Novel Nano-OLED Based Probes for Very High Resolution Optical Microscopy.

[摘要] Near-field scanning optical microscopy (NSOM) has been applied in the study ofnanomaterials, microelectronics, photonics, plasmonics, cells, and molecules. However,conventional NSOM relies on optically pumped probes, suffering low optical transmission,heating of the tip, and poor reproducibility of probe fabrication, increasing the cost,impeding usability, reducing practical imaging resolution, and limiting NSOM’s utility.In this thesis, I demonstrate a novel probe based on a nanoscale, electricallypumped organic light-emitting device (OLED) formed on the tip of a low-cost, commerciallyavailable atomic force microscopy (AFM) probe. I describe the structure, fabrication,and principles of this novel probe’s operation, and discuss its potential to overcomethe limitations of conventional NSOM probes. The broader significance of this work inthe field of organic optoelectronics is also discussed.Briefly, OLEDs consist of organic thin films sandwiched between two electrodes.Under bias, electrons and holes are injected into the organic layers, leading to radiativerecombination. Depositing a small molecular OLED in vacuum onto a pyramid-tippedAFM probe results in a laminar structure that is highly curved at the tip. Simple electricalmodeling predicts concentration of electric field and localized electron injection into theorganic layers at the tip, improving the local charge balance in an otherwise electronstarvedOLED. Utilizing an ;;inverted” OLED structure (i.e. cathode on the ;;bottom”),light emission is localized to sub-200 nm sized, green light emitting regions on probe verxxvtices; light output power in the range of 0.1-0.5 nanowatts was observed, comparable tothat of typical fiber based NSOM probes but with greater power efficiency. Massive arraysof similar sub-micron OLEDs were also fabricated by depositing onto textured siliconsubstrates, demonstrating the superior scalability of the probe fabrication process(e.g. relative to pulled glass fibers).The investigation of the effect of non-planar substrate geometry on charge injection,transport and recombination provides broader insights into OLEDs made on roughsubstrates, general understanding of OLED operation (e.g. filamentary charge conduction)and degradation, and potentially helps to improve technologically important ;;inverted”OLED structures.

[发布机构] University of Michigan

[效力级别] Organic Light Emitting Devices

[关键词] High Resolution Optical Microscopy;Organic Light Emitting Devices;Effect of Non-planar Substrate Geometry on Optoelectrical Performances of Organic Light Emitting Devices;Modification of Atomic Force Microscopy Probes;Nano-scale Light Source;Electrical Engineering;Materials Science and Engineering;Engineering;Materials Science and Engineering