Characterization techniques accessible to Ramki Kalyanaraman's group

Please get in touch if you would like to use one of our capabilities

We have capability to perform measurements of magnetic hysteresis in nanoscale structure using the surface magnetio-optical Kerr effect technique (SMOKE) in fields up to 0.7T and in various orientations. Fig. 1 shows the experimental schematics of the SMOKE apparatus. The basic set-up consists of a vibration free table which houses the electromagnet, electronics [consisting of two lock-in amplifiers, photoelastic modulator (PEM), and detector] and the optical components (the monochromatic 635 nm diode laser light source, lenses, and glan-thompson polarizers). The randomly polarized monochromatic light passes sequentially through a linear polarizer inclined at a desired angle and an objective lens to decrease beam spot size to 80 micro m). The polarizer angle is set to produce p-polarized light. A sample holder is located at the center of two adjustable pole pieces of the electromagnet, and the sample orientation with respect to the external magnetic field direction can be freely adjusted. In the polar geometry, the external magnetic field direction is perpendicular to the sample plane. In the longitudinal geometry, the external magnetic field direction is parallel to the sample plane. The plane of incidence is parallel to the field in both orientations. The reflected light, after interacting with the sample surface, passes through the PEM and another linear polarizer, which functions as an analyzer. The analyzer angle is set to 45°. The PEM at 50 kHz provides a reference signal (1f = 50 kHz and 2f = 100 kHz) for each lock-in amplifier. The light is detected by a biased high speed silicon detector and the output AC signal is sent to the lock-in amplifier (Stanford Research Systems, SR-830 & SR-530) to filter out unwanted noise. The DC signal from the lock-in amplifier goes to a computer through GPIB bus. The bipolar power supply for the electromagnet is remotely controlled by the computer. The digital interface card makes it possible to control the power supply output by means of digital input signals via the GPIB bus using SCPI commands from the computer. Therefore, the final output is a plot of the intensity of light versus the strength of the magnetic field. This SMOKE system is remotely and automatically controlled through a LabVIEW™ driver. Typically, multiple magnetic field loops were made for the measurements in order to improve the signal-to-noise ratio.

Besides the fabrication and basic optical characterization facilities, there are various university-wide facilities that are available on hourly or yearly rates.
  • Scanning Electron Microscope - Hitachi S-4500: A Hitachi S-4500 field-emission SEM in the SERF facility will be used to make morphological studies of the films . This SEM has a very high spatial resolution at all of its working voltages: 4 nm at 1 kV and 1.5 nm from 15 kV to 30 kV. The voltage can be varied in 0.1 kV steps over the entire range. A Noran EDS system allows chemical analysis of all elements heavier than beryllium, and also provides facilities for digitizing and processing images from the SEM.
  • As part of the JIAM Facility, we have access to a Zeiss Libra 200 TEM/STEM. This is a 200kV TEM equipped with energy filter and monochromator with a spatial resolution of around 3Å in Z-contrast mode. It is designed to allow cryo-tomography and diffraction experiments with high angles. The energy resolution in electron energy-loss spectroscopy surpasses the energy resolution of synchrotrons in X-ray absorption spectroscopy.

  • Also part of the JIAM Facility is a Zeiss Auriga Crossbeam Dual Beam FIB. This focussed ion beam machine is equipped with a STEM detector, backscatter detector and gas injection system. Other TEM’s, including STEM VG HB501 UX, at STEM VG HB601 U, STEM VG HB603 U and TEM/STEM FEI Titan S80-300 are available at ORNL and may be accessed through collaborations and/or SHARE proposals, when required.
  • TEM Sample Preparation For sample preparation, all the necessary state of the art equipment is available at UTK; this includes ion mills, dimplers and tripods.
  • Send us a message by email to ramki @ utk dot edu!