Raster tunnel potentiometry

Sketch of the grid tunnel potentiometry

The Rastertunnelpotentiometrie ( English scanning tunneling potentiometry , STP ) is a modification of the scanning tunneling microscope and was developed by P. Pohl DW Muralt and 1986th With the help of the STP it is possible to record the local electrochemical potential of a surface simultaneously with the associated morphology of the surface with nanometer accuracy. ${\displaystyle \mu _{ec}}$

Measuring principle

A transverse voltage is applied across an electrically conductive sample surface via two contacts . A landscape of potential forms on the sample surface. A tunnel tip is brought into tunnel contact with the surface and connected to the transverse voltage contacts via a potentiometer . The resulting contact geometry corresponds to the principle of a Wheatstone measuring bridge : The potentiometer is set in such a way that the current over the tunnel tip disappears (bridge adjustment). If the tunnel tip moves over the sample surface, the local potential changes. Therefore, the bridge is automatically rebalanced continuously. An alternating voltage is applied to the tunnel contact between the tunnel tip and the sample ${\displaystyle \ U_{Quer}}$ ${\displaystyle {\tilde {U}}}$given which produces an alternating current signal. The effective value of this alternating current signal is used to control the distance to the tunnel tip so that it follows the sample surface without touching it. The regulation for the bridge balancing takes the temporal mean of the tunnel current and therefore does not "see" the alternating current component.

application

The electrochemical potential is linked to the current transport on the sample surface. Since the STP simultaneously records the morphology of the sample, changes in structures on the surface can be assigned. A jump from, for example, correlates with a surface structure, indicates a scattering of the conduction electrons on this structure. The structure can therefore also be interpreted as “nanoresistance”. Thus, with the help of the STP, it is possible to examine and measure the local electricity transport on the nanometer scale. ${\displaystyle \mu _{ec}}$ ${\displaystyle \mu _{ec}}$ ${\displaystyle \mu _{ec}}$ ${\displaystyle \mu _{ec}}$

See also

• Surface chemistry

literature

• P. Muralt, DW Pohl: Scanning tunneling potentiometry . In: Appl. Phys. Lett. tape 48 , 1986, pp. 514-516 , doi : 10.1063 / 1.96491 .
• JP Pelz, RH Pohl: Tip-related artifacts in scanning tunneling potentiometry . In: Phys. Rev. B . tape 41 , 1990, pp. 1212 , doi : 10.1103 / PhysRevB.41.1212 .
• MA Schneider, M. Wenderoth, AJ Heinrich, MA Rosentreter and RG Ulbrich: Current transport through single grain boundaries: A scanning tunneling potentiometry study . In: Appl. Phys. Lett. tape 69 , 1996, pp. 1327 , doi : 10.1063 / 1.117583 .
• M. Rozler, MR Beasley: Design and performance of a practical variable-temperature scanning tunneling potentiometry system . In: Rev. Sci. Instrum. tape 79 , 2008, p. 073904 , doi : 10.1063 / 1.2953097 .
• CA Bobisch, R. Möller: Electron Transport at Surfaces and Interfaces . In: CHIMIA . tape 66 , no. 1 , 2012, p. 23-30 , doi : 10.2533 / chimia.2012.23 .
• AP Baddorf: Scanning Tunneling Potentiometry In: S. Kalinin, A. Gruverman (Ed.): Scanning Probe Microscopy . Springer, New York 2008, ISBN 978-0-387-28667-9 , pp. 11-30.