Imaging modes in force regulated near-field scanning optical microscopy: Amplitude, polarization, and interference contrast

This dissertation describes the force regulated near-field scanning optical microscope (NSOM) and two important adaptations: one for imaging polarization contrast with a linear response, and the other for interference imaging. An introduction to near- field optics is first presented, followed by a description of the background to this work that includes the relevant references to the literature and previous results. A simple theoretical description of the NSOM in terms of scalar fields is then presented, followed by an exposition of an early but relevant rigorous vectorial interpretation of the experiment. The basic force regulated NSOM is presented: its parts, operation, and construction is described and discussed, and its imaging capabilities are shown and discussed with results from different samples. In particular, the ability of the system to simultaneously image topographical and optical characteristics of the samples is described, and the importance of separating the optical and topographical information for the correct operation of the microscope is stressed. An adaptation to the basic NSOM that permits imaging sample-dependent polarization variations with sub-wavelength resolution and with a linear sensitivity is then discussed and analyzed. Results are shown for several samples that include metal on quartz, magneto-optic media, and polymers. Lastly, an interferometric arrangement of the NSOM is presented that allows imaging of phase variations, as well as polarization variations, with a significant signal enhancement achieved with the use of a pseudo-heterodyning technique

Characterization of Atomic Force Microscopy and Electrical Probing Techniques for IC Metrology

A novel atomic force microscope (AFM) is used to image a microlithographic sample. The AFM operates in the non destructive non-contact mode, uses glass tips as opposed to tungsten or silicon, and has an optical interferometric detection system. Its estimated lateral resolution is under 10 nanometers and much better in the z direction. A sample consisting of chrome features on quartz was produced for measurements using AFM and electric probe techniques. The features are single and grouped lines on the order of 1 .tm incorporated into an electric probe pad layout. Dimensions of these features are determined from the AFM images by relating their sizes in pixels to the excursions of the scanners during the formation of the images. These results are compared with measurements obtained through electric probing techniques

Near Field Optical Microscopy Characterization of IC Metrology

Images of a microlithographic sample obtained using a new near field scanning optical microscope (NSOM) that uses force regulation of the sample-tip separation are presented. The NSOM is a research instrument fitted with a metal covered glass tip probe that defines a small aperture at the sharp end. The aperture is estimated to be on the order of 100 nanometers in diameter resulting in a resolution exceeding that of diffraction limited systems. This form of microscopy can be done both in the transmission and the reflection modes. The force regulation mechanism produces a simultaneously obtained scanned force microscope (SFM) image of the topography thus permitting correlative imaging of the sample. The samples are imaged in transmission and reflection near field optical format, with white light and with coherent light. The results are compared with other forms of IC imaging and characterization, namely scanned force microscopy (SFM) and scanning electron microscopy (SEM)

Detection of Intra-Tumor Self Antigen Recognition during Melanoma Tumor Progression in Mice Using Advanced Multimode Confocal/Two Photon Microscope

Determining how tumor immunity is regulated requires understanding the extent to which the anti-tumor immune response “functions” in vivo without therapeutic intervention. To better understand this question, we developed advanced multimodal reflectance confocal/two photon fluorescence intra-vital imaging techniques to use in combination with traditional ex vivo analysis of tumor specific T cells. By transferring small numbers of melanoma-specific CD8+ T cells (Pmel-1), in an attempt to mimic physiologic conditions, we found that B16 tumor growth alone was sufficient to induce naive Pmel-1 T cell proliferation and acquisition of effector phenotype. Tumor -primed Pmel-1 T cells, are capable of killing target cells in the periphery and secrete IFNγ, but are unable to mediate tumor regression. Within the tumor, Pmel-1 T cells have highly confined mobility, displaying long term interactions with tumor cells. In contrast, adoptively transferred non tumor-specific OT-I T cells show neither confined mobility, nor long term interaction with B16 tumor cells, suggesting that intra-tumor recognition of cognate self antigen by Pmel-1 T cells occurs during tumor growth. Together, these data indicate that lack of anti-tumor efficacy is not solely due to ignorance of self antigen in the tumor microenvironment but rather to active immunosuppressive influences preventing a protective immune response