Koala TetraProbe - Electrical characterization at the nanoscale
Ultra Compact Multi-Tip Scanning Probe Microscope / Nanoprober for electrical characterization at the nanoscale.
The ultra compact Koala TetraProbe STM integrates four independent STM units within a diameter of 50 mm resulting in an unsurpassed mechanical stability, enabling atomic resolution imaging with each tip.
Modular and compact design based on the KoalaDrive® nanopositioner
Each tip can be positioned independently
Tip coarse positioning with optical microscope/SEM control
Simultaneous tunneling and scanning with all four tips
Atomic resolution with each tip
Tip exchange and sample exchange in situ
Software controlled switching between current probe and voltage probe for each tip
Software allows virtually any possible "concerted" spectroscopic measurements involving the four tips and the sample
Four tip STM/AFM combination and low temperature version available
Local potential measurements on the nanoscale
Controlled nondestructive measurements in spectroscopy mode
Four point measurements with free positionable local probes on structured samples
Real time optical microscope movie of the positioning of the sample and four tips on a structured wafer. The structured rectangles have a size of 30 μm x 50 μm.
Sketch of two of the four modular units of the Koala TetraProbe. Each unit consists of a KoalaDrive used for the coarse tip approach towards the sample. The KoalaDrive is fixed to a plate (resting on three balls fixed to three tube piezo elements). The plate is moved according to the design of the beetle STM allowing for a coarse motion in the xy-directions. The xyz-scanning of the tip is also performed by these three piezo elements.
SEM view of the tips. Tip shadows indicate the tip-sample distance
Atomically resolved image of the Si(111)-7x7 surface
Surface conductivity determined by distance dependent four probe measurements:
The surface and step conductivities of the Si(111)-7x7 were measured. More information can be found in Phys. Rev. Lett. 115 (2015) 066801.
The anisotropy of the surface conductance can be determined using rotated tip configurations (optical microscope view). More information can be found in Phys. Rev. Lett. 115 (2015) 066801.
Resistance / dopant profiling along freestanding GaAs nanowires:
Resistance profile along a nanowire. More information can be found in Appl. Phys. Lett. 103 , 143104 (2013).
Movie of an STM tip moving along a GaAs nanowire measuring a four point probe resistance profile
Movie of an elastic bending of a GaAs nanowire (left). SEM zoom to nanowires (right).
Scanning tunneling potentiometry with a four tip STM:
(left:) Potential map on a Si(111)-7x7 surface during current flow from top to bottom. (right:) Potential map of a Si(111)/Ag-sqrt3 with overlaid topography. More information can be found in here.
Multiprobe measurements on Sb2Te3 nanowires.
Potential measurements along a 2 μm long wire segment.
Multiprobe measurement on a freestanding topological insulator nanowire:
Customer specific extensions, like for example optical fibers brought close to the tip/sample regions by a fiber positioner integrated in the TetraProbe system can be provided. A low temperature version of the TetraProbe system is available as well.
Some results are discussed this application note
The KoalaDrive® is licensed by Forschungszentrum Jülich
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