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Molybdenum Oxide MoO3 Evaporation Process Notes

Molybdenum Oxide (MoO3) General Information

Molybdenum oxide is a chemical compound with a chemical formula of MoO3. It is white to pale yellow in color with a melting point of 795°C, a density of 4.69 g/cc, and a vapor pressure of 10-4 Torr at ~900°C. It is primarily used to manufacture pure molybdenum metal. It is evaporated under vacuum to make transparent electrodes for photovoltaic cells.

Molybdenum Oxide MoO3 Specifications

Material TypeMolybdenum Oxide
Color/AppearanceWhite to Pale Yellow, Crystalline Solid
Melting Point (°C)795
Theoretical Density (g/cc)4.69
Type of BondIndium, Elastomer
Z Ratio**1.00
Thermal Evaporation Techniques Boat:  Mo
Basket:  Mo
Crucible:  Al2O3, BN
Temp. (°C) for Given Vap. Press. (Torr) 10-4:  ~900
CommentsSlight oxygen loss.

** The z-ratio is unknown. Therefore, we recommend using 1.00 or an experimentally determined value. Please click here for instructions on how to determine this value.


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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