Paper NS+AS-TuA11
High Precision local electrical Probing: A New Low Temperature 4-Tip STM with Gemini UHV-SEM Navigation

Tuesday, November 1, 2011, 5:20 pm, Room 203

A major challenge in the development of novel devices in nano- and molecular electronics is their interconnection with larger scale electrical circuits required to control and characterize their functional properties. Local electrical probing by multiple probes with STM precision can significantly improve efficiency in analyzing individual nano-electronic devices without the need of a full electrical integration. Among a very few commercial approaches, the Omicron UHV NANOPROBE has been established as a suitable instrument for local electrical probing in UHV on nano-structures down to structure sizes in the 10 nm range. The mayor technical requirements for such sophisticated instrumentation are:

· Rapid and simultaneous SEM navigation of four local STM probes on small structures

· Localization of nanostructures by high resolution SEM (UHV Gemini)

· Individual probe fine positioning by atomic scale STM imaging

· STM based probe approach for "soft-landing" of sharp and fragile probes and controlled electrical contact for transport measurements

· Preparation techniques towards sharp and clean and STM tips

· Suitable low noise signal re-routing for transport measurements with third party electronics

Although the UHV NANOPROBE has been successfully used for various applications, today´s scientific requirements motivated the development of the next generation probing system. We will present the newly developed LT NANOPROBE which takes experimental capabilities one step further and opens up new research opportunities in nano-electronics, spintronics, and molecular electronics. Besides SEM/STM probe fine navigation and imaging, the excellent STM performance level of the LT NANOPROBE expands applications to tunneling spectroscopy and even the creation or modification of nano-structures by an ultimately precise STM probe. The R&D project has been driven by the following major milestones:

· Operation at temperatures of T<5 K for STM imaging and STM based probing

· SEM navigation at base temperature T<5 K

· Simultaneous operation of STM and SEM at base temperature

· Thermal equilibrium of sample and probes for (i) extremely low thermal drift and electrode positioning accuracy in time and (ii) defined temperature of the local electrical contact and

· Performance and stability level of each individual STM Probe suitable for STM spectroscopy and atom manipulation

First evaluation measurements with the system installed at the Forschungszentrum Jülich will be presented: STM on Au(111) with pm stability, STS revealing the superconducting gap of a Nb tip with approx. 3meV gap size, and transport measurements on nanowires at T<5K.