Localized Interface Optical-phonon Modes Research Articles

Influence of ternary mixed crystal defect layer on the localized interface optical-phonon modes in a finite superlattice

Within the framework of dielectric continuum theory, we study the effect of ternary mixed crystal defect layer on the localized interface optical-phonon modes in a finite superlattice by using a transfer matrix method. In such a finite superlattice, the evolution of all the interface modes can be clearly tracked. Our numerical results show there exist two types of localized modes and their macroscopic electrostatic potentials mostly locate in the vicinity of the defect layer or surface layer, respectively. As the relative widths and nature of the structural cell or the defect layer are altered, the localized characteristics of these modes are significantly influenced. Though the conservation of the total number of localized modes is broken, the conservation of the total number of all interface modes including both the extended modes and localized modes is still kept for every value of the wavevector q‖.

The evolution of the localized interface optical-phonon modes in a finite superlattice with a structural defect

Using a transfer matrix method, we study the property of the interface optical-phonon modes (IOPMs) in a finite semiconductor superlattice (SL) with a structural defect layer in the dielectric continuum approximation. The results show that in such a structure there exist two types of localized IOPMs. They may appear either in the minigap or below and above the bulk bands, and their macroscopic electrostatic potentials are located in the vicinity of the defect layer or surface layer. The evolution of the modes localized in the vicinity of a different interface can clearly be tracked. In some cases, the degeneracy between localized IOPMs may occur, but the conservation of the total number of IOPMs is always kept for every value of the transversal wave number.

Effect of different coupling on localized interface optical-phonon modes in N-constituent superlattices with a defect layer

In the dielectric continuum approximation, we study the effect of different styles of coupling on the localized interface optical-phonon modes in two coupled semi-infinite N-constituent superlattices with a structural defect layer. The defect layer is composed of frequency-dependent or frequency-independent dielectric medium. The influence of the material and structural parameters of the defect layer on the localized interface optical-phonon modes is investigated in detail. Our results show that the localized modes exhibit peculiar characteristics in multi-constituent superlattices with a defect layer, substantially different from those of the conventional dual-constituent sample. A simple physical picture is presented to explain these results.

Localized interface optical-phonon modes in graded3C−SiC/Siheterojunctions

We study the properties of localized interface optical-phonon modes in $\mathrm{Si}/3C\ensuremath{-}\mathrm{SiC}$ heterojunctions within the framework of the dielectric continuum theory. Our model calculation takes into account the existence of an interfacial nonabrupt transition region, whose thickness is considered varying from 0.5 to 2.5 nm. Numerical results reveal some interesting properties of the interface effects, which can substantially shift (up to $20{\mathrm{cm}}^{\ensuremath{-}1})$ the high-frequency antisymmetric interface modes found in the abrupt case. Moreover, optical-phonon modes emerge in the low-frequency range of the spectrum, which are sensitive to the value of the nonabrupt interface thickness.

Influence of the structural defects on localized interface optical-phonon modes in periodically layered heterostructures

The existence and characteristics of the localized interface optical-phonon modes in periodically layered heterostructures with a defect layer consisting of ternary mixed crystal Al x Ga 1− x As are studied in the dielectric continuum approximation. A comparison of the localized and extended interface optical phonon modes between the presented structure and GaAs/AlAs superlattice structure with defect layers is addressed. We find that the frequencies and localization degree of the localized modes depend on the concentration and thickness of the defect layer. Specially, the symmetric localized modes are more sensitive to the concentration of the defect layer than the antisymmetric modes. It is expected that the localized modes can be artificially controlled by adjusting the parameters of the presented micro-structures.

Localized interface optical phonon modes in a semi-infinite superlattice with a caplayer

We investigate the existence and characteristics of the localized interface opticalphonon modes (IOPMs) in a semi-infinite AlAs–GaAs superlattice with a caplayer consisting of ternary mixed crystal Alx Ga1−x As inthe dielectric continuum approximation. We find that the introductionof two-mode behaviour of the ternary mixed crystal of the cap layer orthe semi-infinite uniform dielectric medium leads to rich and variedlocalized mode spectra with interesting features. Moreover, it is alsofound that the localized IOPMs are sensitive to the concentrationx, thethickness of the cap layer and the type of semi-infinite uniform dielectric medium.A brief analysis of these results is given. It is expected that the localized IOPMscan be artificially controlled by adjusting the parameters of the proposedmicro-structures.

Localized interface optical-phonon modes in two coupled semi-infinite superlattices

The existence and features of the localized interface optical-phonon modes (IOPM's) in two coupled semi-infinite superlattices with a frequency-independent defect layer are investigated in the dielectric continuum approximation. A comparison of the localized IOPM's between structures with frequency-independent defect layer (type I structure) and frequency-dependent defect layer (type II structure) is made. We find that the antisymmetric localized modes in type I structure display interesting features significantly different from those in the type II structure. The existence and localization of the antisymmetric modes in type I structure strongly depend on the nature of the defect layer, transverse wave number, the thickness of the defect layer and the constituent layers. However, the symmetric localized modes are not sensitive to the nature and thickness of the defect layer.

Surface Defection of TiO2 Particles by High Temperature Vapor Reduction Method

In the framework of dielectric continuum theory and applying transfer matrix method, we study the properties of localized interface optical-phonon modes (IOPM's) in triple-constitution semiconductor superlattices (SL's) with a structural defect layer. Numerical results reveal some interesting and novel properties of minigaps and localized IOPM's, substantially different from those of the conventional dual-constituent SL's. We also present a simple physical picture to interpret these properties.

Effect of structural defects consisting of ternary mixed crystals on localized interface optical modes in superlattices

The localized interface optical-phonon modes lying in a minigap of AlAs-GaAs superlattice with structural defects consisting of ternary mixed-crystal ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ are studied in the dielectric continuum approximation. We find that three localized interface optical modes appear in each frequency minigap for certain structural parameters. Two of them are antisymmetric with respect to the center of the defect layers and display interesting features significantly different from those in the structure with a binary crystal defect layer. However, the third mode with symmetric property shows similar behavior as that in the structure with a binary crystal defect layer.

Characteristics of the Localized Interface Optical-phonon Modes in Triple-constitution Superlattices with Defect Layers

In the framework of dielectric continuum theory and applying transfer matrix method, we study the properties of localized interface optical-phonon modes (IOPM's) in triple-constitution semiconductor superlattices (SL's) with a structural defect layer. Numerical results reveal some interesting and novel properties of minigaps and localized IOPM's, substantially different from those of the conventional dual-constituent SL's. We also present a simple physical picture to interpret these properties.

Localized interface optical-phonon modes in superlattices with structural defects

Localized interface optical-phonon modes in superlattices with structural defects