Graded interface

The growth of superlattices Is one of the key Issues In MOCVD reactor analysis and design. In addition to growing highly uniform, pure Aims one must be able to form sharp or accurately graded Interfaces between... 

Madan et al. [515] have presented the effect of modulation on the properties of the material (dark conductivity and photoconductivity) and of solar cells. They also observe an increase in deposition rate as a function of modulation frequency (up to 100 kHz) at an excitation frequency of 13.56 MHz, in their PECVD system [159]. The optimum modulation frequency was 68 kHz, which they attribute to constraints in the matching networks. Increasing the deposition rate in cw operation of the plasma by increasing the RF power leads to worse material. Modulation with a frequency larger than 60 kHz results in improved material quality, for material deposited with equal deposition rates. This is also seen in the solar cell properties. The intrinsic a-Si H produced by RF modulation was included in standard p-i-n solar cells, without buffer or graded interface layers. For comparison, solar cells employing layers that were deposited under cw conditions were also made. At a low deposition rate of about 0.2 nm/s, the cw solar cell parameters... 

Advantages 1) Low Temperature 2) Controllable Composition 3) Step Coverage 4) Pinhole Free 5) Fast Deposition Rates 6) Can Produce Graded Interfaces... 

One potential problem with conventional free-radical copolymerization is that the reactivity ratios of the two monomers tend to be different from one another [6]. On one hand this leads to non-random sequences of the monomers on a single chain (usually the product of the reactivity ratios is less than one so that there is a tendency to form alternating sequences) and, on the other, to substantial composition drift if the polymerization is carried out in bulk to high conversions. Random copolymers with a range of compositions as a result of composition drift may however be useful in practice, allowing a compositionally graded interface to be formed. 

Grade Interface material Reinforcement (type of Fiber) Volume fraction (vol%) Tensile strength (MPa) Tensile modulus (GPa) Flexural strength (MPa) Density (Mg/m )... 

Constructing an optical model. In the data analysis procedure in ellipsometry, an optical model corresponding to the investigated sample structures must be constructed firstly. An optical model is represented by the complex refractive index and layer thickness of each layer, normally, it consists of an air/thin film/ substrate structure. It should be decided if any layer is anisotropac at this stage, and whether or not interface layers are to be modeled as a single effective medium approximation, or is a more complicated graded interface to be used for the sample. 

I.M. Low, Depth-profiling of phase composition in a novel Ti3SiC2-TiC system with graded interfaces, Mater. Lett. 58 (2004) 927. 

A graded interface during reactive deposition may be formed by control of the availability of the reactive material e.g. oxygen, nitrogen, or carbon. For example, an interface between... 

Graded interface (film formation) When the interfacial region between a film and a substrate has a composition or properties that vary throughout the thickness. See also Interphase material. 

Reactively graded interface (film formation) A graded interface formed by changing the... 

Low, I. M. (2004). Depth-Profiling of Phase Composition in a Novel TijSiC -TiC System with Graded Interfaces. Materials Letters, 58, 927-930. doi 10.1016/j. matlet.2003.07.038. 

Low, I. M., Oo, Z. (2002). Diffraction Studies of a Novel TijSiCj-TiC System with Graded Interfaces. J. Aust. Ceram. Soc., 38,112-115. 

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