A semiautomatic algorithm for rutherford backscattering analysis
01 Apr 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms (North-Holland)-Vol. 15, pp 227-231
TL;DR: In this paper, nonlinear least squares techniques have been applied to Rutherford backscattering spectrometry (RBS), allowing routine multivariable fits of simulated spectra to experimental data.
Abstract: Nonlinear least squares techniques have been applied to Rutherford backscattering spectrometry (RBS), allowing routine multivariable fits of simulated spectra to experimental data. Once a qualitatively correct simulation is made, this algorithm varies parameters of the simulation to obtain quantitative results. Optimization is done according to a maximum likelihood chi-squared definition, so that the best fit values of parameters and their uncertainties can be determined. Convergence of the algorithm is rapid for practical problems, allowing a typical four-variable fit to be accomplished in 30 seconds on a VAX 11/750. This algorithm allows confident treatment of spectra which might otherwise be considered too complex. An implementation of the algorithm is incorporated as part of an RBS analysis and simulation package, making it readily available for routine RBS analysis.
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TL;DR: This work reports fast, low-temperature, deliberately partial, or complete anion-exchange in highly luminescent semiconductor nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I).
Abstract: Postsynthetic chemical transformations of colloidal nanocrystals, such as ion-exchange reactions, provide an avenue to compositional fine-tuning or to otherwise inaccessible materials and morphologies. While cation-exchange is facile and commonplace, anion-exchange reactions have not received substantial deployment. Here we report fast, low-temperature, deliberately partial, or complete anion-exchange in highly luminescent semiconductor nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I). By adjusting the halide ratios in the colloidal nanocrystal solution, the bright photoluminescence can be tuned over the entire visible spectral region (410–700 nm) while maintaining high quantum yields of 20–80% and narrow emission line widths of 10–40 nm (from blue to red). Furthermore, fast internanocrystal anion-exchange is demonstrated, leading to uniform CsPb(Cl/Br)3 or CsPb(Br/I)3 compositions simply by mixing CsPbCl3, CsPbBr3, and CsPbI3 nanocrystals in appropriate ratios.
1,794 citations
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TL;DR: SIMNRA as discussed by the authors is a Microsoft Windows program for the simulation of backor forward scattering spectra for ion beam analysis with MeV ions, which can calculate spectra of any ion-target combination including incident heavy ions and any geometry including backscattering, forward scattering, and transmission geometries.
Abstract: This document describes the use of the program SIMNRA and the physical concepts implemented therein. SIMNRA is a MicrosoftWindows program for the simulation of backor forward scattering spectra for ion beam analysis with MeV ions. SIMNRA is intended for the simulation of spectra with Rutherford scattering cross-sections (RBS), non-Rutherford cross-sections (EBS), nuclear reactions (NRA), elastic recoil detection analysis (ERDA) with light and heavy incident ions, and medium energy ion scattering (MEIS). SIMNRA can calculate spectra for any ion-target combination including incident heavy ions and any geometry including backscattering, forward scattering, and transmission geometries. Arbitrary multi-layered foils in front of the detector and arbitrary multi-layered windows (such as exit windows for an external beam) in front of the sample can be used. Several different stopping power data sets are available. Energy loss straggling is calculated including the corrections by Chu and Yang to Bohr’s theory, energy loss straggling propagation in thick layers is taken into account. Additionally the effects of multiple small-angle and plural large angle scattering can be calculated approximately as well as surface and substrate roughness. Many non-Rutherford and nuclear reaction cross-sections for incident protons, deuterons, 3He-, 4He-, 6Liand 7Li-ions are included. Data fitting (layer thicknesses, compositions etc.) is possible by means of the Simplex algorithm. OLE automation allows automated analysis of large numbers of spectra and the development of new applications. SIMNRA supports the IBA data format (IDF) for data storage and exchange of data between different simulation programs. SIMNRA is easy to use due to the graphical Microsoft Windows user interface: SIMNRA makes full use of the graphics capacities of Windows. SIMNRA shell extensions extend the abilities of Windows Explorer and Windows Search, thus allowing a seamless integration of SIMNRA into the Windows system.
596 citations
Cites background or methods from "A semiautomatic algorithm for ruthe..."
...• RUMP: Read RBS File...: This menu item allows to read a binary RBS-file produced by RUMP containing experimental parameters (Type of incident particles, incident energy, scattering geometry, etc.) and spectral data....
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...You can read these files with the command File: Read RUMP, see section 3.12.2....
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...This may result in differences of ±0.5 channels between RUMP and SIMNRA, if a non-integer starting channel is used....
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...The default file extension of sample description files is *.LCM. Note 1: RUMP stores the description of the sample and the absorber foil in sample description files (*.LCM)....
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...The most common program is Doolittle’s RUMP [36, 37]....
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TL;DR: In this article, the properties of Ga2O3 thin films deposited by electron-beam evaporation from a high-purity single-crystal Gd3Ga5O12 source are reported.
