Imperfections in type I and type II diamonds

1962 ◽  
Vol 270 (1343) ◽  
pp. 538-552 ◽  
Keyword(s):  
Ultra Violet ◽  
Type I ◽  
Type Ii ◽  
Dislocation Loops ◽  
Screw Dislocations ◽  
X Ray ◽  
Transmission Electron ◽  
Infra Red ◽  
High Concentrations ◽  
Absorption Measurements

Natural diamonds have been thinned sufficiently by oxidation at 750 °C in oxygen or at 1350 °C in carbon dioxide for examination by transmission electron microscopy. Type I and type II diamonds as classified by infra-red and ultra-violet absorption measurements have been investigated and a difference in the nature of the imperfections in the two types has been found. Impurity platelets are present on {100} planes in type I diamonds and the relevant impurity has been identified as most probably nitrogen, since the density of platelets can be explained only by the high concentrations of nitrogen found in such diamonds by other workers. The presence of the nitrogen in platelet form can explain anomalous X-ray spikes reported around the normal Laue spots and also the fact that the nitrogen has been found to be present in a non-paramagnetic form. Small dislocation loops have been revealed on {111} planes near the nitrogen platelets and have been attributed to the condensation of vacancies following the formation of the platelets. Both these types of imperfection are absent in type II diamonds. Defects common to both types are dislocations and also long narrow dislocation dipoles which are considered to be formed by the movement of screw dislocations containing long jogs through the crystal at high temperatures. It is suggested that type II diamonds may have grown in nitrogen-free conditions at temperatures similar to those required for type I diamonds and have cooled slowly or they may have grown at lower temperatures than type I diamonds.

Type II Dislocation Loops and their Effect on Strain in Ion Implanted Silicon as Studied by High Resolution X-ray Diffraction

1995 ◽  
Vol 378 ◽  
Author(s):  
R. H. Thompson ◽  
V. Krishnamoorthy ◽  
J. Liu ◽  
K. S. Jones
Keyword(s):  
High Resolution ◽  
Type Ii ◽  
Dislocation Loops ◽  
X Ray Diffraction ◽  
Empirical Constant ◽  
Plan View ◽  
X Ray ◽  
Transmission Electron ◽  
Measured Strain ◽  
P Type

AbstractP-type (100) silicon wafers were implanted with 28Si+ ions at an energy of 50 keV and to doses of 1 × 1015, 5 × 1015 and 1 × 1016 cm−2, respectively, and annealed in a N2 ambient at temperatures ranging from 700°C to 1000°C for times ranging from 15 minutes to 16 hours. The resulting microstructure consisted of varying distributions of Type II end of range dislocation loops. The size distribution of these loops was quantified using plan-view transmission electron microscopy and the strain arising from these loops was investigated using high resolution x-ray diffraction. The measured strain values were found to be constant in the loop coarsening regime wherein the number of atoms bound by the loops remained a constant. Therefore, an empirical constant of 7.7 × 10−12 interstitial/ppm of strain was evaluated to relate the number of interstitials bound by these dislocation loops and the strain. This value was used successfully in estimating the number of interstitials bound by loops at the various doses studied provided the annealing conditions were such that the loop microstructure was in the coarsening or dissolution regime.

X-ray Bragg reflexion, ‘spike’ reflexion and ultra-violet absorption topography of diamonds

1964 ◽  
Vol 281 (1386) ◽  
pp. 310-322 ◽  
Keyword(s):  
Ultra Violet ◽  
Perfect Crystal ◽  
Type I ◽  
Type Ii ◽  
High Definition ◽  
Characteristic Type ◽  
X Ray ◽  
The Matrix ◽  
Definition Of ◽  
Subsequent Diffusion

The relation between X-ray diffracting properties and ultra-violet absorption has been studied point by point on polished plates of diamond having thicknesses from 0-1 mm to more than 1 mm and edge lengths from 2 mm to more than 1 cm. Most specimens exhibit marked non-uniformity of ultra-violet absorption. The intensity of the ‘spike’ X-ray reflexions was found to be roughly proportional to ultra-violet absorption, point by point, a t least in the range of weak and moderate spike intensities. Hence it is concluded that the platelets responsible for the ‘spikes’ are also responsible for the characteristic type I absorptions. However, high values of spike intensity and ultra-violet absorption have only been observed in relatively perfect crystal regions with a low density of grown-in dislocations as determined by X-ray topography; and it is suggested that in imperfect regions containing many grown-in dislocations impurity precipitation in the form of platelets coherent with the matrix may have been inhibited or pre-empted by precipitation in some other way. Thus the absence of ‘ spikes ’ and characteristic type I absorptions may not necessarily imply absence of impurity. On the other hand, some regions of high ultra-violet transparency can be highly perfect; hence lattice imperfection is not necessarily associated with type II optical characteristics. A comparison of ‘spike’ intensity in equivalent cube directions, made on a specimen selected for the high definition of its ‘spike’ topograph features, showed that where platelet precipitation was present it had occurred equally on all cube planes. The sharpness of boundaries between regions of high and low ultra-violet absorption and the association of such boundaries with growth stratifications revealed by Bragg reflexion topographs suggest that they correspond to variations of concentration of grown-in impurity in the crystal, no detectable subsequent diffusion having taken place.

