Home | People | Projects | Techniques | Publications | Contact | Links

Advanced Combinatorial Molecular Beam Epitaxy (MBE)
MBE is a set of versatile techniques for synthesizing and characterizing epitaxial structures with precise control. The low energy molecular or atomic beams are produced thermally in ultrahigh vacuum (UHV), and as the molecules or atoms land on a heated substrate surface facing the beams, nanostructures form. What distinguishes MBE from other deposition techniques are its precise control of deposition parameters and the available in-situ characterization techniques. Combinatorial MBE is a powerful approach we practice that synthesizes and characterizes a large number samples with a range of compositions and growth parameters on a single substrate.
Magnetooptic Kerr Effect (MOKE)
The Magnetooptic Kerr Effect is used to study the magnetic properties of our samples.  When linearly polarized laser light reflects off a magnetized sample, it undergoes a change in its polarization state that can be measured.  This change is caused by off-diagonal elements in the dielectric tensor of the material as a consequence of spin-orbit coupling.
Superconducting Quantum Interference Device (SQUID)
The SQUID magnetometer at UNC is a Quantum Design MPMS system. It can measure from 2-400K in fields upto 5.5 Tesla. A large variety of samples are investigated using this system, including GMR and CMR materials, Carbon nanotubes, Heusler alloys, metallic spin-glasses and others.

UHV Magnet Cryostat
Within this Janis-built UHV magnet cryostat, scanning probe microscopy (SPM)/spectroscopy and magnetooptical measurements are conducted in a temperature range between 1.6K and 350K and a field range of up to 3 Tesla. The instrument is capable of simultaneous microscopy and spectroscopy techniques in a variety of imaging and metrology modes including tunneling, topographic, dielectric constant/conductance, and magnetic resonance, using scanning tunneling microscopy and evanescent microwave probe microscopy. The precision xyz sample stage with a large travel range (1.5 cm) allows SPM measurements to be conducted over an entire ternary combinatorial sample. The instrument makes it possible to probe nanoscale surface structure, magnetism, and electronic states, including quantitative measurement of spin polarization using superconducting point contact Andreev reflection.
Scanning Tunneling Microscopy (STM)
This is a room temperature UHV scanning probe microscope (SPM) (Park Scientific SPM VP). It is capable of both STM and AFM for in-situ studies of surface structure and morphology of MBE-grown materials.
Synchrotron X-Ray Studies at Argonne National Lab (XRD)
Synchrotron radiation is used to carry out x-ray diffraction/spectroscopy experiments at the Advanced Photon Source in Argonne National Laboratory. Its high intensity, micron-sized beam allows for studies of structural properties and composition of combinatorial samples, using x-ray diffraction and fluorescence spectroscopy techniques. The source’s tunable energy is also used to probe local structures, such as chemical order, oxidation state, and bond length.
Reflection High Energy Electron Diffraction (RHEED)
Reflection High Energy Electron Diffraction (RHEED) has been the work horse for real-time quantitative characterization of epitaxial growth, owing to its surface sensitivity, large working distance, and the reflection geometry compatible with deposition. The grazing incident angle for the RHEED beam with respect to the surface, typically 1-2 degrees gives rise to a very small penetration depth, resulting in a diffraction pattern that is sensitive to only the outer most surface layer. Therefore, by monitoring the RHEED patterns (diffracted electrons) during growth and across the sample, evolution of surface structures can be examined systematically.
"Rheed" more...