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Zirconium Zr Notes


Zirconium (Zr) General Information

Zirconium is a classified as a transition metal on the Periodic Table. It has a density of 6.49 g/cc, a melting point of 1,852°C, and a vapor pressure of 10-4 Torr at 1,987°C. It is silvery-white in appearance and its propensity for corrosion resistance makes it heavily used by the chemical industry. Zirconium can be found in surgical appliances, superconductive magnets, and the cladding of nuclear reactors. It is also utilized as an alloying agent for steel. Its compound, zirconia, is often a substitute for diamonds in jewelry. Zirconium, along with its alloys and compounds, is evaporated under vacuum for optical coatings, semiconductors, and data storage devices.

Zirconium Zr Specifications

Material TypeZirconium
SymbolZr
Atomic Weight91.224
Atomic Number40
Color/AppearanceSilvery White, Metallic
Thermal Conductivity22.7 W/m.K
Melting Point (°C)1,852
Coefficient of Thermal Expansion5.7 x 10-6/K
Theoretical Density (g/cc)6.49
SputterDC
Max Power Density
(Watts/Square Inch)
50*
Type of BondIndium, Elastomer
Z Ratio0.6
E-BeamExcellent
Thermal Evaporation Techniques Boat:  W
Temp. (°C) for Given Vap. Press. (Torr) 10-8:  1,477
10-6:  1,702
10-4:  1,987
Export Control (ECCN) 1C234
CommentsAlloys with W. Films oxidize readily.

* 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.