3 Diffusion in compound semiconductors

Dutt, M. B.; Sharma, B. L.

doi:10.1007/10426818_10

Cited by 12 publications

(14 citation statements)

References 329 publications

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“…Relative to their bulk crystalline analogues, the reduced volume of nanoscale materials significantly relaxes the kinetic demands of solid-state diffusion. For example, using bulk diffusion coefficients, Ag + , Cu + , and Au + ions can diffuse the entire length of a 5 nm diameter InAs crystal in less than a second at ambient temperature. , Thus, the diffusion-mediated propagation of the reaction zone may no longer be rate limiting for many nanoscale cation exchange reactions . Indeed, time-resolved micro-X-ray absorption spectroscopy (XAS) and stopped flow absorption measurements of the topotaxial Ag + exchange of 3.5 nm CdSe nanocrystals indicate rapid conversion ( t 1/2 < 100 ms), a strong dependence on the concentration of the coordinating ligand, and second-order kinetics consistent with a rate-limiting surface reaction step .…”

Section: Mechanistic Insights Into Nanoscale Cation Exchangementioning

confidence: 99%

Section: ■ Mechanistic Insights Into Nanoscale Cation Exchangementioning

confidence: 99%

“…Indeed, solidstate diffusion limitations in bulk crystallites often necessitate the application of high temperatures and pressures to achieve rapid product formation. 11 As an example, Ag + , which possesses a relatively high ion diffusivity, 17 sluggishly converts a thin film (500 nm) of CdSe to Ag 2 Se, requiring several hours at 80 °C, 18 whereas the similar reaction in CdSe nanocrystals (see above) proceeds to completion in ≪1 s at room temperature. 7 In the subsequent section, we will highlight recent mechanistic studies of ion exchange kinetics at the nanoscale to illustrate the mechanistic consequences of relaxing limitations on solid-state ion diffusion.…”

Section: ■ Introductionmentioning

confidence: 99%

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Cation Exchange: A Versatile Tool for Nanomaterials Synthesis

2013

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The development of nanomaterials for next generation photonic, optoelectronic, and catalytic applications requires a robust synthetic toolkit for systematically tuning composition, phase, and morphology at nanometer length scales. While de novo synthetic methods for preparing nanomaterials from molecular precursors have advanced considerably in recent years, postsynthetic modifications of these preformed nanostructures have enabled the stepwise construction of complex nanomaterials. Among these postsynthetic transformations, cation exchange reactions, in which the cations ligated within a nanocrystal host lattice are substituted with those in solution, have emerged as particularly powerful tools for fine-grained control over nanocrystal composition and phase. In this feature article, we review the fundamental thermodynamic and kinetic basis for cation exchange reactions in colloidal semiconductor nanocrystals and highlight its synthetic versatility for accessing nanomaterials intractable by direct synthetic methods from molecular precursors. Unlike analogous ion substitution reactions in extended solids, cation exchange reactions at the nanoscale benefit from rapid reaction rates and facile modulation of reaction thermodynamics via selective ion coordination in solution. The preservation of the morphology of the initial nanocrystal template upon exchange, coupled with stoichiometric control over the extent of reaction, enables the formation of nanocrystals with compositions, morphologies, and crystal phases that are not readily accessible by conventional synthetic methods.

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Section: Mechanistic Insights Into Nanoscale Cation Exchangementioning

confidence: 99%

Section: ■ Mechanistic Insights Into Nanoscale Cation Exchangementioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Cation Exchange: A Versatile Tool for Nanomaterials Synthesis

2013

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“…Thicker samples result in decreasing energy of the electron beams and increasing the scattering as well as complexity from the bigger distribution of energy and at the end declined resolution is obtained. Most of the synthetic chalcogen materials or metal chalcogenides are firstly being visualized with the aid of SEM and TEM before any other theoretical modeling or use of methods for analysis [15,20,24,50,56,62,[68][69][70].…”

Section: Methods For Chalcogen Materials Characterizationmentioning

confidence: 99%

Modern Analytical Chemistry Methods for Chalcogen Materials Analysis and Characterization

Wonorahardjo¹,

Fariati²,

Dasna³

2019

Chalcogen Chemistry

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Analytical methods are needed to elucidate modern and complex compounds as well as to describe their physical properties. The underlying principles of chalcogen chemistry as well as the natural abundance of chalcogen elements are the base of building many biological substances, including sophisticated materials for future applications. Thus, the need for modern and state-of-the art analytical methods and techniques to characterize them, is obvious. In this chapter, challenges in analytical methods for chalcogen compounds and materials, as well as some examples of natural or synthesized materials or their combinations, including biomaterials, are discussed. Modern methods for chalcogen compounds analysis and structural determination discussed include: UV-Visible and infrared spectroscopy (UV-Vis and IR), thermo analysis, electrochemistry, magnetic analysis, chromatography, X-ray methods (mostly XRF, XRD, and EDX), high-resolution microscopy (SEM and TEM), multinuclear NMR, computational analysis, and bioassay. Also, the historical background and nature of chalcogen elements, including reactivity and magnetic properties as well as thermal behavior, common compounds of chalcogen elements: organic and inorganic materials, complex chalcogen materials, will be briefly discussed.

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“…An appropriate quantity of heavily doped GaAs:Te was added to introduce the dopant. Te was chosen as the dopant because of its low diffusivity in the solid phase 7 and its relatively low vapor pressure 8 . The crucible was contained inside a silica process tube with Pd-diffused flowing hydrogen gas at 1 atmosphere.…”

mentioning

confidence: 99%

Far-infrared absorption in GaAs:Te liquid phase epitaxial films

Cardozo

Häller

Reichertz

et al. 2003

Applied Physics Letters

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The far-infrared absorption spectrum of n-type GaAs is of interest for applications such as GaAs photoconductors and Blocked Impurity Band (BIB) detectors. The linear optical absorption coefficients α for three n-type GaAs films of varying doping concentrations have been measured in the range of 10 to 100 cm -1 using Fourier Transform Infrared Spectrometry. These results show α having maximum values of between 46 cm -1 at 1x10 15 cm -3 and approximately 800 cm -1 at 2.1x10 16 cm -3 . The formation and widening of a donor impurity band with increasing impurity concentration is clearly demonstrated.

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3 Diffusion in compound semiconductors

Cited by 12 publications

References 329 publications

Cation Exchange: A Versatile Tool for Nanomaterials Synthesis

Cation Exchange: A Versatile Tool for Nanomaterials Synthesis

Modern Analytical Chemistry Methods for Chalcogen Materials Analysis and Characterization

Far-infrared absorption in GaAs:Te liquid phase epitaxial films

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