A dual site growth model of gallium arsenide epitaxial layers from the gas phase

1987 ◽  
Vol 52 (5) ◽  
pp. 1131-1159
Author(s):  
Emerich Erdös ◽  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Growth Rate ◽  
Gallium Arsenide ◽  
Gas Phase ◽  
Quantitative Description ◽  
The Other ◽  
Rate Equations ◽  
Partial Pressures ◽  
The Individual ◽  
Rate Controlling Step ◽  
Dual Site

For a quantitative description of the epitaxial growth rate of gallium arsenide, a model is proposed including two rate controlling steps. One of these steps is the diffusion of gaseous components between the gas phase and the epitaxial layer surface, and the other step is of chemical nature, i.e. either the surface reaction or adsorption or desorption of one of the gaseous components. In the model considered, an active dual site is involved in the second rate controlling step, and twelve mechanisms are proposed for which the pertinent rate equations are derived. The individual mechanisms differ one from the other not only by the kind of the rate controlling step but also by the occupation of the dual site, viz. in the both direct and reversed direction. The proposed model is confronted with the dependences of the growth rate on partial pressures of components in the feed found by experiment. The results are discussed with regard to the possibility of individual mechanisms and of the model as a whole, and also with respect to their applicability and to the direction of further investigations.

A polycentric growth model of gallium arsenide epitaxial layers from the gas phase with simultaneous diffusion, adsorption and chemical reaction

1988 ◽  
Vol 53 (12) ◽  
pp. 2995-3013
Author(s):  
Emerich Erdös ◽  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Growth Rate ◽  
Gallium Arsenide ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Surface Reaction ◽  
Quantitative Description ◽  
The Other ◽  
Rate Equations ◽  
Impact Interaction ◽  
Partial Pressures

For a quantitative description of the epitaxial growth rate of gallium arsenide, two models are proposed including two rate controlling steps, namely the diffusion of components in the gas phase and the surface reaction. In the models considered, the surface reaction involves a reaction triple - or quadruple centre. In both models three mechanisms are considered which differ one from the other by different adsorption - and impact interaction of reacting particles. In every of the six cases, the pertinent rate equations were derived, and the models have been confronted with the experimentally found dependences of the growth rate on partial pressures of components in the feed. The results are discussed with regard to the plausibility of individual mechanisms and of both models, and also with respect to their applicability and the direction of further investigations.

A quantitative model of epitaxial layers growth from the gas phase with a simultaneous participation of diffusion, adsorption, and chemical reaction

1986 ◽  
Vol 51 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Emerich Erdös ◽  
Jiří Laitner ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Growth Rate ◽  
Gas Phase ◽  
Epitaxial Layer ◽  
Chemical Nature ◽  
Quantitative Description ◽  
Physical Nature ◽  
Rate Equations ◽  
Layer Surface ◽  
Active Centre ◽  
Rate Controlling Step

For a quantitative description of the epitaxial growth rate of gallium arsenide, a model has been proposed including two rate controlling steps, namely one step of physical nature and the other one of chemical nature. As the step of physical nature, the diffusion of gaseous components between the gas phase and the epitaxial layer surface has been considered, and from the steps of chemical nature the adsorption of gaseous components on the epitaxial layer surface and a heterogenous surface reaction have been taken into account. According to the kind of the chemical rate controlling step, five mechanisms have been proposed, where a one - centre model was used in all cases, i.e. the idea that the rate controlling step takes place under participation of one active centre. For all the mechanisms considered, the pertaining rate equations have been derived, which were confronted with the experimentally found dependences of the growth rate on partial pressures of components in the feed. The results are discussed both from the view point of plausibility of individual mechanisms and from the point of view of their applicability and of the next research direction.

