Localized current injection and submicron organic light-emitting device on a pyramidal atomic force microscopy tip.

An organic light-emitting device was fabricated on a commercial atomic force microscopy (AFM) probe having a pyramidal tip by a lithography-free vacuum thermal evaporation (VTE) process. The line-of-sight molecular transport characteristic of VTE results in controlled thickness variation across the nonplanar substrate, such that localized current injection occurs at the tip region. Furthermore, the high curvature of the AFM tip vertex concentrates the electric field, causing highly localized bipolar charge injection, accompanied by photon emission from a region less than a micrometer across. This light source exhibits a range of features potentially attractive for applications such as probe-based optical microscopy, nanoscale light sensing, and chemical detection.