LT NANOPROBE

The unprecedented stability and drift performance of the LT NANOPROBE opens the route towards multi-probe transport measurements of planar atomic or molecular nano-scale systems. So far the stability of single atom contacts and probe navigation with real atomic precision has only been accessible by single probe SPM experiments. Parallel STM imaging of probes is crucial to control the individual points of contact and to identify the minimal distance between probes by inter-probe tunnelling.

Transport measurements with atomic scale precision Four independent atomic resolution SPMs for probe approach and imaging Extremely low thermal drift at T < SK Simultaneous SEM imaging at low temperatures for rapid tip navigation STM spectroscopy and atom manipulation QPlus nc-AFM The Low Temperature NANOPROBE defines a new class of analytical instrumentation that merges SEM-navigated local transport measurements with atomic scale precision, high performance STM imaging, spectroscopy, and manipulation at LHe temperatures.

For the navigation of four independent STM probes, simultaneous SEM imaging is indispensable as it bridges dimensions from the mm-scale down to the nm-scale. The SEM enables a large field of view for probe coarse positioning as well as fine positioning and rapid localisation of nanometer-sized structures.

The UHV Gemini column is the ultimate tool for that purpose. It offers unsurpassed resolution under true UHV conditions and at low temperatures. In combination with the LT NANOPROBE, the in-lens Secondary Electron Detector (SED) represents a key advantage: only one small access port is needed in the thermal shield compartment of the microscope stage (at T <5 K). Thus thermal impact is minimised, while still offering a suitable signal for high resolution imaging. Alternatively, other UHV SEM columns or optical microscopes can cover the lower resolution range if sample structures do not require ultimate resolution.

Four SPMs
The microscope stage carries four individual SPM modules with independent and guided 3D coarse positioning of XYZ = 5 x 5 x 3mm. The sample can be independently positioned by XY = 4 x 4mm. Our 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 atomic resolution STM imaging is achieved by shared stack scanners with a range of 1.5µm x 1.5µm at 5K. For ultimate STM performance the microscope stage employs an effective eddy current-damped spring suspension.

Sample & tip exchange 
A fast and secure tip and sample exchange is crucial for ease of use and high throughput. Samples and spring loaded tip carriers can easily be exchanged by wobble stick.

Thermal shielding 
An efficient thermal shield compartment allows for temperatures well below 5 K, extremely low thermal drift and thermal equilibrium of sample and probes. In addition, high resolution SEM navigation requires a small SEM working distance and thus makes a dedicated STM concept indispensable. A sophisticated shared stack scanner allows for a very compact and flat design, while ensuring highly linear, orthogonal and stable STM scanning characteristics.

Magnetic Fields 
A compact superconducting coil is mounted beneath the sample plate and provides a vertical magnetic field of 20 mT.

The possibilities for smart transfer of tips and samples throughout the complete UHV chamber and into the LT NANOPROBE stage are fundamental for comfortable routines and processes.

Fast Entry Locks
The LT NANOPROBE offers two different fast entry locks (FEL), located opposite to each other on both sides of the system. This positioning allows for easy provision of tips and samples. Two wobble sticks - both right angled to the transfer rods of the FEL - are taking over the 'inner tasks' like adjustment, handling, positioning or 'parking' of tips and samples within the 28-position-carousel. Various lock valves assure for short pump-down times as well as stable vacuum conditions.

Pumping system
The pumping is realized via efficient turbo- and ion-pumps. The manipulator in the preparation chamber allows for tip and sample preparation, sputtering and depositioning.