Niobium (Nb) Wire Evaporation Materials
Niobium (Nb) Wire 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 .
Niobium (Nb) General Information
Niobium is classified as a transition metal on the Periodic Table of Elements. It is often found in nature with tantalum; hence it mimics many of its properties. It has a melting point of 2,468°C, a density of 8.57 g/cc, and a vapor pressure of 10-4 Torr at 2,287°C. While typically metallic gray in color, it is known to take on a bluish tinge when exposed to air. It is used in various superconducting alloys and is a common element in jewelry production. Niobium and its compounds and alloys are evaporated under vacuum to make semiconductor, optical and wear resistant coatings.
Niobium (Nb) Specifications
Material Type | Niobium |
Symbol | Nb |
Atomic Weight | 92.90638 |
Atomic Number | 41 |
Color/Appearance | Gray, Metallic |
Thermal Conductivity | 54 W/m.K |
Melting Point (°C) | 2,468 |
Coefficient of Thermal Expansion | 7.3 x 10-6/K |
Theoretical Density (g/cc) | 8.57 |
Z Ratio | 0.492 |
E-Beam | Excellent |
E-Beam Crucible Liner Material | FABMATE® |
Temp. (°C) for Given Vap. Press. (Torr) |
10-8: 1,728 10-6: 1,977 10-4: 2,287 |
Comments | Attacks W source. |
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 Niobium (Nb)
Niobium 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 niobium deposition.
E-beam Evaporation of Niobium (Nb)
Niobium is rated 'excellent' for e-beam evaporation. However, the process can be difficult and should be monitored very closely. We recommend using a fixed, focused beam and slowly pre-melting pellets to avoid spitting.
Due to its high melting point (2,468°C), niobium requires high powers in order to achieve an effective deposition rate. If the starting material is in pellet form, there is a high risk that even at high powers the pellets will not melt together uniformly which will increase the likelihood of the e-beam burning through the pellets and hitting the crucible. This can be evidenced by a sudden and steep fall-off of the deposition rate. It is then possible for the e-beam to drill a hole through the crucible liner and into the e-gun hearth. For these reasons, the e-beam evaporation of niobium should be closely monitored through welder's shade 9 glass. Great care should be taken during the entire evaporation cycle due to the high degree of difficulty and risk of equipment damage.
Some customers prefer to use a pre-machined slug (or starter source) as opposed to pellets. The two main benefits of using a starter source are ease of use and handling as well as superior packing density. We have also found that using a rod for high temperature materials like niobium helps to 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 and eliminates the problem of partially melted pellets. Niobium 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® crucible liner. 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 | Part Number | Price | In Stock | Add To Cart | |
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Material | Description | Size | Quantity | Purity | Part Number | Price | In Stock | Add To Cart | |
Niobium |
NIOBIUM WIRE, |
0.020" Dia. | Per ft., 10 min. | 99.95% pure Ex Ta | EVMNB.020 | P.O.R. |