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Iron Fe Notes


Iron (Fe) General Information

Iron is the most commonly used metal in the world. It is metallic-gray in color, ductile, ferromagnetic, and rusts easily when exposed to oxygen. It has a melting point of 1,535°C, a density of 7.86 g/cc, and a vapor pressure of 10-4 Torr at 1,180°C. Iron is found in a vast array of products including tools, automobiles, and machinery. When alloyed with carbon, steel is created which is an essential component for building construction and automobile manufacturing. Iron also has biological importance as it is responsible for carrying oxygen in blood. It is evaporated under vacuum to form layers in the production of semiconductors, magnetic storage media, and fuel cells, just to name a few.

Iron Fe Specifications

Material TypeIron †
SymbolFe
Atomic Weight55.845
Atomic Number26
Color/AppearanceLustrous, Metallic, Grayish Tinge
Thermal Conductivity80 W/m.K
Melting Point (°C)1,535
Coefficient of Thermal Expansion11.8 x 10-6/K
Theoretical Density (g/cc)7.86
SputterDC
Max Power Density
(Watts/Square Inch)
50*
FerromagneticMagnetic Material
Z Ratio0.349
E-BeamExcellent
Thermal Evaporation Techniques Boat:  W
Coil:  W
Basket:  W
Crucible:  Al2O3
E-Beam Crucible Liner MaterialFABMATE®
Temp. (°C) for Given Vap. Press. (Torr) 10-8:  858
10-6:  998
10-4:  1,180
CommentsAttacks W. Films hard, smooth. Preheat gently to outgas.

† Magnetic material (requires special sputter source).

‡ One run only.

* This is a recommendation based on our experience running these materials in KJLC guns. The ratings are based on unbonded targets and are material specific. Bonded targets should be run at lower powers to prevent bonding failures. Bonded targets should be run at 20 Watts/Square Inch or lower, depending on the material.

Z-Factors

Empirical Determination of Z-Factor

Unfortunately, Z Factor and Shear Modulus are not readily available for many materials. In this case, the Z-Factor can also be determined empirically using the following method:

  • Deposit material until Crystal Life is near 50%, or near the end of life, whichever is sooner.
  • Place a new substrate adjacent to the used quartz sensor.
  • Set QCM Density to the calibrated value; Tooling to 100%
  • Zero thickness
  • Deposit approximately 1000 to 5000 A of material on the substrate.
  • Use a profilometer or interferometer to measure the actual substrate film thickness.
  • Adjust the Z Factor of the instrument until the correct thickness reading is shown.

Another alternative is to change crystals frequently and ignore the error. The graph below shows the % Error in Rate/Thickness from using the wrong Z Factor. For a crystal with 90% life, the error is negligible for even large errors in the programmed versus actual Z Factor.

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