A Parametric Study of Spin Coating over Topography

Abstract

The spin coating of polymer solutions onto silicon substrates was investigated using both commercially formulated polyimide precursors and model polymer solutions. The latter included solutions of polystyrene, polymethyl methacrylate and poly(ethylene oxide) in appropriate solvents. Experiments were conducted to determine the influence of the various process, material, and geometrical variables on the thickness and thickness uniformity of films deposited on planar as well as patterned substrates; dry film thickness was measured with the help of profilometry. For flat substrates, the film thickness decreased with increasing spin speed, and, in the case of volatile solvents, increasing solvent volatility led to thicker films. Although solution viscosity could be changed by changing either the polymer concentration or the molecular weight, film thickness was more sensitive to changes in concentration. Process conditions that gave thicker films also tended to yield more uniform films. From experiments on substrates with topography, it is concluded that low spin speeds in conjunction with concentrated solutions of low molecular weight polymer in nonvolatile solvents favor planarization.

Adsorptive removal of hazardous anionic dye “Congo red” from wastewater using waste materials and recovery by desorption

“…The values of E for both Congo red-bottom ash and Congo reddeoiled soya systems are found to be within the range 8-16 kJ mol À1 , suggesting that chemisorption is responsible for the adsorption process for both systems [49].…”

Effect of attapulgite calcination on heavy metal adsorption from acid mine drainage

“…So reuse is limited, unlike unactivated attapulgite which has a higher specific surface area, allowing reuse. ΔS 0 values for unactivated attapulgite are higher than those of activated attapulgite, showing more affinity of unactivated attapulgite for metal ions than activated attapulgite [25], hence metals are immobilized more in unactivated attapulgite than in activated attapulgite. Q max for Fe, Mn, Co, Cu and Ni for activated attapulgite are higher than those of unactivated attapulgite since an optimum solid loading of 2.5% was used for activated attapulgite as compared to 10% for unactivated attapulgite.…”

“…The values of ΔH 0 for Ni and Fe were −2.47 kJ/mol and −1.93 kJ/mol indicating that the adsorption process was exothermic. The values of ΔS 0 for Co, Cu, Mn and Fe were 170.8 J/mol, 332 J/mol, 250.1 J/ mol and 72.13 J/mol, respectively, indicating the affinity of the activated attapulgite for the metals ions and some structural changes at the adsorbate and adsorbent interface [25]. The value for ΔS 0 for Ni −7.17 J/mol indicates a decrease in randomness at the solid/ solution interface [26].…”

Equilibrium isotherm analysis of the sorption of congo red by palm kernel coat

“…The enthalpy change, ΔH o , is negative indicating that the biosorption reaction is exothermic. The positive values of ΔS o reflects the affinity of the PKC for CR and suggest some structural changes in CR and PKC interaction [29]. In addition, positive value of ΔS o shows increasing randomness at the solid/liquid interface during the biosorption of CR onto PKC.…”