Calcium Ca Evaporation Process Notes
Calcium is classified as an alkaline earth metal on the Periodic Table. It is silvery-white in appearance and soft enough that it can be cut with a sharp knife. It is known to easily oxidize when exposed to the atmosphere. Calcium has a density of 1.54 g/cc, a melting point of 839°C, and a vapor pressure of 10-4 Torr at 459°C. Calcium is an essential building block for human life as it is found in abundance in human skeletons and teeth. Calcium and its compounds are also used to produce commercial concrete and cement. Calcium, along with its alloys and compounds, is evaporated under vacuum to make optical storage media, superconductors, and anti-reflective layers.
Calcium Ca Specifications
|Color/Appearance||Silvery White, Metallic|
|Thermal Conductivity||200 W/m.K|
|Melting Point (°C)||839|
|Coefficient of Thermal Expansion||22.3 x 10-6/K|
|Theoretical Density (g/cc)||1.54|
|Max Power Density|
|Thermal Evaporation Techniques||
Crucible: Al2O3, Q
|Temp. (°C) for Given Vap. Press. (Torr)||
|Comments||Corrodes in air.|
* 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.