Low Temperature Scanning Tunneling Microscopy - STM


The Scanning Tunneling Microscope (STM) enables the study of the topography and the electronic structure of conductive surfaces down to the atomic level. It was the first developed in the growing class of scanning probe techniques. Operating at low temperatures leads to additional benefits. Due to the reduced thermal noise the energy resolution is enhanced allowing to resolve details in spectroscopic measurements otherwise unaccessible. The vacuum level and the stability of the microscope are usually enhanced allowing long undisturbed observation times of the same area, or of the same atom. Some materials change there behavior at low temperatures (Superconductivity, formation of charge density waves) which are only observable below the respective transition temperature.

Facilities

Currently, the 4 K laboratory is operational, while the mK laboratory is under construction.



4K Laboratory


mK Laboratory

Results

As of now, a couple of 'test' measurements were performed using the 4 K system. Due to the unusual results found, some of the measurements where rather extensive and the findings should be published soon.

Gold/Mica (Step motion at 4.2 K)
NbSe2 (Vortices and more)
Fe/Au (111) (This was really just a test)
Silicon (The main project)


Publications


J. Lee, M. Dreyer, H. Wang and B. Barker, Ultra-slow vortex dynamics of a type II superconductor subject to magnetic field decay, to be published
M. Dreyer, J. Lee, H. Wang and B. Barker, Local distortions in slow moving vortex lattice, to be published
H. Wang, M. Dreyer, J. Lee and B. Barker, to be published


Presentations

  1. UHV LT-STM system with Sample and Tip Exchange. Presented at the American Physical Society March meeting, Baltimore, Maryland, USA, March 13-17, 2006.
  2. Vortex Dynamics Investigated using Low Temperature Scanning Tunneling Microscopy: Collective Motion and Collective Pinning of Vortices in NbSe2, American Physical Society March meeting, Baltimore, Maryland, USA, March 13-17, 2006.
  3. Low temperature scanning tunneling microscopy study on electronic standing waves and step motion on Au(111) surface, American Physical Society March meeting, Baltimore, Maryland, USA, March 13-17, 2006.
  4. Investigation of Collective Motion of Vortices in NbSe2 using Scanning Tunneling Microscopy, International Conference on Nanosciences and Technology 2006, Basel, Switzerland, July 31-August 4, 2006.
  5. Standing Distortion Waves in Moving Vortex Lattices Observed by STM. Presented at the International Conference on Nanosciences and Technology 2006, Basel, Switzerland, July 31-August 4, 2006.
  6. Local vortex-defect interaction in moving vortex lattices observed by STM. Presented at the American Physical Society March meeting, Denver, Colorado, USA, March 5-9, 2007.
  7. Analysis of collective pinning and depinning of the flux line lattice in pristine 2HNbSe2, American Physical Society March meeting, Denver, Colorado, USA, March 5-9, 2007.
  8. Low Temperature STM Study of Vortex Motion on Fe doped NbSe2, American Physical Society March meeting, Denver, Colorado, USA, March 5-9, 2007.
  9. STM study of slow moving vortex lattices in NbSe2. Presented at the IVC-17/ICSS-13 and ICN+T2007 meeting, Stockholm, Sweden, July 2-6, 2007.


Collaborations


Prof. Eva Andrei
(Rutgers University)
Prof. Bob Anderson (University of Maryland)
Prof. Chris Lobb (University of Maryland)
Prof. Fred Wellstood
(University of Maryland)
Sudeep Dutta, Ph.D. (University of Maryland)