Donald R. Preuss

Laser recording in tellurium suboxide thin films

Tellurium suboxide (TeOx) films prepared by coevaporation consist of tiny grains of tellurium embedded in a TeO2 matrix. The size of the tellurium grains depends on the preparation conditions. Except for samples with exceedingly small grains, crystalline diffraction patterns can be observed by using selected‐area electron diffraction even though these samples show amorphous x‐ray diffraction patterns. Heat treatment causes a transition in optical properties and the appearance of peaks for crystalline tellurium in x‐ray diffraction. Thermal writing with a focused diode laser on both heat‐treated and as‐deposited samples gave recorded marks with high sensitivity and good contrast, although an incubation period of many seconds is required for the full development of the marks. The observed laser recording behavior cannot be explained by a simple amorphous‐to‐crystalline transition, and a new writing mechanism is proposed.

P-175: Enhanced Outcoupling of Light from Organic Light-Emitting Diodes by Microlens Arrays Based on Breath-Figure Template

We present a bottom-up method of fabricating microlens arrays based on a template of close-packed microvoids created by self-assembly and subsequent evaporation of condensed water droplets on the surface of a polymer solution exposed to humid air. The pattern of microvoids is transferred to an optically transparent, thermally curable elastomer to form the microlens array. The method offers advantages over conventional top-down microfabrication approaches in terms of easy fabrication, high fill factor, and near-optimum shape of the microlenses. Attachment of the microlens array to the glass substrate of an OLED device results in a significant increase in total emission and external quantum efficiency. These experimental results are compared to the predictions of a hybrid ray optics/wave optics model that can be used to gain further understanding and to help optimize the system.