Dahod ◽  
Nannan Mao ◽  
Shao-Liang Zheng ◽  
William Tisdale
Keyword(s):  
Crystal Structures ◽  
Periodic Variation ◽  
Two Dimensional ◽  
Halide Anion ◽  
Structural Distortions ◽  
Spacer Layer ◽  
Halide Perovskites ◽  
Spacer Chain Length ◽  
A Site ◽  
Lead Halide

We report the cooling-induced crystallization of layered two-dimensional lead halide perovskites with controllable inorganic quantum-well thickness (<i>n</i> = 1, 2, 3, 4)<i>,</i> organic spacer chain length (butyl-, pentyl-, hexylammonium), A-site cation (methylammonium, formamidinium), and halide anion (iodide, bromide). We report crystal structures for the iodide family as a function of these compositional parameters, and across their temperature dependent phase transitions. In general, lower symmetry crystal structures, increasing extents of organic-spacer interdigitation, and increasing organic-spacer corrugation tilts are observed at low temperature. In addition, greater structural distortions are seen in lead halide octahedra closest to the organic spacer layer, and larger-<i>n­ </i>structures exhibit periodic variation in Pb-I bond lengths. We also provide detailed guidance regarding the combination of synthetic parameters needed to achieve phase-pure crystals of each composition, and discuss difficulties encountered when trying to synthesize particular members of the 2D perovskite family containing formamidinium or cesium as the A-site cation. These results provide a foundation for understanding structural trends in 2D lead halide perovskites and the effect these trends have on their thermal, electrical, and optical properties.

Spectrophotometric measurements of objective-prism spectra

1966 ◽  
Vol 24 ◽  
pp. 118-119
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Progress Report ◽  
Two Dimensional ◽  
Objective Prism ◽  
Made In

I should like to give you a very condensed progress report on some spectrophotometric measurements of objective-prism spectra made in collaboration with H. Leicher at Bonn. The procedure used is almost completely automatic. The measurements are made with the help of a semi-automatic fully digitized registering microphotometer constructed by Hög-Hamburg. The reductions are carried out with the aid of a number of interconnected programmes written for the computer IBM 7090, beginning with the output of the photometer in the form of punched cards and ending with the printing-out of the final two-dimensional classifications.

Introductory paper

1966 ◽  
Vol 24 ◽  
pp. 3-5
Author(s):  
W. W. Morgan
Keyword(s):  
Line Intensity ◽  
Classification Scheme ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Dimensional Array ◽  
Rr Lyrae ◽  
Metallic Line ◽  
Introductory Paper ◽  
Parameter Varying ◽  
Definition Of

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.

A one-dimensional self-gravitating stellar gas

1966 ◽  
Vol 25 ◽  
pp. 46-48 ◽  
Author(s):  
M. Lecar
Keyword(s):  
Gravitational Field ◽  
Phase Space ◽  
Motion Picture ◽  
Space Distribution ◽  
Two Dimensional ◽  
One Dimensional ◽  
Phase Space Distribution ◽  
Dimensional Phase Space ◽  
The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

Analysis of the 9th November 1990 flare

2000 ◽  
Vol 179 ◽  
pp. 229-232
Author(s):  
Anita Joshi ◽  
Wahab Uddin
Keyword(s):  
Image Processing ◽  
Two Dimensional ◽  
Temporal Behaviour ◽  
Contour Maps ◽  
Dimensional Measurements ◽  
Processing Software ◽  
Image Processing Software

AbstractIn this paper we present complete two-dimensional measurements of the observed brightness of the 9th November 1990Hαflare, using a PDS microdensitometer scanner and image processing software MIDAS. The resulting isophotal contour maps, were used to describe morphological-cum-temporal behaviour of the flare and also the kernels of the flare. Correlation of theHαflare with SXR and MW radiations were also studied.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

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