Since 2000, the low-temperature scanning tunneling microscope (LT-STM) is an essential part of CreaTec's product range. In addition to its nanoanalytical capabilities, it allows the precise manipulation of atoms and molecules at temperatures from 4 to 300 K. Starting with our proven beetle-type STM with highest spectroscopy performance, we have continuously developed this instrument to three different scanning probe systems: a 4 K LT-STM, a combined 4 K LT-STM/AFM, and a 1 K LT-STM system.
The 4 K microscopes are available as beetle-type scanners and PAN-type sliders, with different options like e.g. magnetic field, optical access and high-frequency cabling. All these microscopes offer ultimate STM, STS and IETS performance including one of the longest LHe hold times, extremely low drift rates and outstanding stability (dz<1 pm) compared to similar low-temperature SPM systems. State-of-the-art spectroscopy and atom manipulation can be performed on metals, semiconductors, insulators, superconductors and carbon at low temperatures. The 4 K LT-STM/AFM is also well adapted for experiments at variable temperatures ranging from 5 to 300 K. Our fully compatible low-temperature atomic force microscope (AFM) was introduced in 2007 allowing for simultaneous measurements of force and tunneling current without cross-talk using constant frequency or constant height control.
CreaTec STM electronics are based on a digital design. A DSP (digital signal processor) controls the scanning parallel (x, y) to the surface as well as the tip/sample separation. All scanning/feedback parameters are fully controlled through the STM program. An additional high voltage amplifier and a current preamplifier complement the electronics. There are options to read data from external devices, too.
In addition to standard features like 3D image rendering, histogram etc. it also includes a flexible atomic manipulation part with lateral manipulation in constant current and constant height mode, vertical manipulation and tip forming.
The CreaTec Besocke type SPM head is used around the world for more than 20 years now. It’s proven stability and reliability has led to many well-known scientific publications. The simple design principle of our Besocke SPM allows the coarse motion of the tip (XYZ) across the sample over a large scale (up to several mm) utilizing the slip stick motion of just one single part (a ring with integrated ramp). Nothing can get stuck at low temperature – like in so many other SPM designs. Two sets of piezos (three coarse piezos and one main piezo) allow to drive the scanner with many different modes of operation: XYZ with coarse or main piezo or in a mixed mode e.g. XY-coarse, Z-main. These redundant operation modes make our Besocke type SPM very robust. The symmetric design of the SPM and the use of thermally highly conductive materials ensure the stable operation at variable temperature. The spring suspension and integrated eddy current damping decouple external noise very efficiently.
The sample is completely isolated from the sample holder.
The sample heating is integrated into the sample holder - thus will also be transferred with the sample and may be replaced easily. The heater system is very robust and allows to heat the samples >1000°C without degassing. This allows preparation of Si(111) 7x7 surfaces in less than 30min.
Up to 6 sample contacts are standard. Usually two are used as current leads for heating, two are connected to a thermocouple (type K).
The complete sample transfer from the He-cooled manipulator (T<10K) into the SPM is done with a cold sample. This means that the sample can be prepared and analyzed in the preparation / analysis chamber and transferred directly into the SPM without any intermediate warming up.
Due to the space available on the sample holder there are even versions with multiple samples mounted to just one holder. This allows, for instance, tip preparation on one sample (e.g. Pt(111) ) and measuring at the other (e.g. Si(111) )– without the need for tip / sample exchange and successive cooldown steps to achieve the best performance in spectroscopy.
All types of STM / qPlus –AFM measurements are possible: STS, IETS, df(z,U), etc.