Applying solid immersion near-field optics to Raman analysis of strained silicon thin films

A solid immersion lens (SIL) is applied with Raman spectroscopy to selectively analyze strained silicon thin films. The SIL was fabricated using a high index optical fiber, n=1.9. The fabrication allows for integration with an atomic force microscope (AFM) for repeated approach and feedback of the SIL to the surface. The evanescent field emanating from the SIL was investigated using near-field optical microscopy and the decay length was ∼150 nm. This was then combined with a Raman spectrometer coupled to an online AFM having a completely free optical axis permitting optical investigations of opaque samples such as strained silicon.