Materials Characterization

Electrical and Magnetic Characterization

A Janis Cryogenic 10 T superconducting magnet with variable temperature insert operating from 1.25 to 325 K is present in Prof. Leighton’s lab. The system is equipped with calibrated high field thermometers, temperature controller, level meter, pumps, and electronics for DC (current source, voltage source, nanovoltmeter and source/measure unit) and AC (resistance bridge or lock-in) transport measurements. Using combined temperature control on the variable temperature insert and the sample stage heater temperature stability of order 1 mK can be achieved at 10 K. The system is capable of measuring resistivity, Hall effect, magnetoresistance and photoconductivity (via an optical fiber), and has a second probe which enables sample rotation in both planes. One probe is wired with sub-miniature stainless steel coaxial cables to enable low noise, high impedance measurements. A home-built oven insert provides access to temperatures up to 1000 K (in an O2 atmosphere if required) for high temperature transport measurements. In addition to this system we also have a high-throughput transport probe where resistivity measurements (using a second AC resistance bridge) can be made from 4.2 - 300 K by insertion in a helium dewar

Physical Property Measurement System: A cryogen-free Quantum Design PPMS (Physical Property Measurements System) with a temperature range between 1.7 K to 400 K and a 9 T magnet is present in Prof.  Leighton’s lab. The system is equipped with a VSM (Vibrating Sample Magnetometry) option enabling high throughput magnetometry from 1.7 K to 1000 K. Additionally, Prof. Jalan’s lab has another fully operational cryogen-free Quantum Design PPMS Dynacool with a temperature range of 1.8 K to 400 K and a 9 T magnet. This system is also equipped with a thermal transport unit enabling thermal conductivity and Seebeck coefficient measurements from 1.8 K to 400 K.

SQUID Magnetometer: The Center has two Quantum Design XL7 SQUID systems, with 7T, 1.7 K field/temperature platforms. These systems are capable of measurements up to 800K (using an oven insert), a sample rotation (horizontal and vertical planes), AC susceptibility measurements, ultra-low-field operation, and a reciprocating sample option for higher throughput and sensitivity.

Other Resources

The College of Science and Engineering Characterization Facility provides access to many characterization tools that are operated as shared facilities and are available to the entire university on a “charge hourly” basis. The following instruments are available:
  • High-Resolution Thin Film Diffractometer: This provides high-resolution, wide-angle diffraction measurements of thin films and superlattices, rocking curve and reflectivity measurements, in-plane diffraction, reciprocal space mapping and pole figure measurements.
  • Wide Angle X-ray Diffractometers: There are four diffraction units. One is capable of diffraction between 4 K to 1400 K, a second has a high-intensity source and a 1-D line detector.
  • Laue Diffractometer: The Laue diffractometer provides a high-throughput method of measuring crystal orientation.
  • Microdiffractometer: This system has a sensitive 2D detector, useful for measurements of thin-film polycrystalline samples. Texture and single crystallinity can easily be determined.
  • Low Angle Diffractometers and Grazing Incident Reflectometers: There are three units. One is equipped with 2D-area detector.
  • Scanning Probe Microscope: Atomic force microscopy, scanning tunneling microscopy and near-field scanning optical microscopy. There are three Digital Instruments Nanoscope III units, one of which is capable of nanoindentation.
  • Scanning Electron Microscopes: There are four scanning electron microscopes based on field-emission guns. Their capabilities include energy dispersive spectroscopy, crystallographic analysis, and texture mapping.
  • Transmission Electron Microscopes: There are four transmission electron microscopes. These instruments are capable of electron energy loss spectroscopy and energy dispersive spectroscopy. The abberation-corrected FEI Titan 80-300 kV FEG TEM is capable of scanning TEM.
  • Other Characterization Instruments: The Characterization Facility also has instruments for optical microscopy, Auger electron spectroscopy, secondary ion mass spectroscopy, X-ray photoelectron spectroscopy, and other techniques.
 
The Minnesota Nano Center at the University of Minnesota maintains a state of art fabrication facility with 3000 square feet of class 10 space and 2700 square feet of class 100 space. The MNC has tools for:
  • Photolithography: Available photolithographic patterning tools include masking capabilities for feature sizes down to 1.5 microns.
  • Electron Beam Lithography: The Vistec EBPG 5000+ 100kV system is capable of linewidths less than 10 nm and large area patterning.
  • Etching: Ion milling, deep trench etching, and several reactive ion etching tools are available.
  • Deposition: The available instruments include several evaporators (thermal and electron beam for metals and alloys), sputtering systems (r.f. and d.c.), and tools for plasma-enhanced chemical vapor deposition, and atomic layer deposition.
  • Other techniques: including wire bonding, rapid thermal annealing, profilometry, and ellipsometry.