Direct Nucleation of Crystalline SiGe on Substrates by Reactive Thermal CVD with Si2H6 and GeF4

1997 ◽  
Vol 467 ◽  
Author(s):  
Fumio Yoshizawa ◽  
Kunihiro Shiota ◽  
Daisuke Inoue ◽  
Jun-ichi Hanna
Keyword(s):  
Growth Rate ◽  
Gas Phase ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Film Growth ◽  
Early Stage ◽  
Gaseous Mixture ◽  
The Other ◽  
Thermal Cvd ◽  
Initial Deposition

ABSTRACTPolycrystalline SiGe (poly-SiGe) film growth by reactive thermal CVD with a gaseous mixture of Si2H6 and GeF4 was investigated on various substrates such as Al,Cr, Pt, Si, ITO, ZnO and thermally grown SiO2.In Ge-rich film growth, SEM observation in the early stage of the film growth revealed that direct nucleation of crystallites took place on the substrates. The nucleation was governed by two different mechanisms: one was a heterogeneous nucleation on the surface and the other was a homogeneous nucleation in the gas phase. In the former case, the selective nucleation was observed at temperatures lower than 400°C on metal substrates and Si, where the activation of adsorbed GeF4 on the surface played a major role for the nuclei formation, leading to the selective film growth.On the other hand, the direct nucleation did not always take place in Si-rich film growth irrespective of the substrates and depended on the growth rate. In a growth rate of 3.6nm/min, the high crystallinity of poly-Si0.95Ge0.05in a 220nm-thick film was achieved at 450°C due to the no initial deposition of amorphous tissue on SiO2 substrates.

A dual equilibrium diffusion model for epitaxial growth of gallium arsenide layers from the gas phase and an a priori computation of growth rates

1984 ◽  
Vol 49 (11) ◽  
pp. 2425-2436 ◽  
Author(s):  
Emerich Erdös ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Gallium Arsenide ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
A Priori ◽  
Boundary Layer Theory ◽  
View Point ◽  
Chemical Equilibria ◽  
Rate Controlling Step

A model is proposed and quantitatively treated of epitaxial growth of gallium arsenide layers, where the rate controlling step consists in the diffusion of reactants through a stagnant gas film adhering to the substrate, and where chemical equilibria are established between the reactants in the main gas stream and at the surface of substrate. The boundary layer theory is applied to the hydrodynamic part of the model which is simplified by introducing a mean effective film thickness, and the system of Ga-As-Cl-H is reduced to six molecular species and to three chemical reactions. With this basis and using estimated values of diffusion coefficients, the growth rates of epitaxial gallium arsenide layers have been a priori computed in dependence of the feed rate, its composition and on temperature. The predicted three dependences are discussed from the view-point of their courses and of the significance of computed results.

scholarly journals Die Kinetik des thermischen Zerfalls von ClNO2 / Thermal Decomposition of ClNO2

1978 ◽  
Vol 33 (9) ◽  
pp. 1037-1047 ◽  
Author(s):  
H.-D. Knauth ◽  
H. Martin
Keyword(s):  
Thermal Decomposition ◽  
Time Dependence ◽  
Gas Phase ◽  
Reaction Scheme ◽  
The Other ◽  
Rate Equations ◽  
Standard State ◽  
Inert Solvent ◽  
State 1 ◽  
Overall Reactions

ClNO2 decomposes incompletely at temperatures between 353 K and 373 K in the nonpolar inert solvent C7F15Cl according to 2 ClNO2=2 NO2+Cl2. (a) Some ClNO is formed as by-product according to 2 ClNO2 = 2 ClNO+O2 . (b) The reactions were followed photometrically by the arising NO2 . The time dependence of the brutto-reaction is described on the basis of the reaction scheme ClNO2⇄NO2+Cl (1, - 1); NO3+NO2⇄NO+O2+NO2 (5, - 5); ClNO2+ClNO2⇄Cl2+2NO2 (2, - 2); NO+ClNO2⇄ClNO+NO2 (6, - 6); Cl+ClNO2⇄Cl2+NO2 (3, - 3); ClNO+ClNO2⇄NO±Cl2+NO2 (7, - 7);NO2+ClNO2⇄NO3±ClNO (4, - 4); Cl+ClNO⇄Cl2+NO (8, - 8). Arrhenius parameters for the steps (1) and (2) were obtained: A1/s-1 = 1016.47±0.78, E1/kJ mol-1 = 152.3 ± 5.4;A2/cm3 mol-1 s-1 = 1012.99±0.02 E2/kJ mol-1 = 88.7 ± 0.8. The other parameters entering the rate equations were determined at 373 K as k-1/k3 = 1.5 ± 0.3; k4/cm3 mol-1 s-1 = 0.17; k7/cm3 mol-1 s-1 = 11.2. The enthalpies and entropies of the overall reactions (a), (b) and N2O4 = 2 NO2 (c) were measured directly (c) or indirectly: (a) (b) (c) ⊿RH/kJ mol-1 46.4 83.7 65.3 ⊿RS/J K -1 mol-1 61.8 85.7 97.8 (standard state 1 mol cm-3, T = 363 K). Former investigations of the reaction in the gas phase and in solution which were interpreted exceptionally by step (1) followed by the fast step (3) are now interpreted on the basis of the new reaction scheme discussed here and are found to be consistent with it.