Abstract: Properties of Ga2O3 thin films deposited by electron‐beam evaporation from a high‐purity single‐crystal Gd3Ga5O12 source are reported. As‐deposited Ga2O3 films are amorphous, stoichiometric, and homogeneous. Excellent uniformity in thickness and refractive index was obtained over a 2 in. wafer. The films maintain their integrity during annealing up to 800 and 1200 °C on GaAs and Si substrates, respectively. Optical properties including refractive index (n=1.84–1.88 at 980 nm wavelength) and band gap (4.4 eV) are close or identical, respectively, to Ga2O3 bulk properties. Reflectivities as low as 10−5 for Ga2O3/GaAs structures and a small absorption coefficient (≊100 cm−1 at 980 nm) were measured. Dielectric properties include a static dielectric constant between 9.9 and 10.2, which is identical to bulk Ga2O3, and electric breakdown fields up to 3.6 MV/cm. The Ga2O3/GaAs interface demonstrated a significantly higher photoluminescence intensity and thus a lower surface recombination velocity as compared to ...
396 citations
TL;DR: This work reports a facile colloidal synthesis method for obtaining FAPbI3 and FA-doped CsPbI 3 NCs that are uniform in size and nearly cubic in shape and exhibit drastically higher robustness than their MA- or Cs-only cousins with similar sizes and morphologies.
Abstract: Colloidal nanocrystals (NCs) of APbX3-type lead halide perovskites [A = Cs+, CH3NH3+ (methylammonium or MA+) or CH(NH2)2+ (formamidinium or FA+); X = Cl–, Br–, I–] have recently emerged as highly versatile photonic sources for applications ranging from simple photoluminescence down-conversion (e.g., for display backlighting) to light-emitting diodes. From the perspective of spectral coverage, a formidable challenge facing the use of these materials is how to obtain stable emissions in the red and infrared spectral regions covered by the iodide-based compositions. So far, red-emissive CsPbI3 NCs have been shown to suffer from a delayed phase transformation into a nonluminescent, wide-band-gap 1D polymorph, and MAPbI3 exhibits very limited chemical durability. In this work, we report a facile colloidal synthesis method for obtaining FAPbI3 and FA-doped CsPbI3 NCs that are uniform in size (10–15 nm) and nearly cubic in shape and exhibit drastically higher robustness than their MA- or Cs-only cousins with sim...
368 citations
02 Mar 1994-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: A short review of published computer methods for ion scattering is presented in this paper, where the main methods and approaches on our RBX computer program can use any particle-target combination and beam energy between 100 keV and 10 MeV.
Abstract: Since the seventies a large number of computer methods have been developed for data analysis in Rutherford backscattering spectrometry (RBS). A short review of published computer methods for ion scattering is presented. The majority of programs can be divided into two categories: the interactive spectrum synthesis and the spectrum analysis codes. In this paper recent trends and problems in the area of spectrum simulation are presented. I demonstrate the main methods and approaches on our RBX computer program. The program can use any particle-target combination and beam energy between 100 keV and 10 MeV. The calculations and fitting methods of non-Rutherford scattering cross section are included. The contributions from electronic screening, the corrected Bohr straggling and the geometrical straggling are discussed. The useful techniques for extracting an accurate depth-concentration profile directly from RBS or ERDA spectrum are discussed. Some examples of the discussed methods are also given.
310 citations
References
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01 Jun 1985-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: Estimates of the number of arithmetic operations used by the program for any simulation to demonstrate the tradeoffs between accuracy, computation time, and algorithm sophistication are provided.
Abstract: A computer program which simulates Rutherford backscattering spectra is currently in use at Cornell University and other institutions. Straggling and detector resolution are among the effects included. Samples are considered to be made up of a finite number of layers, each with uniform composition. The emphasis in the mathematics is on accuracy beyond that of iterated surface approximation methods. Thicker layers can thus be analyzed without a net loss in accuracy. The mathematical description of the sample can then have fewer layers and fewer calculations are required. This paper provides estimates of the number of arithmetic operations used by the program for any simulation to demonstrate the tradeoffs between accuracy, computation time, and algorithm sophistication.
2,551 citations
TL;DR: In this article, the problem of fitting curves to histograms in which the data obey multinomial or Poisson statistics is examined in light of standard results found in the statistics literature, and a sufficient condition for equality of the area under the fitted curve and the number of events on the histogram is clarified.
422 citations
TL;DR: A new method for minimising a sum of squares of non-linear functions is described and is shown to be more efficient than other methods in that fewer function values are required.
Abstract: A new method for minimising a sum of squares of non-linear functions is described and is shown to be more efficient than other methods in that fewer function values are required.
83 citations
IBM1
TL;DR: A computer-based interactive nuclear backscattering analysis system can develop moderate competence with the system after only brief instruction because of the menu-driven organization, andPublishable quality figures can be obtained without any computer expertise.
29 citations