Interfaces abruptness

D.I. Fotiadis, A.M. Kremer, DP. McKenna, and K.F. Jensen. Complex Flow Phenomena in Vertical MOCVD Reactors Effects on Deposition Uniformity and Interface Abruptness. J. Cryst. Growth, 85 154—164,1987. 

Very low pressure processes (—1.3 Pa) have also been used for the growth of single-crystalline Si at relatively low temperatures (22, 23). Low-pressure operation is also advantageous for the growth of compound-semiconductor superlattices by reducing flow recirculations and improving interface abruptness (24). 

Abrupt-type interface (film formation) See Interface, abrupt. 

Interface, abrupt The interface that is formed between two materials (A and B) in contact where there is no diffusion, mixing, or chemical compound formation in the interfacial region. The transition of A to B in the length of a lattice parameter (=3 A). See also Interface. 

The presence of a spike at the heterojunction relies on the junction being abrupt on the atomic scale. Many billions of dollars worth of research have led to significant enhancements in crystal growth methods and to understanding and controlling the interface abruptness so that phenomena such as spikes at the interfaces can be used. Applications of heterojrmction discontinuities are mentioned briefly in Sections 3.5 and 3.6. 

The idea that unsymmetrical molecules will orient at an interface is now so well accepted that it hardly needs to be argued, but it is of interest to outline some of the history of the concept. Hardy [74] and Harkins [75] devoted a good deal of attention to the idea of force fields around molecules, more or less intense depending on the polarity and specific details of the structure. Orientation was treated in terms of a principle of least abrupt change in force fields, that is, that molecules should be oriented at an interface so as to provide the most gradual transition from one phase to the other. If we read interaction energy instead of force field, the principle could be reworded on the very reasonable basis that molecules will be oriented so that their mutual interaction energy will be a maximum. 

Gold is an example of a metal that does not form a silicide, and one may therefore expect the Au/Si interface to be abrupt. The structures of Au on Si (111) are interesting in that the unit cell is much smaller than that of the well known (7 X 7)... 

The eorresponding result for the surface tension [9] provides quite reasonable accuracy for a Leonard Jones fluid or an inert gas fluid, except helium whieh displays large quantum effeets. Thus we ean eonelude that the leading mechanisms of surface tension in a simple fluid is the loss of binding energy of the liquid phase at the gas-liquid interface and the seeond most important meehanism is likely to be the adsorption-depletion at the interface whieh ereates a moleeularly smooth density profile instead of an abrupt step in the density. 

Figure 5.21 shows that the analysis of the fine lamellae included both the W-rich and W-poor phases, and does not reveal any deviation from the original W-composition of the alloy. There is an abrupt change of solute concentration at the interface, consistent with the discontinuous mechanism of transformation. 

Figure 5 shows the diffusion of a solute into such an impermeable membrane. The membrane initially contains no solute. At time zero, the concentration of the solute at z = 0 is suddenly increased to c, and maintained at this level. Equilibrium is assumed at the interface of the solution and the membrane. Therefore, the corresponding membrane concentration at z = 0 is Kc1. Since the membrane is impermeable, the concentration on the other side will not be affected by the change at z = 0 and will still be free of solute. This abrupt increase produces a time-dependent concentration profile as the solute penetrates into the membrane. If the solution is assumed to be dilute, Fick s second law Eq. (9) is applicable ... 

At the interface the composition changes from x = xx to x — (1 — x ). This change is not abrupt, but occurs over an interfacial... 

In order to estimate the coefficient 7 we consider the hypothetical situation in which the composition at the interface changes abruptly from... 

Based on the above results and discussion, the mechanism for the rhythmic oscillations at the oil/water interface with surfactant and alcohol molecules may be explained in the following way [3,47,48] with reference to Table 1. As the first step, surfactant and alcohol molecules diffuse from the bulk aqueous phase to the interface. The surfactant and alcohol molecules near the interface tend to form a monolayer. When the concentration of the surfactant together with the alcohol reaches an upper critical value, the surfactant molecules are abruptly transferred to the organic phase with the formation of inverted micelles or inverted microemulsions. This step should be associated with the transfer of alcohol from the interface to the organic phase. Thus, when the concentration of the surfactant at the interface decreases below the lower critical value, accumulation of the surfactant begins and the cycle is repeated. Rhythmic changes in the electrical potential and the interface tension are thus generated. 

These two features exemplify the behavior of interface states, which are states that are not seen for either component of a bimetallic surface alloy but which exist because of the abrupt change in electronic properties at the interface. 

ARUPS results have identified unique electronic interface states for the Cu/Ru(0001) system. These states are not present in either metal separately but exist because of the abrupt change in properties at the interface. 

Infringement patent information searches, 18 207, 233-234, 241 Infusion mashing, 3 577-578 InGaAsP alloy, abrupt interfaces in,... 

The limiting current density may be defined as the current density at which the depression of the Na+ concentration at the interface of the membrane s sulphonic and carboxylic layers results in an abrupt rise in cell voltage and drop in current efficiency. 

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