Semiconductors deformation mechanisms

S. Guruswamy, K. T. Faber, and J. P. Hirth, Mechanical Behavior of Compound Semiconductors S. Mahajan, Deformation Behavior of Compound Semiconductors J. P. Hirth, Injection of Dislocations into Strained Multilayer Structures... 

Such electron-phonon interactions directly proportional to the dilatation are called deformation potentials, a concept first introduced by Bardeen and Shockley (see, for example, Shockley, 1950). This is indeed the dominant mechanism for electron-phonon interaction in covalent semiconductors, and the interaction with transverse waves is weaker. 

Simultaneously, processes of plastic deformation, fracture and interactions with the environment, and counterbody can occur. The latter ones have been studied by mechanical engineers and tribologists, but the processes of phase transformations at the sharp contact have been investigated for only a few materials (primarily, semiconductors) and the data obtained so far can only be considered preliminary. One of the reasons for the lack of information may be the fact that the problem is at the interface between at least three scientific fields, that is, materials science, mechanics, and solid state physics. Thus, an interdisciplinary approach is required to solve this problem and understand how and why a nonhydrostatic (shear) stress in the two-body contact can drive phase transformations in materials. 

Mechanisms of phase transformations in ceramics can be different from those in semiconductors, but pressure- or deformation-induced amorphization has been observed for both classes of materials. Even the hardest material known— diamond—experiences a phase transformation under contact load. Changes in structure and density have also been reported for amorphous materials, such as silica glass. Recent studies suggest indentation-induced phase transformations in intermetallic compounds and thus other classes of materials may show a similar behavior as well. 

O connor, B.T., 2013. Using mechanical deformation to elucidate structure-property relationships in polymer semiconductors. 223rd ECS Meeting, May 12-17, 2013. 

Silicon (Si) with an atomic number of 14 is a covalent material with wide-ranging application as a semiconductor in industry in devices and solar panels. Here our interest is primarily limited to the structure of amorphous Si and its mechanical behavior in its glassy range. In its crystalline form Si has a diamond-cubic structure with an atomic coordination number of 4 and has a relatively low density of Po = 2330 kg/m at room temperature. The diamond-cubic crystal structure of Si, for purposes of crystal plasticity, acts very similarly to fee metals and has most of the deformation characteristics of the fee structure. These characteristics, which have been studied intensively, are of no interest here. A summary of the low-temperature crystal plasticity of crystalline Si can be found elsewhere (Argon 2008). 

The adhesion of particles by such mechanisms is vitally important in Pharmaceuticals, xerography, semiconductors, printing, and agriculture. Many articles are written on these topics each year. A particular contribution has been made by Rimai, Demejo and Bowen in understanding the adhesion of toner particles which must transfer from a photoconductor to a receiva-. JKR behavior was observed for glass spheres on polyurethane, as shown in Fig. 9.22. Curious effects of large deformation, engulfment and hysteresis were seen. This hysteresis is to be considered next. 

Metals that have a compressibility of the same order of magnitude as covalent solids are much softer mechanically and more plastic than ceramics because the bonding electrons are in interstices and are much more easily displaced under stress than in ionic or covalent compounds. Owing to the mobility of the valence electrons, defects and dislocations have a different electronic behavior in metals than in rigid semiconductors. The barrier against plastic deformation is approximately proportional to the bandgap (which naturally follows from the model). 

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