Adsorbate-Induced Skin Stress Bonding Effect

5 Adsorbate-Induced Skin Stress Bonding Effect 24.5.1 Observations 

Atoms at the pure metal surfaces relax inwardly and reconstruct in the surface planes because of the spontaneous bond contraction and the derived tensile stress. The stress-induced inward relaxation is quite common despite the discrepancy in 

However, adsorbate could induce various kinds of stresses accompanied with versatile patterns of relaxation and reconstruction [59, 81, 82]. The spacing between the first and the second atomic layers expands if an adsorbate such as C, N, and O buckles into space between the atomic layers even if there is contraction of bonds between the adsorbates and the host atoms [81]. For example, H, C, N, O, S, and CO adsorbates on a metal surface could change the surface stress and cause surface reconstmction because of bond making and breaking. Surface adsorption of sodium ions also increases the stiffness of a microcantilever [83]. 

A full understanding of the adsorbate-induced stress may help to explain the adsorbate-induced slope change in the temperature dependence of the surface tension such as Sn liquid, as shown in Fig. 24.4. Charge repopulation and polarization upon chemisorption should provide forces driving the observed reconstruction and the measured stress. 

XRD and Raman measurement of the residual stresses of the TiATiC/diamond interfaces at different stages in diamond growth revealed that carbon addition could change the tensile stress of the Ti specimen into compressive [97]. As shown in Table 24.4, the tensile stress dominates in the pure Ti surface and the carbon turns the tensile surface stress of the Ti into compression upon TiC interlayer formation. The compressive stress in the TiC interlayer and the tensile stress of the Ti are reduced gradually with the thickness increases in the grown diamond Aims. 

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