ION CHANNELING AND PIXE STUDIES OF S IMPLANTATION IN GaAs

1992 ◽  
Vol 02 (02) ◽  
pp. 151-159
Author(s):  
LIU SHIJIE ◽  
WANG JIANG ◽  
HU ZAOHUEI ◽  
XIA ZHONGHUONG ◽  
GAO ZHIGIANG ◽  
...  
Keyword(s):  
Room Temperature ◽  
Dislocation Loops ◽  
Good Recovery ◽  
Electrical Measurements ◽  
X Ray ◽  
Defect Complexes ◽  
Ion Channeling ◽  
Transmission Electron ◽  
Activation Efficiency ◽  
Very High

GaAs (100) crystals were implanted with 100 keV S+ to a dose of 3×1015 cm−2 in a nonchanneling direction at room temperature, and treated with rapid thermal annealing (RTA). He+ Rutherford backscattering and particle-induced X-ray emission in channeling mode in combination with transmission electron microscopy (TEM) were used to study the damage and the lattice location of S atoms. It is revealed that the RTA at 950 °C for 10 sec has resulted in a very good recovery of crystallinity with a few residual defects in the form of dislocation loops, and a very high substitutionality (~90%). The activation efficiency and the Hall mobility of the implanted samples are found to be low after the electrical measurements. Based on these results an extended dopant diffusion effect for the residual defects and a correlation between the electrical properties and defect complexes are suggested.

Conversion of platelets into dislocation loops and voidite formation in type IaB diamonds

1995 ◽  
Vol 449 (1936) ◽  
pp. 295-313 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Local Mode ◽  
Diamond Structure ◽  
Dislocation Loops ◽  
X Ray ◽  
Regular Type ◽  
Transmission Electron ◽  
Stable Conditions ◽  
The One

Type la natural diamonds have been heated in the temperature range of 2400-2700°C under stabilizing pressures. The specimens studied are mainly regular type IaB diamonds. Transmission electron microscopy studies of treated speci­mens show that platelets are converted to interstitial ½ a 0 <011> dislocation loops; voidites are also formed. When all the platelets have been converted, the ex­perimental features associated with them also disappear, i. e. the X-ray extra reflections (spikes), the B' local-mode absorption and the lattice absorption in the one-phonon region termed the D spectrum. It is discovered that when diamonds are heated under graphite-stable rather than diamond-stable conditions, the rate of conversion is considerably enhanced; for instance, at 2650°C there is an increase in the rate of about three orders of magnitude. This enhancement is considered to be due to the instability of the diamond structure itself and a reason for this enhancement is suggested.

Abundance of halloysite neoformation in soils developed from crystalline rocks. Contribution of transmission electron microscopy

Clay Minerals ◽  
1992 ◽  
Vol 27 (1) ◽  
pp. 35-46 ◽  
Author(s):  
R. Romero ◽  
M. Robert ◽  
F. Elsass ◽  
C. Garcia
Keyword(s):  
Thermal Analyses ◽  
Crystalline Rocks ◽  
Metamorphic Rocks ◽  
X Ray Diffraction ◽  
Nw Spain ◽  
X Ray ◽  
Transmission Electron ◽  
High Concentrations ◽  
Bioclimatic Conditions ◽  
Mineralogical Phases

AbstractThe soils developed from crystalline and metamorphic rocks in Galicia (NW Spain), are characterized by high concentrations of 1 : 1 phyllosilicates and gels. Thermal analyses, X-ray diffraction after formamide treatment, and IR spectroscopy in the OH vibration range have been performed on the clay fractions, but do not discriminate clearly between the different associated mineralogical phases. HRTEM studies linked with microdiffraction and microanalyses have led to the identification of several types of gel which transform into goethite, gibbsite, clay precursors, and/ or halloysite according to their composition (Fe, Al or Si-Al). Halloysite-like minerals are the main constituents and they have a great variety of morphologies: lamellar, spheroidal, tubular, platy or poikilitic. In general, halloysite and gel formation on crystalline rocks is related to the bioclimatic conditions, involving high hydrolysis in the presence of organic matter. This halloysite seems to be a metastable mineral which would evolve into kaolinite with increasing weathering time.

