Boron- and stoichiometry-related defect engineering during B2O3-free GaAs crystal growth

<p>Defect engineering can enhance key properties of metal-organic frameworks (MOFs). Tailoring the distribution of defects, for example in correlated nanodomains, requires characterization across length scales. However, a critical nanoscale characterization gap has emerged between the bulk diffraction techniques used to detect defect nanodomains and the sub-nanometre imaging used to observe individual defects. Here, we demonstrate that the emerging technique of scanning electron diffraction (SED) can bridge this gap. We directly image defect nanodomains in the MOF UiO-66(Hf) over an area of ca. 1 000 nm and with a spatial resolution ca. 5 nm to reveal domain morphology and distribution. Based on these observations, we suggest possible crystal growth processes underpinning synthetic control of defect nanodomains. We also identify likely dislocations and small angle grain boundaries, illustrating that SED could be a key technique in developing the potential for engineering the distribution of defects, or “microstructure”, in functional MOF design.</p>

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Direct Imaging of Correlated Defect Nanodomains in a Metal-Organic Framework

10.26434/chemrxiv.12024402 ◽

2020 ◽

Author(s):

Duncan Johnstone ◽

Francesca Firth ◽

Clare P. Grey ◽

Paul A. Midgley ◽

Matthew Cliffe ◽

...

Keyword(s):

Crystal Growth ◽

Electron Diffraction ◽

Metal Organic Framework ◽

Metal Organic Frameworks ◽

Synthetic Control ◽

Defect Engineering ◽

Nanoscale Characterization ◽

Metal Organic ◽

Image Defect ◽

Scanning Electron

<p>Defect engineering can enhance key properties of metal-organic frameworks (MOFs). Tailoring the distribution of defects, for example in correlated nanodomains, requires characterization across length scales. However, a critical nanoscale characterization gap has emerged between the bulk diffraction techniques used to detect defect nanodomains and the sub-nanometre imaging used to observe individual defects. Here, we demonstrate that the emerging technique of scanning electron diffraction (SED) can bridge this gap. We directly image defect nanodomains in the MOF UiO-66(Hf) over an area of ca. 1 000 nm and with a spatial resolution ca. 5 nm to reveal domain morphology and distribution. Based on these observations, we suggest possible crystal growth processes underpinning synthetic control of defect nanodomains. We also identify likely dislocations and small angle grain boundaries, illustrating that SED could be a key technique in developing the potential for engineering the distribution of defects, or “microstructure”, in functional MOF design.</p>

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Use of Growth-Rate/Temperature-Gradient Charts for Defect Engineering in Crystal Growth from the Melt

Crystals ◽

10.3390/cryst10100909 ◽

2020 ◽

Vol 10 (10) ◽

pp. 909

Author(s):

Thierry Duffar

Keyword(s):

Growth Rate ◽

Crystal Growth ◽

Temperature Gradient ◽

Growth Conditions ◽

Industrial Applications ◽

Physical Models ◽

Production Yield ◽

Defect Engineering ◽

Pedagogic Tool ◽

Simple Growth

As the requirements in terms of crystal defect/quality and production yield are generally contradictory, it is necessary to develop methods in order to find the best compromise for the growth conditions of a given crystal. Simple growth-rate/temperature-gradient charts are a possible tool in this respect. After the recall of the classical analytical equations useful for describing the process and defect engineering, a simple pedagogic case explains the building and use of such charts. The more complex application to the directional casting of photovoltaic Si necessitated the development of new physical models for twinning and equiaxed growth. This allowed plotting charts that proved useful for industrial applications. The conclusions discuss the drawbacks and advantages of the method. It finally proves to be a pedagogic tool for teaching crystal growth engineering.

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200mm GaAs crystal growth by the temperature gradient controlled LEC method

Journal of Crystal Growth ◽

10.1016/s0022-0248(01)00953-8 ◽

2001 ◽

Vol 225 (2-4) ◽

pp. 561-565 ◽

Cited By ~ 19

Author(s):

A. Seidl ◽

S. Eichler ◽

T. Flade ◽

M. Jurisch ◽

A. Köhler ◽

...

Keyword(s):

Crystal Growth ◽

Temperature Gradient ◽

Gaas Crystal

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First Principles Calculation for Point Defect Behavior, Oxygen Precipitation and Cu Gettering in Czochralski Silicon

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.108-109.365 ◽

2005 ◽

Vol 108-109 ◽

pp. 365-372 ◽

Cited By ~ 1

Author(s):

Koji Sueoka ◽

S. Shiba ◽

S. Fukutani

Keyword(s):

Crystal Growth ◽

Point Defect ◽

First Principles ◽

First Principles Calculation ◽

Interstitial Oxygen ◽

Defect Engineering ◽

Czochralski Silicon ◽

Oxygen Precipitation ◽

Initial Stage ◽

P Type

Theoretical consideration for technologically important phenomena in defect engineering of Czochralski silicon was performed with first principles calculation. (i) Point defect behaviour during crystal growth, (ii) enhanced oxygen precipitation in p/p+ epitaxial wafers, and (iii) Cu gettering by impurities are main topics in this work. Following results are obtained. (i) Interstitial Si I is dominant in p type Si while vacancy V is dominant in n type Si during crystal growth when dopant concentration is higher than about 1x1019atoms/cm3. (ii) In initial stage of oxygen precipitation including a few interstitial oxygen (O) atoms, BOn complex is more stable than On complex. The diffusion barrier of O atom in p+ Si is reduced to about 2.2eV compared with the barrier of about 2.5eV in intrinsic Si. (iii) In substitutional B, Sb, As, P and C atoms, only B atom can be an effective gettering center for Cu.

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