A Method to Obtain Vertical Near-field Interaction in Scattering Type Near-field Optical Microscopy


While a conventional microscope (~250 nm optical resolution) is not suitable for the nano-world structures imaging (one millionth of a millimeter), Scanning near-field optical microscopy (SNOM) is capable of a super-resolution (~10 nm) imaging and surface topology, providing a spectroscopic characterization of nano-structures in a routine fashion and without using any fluorophores.

The scattering type SNOM (s-SNOM) or aperture-less SNOM (ANSOM) use a laser attached to the probe's tip that interacts with the specimen's surface. The imaging resolution is defined by the tip's aperture diameter. Combined with an infrared light source, the s-SNOM/ANSOM has been widely used for chemical-sensitive imaging and nano-spectroscopy: in polymer identification, biological molecules imaging and characterization of low-dimensional materials, e.g. graphene plasmons, boron nitride nano-tubes, block copolymers, proteins etc. While effectively providing a 2-D surface imaging, s-SNOM near-field sensitivity in vertical (i.e. normal to sample's surface) direction remains limited due to the large far-field background and complex tip-movement patterns. An extension of s-SNOM capability towards obtaining an improved vertical nearfield information would enable a better study of the bound electric fields at the surface. This is particularly important for the materials with the plasmonic or polaritonic phenomena.

Competitive Advantage

An improved s-SNOM method for the vertical tip-sample response reconstruction:

1. Relies only on the time-varying scattering signal from the detector and tip oscillation parameters (in tapping mode)

2. Does not depends on any particular near-field interaction model

3. The interaction curves from all harmonic responses resulting in a single curve

4. The interaction curves do not require a physical tip retraction from the sample surface (in the tapping mode), leading to a (lock-in) time reduction

5. The interaction curve can further be used to derive the tip approach curvesmore efficiently than current s-SNOM methods

Lehigh Tech ID # 062115-01


The global microscopy market is expected to reach $9.69 billion in 2020 with the conventional optical microscopes market being accounted for ~39% the share. Super resolution microscopes are expected to serve the market as a future growth opportunity. Scanning probe microscopy considered to be a faster growing market with a CAGR of 18.1% taking its share from the conventional optical microcopy.

Lehigh University is looking for a partner for further development and commercialization of this technology through a license. The inventor is available to collaborate with interested companies.

App Type Country Serial No. Patent No. File Date Issued Date Expire Date
Provisional [PR] United States 62/195,617 7/22/2015   7/22/2016
For Information, Contact:
Alan Snyder
VP, Research & Grad Programs
Lehigh University
Xiaoji Xu
Le Wang