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A comparative analysis including modeling and experimental evaluation of a spalling process of silicon (Si) substrates was accomplished to define the optimum condition for uniform spalling. The residual stresses in Nickle (Ni) films on Si substrates have been evaluated. Different thicknesses of Ni films electroplated on Si(100) and Si(111) substrates have been used to predict the steady-state spalling depth and crack propagation direction. This study focuses on identifying the key variables; including the Ni film thickness (h) and critical stress needed to peel-off uniform thin layers from a Si substrate. The residual stresses (thermal and epitaxial) in the Ni films have been evaluated through experiment and modeling analysis to distinguish the sources of stress generation. Different thicknesses of spalled films from Si substrates were defined to investigate the influence of the stress intensity factors (KI, KII and KIII) and the energy release rate (J1) on the steady state spalling process. Finally, the critical normal stress (σII) versus h has been determined to predict the spalling depth with uniform thickness. [ABSTRACT FROM AUTHOR]

Abstract: Anatase TiO2 film (100–1000 nm thick) grown on glass, sapphire (0001), and Si (100) substrates by pulsed dc-magnetron reactive sputtering were evaluated for stress and strain analysis using Raman spectroscopy and curvature measurement techniques. The X-ray analysis revealed that films prepared for this study were purely anatase, and the measurements indicate that the film exhibit that (101) is the preferred growth orientation of the crystallites, especially for the film thicker than 100 nm. Curvature measurements and Raman spectroscopy, with 514.5 nm excitation wavelength, phonon line shift were used for stress analysis. A comparison between Raman lineshapes and peak shifts yields information on the strain distribution as a function of film thickness. The measurements of residual stresses for crystalline anatase TiO2 thin film showed that all thin film were under compressive stress. A correlation between Raman shifts and the measured stress from the curvature measurements was established. The behavior of the anatase film on three different substrates shows that the strain in film on glass has a higher value compared to the strain on sapphire and on silicon substrates. The dominant 144 cm−1 E g mode in anatase TiO2 clearly shifts to a higher value by 0.45–5.7 cm−1 depending on the type of substrate and film thickness. The measurement of the full width at half maximum values of 0.59–0.80 (2θ°) for the anatase (101) peaks revealed that these values are greater than anatase powder 0.119 (2θ°) and this exhibits strong crystal anisotropy with thermal expansion. [Copyright &y& Elsevier]