An ultra-high vacuum, dc-magnetron (triode) sputtering system, located in the Physics and Astronomy Department at Michigan State University, has been used to grow polycrystalline and amorphous films and multilayers. The sputtering system contain four independent Simard triode sputtering guns with a 2.25" x 0.25" (diameter x thickness) target size and two circular diode magnetron guns from Angstrom Sciences with a one inch target size. This system has substrate cooling capability that allows cooling the substrates down to about -90ºC. A PC running a custom program monitors the plasma voltage, target current, and deposition rate of all sputtering guns. This automated software also controls two stepper motors. These motors accurately position samples over the desired target and control the deposition shutter assembly.
A new high temperature chamber top assembly has been designed to grow epitaxial films and multilayers as well as regular polycrystalline films and multilayers. Two substrate heater assemblies were designed for this system. One with cooling and heating capability, ranging from below room temperature to about 700º C. The second, for high temperature growth, ranging from 700º C to 1200º C. The general principal behind the design of these heaters was based on two heating techniques: (1) Heating by radiation (photons) for 700º C -1200º C and (2) Heating by conduction (phonons) for below 700º C.
Our sputtering facilities also have a smaller high vacuum chamber that contains Commonwealth 3-cm Ion source, RADAK Knudsen cell, 1.3" magnetron sputtering gun, a thermal evaporation assembly (capable of using Boats or Baffled Box), and a load luck. This system is used as a side facility for microfabrication using photo-lithography and e-beam-lithography.
SQUID Facilities
Physics/Astronomy Department has two SQUID susceptometers from Quantum Design, Inc. Both systems have the capability of making fast, precise measurements of the dc magnetic properties of materials over a wide range of temperatures and applied fields. They are capable of resolving variations in magnetic moment as small as 10-8 emu. One of the systems has the capability of measuring the ac susceptibility over a wide range of frequencies and ac magnetic fields. The ac SQUID also has a Low Field capability, which allows the user to achieve very low residual fields. An Environmental Magnetic Shield is added, which provides attenuation of external magnetic fields. The ac measuring field can be varied from 0.0001 to 5.94 Gauss with a frequency of range of 0.00035 to 1512 Hz, while the High Field SQUID system provides temperatures from 2 to 400 K and fields up to 5.5 Tesla, the ac one covers the temperature range 2 to 350 K with magnetic fields up to 1 Tesla.
The High Field SQUID is capable of measuring both the Longitudinal and Transverse moments. This system also has the Vertical and Horizontal Sample Rotator that permit users to rotate samples 360 degrees about the longitudinal and orthogonal axis under computer control.Both systems have External Device Controller, which allow user to measure the Resistivity or Magnetoresistance of desired samples.