scholarly journals Magnitude and pattern of compensatory growth in rats after cold exposure

Development ◽  
1969 ◽  
Vol 21 (3) ◽  
pp. 407-416
Author(s):  
Marjorie M. C. Lee ◽  
P. C. Chu ◽  
H. C. Chan
Keyword(s):  
Growth Rate ◽  
Compensatory Growth ◽  
Relative Rate ◽  
Normal Growth ◽  
The Other ◽  
Regulatory Control ◽  
Catch Up ◽  
Common Observation ◽  
The Individual ◽  
Favorable Conditions

It is a common observation that normal growth is affected or suppressed in young individuals by environmental adversities and physical disturbances. On the other hand, when health or favorable conditions are restored, the tempo of growth promptly accelerates as if the individual is trying to make up for the growth debt incurred. Tanner has referred to this increased growth rate after diseases or starvation as compensatory or ‘catch-up’ growth, a topic on which he has written eloquently and fully in a number of articles (1963 a, b). He considers this compensatory growth as a ‘self-stabilizing’ or ‘target-seeking’ phenomenon in the regulatory control of growth. Growth of young rats is slowed by severe cold and increased by warmth (Heroux & Gridgeman, 1958; Chevillard, Portet & Cadot, 1963). The aim of the present investigation is to show the magnitude and pattern of compensatory growth in rats after single and repeated cold exposures; to evaluate age differentials in this response; and to study the pattern and relative rate of compensatory growth in the various bony segments of the appendages.

Evaluation of beef breeds for rangeland weaner production in Zimbabwe 2. Productivity of crossbred cows and heterosis estimates

1988 ◽  
Vol 47 (3) ◽  
pp. 361-367 ◽  
Author(s):  
H. P. R. Tawonezvi ◽  
H. K. Ward ◽  
J. C. M. Trail ◽  
D. Light
Keyword(s):  
Growth Rate ◽  
Reproductive Performance ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Live Weight ◽  
The Other ◽  
Crossbred Cows ◽  
Productivity Indices ◽  
The Individual ◽  
Zebu Cows

ABSTRACTCrossbred cows were evaluated for reproductive performance and live weight, and for pre-weaning growth and viability of progeny sired by seven unrelated breeds. They were also evaluated on overall productivity expressed as weight of weaned calf per cow mated per year, per 100 kg of cow per year and per 100 kg metabolic weight of cow per year. The cows comprised reciprocals of Africander with Mashona, Nkone, Brahman and Sussex, one-way crosses sired by Sussex out of Mashona, Nkone and Brahman dams, and by Charolais out of Africander, Mashona, Nkone, Brahman and Sussex dams. These represented sanga × sanga, sanga × zebu, Bos taurus × sanga, Bos taurus × zebu and Bos taurus × Bos taurus crossbred types. Bos taurus × zebu crosses were superior to other breed types for all the three productivity indices and for virtually all the individual components of these. There was little difference between the other four breed types in overall productivity of components of these. Differences between reciprocals were observed in sanga × sanga and sanga × zebu, cows with Africander dams being more productive than reciprocals with Mashona, Nkone and Brahman dams. The Bos taurus × Bos taurus cross was inferior in overall productivity primarily due to large cow weight and relatively low growth rate of progeny. Progeny sired by Friesian, Simmental and Brahman had higher weaning weights than those sired by Hereford, Aberdeen Angus, Africander and Tuli. Overall, heterosis was positive for all traits and averaged 0·15 for the three measures of cow productivity. Heterosis was three times higher in the Bos taurus × Bos indicus cross than in the Bos indicus crosses.

