Heterostructures transitivity

Cathodoluminescence microscopy and spectroscopy techniques are powerful tools for analyzing the spatial uniformity of stresses in mismatched heterostructures, such as GaAs/Si and GaAs/InP. The stresses in such systems are due to the difference in thermal expansion coefficients between the epitaxial layer and the substrate. The presence of stress in the epitaxial layer leads to the modification of the band structure, and thus affects its electronic properties it also can cause the migration of dislocations, which may lead to the degradation of optoelectronic devices based on such mismatched heterostructures. This application employs low-temperature (preferably liquid-helium) CL microscopy and spectroscopy in conjunction with the known behavior of the optical transitions in the presence of stress to analyze the spatial uniformity of stress in GaAs epitaxial layers. This analysis can reveal,... 

We now deal with the structures that molecules build on substrate surfaces at full coverage, that is in the ML regime. Such hybrid systems are known as heterostructures. H. Kroemer dehned heterostructures as heterogeneous semiconductor structures built from two or more different semiconductors, in such a way that the transition region or interface between the different materials plays an essential role in any device action (Kroemer, 2001). The term heterostructure can be generalized to any... 

Within the experimental error these organic/organic heterostructures exhibit transitivity, in the sense that... 

The question of commutativity and transitivity was previously raised for inorganic semiconductors of groups IV, III-V and II-VI (Katnani Margaritondo, 1983). When prepared under controlled conditions, Ge/Si and Si/Ge heterostructures... 

There are different criterion of how to classify solid-solid interfaces. One is the sharpness of the boundary. It could be abrupt on an atomic scale as, for example, in III-IV semiconductor heterostructures prepared by molecular beam epitaxy. In contrast, interdiffusion can create broad transitions. Surface reactions can lead to the formation of a thin layer of a new compound. The interfacial structure and composition will therefore depend on temperature, diffusion coefficient, miscibility, and reactivity of the components. Another criterion is the crystallinity of the interface. The interface may be crystalline-crystalline, crystalline-amorphous, or completely amorphous. Even when both solids are crystalline, the interface may be disturbed and exhibit a high density of defects. 

It has been found for various III/V heterostructures that bandoffsets can be obtained via an internal reference rule for transition metals [18,19], This method was applied to predict the valence-band offset of the GaN/AIN heterostructure [20], However, as demonstrated by Heitz et al [10], the internal reference rule fails for the GaN/GaAs heterostructure. 

Ultraviolet Raman spectroscopy has emerged as a powerful technique for characterization of nanoscale materials, in particular, wide-bandgap semiconductors and dielectrics. The advantages of ultraviolet excitation for Raman measurements of ferroelectric thin films and heterostructures, such as reduced penetration depth and enhanced scattering intensity, are discussed. Recent results of application of ultraviolet Raman spectroscopy for studies of the lattice dynamics and phase transitions in nanoscale ferroelectric structures, such as superlattices based on BaTiOs, SrTiOs, and CaTiOs, as well as ultrathin films of BaTiOs and SrTi03 are reviewed. 

UPD-OPD transition phenomena can be used for the deposition of heterostructured ultrathin metal films from multicomponent Mef systems using, for example, the polarization routine for i = 2 shown in Fig. 6.16. 

Recent developments in solid state solutions of AlN/SiC/InN/GaN open up the possibility of a new generation of heterostructure devices based on SiC. Single crystal epitaxial layers of AlN/SiC/InN have been recently demonstrated by Dmitriev [4]. A whole range of solid state solutions has been grown. Recently Dmitriev et al [5] reported on an (AlNx-SiC,.x)-(AlNySiC,.y) p-n junction. Solid state solutions of AlN-SiC [6,7] are also expected to lead to direct gap ternary materials for UV and deep blue optoelectronics, including the development of visible lasers. The direct to indirect bandgap transition is predicted to occur at between 70 and 80 % of AIN in SiC. 

Lateral photoconductivity spectra and photofield electron emission of multilayer Ge/Si heterostructures with Ge quantum dots were studied at 77 and 300 K. Measurements of lateral photoconductivity spectra at 77 K showed the presence of localized states in the potential well. The photocurrent with limiting energies of 0.3 eV and 0.33 eV can be attributed to electron transitions from localized to delocalized states. A correlation between the regularities of the photoconductivity and photofield emission from such systems was revealed. 

This chapter presents a critical review on the newly developed procedures for multidimensional electrode nanoarchitecturing for Li- and Na-ion batteries. Starting from nt-Ti02 utilization, first-row transition metal oxide nanocomposites are examined. Metal foams for 2D and 3D battery architectures and graphene-transition metal oxide heterostructures with unusual performance for battery applications are discussed. 

Graphene—Transition Metal Oxide Heterostructures for Battery Applications 383... 

Graphene-Transition Metai Oxide Heterostructures for Battery Appiications 385... 

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