ITO Sheet Resistance Definition and Significance

Why do Diamond Coatings produce ITO coatings at diverse sheet resistances? To explain this, it is best to start with the general sheet resistance definition, the dependence of ITO sheet resistance on coating thickness and the potential effect this has on the coating’s transparency.

Sheet Resistance Definition

Denoted in units of ohms/sq., sheet resistance is the measurement of resistance within thin films of nominally uniform thickness. Commonly utilized to characterize conductive or semi-conductive materials’/coatings’ uniformity (which is, among other things, important for quality assurance, sheet resistance:

• Is measured either directly via four probe/terminal sensing measurement or indirectly via testing devices using non-contact eddy current
• Does, unlike resistance or resistivity (which is denoted in ohms), not vary under scaling of film contacts.

The latter essentially means that if a sheet has, for instance, a sheet resistance of 20 ohms/sq., its actual resistance is 20 ohms, irrespective of its size. This in turn means sheet resistance can be employed to compare electrical properties of significantly differently sized devices.

ITO Sheet Resistance

Transparent and highly conductive, indium tin oxide (ITO) coatings can be deposited onto diverse substrates (i.e. glass, acrylic, PET/PEN films and polycarbonate) for many different research and industrial applications including, among others:

• Antistatic coatings, architectural windows (energy conversation) and electroluminescent lamps
• EMI shielding, flat-panel displays and glass doors (supermarket freezers
• Heater windows, liquid crystal & plasma displays
• Polymer-based electronics. smart windows and solar cells
• Thin film photovoltaics, touch screens/panels and more

Naturally, different applications require different levels of conductivity – and the lower an ITO coating’s sheet resistance, the greater its conductivity. This is, of course, why we produce ITO coatings with varying sheet resistances – and we achieve these different sheet resistances by varying the thickness of the coating, with greater thicknesses resulting in lower sheet resistances.

Coating Thickness vs. Transparency

So, what about the effect of increasing coating thickness on its transparency, or optical transmission? Well, while it should be noted that transmission can drop significantly with increasing thickness in the near-infra red wavelength range, the effect of an increase in thickness on transmission rates is negligible within the visible range.

Learn More

Need to know more? For more detailed information on ITO coatings, suitable sheet resistance options for your project and more, please feel free to contact us today.