Silicon, deformation behavior

Mahajan, Deformation Behavior of Compound Semiconductors J. P. Hirth, Injection of Dislocations into Strained Multilayer Structures D. Kendall, C. B. Fleddermann, and K. J. Malloy, Critical Technologies for the Micromachining of Silicon... 

Haq, A., Munroe, P., Hoffman, M., Martin, P., Bendavid, A., 2010. Effect of coating thickness on the deformation behavior of diamond-hke carhon-silicon system. Thin Sohd Films 518, 2021-2028. 

We mentioned in Section 4.1 that whether a material deforms under applied stress is a matter of the magnitudes of the shear force exerted and the time of observation. It is common to use silicone putty (known as Silly Putty) to illustrate the above statement. If you have enough patience, you will notice that silly putty is a highly viscous material (although you may not think of it that way) that will find its own level when placed in a container. In this sense, it behaves like a liquid. On the other hand, as its name is meant to suggest, a ball of Silly Putty will also bounce when dropped to the floor. That is, under severe and sudden deformation, it behaves like a solid. The behavior of the Silly Putty thus brings to our attention the importance of time scales and deformation rates in classifying the flow behavior of materials. 

The behavior of cavities during deformation also depends on the refractoriness of the bonding matrix. In a recent study,33,34 stable cavities were observed to form at the grain boundaries of a grade of silicon nitride containing 4wt.% yttria, even though there was very tittle glass at these boundaries Fig. 4.14a. The cavities observed were reminiscent of Hull-... 

Generally, it is observed that elastomers at very low temperature become brittle and fracture with little detectable Inelastic deformation. Andrews, Reed, and co-workers (5-6) have demonstrated that prestralnlng the rubber before cooling can drastically modify its fracture behavior. In their studies and subsequent studies by others (7-8) a variety of rubbers ranging from natural rubber to silicone were prestrained ( 100% at room temperature) before reducing the temperature to -100°C or below. When further stressed at these low temperatures, the rubbers did... 

Hot plastic deformation with forging changes the behavior of all alloys of the Ti-Si-system favorably. As it is seen the elongation of forged alloys decreases with silicon increase not so drastically as in as-cast state namely from 31-32% in original BT1-0 alloy only to 8-9% in Ti-5.7wt.% Si alloy practically monotonously. There is no more well-known drop of plasticity to zero at around 2-wt.% Si [1, 7], At 2.0-wt.% Si deformed Ti-Si-alloy has 16-17% plasticity. Strength of deformed Ti-Si-alloys increases monotonously too from 800 MPa of the original BT1-0 alloy to 1050 MPa at 5.7-wt.% Si with no maximum at 4.0-wt.% Si. 

Scanning electron microscopy revealed the formation of debris around the indentation contact area in diamond [196] (Fig. 41a). This correlates with the behavior of silicon and germanium under contact loading, where the formation of plastic extrusions around indentations is believed to be indicative of the pressure-induced metallization (see Section 2.4). The formation of ductile extrusions was reported along the edges of the Vickers impression in diamond and around the deformed top of the diamond indenter [196] (Fig. 41), suggesting that similar transformations occurred in both the indenter and the crystal. 

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). 

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