Papers by Author: Muhammad M. Morshed

Abstract: The mechanical performance of DLC coatings on 316L stainless steel deposited by a saddle field fast atom beam source has been evaluated using the four point bend (FPB) test. Two different deposition parameters, pressure and current were varied when depositing the films. Load-displacement measurements were carried out during the bend test to determine the load corresponding to crack initiation. This load designated as the cohesive strength of the coating which is also called the cracking resistance of coating and provides a measure of the strength of the coating. The cohesive strength of the coating was calculated based on elementary beam theory. Scanning Electron Microscopy (SEM) was used to determine the location of the crack. Finite element analysis was used to predict the stress distribution across the coating thickness. The experimental work on FPB tests has been used to support the numerical (finite element) model for the determination and prediction of film cohesive strength. It was observed that at lower deposition current, the cohesive strength increases with increased deposition pressure whereas, for higher deposition current, these values do not increase with increasing deposition pressure. The model takes into account the film’s Young’s modulus, thickness and deposition pressure and current, and has shown that it is capable of predicting film cohesive strength when combined with a theoretical formulation for brittle fracture. It has been observed that the maximum stress develops at the outer surface of the film and propagates through the film-substrate interface. This result has only been validated for films with higher Young’s modulus compared to that of the substrate material.

Abstract: Meso-scale structures are formed on a silicon surface using a sulphur hexafluoride (SF6) based dry etching process. Etched feature parameters, including etch rate, trench profile, and selectivity are explored using an optical emission spectroscopy and a resonance hairpin probe. With increasing process power, the etch rate was observed to increase, which was correlated with an observed increase in intensity of fluorine emission. Damage of the photoresist with increasing power was observed and a marked increase in hydrogen (H) emission was found to indicate this fault. The electron density and the sidewall roughness were also found to increase with higher reactor power. The e-SF6 collisions contribute to the production of atomic fluorine, which etches the silicon by the dissociative ionization (SF+5 and F or SF+3 and F) and electron impact dissociation (SF5 and F).

Abstract: Microfluidics is a technology where application span the biomedical field and beyond. Single cell analysis, tissue engineering, capillary electrophoresis, cancer detection, and immunoassays are just some of the applications within the medical field where microfluidics have excelled. The development of microfluidic technology has lead to novel research into fuel cells, ink jet printing, microreactors and electronic component cooling areas as diverse as food, pharmaceutics, cosmetics, medicine and biotechnology have benefited from these developments. Since laminar flow is prevailing at most flow regimes in the micro-scale, thorough mixing is a challenge within microfluidics. Therefore, understanding the flow fields on the micro-scale is key to the development of methods for successfully microfluidic mixing applications.