Si diffusion path for pit-free graphene growth on SiC(0001)

Besides the atomic surface structure, diverging in special cases with respect to the bulk structure, the real structure of a surface Is determined by the step structure. Using the decoration technique /1/ it is possible to image step structures having step heights down to a single lattice plane distance electron-microscopically. For a number of problems the knowledge of the monatomic step structures is important, because numerous problems of surface physics are directly connected with processes taking place at these steps, e.g. crystal growth or evaporation, sorption and nucleatlon as initial stage of overgrowth of thin films.To demonstrate the decoration technique by means of evaporation of heavy metals Fig. 1 from our former investigations shows the monatomic step structure of an evaporated NaCI crystal. of special Importance Is the detection of the movement of steps during the growth or evaporation of a crystal. From the velocity of a step fundamental quantities for the molecular processes can be determined, e.g. the mean free diffusion path of molecules.

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Gastroretentive System of Fluvastatin Sodium by Using Natural Mucilage and Synthetic Polymer

International Journal of Drug Delivery Technology ◽

10.25258/ijddt.v4i2.8856 ◽

2014 ◽

Vol 4 (2) ◽

Author(s):

Umamaheswara G. ◽

Anudeep D.

Keyword(s):

Half Life ◽

Release Kinetics ◽

Kinetic Studies ◽

Diffusion Path ◽

Synthetic Polymer ◽

In Vitro Dissolution ◽

Direct Compression ◽

Drug Content ◽

Biological Half Life

Fluvastatin sodium is a novel compound used as cholesterol lowering agent which acts through the inhibition of 3- hydroxyl-3- methyl glutaryl- coenzyme A (HMG-Co A) reductase. It has short biological half life (1-3h) in humans required a dosing frequency of 20 to 40mg twice a day. Due to its short variable biological half life it has been developed to a sustained gastroretentive system with a natural and synthetic polymer and to study how far the natural mucilage improves the sustained activity. Floating tablets were prepared by direct compression method using in combination of natural mucilage and synthetic polymer. Prior to the preparation of tablets the physical mixtures were subjected to FT IR studies and pre compression parameters. After preparation of tablets they were subjected to various tests like swollen index, drug content, In vitro dissolution and release kinetics with pcp disso software etc. The tablets prepared by direct compression shown good in thickness, hardness and uniformity in drug content, the prepared tablets floated more than 12h except FS1 and FS2 shows 9 and 11h. Swollen index studies shows with increase in concentration of polymer the swelling increases the diffusion path length by which the drug molecule may have to travel and cause lag time. In vitro results shows that on increasing the amount of hibiscus polymer the sustain activity is increased because of its integrity and forms a thick swollen mass and reduces the erosion property of the HypromelloseK100M, kinetic studies shows that FS 1, FS2, FS3 followed the Korsmeyer peppas model and the rest FS 4, FS 5, FS6 follows the zero order respectively. Based on n value indicating that the drug release followed super case II transport mechanism due to the erosion of the polymer.

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Graphene growth by metal etching on Ru(0001)

Physical Review B ◽

10.1103/physrevb.80.235422 ◽

2009 ◽

Vol 80 (23) ◽

Cited By ~ 42

Author(s):

E. Starodub ◽

S. Maier ◽

I. Stass ◽

N. C. Bartelt ◽

P. J. Feibelman ◽

...

Keyword(s):

Graphene Growth ◽

Metal Etching

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Role of dislocations in nitride laser diodes with different indium content

Scientific Reports ◽

10.1038/s41598-020-79528-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Agata Bojarska-Cieślińska ◽

Łucja Marona ◽

Julita Smalc-Koziorowska ◽

Szymon Grzanka ◽

Jan Weyher ◽

...

Keyword(s):

Quantum Wells ◽

Defect Density ◽

Laser Diodes ◽

Diffusion Path ◽

Vapour Phase ◽

Indium Content ◽

Nonradiative Recombination ◽

Light Emitters ◽

Vapour Phase Epitaxy

AbstractIn this work we investigate the role of threading dislocations in nitride light emitters with different indium composition. We compare the properties of laser diodes grown on the low defect density GaN substrate with their counterparts grown on sapphire substrate in the same epitaxial process. All structures were produced by metalorganic vapour phase epitaxy and emit light in the range 383–477 nm. We observe that intensity of electroluminescence is strong in the whole spectral region for devices grown on GaN, but decreases rapidly for the devices on sapphire and emitting at wavelength shorter than 420 nm. We interpret this behaviour in terms of increasing importance of dislocation related nonradiative recombination for low indium content structures. Our studies show that edge dislocations are the main source of nonradiative recombination. We observe that long wavelength emitting structures are characterized by higher average light intensity in cathodoluminescence and better thermal stability. These findings indicate that diffusion path of carriers in these samples is shorter, limiting the amount of carriers reaching nonradiative recombination centers. According to TEM images only mixed dislocations open into the V-pits, usually above the multi quantum wells thus not influencing directly the emission.

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