Crystal Growth

Highly Rigid and Stable Porous Cu(I) Metal-Organic Framework with Reversible Single-Crystal-to-Single-Crystal Structural Transformation

by Sudip Mohapatra

Epitaxy and chemical reactions during thin-film formation from low-energy ions: new kinetic pathways, new phases, and new properties

by Nicole Herbots

Nicole Herbots, O.C. Hellman
ARIZONA STATE UNIVERSITY, Departmentof PhysicsandAstronomy, Tempe AZ 85287
0. Vancauwenberghe* MASSACHUSETTS INSTITUTE OFTECHNOLOGY, DepartmentofMaterialsScience & Engineering,Cambridge, MA 02139

Ref: Mat. Res. Soc. Symp. Proc. Vol. 235. pp. 749-762 (1992)

ABSTRACT
Three important effects of low energy direct Ion Beam Deposition (IBD) are the athermal incorporation of... more ABSTRACT
Three important effects of low energy direct Ion Beam Deposition (IBD) are the athermal incorporation of material into a substrate, the enhancement of atomic mobility in the subsurface, and the modification of growth kinetics it creates. All lead to a significant lowering of the temperature necessary to induce epitaxial growth and chemical reactions. The fundamental understanding and new applications of low temperature kinetics induced by low energy ions in thin film growth and surface processing of semiconductors are reviewed. It is shown that the mechanism of IBD growth can be understood and computed quantitatively using a simple model including ion induced defect generation and sputtering, elastic recombination, thermal diffusion, chemical reactivity, and desorption. The energy, temperature and dose dependence of growth rate, epitaxy, and chemical reaction during IBD is found to be controlled by the net recombination rate of interstitials at the surface in the case of epitaxy and unreacted films, and by the balance between ion beam decomposition and phase formation induced by ion beam generated defects in the case of compound thin films. Recent systematic experiments on the formation of oxides and nitrides on Si, Ge/Si(100), heteroepitaxial SixGe1−x/Si(100) and GaAs(lOO) illustrate applications of this mechanism using IBD in the form of Ion Beam Nitridation (IBN), Ion Beam Oxidation (IBO) and Combined Ion and Molecular beam Deposition (CIMD). It is shown that these techniques enable (1) the formation of conventional phases in conditions never used before, (2) the control and creation of properties via new degrees of freedom such as ion energy and lowered substrate temperatures, and (3) the formation of new metastable heterostructures that cannot be grown by pure thermal means.

Porous Organic Cage Nanocrystals by Solution Mixing

by Sam Chong

2012 JACS paper on organic cages nanocrystal fabrication.

We present here a simple method for the bottom-up fabrication of microporous organic particles with surface areas in... more We present here a simple method for the bottom-up fabrication of microporous organic particles with surface areas in the range 500–1000 m2 g–1. The method involves chiral recognition between prefabricated, intrinsically porous organic cage molecules that precipitate spontaneously upon mixing in solution. Fine control over particle size from 50 nm to 1 μm can be achieved by varying the mixing temperature or the rate of mixing. No surfactants or templates are required, and the resulting organic dispersions are stable for months. In this method, the covalent synthesis of the cage modules can be separated from their solution processing into particles because the modules can be dissolved in common solvents. This allows a “mix and match” approach to porous organic particles. The marked solubility change that occurs upon mixing cages with opposite chirality is rationalized by density functional theory calculations that suggest favorable intermolecular interactions for heterochiral cage pairings. The important contribution of molecular disorder to porosity and surface area is highlighted. In one case, a purposefully amorphized sample has more than twice the surface area of its crystalline analogue.

Measurement of residual stress in EFG ribbons using a phase-shifting IR photoelastic method

by Miguel Centeno Brito

published in Solar Energy Materials and Solar Cells, 2005

This paper reports on the measurement of residual stress in EFG silicon ribbons for solar cell applications using the... more This paper reports on the measurement of residual stress in EFG silicon ribbons for solar cell applications using the phase-shifting infrared (IR) photoelastic method. The samples analysed were wafers cut from EFG octagons with 100mm face width and from EFG 125mm face-width octagon under development. Experimental results show that the distribution of
residual stress in both types of samples is similar, within measurement uncertainties. The average residual stress in the samples is about 8 MPa. Maximum stresses of around 30MPa are associated with twin and grain boundaries. Significant variations of stress along the growth direction, possibly related to buckling, were also measured.

SILICON RIBBON TECHNOLOGIES BASED ON THE SDS PROCESS

by Miguel Centeno Brito

presented at the 26th PVSEC, Hamburg 2011

The major drawback for PV penetration is the cost. Although remarkable progress on solar cell processing has been... more The major drawback for PV penetration is the cost. Although remarkable progress on solar cell processing has been reported in recent years, a much smaller evolution has been seen on what should be one of the key points to address – the wafer production itself, which represents nearly half of the module cost for silicon based technologies. This paper presents the silicon ribbon technologies based on the SDS (Silicon over Dust Substrate)
process, addressing briefly the early technologies and the challenges that lead to the present technology - the continuous mode SDS. The SDS process provides a way to obtain silicon ribbons directly from a gas source.
In the SDS process the silicon pre-ribbons are grown on top of a silicon dust substrate, directly from a gas precursor, silane, followed by a float zone crystallization process. Besides the advantages of avoiding kerf losses from the wafer cutting processes, the growth of silicon ribbons directly from a gaseous feedstock has the benefit of bypassing also intermediate stages such as the Siemens process, reducing potential the manufacturing cost. The measured effective carrier lifetimes were slightly higher than 3!s, with as grown samples without surface passivation. The crystal grains are typically centimeters long and millimeters wide.

