Post by Professor Lake Shore on Jan 31, 2017 17:21:35 GMT -5
Can you provide some general tips on temporarily mounting probe station samples?
There are three methods commonly used: greases and adhesives, tapes, and clamping. With a specified operating range of 1 K to 300 K, a very thin layer of vacuum compatible (low vapor pressure) grease, such as Apiezon N grease, can be used as a coupling agent between device and the top surface of a clean sample holder. Below ~ 210 K, the grease solidifies and can affix a device to the sample stage. When it comes to Apiezon N grease – more is not better. At cryogenic temperatures, a thin coating can fill the microscopic voids in the two surfaces for better thermal contact. However, on-cooling, excess grease will act as an insulating layer between device and stage. Apiezon N grease liquefies near 316 K and is not recommended for higher temperature operation. Depending on application, silver paint, carbon-based adhesives, silver epoxy, or high-temperature grease can also be used.
Because greases and adhesives often need to be cleaned from a sample, a vacuum compatible tape with silicone adhesive offers a cleaner alternative. 3M brand Kapton tape, placed on the corners or edges of a sample, works well for cryogenic applications because it will retain its adhesive properties to as low as 4 K. For certain measurements, a double-sided adhesive tape can be used between the sample and sample holder. You may need to experiment with different types of double-side tape to find one that does not harden or peel away at low temperatures. While convenient, tape may not perform optimally for the lowest temperature applications. Tape on the corners may provide insufficient clamping force, while double-sided tape can act as an additional insulating layer between device and stage.
When possible, Lake Shore recommends clamping the device to the sample stage. Users often make simple clamping fingers to fit their sample and hold them down with M3 screws in the tapped holes intended for the lifter tool. When used in conjunction with thermal grease, mechanical clamping of the device provides the best thermal contact between the sample and sample holder.
Regardless of the method used, be sure to wear nitrile gloves when handling anything inside the probe station (hand oils will contaminate the surfaces, resulting in poor vacuum and thermal performance).