The 1980 measurement used a silicon inversion layer
von Klitzing, Dorda and Pepper measured a two-dimensional electron system formed in a silicon transistor structure. In a strong perpendicular magnetic field, Hall resistance settled onto reproducible plateaus as carrier concentration changed.
The plateau values were insensitive to device geometry under the appropriate conditions. The 1985 award recognized the discovery, which gave electrical metrology a new quantum reference.
A plateau requires a transport state
In an ideal integer plateau with negligible longitudinal response, the Hall conductance is an integer multiple of the conductance quantum. Landau quantization supplies levels, and localization helps produce finite intervals between transitions. A level diagram alone is not the complete transport measurement.
Several checks make a useful standard
Temperature, current, contact quality and longitudinal voltage can reveal departure from the quantized state. Reproducibility across devices matters because a standard must survive changes that should not alter the invariant. Breakdown at high current is part of the operating boundary.
Sources: [1]
Integer band models keep their own scope
The magnetic-edge and Chern-insulator Labs explain levels, boundaries and integer topology in controlled single-particle models. They are reused here. Fractional Hall liquids require correlations and are treated in a separate evidence article, not inferred from an integer Chern number.