The microscope stage carries four individual SPM modules with independent and guided 3D coarse positioning of XYZ = 5x5x3 mm. The sample can be independently positioned by XY = 4x4 mm. Omicron´s patented piezo-electric inertia drives provide highly reliable and efficient navigation with step sizes from a few tens of nm´s up to several hundred nm.

Fine positioning and STM imaging with atomic resolution is achieved by shared stack scanners with 1 µm x 1 µm at 5 K. The sample reception stage is compatible with Omicron´s standard flat sample plates with a maximum sample size of 10 mm x 10 mm. A fast and secure tip and sample exchange is crucial for ease of use and high throughput. Individual probe modules are moved to an exchange position and spring loaded tip carriers can easily be exchanged by wobblestick. 28 samples or tips are accessible from the stage-integrated storage carousel.

The use of a high resolution SEM column for tip navigation from above implies an unconventional cryostat concept. A specifically designed bath cryostat with LN₂ and LHe reservoirs allow for a measurement time of > 36 hours at T < 5 K and cools the microscope stage from below. LN₂ and LHe double shieldings minimise thermal impact on the stage and employ doors for tip/sample exchange operated by wobblestick. In addition, the sample stage facilitates a controlled thermal coupling for a defined sample temperature and quick sample cool down.

STM is the key to advancing probing technology into the nanometer scale. It ensures extremely accurate probe positioning and STM-based safe tip approach of fragile probe tips having diameters in the range of a few ten´s of nanometers or less. STM imaging is required for final precise positioning of the probe tip when it shadows nm-sized structures in the SEM field of view or if the structures are even smaller than accessible by SEM.

During STM approach the distance control is based on tunnelling current feedback and therefore requires a dedicated low noise I/V converter. When the tunnelling contact is established, the probe-sample distance is well controlled in the nm range. To establish an electrical contact and to control its resistance, the STM feedback is de-activated and the probe is manually approached by piezo scanner z-offset.

However, a permanently connected I/V converter in the signal line prevents transport measurements in four point configuration. Thus, a pA STM compatible and TTL trigger controlled switching technology is used to route signals of the four probes to external BNC connectors. Based on LabVIEW, experimental workflows are integrated with third party measurement electronics.

A compact superconducting coil is mounted beneath the sample plate and provides a vertical magnetic field of 25 mT. To minimise the thermal load generated by significant driving currents, HTSC superconducting current leads are employed.