Lattice silicon nitrides

The rapid developments in the microelectronics industry over the last three decades have motivated extensive studies in thin-film semiconductor materials and their implementation in electronic and optoelectronic devices. Semiconductor devices are made by depositing thin single-crystal layers of semiconductor material on the surface of single-crystal substrates. For instance, a common method of manufacturing an MOS (metal-oxide semiconductor) transistor involves the steps of forming a silicon nitride film on a central portion of a P-type silicon substrate. When the film and substrate lattice parameters differ by more than a trivial amount (1 to 2%), the mismatch can be accommodated by elastic strain in the layer as it grows. This is the basis of strained layer heteroepitaxy. 

Since the major component of lubricant 1 (WSe2) and all components of lubricant 2 are layer lattice transition metal dichalco-genides, it is at first difficult to explain the large differences in frictional behavior observed between LI and L2 composites sliding against silicon nitride. We advance here a hypothesis for involvement of the phosphate additive in adverse reactions both with the ceramic counterface and with lubricant 1. 

Silicon nitride, Si3N4, exists in two forms designated as a and p. The structures and lattice parameters of these forms were determined by X-ray diffraction data. 

The incorporation of A1 in the silicon nitride crystal lattice leads to a reduction of the thermal conductivity of the materials [65,66]. This means that the AI2O3/AIN content in the sintering additives can be used for the tailoring of the thermal conductivity values between 10 and 150 W/mK are possible. 

The powder of silicon nitride of the SHS-Az type can contain in the structure from 40% up to 95% (a-nitride phase as anisotropic whiskers by a diameter 1 pm forming wave structure (Figure 8.2)). The particles of the boron nitride powder of the SHS-Az type are ultra fine and have the disc form, and the diameter of disks at 10-15 of time exceeds their thickness having the linear size about 20 nm. The crystal lattice BN has deformations of turbostrate kind with a degree of three-dimensional order 0.40-0.50. The powder of titanium carbonitride with composition TiCggNog of the SHS-Az type differs from similar powders of traditional technologies of synthesis of more branched structure, typical for formation of... 

Table 2. Summary of POLAD modelling results for physically adsorbed PEO (900 kDa and 200 kDa) on silicon nitride using a hexagonal lattice, c=0.45, Cs=1.0, and a volume fraction of 10 ...

The a P transformation in silicon nitride requires a lattice reconstruction. This type of process occurs usually only when the transforming material is in contact with a solvent. The greater solubility of the more unstable a form drives it into solution after which it precipitates as the less soluble, more stable P form. The predominantly a silicon nitride powder used to produce dense silicon nitride ceramics is observed to transform to the P modification during the sintering process at temperatures in excess of 140QOC when the original a phase is in contact with a M-Si-O-N (M = Mg, Y, etc) oxynitride liquid phase. 

Table 2.14 Lattice parameters of a- and p-modifications of silicon nitride [138]...

A fundamental question not yet resolved regarding stick-slip motion is the exact mechanism for the occurrence of stick-slip with a periodicity of the surface lattice. For interpretation of the stick-slip motion by the Prandtl-Tomlinson model, the tip is commonly treated as a single, pointlike entity without any additional internal degree of freedom. However, the contact area between AFM tip and crystal surface will typically contain some 10 unit cells. Atomic stick-slip was observed even for amorphous silicon and silicon nitride tips [1003] and for crystalline tips, atoms of tip and surface lattice will usually not be in registry, making the observation of stick-slip with a periodicity of the surface lattice surprising. 

Ho has measured the dielectric properties of a wide variety of silicon nitride ceramics (CVD, sintered, hot pressed, differing composition and sintering aids) and of polycrystalline alumina versus single crystal sapphire. His results have shown that the temperature dependence of the dielectric constant is intrinsic to the crystalline lattice properties of the... 

---