Press Contact Assemblies
We have developed a range of press contact assemblies facilitating the rapid and easy mounting of samples for electrical measurement using the Physical Property Measurement System (PPMS) of Quantum Design. With these press contacts, samples can be prepared for measurement in seconds rather than hours.
The assemblies are designed to work with the PPMS resistivity, ac transport or electrical transport measurement options. For four-point electrical measurement, the contacts are aligned linearly, with a 2 mm pitch (see detailed schematic
). Samples up to 4 mm in thickness can be accommodated, so long as they can rest stably on the puck surface. Resistivity, IV curve and critical current measurement are all supported (dependent on the installed measurement option). Hall effect measurement requires a different contact arrangement, also available.
Utilising our extensive experience of measurement using the PPMS instrument, we are also able to custom-design press contact assemblies to address your particular measurement challenges. Contact us for more information, or view the detailed schematic for some of our more common alternative layouts.
These assemblies have been making our lives easier for over twenty years, and are now in use in laboratories around the world. Examples of the types of samples able to be successfully measured are shown in the photographs to the side. Both thin film and bulk samples can be accommodated.
Electrical Transport Option
The new electrical transport measurement option utilises standard resistivity option pucks, and as such any of our press contact assemblies designed for use with the resistivity option will also work with the ETO. Important to note, however, is that only measurement channels 1 and 2 are passed through to the ETO, even though channel 3 remains present.
Van der Pauw Press Contact Assemblies
PPMS Application Note 1076-304 describes a method of performing van der Pauw resistivity measurements on samples of arbitrary geometry. Such measurements are ideally suited to a rapid, hassle-free press contact setup, and we have developed assemblies to facilitate this. Using these, all the connections described in the Application Note are neatly and correctly implemented, leaving the user free to simply acquire and process the data. By selecting appropriate pin positions, a single assembly can support samples of multiple sizes: as standard, contact points spaced 2×2, 4×4, 6×6, and 8×8 mm are available to choose from. Custom arrangements are also available — simply contact us for details.
Note that reversed polarity measurements are trivially implemented in the measurement sequence as a means of improving accuracy through the elimination of offset voltages. A further improvement can be achieved by compensating for geometrical effects by additionally making reciprocal measurements; however since only three PPMS measurement channels are available, this requires the incorporation of a switch system, for example utilising our van der Pauw patch box to provide access to the PPMS measurement lines to reverse the contacts during measurement. More specific details of the measurement procedure are available here.
Van der Pauw Hall effect measurements are also possible in principle. However, the time taken to reverse the polarity of the applied field between measurements can lead to unsatisfactory results. We are presently working on developing the possibility to conduct these measurements in the PPMS rotator, thereby enabling the sample to be rotated quickly through 180° rather than reversing the field.
| Probe material | Full-hard beryllium copper, gold-plated over nickel |
| Probe type | Rounded (standard) Needle point, Pointed, Concave, Serrated (options) |
| Contact resistance | < 100 mΩ |
| Current rating | 3 A continuous |
| Probe travel | 2.5 mm |
| Spring force | 0.8 N at 2 mm travel |
| Durability | 100,000 cycles |
| Functional temperature | 2 – 400 K |
| PC-RES | Resistivity press contact assembly (also suitable for ETO) | £350 |
| PC-ACT | AC transport press contact assembly | £350 |
| PC-HALL-RES | 4-point Hall measurement press contact assembly (RES/ETO) | £350 |
| PC-HALL-ACT | 5-point Hall measurement press contact assembly (ACT) | £350 |
| PC-VDP-RES | Van der Pauw resistivity press contact assembly (RES/ETO) | £350 |
| PC-VDP-ACT | Van der Pauw resistivity press contact assembly (ACT) | £350 |
| PC-TIP-5 | Replacement probe tip, 5-pack | £35 |
The press contact assemblies must be mounted onto an existing puck of the appropriate PPMS option (resistivity or ac transport). This requires a (fully reversible) modification of the puck to be made, which is quite straightforward. Easy-to-follow instructions are available here. Replacement spring-loaded probe tips are available in the event that one becomes fatigued, damaged or contaminated. These are easily user-exchangeable.