Nitrides superlattices

In general, unlike for the perfect epitaxial structures of fully strained materials, for nitride heteroepitaxial layers it is essential to perform not a single scan for a symmetrical reflection, but a set of two- or even three-dimensional maps of symmetrical and asymmetrical reflections. Additionally, for some applications, an intense beam is needed and therefore low-resolution X-ray diffractometry can be sometimes a preferable technique to the commonly used high-resolution XRD. For example, if we examine a heterostructural nitride superlattice, low resolution diffractometry will give us a broader zeroth-order peak (information on the whole layer) but more satellite peaks (information on the sublayers). Therefore, multipurpose diffractometers with variable configurations are the most desirable in nitride research. 

In conclusion, we have reviewed some of the structural optical and electrical properties of amorphous silicon/amorphous silicon nitride superlattices. The regularity and smoothness of the layers, the abruptness of the interfaces. 

Figure 8 Vickers hardness of nitride superlattice structures as a function of superlattice period X. (From Ref. 47, 48.)...

Lin, X.M., Jaeger, H.M., Sorensen, C.M. and Klabunde, K.J. (2001) Formation of long-range-ordered nanocrystal superlattices on silicon nitride substrates. Journal of Physical Chemistry B, 105 (17), 3353-3357. 

H. Morkoc, F. Hamdani, and A. Salvador, Electronic and Optical Properties of IIT-V Nitride based Quantum Wells and Superlattices K. Doverspike and J. /. Pankove, Doping in the 111-Nitrides... 

Matsuoka T (2005) Progress in nitride semiconductors from GaN to InN - MOVPE growth and characteristics. Superlattices and Microstructures 37(1), 19-32... 

Hossain et al [15] measured die cathodoluminescence in undoped aluminium nitride (AIN) thin films at 300, 77 and 4.2 K. These films were grown on sapphire and SiC substrates by LP-MOCVD at 1473 K. As shown in FIGURE 1, two distinct peaks were observed at about 6.1 and 5.9 eV, respectively. The energy position of these peaks increases and the linewidth becomes narrower, as the temperature is decreased. They believed that these two peaks are due to exciton recombination. Recently, MacMillan et al measured cathodoluminescence in AlN-GaN superlattices [16],... 

Figure 3.10 A large, 2d superlattice of 5.5-nin gold Danoparticles ligated with dodecanethiol on a silicon nitride surface. Note hexatic, close-pacfced structure (like pennies on a table top) and the spacing between the nanoparticles, which is filled with the alkane chains of the ligands, which keeps the gold particles fiom touching, which would lead to irreversible aggregation.

In an alternative approach, membranes prepared from a monolayer of dodeca-nethiol-stabilized gold nanopartides with a diameter of 6 nm were obtained via a simple evaporation process on a silicon nitride window area [87] (Figure 5.59). Another example showed that nanopartides could seF-organize in 2-D or 3-D superlattices so as to form supra crystals [88] (Figure 5.60). 

This work was followed by a number of researchers who confirmed the experimental results on various metallic multilayer systems (e.g. Cu/Ni [78-80] as well as on hard epitaxial and polycrystalline superlattices of nitrides, such as TiN/VN... 

A further example of such thin films are the superlattices, which are in principle composed of two different nitrides, such as TiN/NbN and TiN/VN, which are successively deposited by PVD techniques such magnetron sputtering with a thiek-ness in the nm range [127,128]. Hardnesses of up to about 50 GPa were measured on such layers depending on the thiekness of the individual sublayers, ealled wavelength, which reach a maximum at around 5 nm. 

Films of silicon nitride deposited on a-Si H employed in thin-film transistors and superlattice structures have been studied by FTIR-ATR [295]. Hydrogen... 

The linear augmented plane-wave method has been used to study the electronic structure and band edge discontinuities at the (110) interface of diamond and p-BN. By studying N-layer/N-layer C/BN (110) superlattices with N = 1.3 and 5 it has been shown that three layers of each material are sufficient to give a central layer which has a core-level position nearly representative of the bulk. Resultant data are valence band discontinuity=1.42 0.04 eV, which, by using the experimental band gaps (5.5 eV for diamond, 6.2 eV for p-BN), leads to a conduction band discontinuity of 0.7 eV. The lowest conduction band at the interface is the X-point band in boron nitride for a detailed discussion, see [9]. 

Boron-carbon-nitride ceramic is deposited on iron-based sliding parts by chemical vapor deposition (CVD) it is used as rotary compressor shafts, in order to improve the wear resistance [1 to 5]. Such B-C-N coatings have also been applied to dynamic pressure air bearings [6]. In gas-cooled nuclear reactors, °B-enriched B-C-N can be deposited by CVD in the fluid channels of the fuel elements for permanent deactivation in case of an emergency [7]. Radiofrequency or microwave-enhanced CVD is employed in order to deposit a diamond carbon and (3-BN superlattice structure [8]. 

Hardness vs. Crystal Orientation. The hardness varies depending on crystal orientation, the (111) orientation being the hardest as shown in Fig. 11.5.1 Extremely high hardness up to 50 GPa has been reported for epitaxial superlattices of interstitial nitrides sueh as NbN/TiN and VN/TiN.0 1... 

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