Intrinsic stress

The microstmcture and imperfection content of coatings produced by atomistic deposition processes can be varied over a very wide range to produce stmctures and properties similar to or totally different from bulk processed materials. In the latter case, the deposited materials may have high intrinsic stress, high point-defect concentration, extremely fine grain size, oriented microstmcture, metastable phases, incorporated impurities, and macro-and microporosity. AH of these may affect the physical, chemical, and mechanical properties of the coating. 

Multilayer coatings or hlms have been proven to be successful in various applications, especially for wear protection. In multilayer systems, the intrinsic stress can be effectively reduced by designing interface number and composite materials in terms of the application and process technique. Therefore, the multilayer technique by which a specihe functional composite is able to approach received more attention for many years [17,18]. Here we introduce the results on microscale friction and scratch of DLC/DLC and Fe-N/TiN multilayers. 

Hard layer and soft layer combined together can reduce the intrinsic stress of the whole coating [17,18,22-27]. Samples 4, 5, and 6 have higher critical load than that of monolayer A and B. For Samples 5 and 6, no obvious crack occurs during the scratch test. Sample 5 has the highest hardness and reduced elastic modulus among the multilayer samples, and the interfaces in Sample 5 also contribute to scratch resistance. So it has the best micromechanical properties here. 

The stress of oxidized PS layers is always compressive. For porous oxides, values below 108 N nT2 are reported [Ba5], which is nearly one order of magnitude smaller than values of intrinsic stress generated by low-temperature thermal oxidation of bulk silicon. The compressive stress in OPS has successfully been used to lift up released mesoporous films and thereby fabricate 3D microstructures [La9],... 

Windischmann, H. (1987), An intrinsic stress scaling law for polycrystalline thin films prepared by ion beam sputtering , Journal of Applied Physics, 62, 1800-1807. 

Windischmann, H. (1992), Intrinsic stress in sputter deposited thin films , Critical Reviews in Solid State and Material Sciences, 17, 547-596. 

DEPOSITION RATE PHOSPHORUS CONTENT INTRINSIC STRESS... 

If desired, plasma oxide films can be doped much as the plasma nitride film we discussed earlier. In fact, doping with boron and phosphorus has been carried out as an alternative to the standard atmospheric-pressure thermal CVD process for BPSG.11 12 The latter process has the drawbacks of high defect density and poor thickness uniformity, so it was hoped that plasma BPSG would be an improvement. However, there are differences in the films in terms of H2 and N2 content, and their effect on reflow temperature, intrinsic stress and passivation effectiveness had to be examined. 

Note that the residual stress aM — 0 on the elastic properties becomes homogeneous (Ef = Em = EL). While connections between the residual stresses and constituent properties are rigorous, experimental determination is still necessary, because ft is not readily predictable. In general, ft includes terms associated with the thermal expansion difference, ay— am, as well as volume changes that occur either upon crystallization or during phase transformations. For CVI systems, intrinsic stresses may also be present. 

PP, PVDF, and PE are not jointed using solvent cements, but the weld regions contain relatively high levels of intrinsic stress caused by the thermal fusion process. Chemical stress cracking could occur at these welds if exposed to certain chemicals. When performing material compatibility tests for any... 

The overall residual stress in the film is equal to the sum of the thermoelastic component and intrinsic component. In the case of low deposition temperatures, the intrinsic stress is still the main contributing factor to the overall residual stress. In contrast, in the case of high deposition temperatures, the thermoelastic stress predominates. Therefore, while the signs of these stresses are identical, there is an intermediate deposition temperature for which the residual stress is minimised (Figure 2). 

Fig. 2 Schematic representation of changes in thermoelastic stress intrinsic stress a. and overall residual stress o, in a thin film as a function of deposition temperature...

FM. D Heurle and J.M.E. Harper, Note on the Origin of Intrinsic Stresses in Films Deposited Via Evaporation and Sputtering, Thin Solid Films, Vol.171, 1989, p. 81. 

What will happen if ceUs do not have a functional checkpoint The ATR checkpoint is essential for the survival of cells and the embryonic development in mammals (3, 4), which is likely a result of the important function of ATR in coping with the intrinsic stresses during DNA rephcation. On the other hand. 

Since diamond CVD is undertaken at 800 °C, and the stress at the interface is generally very high when the specimen is taken out of the reactor to the ambient environment because of the difference in the thermal expansion coefficients between the CVD diamond film and the substrate. In addition, the intrinsie stress within the CVD diamond film is high if it is polycrystalline. The presence of grain boundaries can be the cause of the intrinsic stress. Thus, reducing both interfacial and intrinsic stresses is an important issue for practical use of CVD diamond films. So far, no effective method has been found to solve this problem. 

Grain boundaries are the major source of the intrinsic stress. 

According to the theoretical calculation, the intrinsic stress at the diamond-Si interface is tensile, and not compressive. Such a tensile stress may be relaxed by plastic deformation of the Si substrate. 

T. Unagami, Intrinsic stress in porous silicon layers formed by anodization in HE solutions, /. Electrochem. Soc. 144, 1835, 1997. 

The intrinsic stress in silicon nitride layers is important especially in micromechanical devices the characteristic features of membranes based on silicon nitride or thin silicon structures covered with silicon nitride are very sensitive to stress variations in these layers. Similar to PECVD-oxide, the intrinsic stress of silicon nitride is influenced by several deposition parameters such as gas flow, deposition temperature, and radiofrequency (RF) power. 

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