Nathan, Stacey, and Brianna receive UROP awards

Congratulations to Nathan Swena, Stacey Murguia, and Brianna Potter for receiving UROP awards!

Nathan Swena, Stacey Murguia, and Brianna Potter receive UROP (Undergraduate Research Opportunity) awards in Fall, 2016 to work on the following projects: 1. Nathan Swena: Background-free IR Spectroscopy Using Apertureless Scanning Near-field Microscopy The ability to perform infrared (IR) spectroscopy on the nanoscale is very important for analyzing and identifying many different material characteristics. IR spectroscopy detects the absorption of IR light by molecular resonances at specific frequencies that depend on the number of bonds, types of bonds and which atoms are bonding. Furthermore, nearly all inorganic and organic compounds have an optical response or “fingerprint” in the mid-IR range. But the ability to perform this is on a small scale is limited by conventional means due to the Abbe diffraction limit (d=λ2nsinθ)[1] which shows that the spatial resolution can only be approximately half of the wavelength. This is a large limitation for mid-IR optical methods, since mid-IR wavelengths range from 2 μm to 20 μm. This would make the best possible spatial resolution limited to about 1 μm, which is not a high enough spatial resolution to be able to see samples in the nanoscale regime. In our experiment we break through this limit by using the scattering-type scanning near-field optical microscope (s-SNOM) which is an advanced optical system based on an atomic force microscope (AFM). Using the tip-scattered light that originates from a highly confined point, the diffraction limit no longer applies and instead the resolution is limited to the radius of the AFM tip. But a difficulty with s-SNOM is the background signal that is not being scattered from the sharp tip. A background-free signal can be accomplished with the use of pseudoheterodyne technique for s-SNOM. Additionally, a new optical technique based on the s-SNOM experimental setup called photo-induced force microscopy (PiFM) has potential to provide background-free optical detection in the mid-IR range. The goal of this research is to achieve nanoscale background-free IR spectroscopy with both pseudoheterodyne and PiFM to study the optical properties of materials without background artifacts. 2. Stacey Murguia: Femto-Newton Thermal Force Measurement Using Shear Force Atomic Force Microscopy
The main goal of this research is to use shear force atomic force microscopy (SF-AFM) based on a quartz tuning fork (QTF) resonator to measure the temperature dependence of frictional forces between a tip and substrate to determine specific information about a material’s thermal properties. Nanothermometers/nanoheaters will accompany the measurement of local temperature changes and be used as a local heat source, where the localized heating will ensure that measured temperature effects are not due to bulk heating of the QTF resonator. With the success of this research, SF-AFM will provide new knowledge of nanoscale temperature distributions and materials thermal properties where sub-continuum effects may exist.
3. Brianna Potter: Near-Field Scanning Microscopy for Nanoscale Graphene Thickness (in collaboration with Prof. Jiyoung Chang) This research is aimed at using photocurrent measurements using Atomic Force Microscopy to determine how the number of layers of graphene in a sample of graphene affects its electronic properties. The process will involve optimizing the growth of both single- and multi-layered graphene. After this, the photocurrent measurements will be made by focusing near-field light on the metallic tip in the AFM. All this will help determine if there is a correlation between the number of layers of graphene and the photocurrent that is measured.