Pyrophosphates of Tetravalent Elements and a Mössbauer Study of SnP2O7

1975 ◽  
Vol 53 (1) ◽  
pp. 79-91 ◽  
Author(s):  
Chung-Hsi Huang ◽  
Osvald Knop ◽  
David A. Othen ◽  
Frank W. D. Woodhams ◽  
R. Allan Howie
Keyword(s):  
Chemical Shift ◽  
Electric Field ◽  
Electric Field Gradient ◽  
The Other ◽  
Type I ◽  
Type Ii ◽  
Transition Elements ◽  
Mössbauer Study ◽  
X Ray ◽  
Ionic Compounds

Cubic M4+P2O7 pyrophosphates of Ti, Zr, Hf, Sn, and Pb have been examined by X-ray powder diffractometry and by infrared, Raman, and Mössbauer 119Sn spectroscopy. The tin compound appeared to be of Chaunac's type I (with P2O7 groups oriented at random) and could be converted to type II (with ordered P2O7 groups) by heating to high temperatures. All the other preparations were of Chaunac's type II. Evidence from lattice parameters and intensity features of the Raman spectra suggests that the cubic MP2O7 pyrophosphates fall in two groups, one containing the compounds of the typical elements (Ge, Sn, Pb) and the other, the compounds of the transition elements. No support has been found for the view that the P—O—P groupings of the pyrophosphate anion in these compounds are linear. The 119Sn chemical shift in SnP2O7 is only slightly less negative than the shift in CuSnF6.4H2O, which makes SnP2O7 one of the most ionic compounds of tetravalent tin known. The observed quadrupole splitting in the Mössbauer spectrum of SnP2O7 arises largely from the contribution of the valence term to the electric field gradient at the Sn atom.

X-ray structure determination of the monoclinic (121 K) and orthorhombic (85 K) phases of langbeinite-type dithallium dicadmium sulfate

2000 ◽  
Vol 56 (6) ◽  
pp. 921-935 ◽  
Author(s):  
A. Guelylah ◽  
G. Madariaga ◽  
W. Morgenroth ◽  
M. I. Aroyo ◽  
T. Breczewski ◽  
...  
Keyword(s):  
Orthorhombic Symmetry ◽  
Type I ◽  
Type Ii ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Distortion Analysis ◽  
Precise Analysis ◽  
Monoclinic Distortion

The structures of the monoclinic and the orthorhombic phases of type I langbeinite Tl2Cd2(SO4)3 have been determined at 121 and 85 K, respectively, by X-ray diffraction. A precise analysis of these structures shows the existence of some differences compared to langbeinites of type II. The monoclinic structure differs very little from the high-temperature cubic structure and the distortion relating the monoclinic structure to the cubic one is very small. SO4 tetrahedra seem to rotate under orthorhombic symmetry in the monoclinic phase. A symmetry distortion analysis of the ferroelectric monoclinic distortion discloses the importance of the secondary modes with orthorhombic symmetry, especially for the O atoms of the SO4 groups.

Study on Band Gap Energy of F Doped TiO2 Nanotubes

2017 ◽  
Vol 889 ◽  
pp. 234-238
Author(s):  
Mohd Hasmizam Razali ◽  
Nur Arifah Ismail ◽  
Mahani Yusoff
Keyword(s):  
Band Gap ◽  
Diffuse Reflectance Spectroscopy ◽  
Small Diameter ◽  
Ultra Violet ◽  
Band Gap Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gap Energy ◽  
Transmission Electron ◽  
Xrd Patterns

Pure and F doped TiO2 nanotubes was synthesized using simple hydrothermal method. The hydrothermal was conducted using teflon-liner autoclave and maintained at 150oC for 24 hours. The characterization of synthesised product was carried out using x-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive of x-ray spectroscopy (EDX) and ultra violet – visible light diffuse reflectance spectroscopy (UV-Vis DRS) for band gap measurements. XRD patterns indicated that anatase TiO2 phase was remained after F doping suggested that fluorine was highly dispersed into TiO2 by substituted with O in the TiO2 lattice to formed TiO2-xFx solid solution. Morphology investigation using TEM found out small diameter of nanotubes structure within 8 – 10 nm of pure and F doped TiO2 nanotubes. The band gap energy (Eg) of both nanotubes samples were almost similar proposing that F doping does not modify the band gap energy.

Supramolecular organization of a H-bonded perylene bisimide organogelator determined by transmission electron microscopy, grazing incidence X-ray diffraction and polarized infra-red spectroscopy

2017 ◽  
Vol 19 (48) ◽  
pp. 32514-32525 ◽  
Author(s):  
Alexandru Sarbu ◽  
Patrick Hermet ◽  
David Maurin ◽  
David Djurado ◽  
Laure Biniek ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grazing Incidence ◽  
Supramolecular Organization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Perylene Bisimide ◽  
Transmission Electron ◽  
Infra Red ◽  
Polarized Ftir

Polarized FTIR and TEM helps determine the supramolecular organization of PBI gelators.

scholarly journals Acemetacin cocrystal structures by powder X-ray diffraction

IUCrJ ◽  
2017 ◽  
Vol 4 (3) ◽  
pp. 206-214 ◽  
Author(s):  
Geetha Bolla ◽  
Vladimir Chernyshev ◽  
Ashwini Nangia
Keyword(s):  
Crystal Structures ◽  
Molecular Electrostatic Potential ◽  
Acid Group ◽  
Mutual Orientation ◽  
Type I ◽  
Type Ii ◽  
Melt Crystallization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrogen Bond Interactions

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM),p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthonR32(9)R22(8)R32(9) with three differentsynamides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, beinganti(type I) orsyn(type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O...H, N...H, Cl...H and C...H interactions. The physicochemical properties of these cocrystals are under study.

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