We report fabrication of ordered polymeric nanodomains and control of their morphology and size by self-organized intensified dewetting of ultrathin polymer films which are selectively exposed to small doses of electron beam (e-beam). Both positive and negative e-beam tone polymers are used to produce variety of highly regular patterns over large area (∼mm2) in significantly lesser time as compared to e-beam lithography. Dewetting of selectively exposed thin films under a mixture of water and organic solvents enables the instability to grow much faster and in very confined domains. Patterns ranging from straight and cross channels, array of circular and square holes, aligned nanowires and square grid to the array of spherical droplets can be fabricated by selection of e-beam exposure patterns and the dewetting conditions. Fabrication of structures with sharp corners and edges becomes possible because of ultralow interfacial tension of polymer in the liquid mixture. Further, the length scale of pattern can be tuned over a wide range which in some case extends from about tenth of the natural wavelength of instability in dewetting (λ m ) to 2λ m . This is a significant improvement over the dewetting on physico-chemically patterned substrate where alignment of polymer structures is lost when substrate patterns are smaller than half of λ m . The dewetting mechanism of e-beam exposed films is proposed as the change in the effective viscosity of e-beam exposed region that leads to the faster growth of instabilities in the low viscous regions and results in the formation of regularly aligned structures. Nonlinear simulations are carried out which show very good agreement with the experimentally obtained patterns.

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The linear stability of freestanding thin films under the influence of attractive van der Waals forces is investigated for three rheological models, viz., Newtonian viscous films, viscoelastic solid films, and Jeffreys viscoelastic liquid films, with the aim of studying the role of rheology on the instability. Thin freestanding viscous films are unconditionally unstable, whereas the shear modulus in thin freestanding solid viscoelastic films governs the onset of instability. Interestingly, elasticity plays a dual role with regard to the stability of freestanding solid and liquid films: while it has a stabilizing influence on the former, it is destabilizing in the latter. Linear stability results of Jeffreys viscoelastic freestanding films are compared with those from supported films in the inertialess limit. The instability of Jeffreys viscoelastic freestanding film is unaffected by the relaxation time, but is enhanced with decrease in the viscosity ratio (μr, the ratio of solvent viscosity to total viscosity). The dominant length scale of instability in Jeffreys viscoelastic freestanding film shifts toward shorter wavelengths with decrease in μr. For μr→0, the maximum growth rate remains bounded in a freestanding viscoelastic film in the presence of inertia, but diverges in its absence, similar to supported viscoelastic films. In general, our results show that freestanding thin films exhibit faster dynamics than supported thin films. The mode of deformation of the freestanding film (viz., bending or squeezing) is not imposed a priori in our analysis and is found to be a squeezing (symmetric) mode with equal amplitudes at the interfaces.