Titanium Dioxide TiO2 Evaporation Process Notes
Titanium dioxide is a chemical compound with a chemical formula of TiO2. It is white in appearance with a density of 4.26 g/cc, a melting point of 1,830°C, and a vapor pressure of 10-4 Torr at ~1,300°C. The largest commercial application of titanium dioxide is as a white pigment for paint due to its brightness and high refractive index. It is also a principal ingredient in sunscreen because of its unique ability to absorb UV light. It is evaporated under vacuum primarily for reflective optical coatings and optical filters.
Titanium Dioxide TiO2 Specifications
|Material Type||Titanium (IV) Oxide|
|Melting Point (°C)||1,830|
|Theoretical Density (g/cc)||4.23|
|Max Power Density|
|Type of Bond||Indium, Elastomer|
|Thermal Evaporation Techniques||
Boat: W, Mo
|E-Beam Crucible Liner Material||FABMATE®, Tantalum|
|Temp. (°C) for Given Vap. Press. (Torr)||10-4: ~1,300|
|Comments||Suboxide, must be reoxidized to rutile. Ta reduces TiO2 to TiO and Ti.|
* 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.
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.