Near-Field Scanning Optical Imaging with Monolithic Silicon Light Emitting Diode on Probe Tip

We describe optical and topographic imaging using a light emitting diode (LED) monolithically integrated on a silicon probe tip for near-field scanning optical microscopy (NSOM). The light emission resulted from a silicon dioxide layer buried between a phosphorus-doped N+ silicon layer and a gallium-doped P+ silicon region created locally at the tip by a focused ion beam (FIB). The tip was employed in a standard NSOM excitation setup. The probe successfully measured optical as well as topographic images of a chromium test pattern with imaging resolutions of 400 nm and 50 nm, respectively. The directional resolution dependence of the acquired images directly corresponds to the shape, size and polarity of the light source on the probe tip. To our knowledge, this report is the first successful near-field imaging result directly measured by such tip-embedded light sources.

Background

Near-field Scanning Optical Microscopy (NSOM) measures optical properties on a sub-wavelength scale with simultaneous topography imaging ¹, and is a powerful tool for exploring nano-scale structures such as inorganic nanoparticles/, organic thin films:‘, and interfaces of biomaterials ‘. A pulled optical fiber with an external laser light source was typically used in NSOMI. Direct integration of light source, in particular monolithic integration of an electrically pumped light source, on scanning probe is highly desirable to further extend the applications of NSOM into otherwise difficult-to-access environments, such as compact pressure or temperature controlled chambers“. Silicon-monolithic light sources, in combination with the integrated circuit technology, will also lead to future data storage devices employing near-field optics”, Here we describe an imaging result of NSOM taken with a nanometer-sized light emitting diode (LED) monolithically integrated on a silicon probe tip. A unique feature of our method is that the imaging characteristics are directly related to the size of the apertureless built-in light source. To our knowledge, this report is the first successful near-field imaging result directly measured by such tip-embedded light sources.