Wei GROUP

Nanofabrication Lab (MP 087 & 089)


Our nanofabrication facilities consist of:

  1. Electron beam writer (+ scanning electron microscope)
  2. Thin-film processing chamber
  3. Sputtering guns (DC & RF)
  4. Ion milling gun
  5. Thermal evaporator
  6. Electron beam evaporator
These instruments are housed in several adjacent labs, equipped with spin-coaters and fumehoods for chemical etching, plus various high-resolution microscopes (optical, SEM, AFM) for sample imaging.  They provide state-of-the-art capabilities for making and imaging nanostructures of various materials, particularly the complex oxides, thus enabling us to carry out "top-down" materials research at the nanoscale.  These nanofabrication facilities are in close proximity to our thin-film deposition and cryomagnetic labs.  This integrated approach allows dedicated feedback between fabrication and characterization.

Electron beam writer for nanolithography



Our electron-beam writer is based on a JEOL-848 scanning electron microscope (SEM) fitted with a beam blanker, picoammeter and nano-pattern generation system (Nabity NPGS) control electronics & software.   It is capable of writing and imaging with a scanning electron beam, and can achieve resolution down to ~20nm at 25keV depending on the material and filament used.  The large-volume sample chamber is equipped with a load-lock hatch for quick sample exchange and a computer-controlled sample stage for large travel.  An on-board ion pump enables lanthanum hexaboride, intead of tungsten, filaments to be used for higher resolution in ultra-high vacuum mode.   Nanolithography is carried out using various electro-resists as masks, applied by spin coating, defined by scanning electron beam, followed by chemical etching.  In the case of complex oxides, we have developed a breakthrough method for making nanostructures, using the principle of selective epitaxial growth in conjunction with pulsed laser thin-film deposition.

Thin-film processing chamber

A multiple-purpose vacuum chamber, supplied by Kurt Lesker Co., is dedicated to materials processing of thin-film samples.  The chamber is completely bakeable and equipped with a large-volume turbomolecular pump to achieve ~10-7Torr base pressure. Multiple port design enables a variety of processes (see below), with the sample holder on a 4-stage carousel, with both button-heating and liquid-nitrogen cooling capabilities.  A load-lock hatch enables quick sample transfer.




This vacuum chamber is equipped for a variety of processes.  First, there are DC and RF sputtering guns for thin-film deposition from 2-inch targets of both non-magnetic and magnetic materials.  An extractable vibrating-quartz head can be used to monitor the film thickness during deposition.  Second, there is an ion-milling gun for physical etching of pattern-masked thin films.  The ion milling can be carried out with the sample holder cooled by liquid nitrogen, to protect the sample from ion damage, which is particularly detrimental to complex oxide materials.  Third, there is a thermal evaporator for deposition of stock materials.  In addition, there is an electron-gun evaporator, with rasterable beam and multiple pockets, to enable the deposition of materials requiring higher energies.