Development of a Near-Field Optical Instrument for the Study of Semiconductor Nanostructures and Student Training

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A near-field optical instrument for the optical characterization and investigation of semiconductor nanostructures will be developed. The instrument relies on the field enhancement at a laser illuminated metal tip. The electric energy density near the tip will be enhanced by 3 to 4 orders of magnitude over the exciting laser light. The tip is held in close proximity over the sample surface so that a highly localized interaction between the enhanced field and the sample is achieved. Increased signal-to-noise ratio due to non-linear effects will allow performance to perform spectroscopic measurements with high spatial resolution. Favorable tip shapes, tip materials and illumination modes will be investigated and a sensitive feedback mechanism will be implemented to assure nondestructive interaction forces (10pN) between tip and sample. The instrument will be applied to optically interact with semiconductor nanostructures on length scales smaller than the extent of their wavefunctions. The instrument will also give valuable feedback on the physical properties of nanostructered materials and thus provide input for improved nanomaterial synthesis. In collaborative projects the instrument will be applied to investigate biological membranes and to study electron/energy transfer between nanoparticles and surfaces. The instrument will also serve for laboratory demonstrations for students attending a course in nano-optics.A new faculty member, his postdoctoral associate and a graduate student will develop a new Near Field Optical Microscope. The instrument will be used to study semiconductor nanostructures and for student training. The new instrument will overcome the limitations of traditional light microscopes which not allow resolving features that are smaller than the wavelength of light. This is why we cannot see individual molecules and particles that form the building blocks of biological tissue and materials. Although these building blocks can be imaged by other techniques such as the electron microscope, the colorful optical properties are lost. Color is an important property since it provides information of the functionality of things: a leaf that is alive is green while a dead leaf is brown. It is therefore useful to find techniques, which extend the optical resolution to smaller length scales, and to make molecules and particles visible. This instrument will have the capability to detect and record the color of the tiny illuminated sample area. By using scanning technique the entire surface of the sample can be covered. Using the stored data a computer can generate an optical image of the entire sample surface. In this way, the instrument will establish an optical image with unprecedented resolution compared with traditional light microscopes.