Molybdenum (Mo) Pellets Overview
We sell these pellets and pieces by unit weight for evaporation use in deposition processes. These approximate materials prices are published to provide budgetary guidelines. Actual prices can vary and may be higher or lower, as determined by availability and market fluctuations. To speak to someone directly about current pricing, please click here .
Molybdenum (Mo) General Information
Molybdenum is categorized as a transition metal on the Periodic Table. It is metallic grey in appearance with a melting point of 2,617°C, a density of 10.2 g/cc, and a vapor pressure of 10-4 Torr at 2,117°C. Due to its strength and high melting point, molybdenum is primarily alloyed with other metals to make corrosion resistant materials and can be found in tools, aircraft parts, and electrical contacts. Molybdenum is evaporated under vacuum to make advanced displays, semiconductors, and sensors.
Molybdenum (Mo) Specifications
Material Type | Molybdenum |
Symbol | Mo |
Atomic Weight | 95.96 |
Atomic Number | 42 |
Color/Appearance | Grey, Metallic |
Thermal Conductivity | 139 W/m.K |
Melting Point (°C) | 2,617 |
Coefficient of Thermal Expansion | 4.8 x 10-6/K |
Theoretical Density (g/cc) | 10.2 |
Z Ratio | 0.257 |
E-Beam | Excellent |
E-Beam Crucible Liner Material | FABMATE®, Graphite |
Temp. (°C) for Given Vap. Press. (Torr) |
10-8: 1,592 10-6: 1,822 10-4: 2,117 |
Comments | Films smooth, hard. |
Suggested QCM Crystal | Alloy Crystal: 750-1002-G10**** |
**** Suggestion based on previous experience but could vary by process. Contact local KJLC Sales Manager for further information
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.
Thermal Evaporation of Molybdenum (Mo)
In a deposition system with normal dimensions, a material with an equilibrium vapor pressure (EVP) of 10-2 Torr will deposit at a rapid rate. Therefore, 10-2 Torr is typically regarded as the EVP one should attempt to achieve during deposition. The only parameter that affects EVP is temperature. We reference various charts or books to determine what temperature is needed to make the material's EVP 10-2 Torr. Molybdenum requires a temperature of ~2,600°C to achieve a vapor pressure of 10-2 Torr.
Molybdenum (Mo) Vapor Pressure Chart
Molybdenum is nearly impossible to deposit by thermal evaporation due to the high power required for the material to evaporate. E-beam evaporation or magnetron sputtering are the recommended methods for molybdenum deposition.
E-beam Evaporation of Molybdenum (Mo)
In a deposition system with normal dimensions, a material with an equilibrium vapor pressure (EVP) of 10-2 Torr will deposit at a rapid rate. Therefore, 10-2 Torr is typically regarded as the EVP one should attempt to achieve during deposition. The only parameter that affects EVP is temperature. We reference various charts or books to determine what temperature is needed to make the material's EVP 10-2 Torr. Molybdenum requires a temperature of ~2,600°C to achieve a vapor pressure of 10-2 Torr.
Molybdenum (Mo) Vapor Pressure Chart
Molybdenum is rated 'excellent' for e-beam evaporation. However, the process can be difficult and should be monitored very closely. Pre-melting molybdenum is a challenge as it tends to not melt into the beam as most metals do.
Due to its high melting point (2,617°C), molybdenum requires high powers in order to achieve an effective deposition rate. At a working voltage of 10kV, we found that 140-150 mA of current was needed in order to reach an acceptable evaporation rate using a FABMATE® crucible liner and molybdenum slug (or starter source). Even at these powers, we have only been able to achieve a deposition rate of 2.2 angstroms per second. Maintaining a deposition rate is also difficult to do. There is risk that the e-beam will bore straight through the material which is evidenced by a sudden and steep fall-off of the deposition rate. While running at these high currents (>125mA), it is possible for the e-beam to then drill a hole through the crucible liner and into the e-gun hearth. For these reasons, the e-beam evaporation of molybdenum should be closely monitored through welder's shade 9 glass. Great care should be taken during the entire evaporation cycle.
Another common problem when e-beam evaporating molybdenum is spitting. Soaking the material for an extended period of time before opening the substrate shutter to deposit the film can reduce this to some degree. Spitting can also be reduced by using a starter source or rod as opposed to evaporation pellets.
We recommend using a pre-machined slug (or starter source) instead of pellets. The two main benefits of using a starter source are ease of use and handling as well as superior packing density. We have found that using a rod for high temperature materials like molybdenum helps reduce the amount of power required for deposition. We machine a rod such that the outer diameter of the rod is not in contact with the cooled walls of the crucible liner. This allows higher temperatures to be achieved at lower powers. Molybdenum will still require high power for evaporation even when using a starter source or rod, but less so than when using pellets.
KJLC® can produce these starter sources or rods. Contact us by clicking here with your e-gun manufacturer, pocket size, and number of pockets in order for us to produce a quote.
We also recommend using a FABMATE® or graphite crucible liner or running molybdenum directly from the hearth of the e-gun. Because not using a crucible liner is not always an option, especially in shared systems, some customers will use a copper crucible liner and place the material in the copper crucible liner instead of placing directly in the hearth.
A key process note is to consider the fill volume of the crucible liner. We find that the melt level of a material in the crucible directly affects the success of the crucible liner. Overfilling the crucible will cause the material to spill over and create an electrical short between the liner and the hearth. The outcome is cracking in the crucible liner. This is the most common cause of crucible liner failure. Placing too little material in the liner or evaporating too much material before refilling can be detrimental to the process as well. When the melt level is below 30%, the e-beam is likely to strike the bottom or walls of the crucible which immediately results in breakage. Our recommendation is to fill the crucible between 2/3 and 3/4 full to prevent these difficulties.
Crucible liners should be stored in a cool, dry place and always handled with gloves or forceps.
See highlighted results that match your result in the table below.
Ordering Table
Material | Description | Size | Quantity | Purity | Notes | Part Number | Price | In Stock | Add To Cart | |
---|---|---|---|---|---|---|---|---|---|---|
Material | Description | Size | Quantity | Purity | Notes | Part Number | Price | In Stock | Add To Cart | |
Molybdenum |
MOLYBDENUM PELLETS, |
1/4" Dia. x 1/2" Length | 1 lb. | 99.95% | — | EVMMO35QXH | P.O.R. | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/4" Dia. x 1/4" Length | 1 lb. | 99.95% | — | EVMMO35QXQ | $408.00 | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/4" Dia. x 1/4" Length | 25 g | 99.95% | — | EVMMO35QXQA | $49.00 | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/4" Dia. x 1/4" Length | 50 g | 99.95% | — | EVMMO35QXQB | $87.00 | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/4" Dia. x 1/4" Length | 100 g | 99.95% | — | EVMMO35QXQD | $102.00 | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/8" Dia. x 1/4" Length | 1 lb. | 99.95% | — | EVMMO35EXQ | P.O.R. | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/8" Dia. x 1/8" Length | 1 lb. | 99.95% | — | EVMMO35EXE | $504.00 | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/8" Dia. x 1/8" Length | 100 g | 99.95% | — | EVMMO35EXED | $144.00 | |||
Molybdenum |
MOLYBDENUM PELLETS, |
1/8" Dia. x 1/8" Length | 250 g | 99.95% | — | EVMMO35EXEJ | $343.00 | |||
Molybdenum |
MOLYBDENUM PIECES, |
Approx. 1/4" x 1/4" Pieces | Per Gram | 99.95% | EVMMO35SPL10 | $0.30 |