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Single crystal sapphire substrates with high quality surface finish and integrity significantly enhance performance and reliability of various microelectronics and LED devices. Traditional Chemical Mechanical Polishing necessitates highly alkaline slurries or ultra-hard abrasives owing to sapphire's ultra-high hardness and chemical inertness. Such trade-off is obviated by utilizing an atmospheric pressure plasma (in He–H 2 O mixture) for chemical action, facilitating higher material removal rate at neutral pH by buffing alone, without abrasives. Plasma induced surface modification is studied by nanoindentation. A 2× improvement in MRR is achieved, and 40× projected. Effects of plasma parameters and polishing conditions on planarization effectiveness are discussed.

A B S T R A C T Solar cells gained significant interest recently due to the rapid increase in fossil fuel costs and renewed attention to sustainability. The effectiveness of a solar cell in energy harvesting hinges on three key characteristics: efficiency of energy conversion, reliability and life expectancy, and cost. All three attributes are critically influenced by surface and interface properties inherent in the design and manufacture of these devices. This paper starts with an exposition of solar cell manufacturing, followed by discussion of efficiency enhancement, reliability issues, and cost and energy footprint reduction. The role of surface and interface modifications in realizing such improvements is assessed. 2014 CIRP.

Stress dependent electrochemical dissolution is identified as one of the key mechanisms governing surface degradation in fretting and crevice corrosion of biomedical implants. In the current study, material removal on a stressed surface of Ti6Al4V subjected to single asperity contact is investigated to identify the influence of contact load, in-plane stress and environment on wear damage. A range of known stress levels are applied to the specimen while its surface is mechanically stimulated in different non-reactive to oxidizing aqueous environments. Evolution of surface degradation is monitored, and its mechanism is elucidated. Implications to life prediction of orthopedic implants are discussed.

A multi-scale model encompassing pad response and slurry behavior is developed to predict scratch propensity in a chemical mechanical planarization (CMP) process. The pad response delineates the interplay between the local particle level deformation and the cell level bending of the pad. The slurry agglomerates in the diffusion limited agglomeration (DLA) or reaction limited agglomeration (RLA) regime. Various nano-scale slurry properties significantly influence the spatial and temporal modulation of the material removal rate (MRR) and scratch generation characteristics. The model predictions are first validated against experimental observations. A parametric study is then undertaken. Such physically based models can be utilized to optimize slurry and pad designs to control the depth of generated scratches and their frequency of occurrence per unit area.

Mechanical load assisted dissolution is identified as one of the key mechanisms governing material removal in fretting and crevice corrosion of biomedical implants. In the current study, material removal on a stressed surface of cobalt-chromium-molybdenum (CoCrMo) subjected to single asperity contact was investigated in order to identify the influence of contact load and residual stress on dissolution rates. A range of known stress levels were applied to the specimen while the surface was mechanically stimulated in ambient conditions as well as different aqueous environments ranging from non-reactive to oxidizing. Dissolution rate was found to display a complex dependence on residual stress and environment.