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The External Quantum Efficiency (EQE) of semi-transparent Bulk Hetero-Junction (BHJ) organic photodiodes processed in air shows significant differences when measured from the front or back side contacts. This difference was found significantly reduced when decreasing the active layer thickness or by applying a negative bias. This work brings new elements to help understanding this effect, providing a large set of experiments featuring different applied voltages, active layers, process conditions, and electron and hole layers. By means of detailed electrical simulations, all these measurements have been found consistent with the mechanisms of irreversible photo-oxidation, modeled as deep trap states (and not as p-type doping). The EQE measurement from front and back sides is thus a simple and efficient way of monitoring the presence and amplitude of oxygen contamination in BHJ organic solar cells and photodiodes. [ABSTRACT FROM AUTHOR]

Photopolymerizable epoxy polyhedral oligomeric silsesquioxane monomers with variable aliphatic spacer have been prepared and cured under UV radiation. Due to their organic/inorganic composition, these materials are promising candidates for microelectronic applications which requires high thermal and mechanical stabilities as well as a low dielectric constant, for example, for the fabrication of electrical interconnects. The authors pointed out by ellipsometric measurements that the use of a sensitizer in addition to the photoinitiator enhances the kinetic of the cationic polymerization of epoxy groups. The polymerization performed either in an EVG770® nanoimprint lithography stepper or under normal atmospheric conditions has been investigated by infrared spectroscopy, delivering information concerning polymerization mechanisms and allowing the optimization of the resin composition. Thermogravimetric analyses have shown that an annealing step is necessary after the UV curing of the resin to eliminate inert residues of the photoinitiator dissociation and thus improving the thermal resistance of the polymer. Finally they have demonstrated that the obtained polymers form interpenetrated networks and that their mechanical properties are retained up to a temperature of 375 °C. [ABSTRACT FROM AUTHOR]

In this article, the authors compare a polymer resist to a thermally curable monomer resist in a full 8 in. wafer thermal nanoimprint lithography process. Using exactly the same imprinting conditions, the authors compare the printing quality and investigate the resist distribution through large area gratings (6×6 mm2) with various densities. It is shown that a liquid monomer solution greatly enhance the printing uniformity because of a much wider resist redistribution and flow during the process. Redistribution of the monomer resist is observed over an entire grating, while it is observed only over a few periods of a grating for the polymer in the same conditions. Furthermore, a low molecular weight resist allows reducing the imprinting force as well as the total cycle time. [ABSTRACT FROM AUTHOR]

In general, fluorinated antisticking layers (F-ASL) are deposited on the imprint stamps to ease their separation from the imprinted resist in UV nanoimprint lithography. However, these layers are found to degrade with repeated imprint operations. A drastic decrease in fluorinated species is observed on the mold surface. Yet, there is still a debate on the nature of the exact mechanisms involved in this degradation. In this paper, electron spin resonance (ESR) is used to investigate the chemical reaction occurring between the fluorinated molecules and the UV curable resist. Free radicals of the resist, generated under UV illumination, have been observed by ESR. The decrease in their corresponding signal in the presence of fluorinated ASL species shows evidence of the chemical reactivity of the resist toward the F-ASL. [ABSTRACT FROM AUTHOR]