Berlin 2012 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 15: Dielectric and ferroelectric thin films

DF 15.4: Talk

Thursday, March 29, 2012, 10:55–11:15, EB 107

Charge storing onto silicondioxide surfaces — •Bjoern Martin, Abhishek Rathi, and Herbert Kliem — Saarland University, Germany

The surface of silicondioxide/silicon structures is charged with the tip of a cantilever in contact mode by application of a voltage. Then, the surface potential is measured contactless using the Kelvin option of an atomic force microscope. On the position of the charged domain a potential difference in relation to the uncharged region is found.

It turns out that the height and the width of this potential difference depend on charging time, charging voltage, sample thickness, and doping of the silicon substrate. SiO₂/n-Si structures with thicknesses of about 10nm to 20nm contacted with negative voltages show the best charging behavior.

Additionally, a transient decay and a transient spread of the surface potential with a time constant of about 10h are observed. This time constant decreases with increasing humidity.

Due to the long-term stability and due to the possibility to reverse the sign of the deposited charges by charging in opposite direction an application of the system as surface charge memory device is thinkable.

It is remarkable and not yet fully understood why positive surface potentials indicating positive charges are found after charging with positive voltages.