This dissertation focuses on the application of Tip-Enhanced Raman spectroscopy (TERS) to non-transparent and non-conductive samples, allowing for the optical characterization of nanoelectronic devices. As such, nano-crystals are analyzed as a model system for the investigation of chemical and structural properties. Furthermore, a novel method for mapping the refractive index of materials with nanometer resolution is presented.
The technological progress of electronics through miniaturization has reached the nanoscale while new materials with high performance and functional properties gain importance. Quality control and the scientific understanding of size effects in electronic nanostructures are required more than ever to consolidate existing technologies and to determine scaling limits of new materials. Conventional techniques, including scanning electron and scanning probe microscopy, provide topographic information but only very limited chemical information to analyze the physical properties of nanomaterials. Chemical and structural sensitivity is available by Raman or infrared spectroscopy, but with a spatial resolution limited to the microscale by the diffraction limit of light. TERS combines the virtues of scanning probe microscopy with those of optical spectroscopy to overcome the diffraction limit through the excitation of surface plasmons on a scanning probe tip to confine light to nanometers.
In this work, a TERS system was installed to operate on opaque samples by employing optical side access. TERS probes were fabricated by electrochemical etching and operated in scanning tunneling microscopy and atomic force microscopy with quartz tuning forks to enable scanning on various surfaces. TERS was then applied to ferroelectric lead titanate nano-crystals on a platinized silicon substrate as a model system for nanostructured, charge-based memory devices at the onset of finite size effects.