Writing in Aphasia Rehabilitation: Cursive vs Manuscript

1976 ◽  
Vol 41 (4) ◽  
pp. 523-529 ◽  
Author(s):  
Daniel R. Boone ◽  
Harold M. Friedman
Keyword(s):  
Correct Response ◽  
The Other ◽  
Read Aloud ◽  
Writing Style ◽  
Reading And Writing ◽  
Manual Responses ◽  
Significant Difference ◽  
Written Form ◽  
The Individual ◽  
Read Number

Reading and writing performance was observed in 30 adult aphasic patients to determine whether there was a significant difference when stimuli and manual responses were varied in the written form: cursive versus manuscript. Patients were asked to read aloud 10 words written cursively and 10 words written in manuscript form. They were then asked to write on dictation 10 word responses using cursive writing and 10 words using manuscript writing. Number of words correctly read, number of words correctly written, and number of letters correctly written in the proper sequence were tallied for both cursive and manuscript writing tasks for each patient. Results indicated no significant difference in correct response between cursive and manuscript writing style for these aphasic patients as a group; however, it was noted that individual patients varied widely in their success using one writing form over the other. It appeared that since neither writing form showed better facilitation of performance, the writing style used should be determined according to the individual patient’s own preference and best performance.

Margaret Mahy: An Adlerian Reading

2008 ◽  
Vol 1 (2) ◽  
pp. 187-199
Author(s):  
KATHRYN WALLS
Keyword(s):  
Young Female ◽  
The Other ◽  
Individual Psychology ◽  
The Novel ◽  
Alfred Adler ◽  
Female Protagonists ◽  
Magical Power ◽  
Margaret Mahy ◽  
The Individual

According to the ‘Individual Psychology’ of Alfred Adler (1870–1937), Freud's contemporary and rival, everyone seeks superiority. But only those who can adapt their aspirations to meet the needs of others find fulfilment. Children who are rejected or pampered are so desperate for superiority that they fail to develop social feeling, and endanger themselves and society. This article argues that Mahy's realistic novels invite Adlerian interpretation. It examines the character of Hero, the elective mute who is the narrator-protagonist of The Other Side of Silence (1995) , in terms of her experience of rejection. The novel as a whole, it is suggested, stresses the destructiveness of the neurotically driven quest for superiority. Turning to Mahy's supernatural romances, the article considers novels that might seem to resist the Adlerian template. Focusing, in particular, on the young female protagonists of The Haunting (1982) and The Changeover (1984), it points to the ways in which their magical power is utilised for the sake of others. It concludes with the suggestion that the triumph of Mahy's protagonists lies not so much in their generally celebrated ‘empowerment’, as in their transcendence of the goal of superiority for its own sake.

Gewalt und Kommunikation

2011 ◽  
Vol 2011 (1) ◽  
pp. 5-28
Author(s):  
Jens Bonnemann
Keyword(s):  
Twentieth Century ◽  
Moral Philosophy ◽  
The Other ◽  
Practical Philosophy ◽  
Valuable Contribution ◽  
Human Species ◽  
Normal Case ◽  
Jean Paul ◽  
Philosophy Of Dialogue ◽  
The Individual

In ethics, when discussing problems of justice and a just social existence one question arises obviously: What is the normal case of the relation between I and you we start from? In moral philosophy, each position includes basic socio-anthropological convictions in that we understand the other, for example, primarily as competitor in the fight for essential resources or as a partner in communication. Thus, it is not the human being as isolated individual, or as specimen of the human species or socialised member of a historical society what needs to be understood. Instead, the individual in its relation to the other or others has been studied in phenomenology and the philosophy of dialogue of the twentieth century. In the following essay I focus on Martin Buber’s and Jean-Paul Sartre’s theories of intersubjectivity which I use in order to explore the meaning of recognition and disrespect for an individual. They offer a valuable contribution to questions of practical philosophy and the socio-philosophical diagnosis of our time.

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