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Disentangling surface, bulk, and space-charge-layer conductivity in Si(111)-(7 x 7)
J W Wells1, J F Kallehauge, T M Hansen
1Institute for Storage Ring Facilities and Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, 8000 Aarhus C, Denmark. jwells@phys.au.dk
Physical Review Letters
|December 13, 2006
Summary
This study presents a new method to measure surface conductivity, revealing a switch from bulk to surface conduction in Si(111)-(7 x 7) below 200 K. The surface conductivity is found to be significantly lower than metallic values.
Area of Science:
- Surface science
- Condensed matter physics
- Materials science
Background:
- Accurate measurement of surface conductivity is crucial for understanding electronic properties of materials.
- The Si(111)-(7 x 7) surface presents a complex case for surface conductivity analysis.
Purpose of the Study:
- To develop and demonstrate a novel approach for extracting genuine surface conductivities.
- To investigate the temperature-dependent conductivity of the Si(111)-(7 x 7) surface.
Main Methods:
- Utilized a microscopic four-point probe technique for conductivity measurements.
- Conducted experiments across a temperature range from room temperature down to 100 K.
- Employed a numerical model to support the interpretation of the four-point probe conductance data.
Main Results:
- Observed that measured conductance aligns with bulk doping levels at room temperature.
- Detected a sharp decrease in conductance by several orders of magnitude below approximately 200 K.
- Identified saturation of conductance at a low-temperature value of ~4 x 10^-8 Omega^-1, independent of bulk doping.
Conclusions:
- Interpreted the abrupt conductivity transition as a switch from bulk to surface conduction.
- The derived surface conductance value is substantially lower than that of typical metals.
- The findings provide a reliable method for surface conductivity extraction and offer insights into Si(111)-(7 x 7) surface electronic behavior.
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