Sheet resistance

The (specific ) surface resistivity describes the electrical resistance of a resistive layer, if - is traversed parallel to the layer of flow, that is - as in the device layer resistance the stream at a narrow side face and an on the opposite narrow side face exits.

Definition

Is the sheet resistivity of a resistive layer having a thickness with an isotropic resistivity

That the thinner the layer ( small), the higher its surface resistance (at constant resistivity ).

In addition, since the following applies:

With

• Electrical resistance
• Electrode pads (electrode over the entire width of two opposite edges)
• Length

Follows

By means of the specific surface resistance of a resistor layer thus the size of the resistor made ​​therefrom are determined by its geometry:

So true for a square layer:

The sheet resistance of the resistance criteria:

Unit

Since the specific resistance has the unit OMEGA.m, the unit of sheet resistance is identical to the unit Ω ( ohm ) of the electric resistance:

For better distinction is therefore often mistakenly given as a unit. Such indexing of physical units is not allowed and provided for as in any standard (see DIN 1301 and ISO 31 ).

Measurement

The sheet resistance of a film can be measured, for example by using the four -point method or the specific Van der Pauw method.