CRYSTALLIZATION OF SILICON SHEET USING AN ELECTRICALLY GENERATED MOLTEN LINE

by Miguel Centeno Brito

presented at the 26th PVSEC, Hamburg 2011

This paper describes a new method for the crystallization of silicon sheet using an electrically generated molten... more This paper describes a new method for the crystallization of silicon sheet using an electrically generated molten line. A thin molten line is created in the sample by applying an electric current and then, using a suitable external thermal gradient, it is forced to travel across the sample crystallizing it. The crystallized sample has columnar cm-sized crystal grains and minority carrier lifetimes of a few microseconds, similar to comparable crystallization techniques.

Garnet sector and oscillatory zoning linked with changes in crystal morphology during rapid growth, North Cascades, Washington

by Alan Boyle

Stowell, H., Zuluaga, C., Boyle, A. & Bulman, G., 2011. Garnet sector and oscillatory zoning linked with changes in crystal morphology during rapid growth, North Cascades, Washington. American Mineralogist, 96(8-9), 1354-1362.

Metamorphic garnet with sector zoning in the cores and oscillatory zoning in the rims grew during rapid heating of... more Metamorphic garnet with sector zoning in the cores and oscillatory zoning in the rims grew during rapid heating of pelitic rocks in the Chiwaukum Schist. These types of compositional zoning are exemplified by sharp, but low amplitude, boundaries between broad petal-shaped sectors and between narrow concentric zones, respectively. Zoning is most obvious in calcium, which is inversely correlated with iron and magnesium content. Garnet habit inferred from the oscillatory calcium zoning and external morphology indicates a growth transition from early crystal forms with both trapezohedral and dodecahedral forms to later crystal forms dominated by trapezohedral faces. This transition is accompanied by changes in compositional sector zoning and may reflect the roles of local growth dynamics and external forcing mechanisms affecting growth of garnet. Subsequent modification of these textures produced patchy zoning in calcium. Electron backscatter diffraction confirms the inferred crystal growth habits and that compositional zoning occurs within single garnet crystals.

Exchange thermobarometry and the peak mineral assemblages indicate that metamorphic conditions reached 640–670 °C at 6.9 kbar. These temperatures are sufficient to allow significant volume diffusion; therefore, preservation of the finely banded compositional zoning in garnet requires rapid heating and cooling. Garnet Sm-Nd ages and indistinguishable zircon U-Pb ages from adjacent orthogneiss bodies confirm that garnet grew rapidly during localized and short-lived heating adjacent to sill-like intrusions of tonalite.

Crystalline cell inclusions: a new diagnostic character in the Cladophorophyceae (Chlorophyta)

by Frederik Leliaert

Leliaert F. & Coppejans E. (2004)
Phycologia 43: 189-203

Crystalline cell inclusions were observed in 45 species of Cladophorophyceae. The crystals can be classified into... more Crystalline cell inclusions were observed in 45 species of Cladophorophyceae. The crystals can be classified into eight morphological types, including needle shaped, prismatic, octahedral, tetrahedral, cubic and globular, and they were found to occur in clusters or as single crystals. In addition to the different morphological types, the crystals are characterized by different chemical compositions. Chemical tests distinguished the crystals as being composed of calcium oxalate, calcium carbonate or proteins. The diversity of crystal types raises the possibility that these structures have systematic value. The occurrence of crystalline structures is compared with previously published phylogenies of the Cladophorophyceae. Some types of crystals were found to be genus or species specific, whereas other types occurred in distantly related groups. The crystalline cell inclusions can be useful diagnostic characters. For example, Cladophoropsis sundanensis and Cladophora coelothrix are distantly related but have similar thallus architecture, and they can be distinguished from one another by the presence or absence of crystals.

Hong P. Vu, Sam Shaw, Loredana Brinza, Liane G Benning (2010) Crystallization of Hematite (α-Fe2O3) under Alkaline Condition: The Effects of Pb Crystal Growth and Design 10 (4):1544–1551 DOI: 10.1021/cg900782

by Liane G. Benning

LiFePO4 Mesocrystals for Lithium‐Ion Batteries

by Jelena Popovic

Reduction of process-induced crystalline defects during silicon wafer processing

by Chun Yee CHEAH

C. Y. Cheah, R. Kumar, & F. K. Yam (2009). "Reduction of process-induced crystalline defects during silicon wafer processing". IEEE Regional Symposium on Micro & Nanoelectronics, Kota Bharu, Malaysia, pp. 545-549.

ISBN 978-967-5048-55-5 (IEEE Electron Devices Society).

Abstract– Crystalline defects generated during wafer processing degrade the electrical properties of semiconductor... more Abstract– Crystalline defects generated during wafer processing degrade the electrical properties of semiconductor devices. This brings deleterious effects on the device quality and reliability. This paper details extended defects created during boron ion-implantation on silicon. Process optimizations have successfully decreased the density of the extended defects. This work discusses the type and source of the extended defects as well as the process optimizations employed. Phenomenological models are proposed to explain the mechanisms involved.

Keywords– Quality and reliability; Crystal defects; Leakage current