Indium tin oxide (ITO)

Indium tin oxide (ITO) is the canonical degenerate n‑type transparent conducting oxide, combining high visible transmittance with low sheet resistance and a mature, scalable manufacturing base. It is deposited industrially by magnetron sputtering for uniform, low-resistivity films. ITO is the workhorse transparent electrode for displays and touch panels, OLED/LED emitters, and a wide range of photovoltaic technologies; oxygen stoichiometry is tuned to balance conductivity and transparency. In photonics, heavily doped ITO exhibits an epsilon-near-zero response in the near-infrared (around the 1.55 µm telecom band), enabling compact electro-optic modulators, plasmonic waveguides, and absorbers, as well as strong nonlinear/ultrafast effects. ITO can also become superconducting at cryogenic temperatures when strongly reduced or ion-intercalated, with reported critical temperatures ranging from sub-kelvin to a few kelvin, depending on the carrier density and processing. Beyond semiconductors and optics, ITO supports transparent heaters, low-emissivity and EMI-shielding window coatings, and ENZ-enabled NIR photodetectors. When even lower resistance is required, it is often paired with ultrathin metals in hybrid stacks, while retaining high transparency.

Deposition of ITO

ITO (indium tin oxide) can be deposited by sputtering here at DTU Nanolab. An ITO target is used and it may be sputtered either non-reactively in Ar or reactively in a mixture of Ar and O₂.

We have acquired a lot of knowledge about ITO deposition in our Cluster Lesker system, and results are summarized on a page here:

Sputtering of ITO in Sputter-System Metal-Oxide (PC1).

Comparison of the methods for deposition of ITO

	Sputter-System(Lesker)	Sputter-System Metal-Oxide(PC1)
Generel description	RF sputtering of an ITO target - reactive sputtering possible	RF sputtering of an ITO target - reactive sputtering possible (not recommended due to arching) Pulsed DC sputtering of an ITO target - reactive sputtering possible
Stoichiometry	Not known	In:Sn:O ~ 39:3:58. Can be tuned by altering deposition conditions.
Film Thickness	few nm - ~ 200 nm	few nm - ~ 1 μm
Deposition rate	0.5-2 nm/min	at least up to ~ 10 nm/min (see conditions)
Step coverage	unknown	unknown
Process Temperature	Up to 400 °C (tool limit)	Up to 600 °C (tool limit)
Substrate size	chips 1x 100 mm wafer 1x 150 mm wafer	chips 10x 100 mm wafer 10x 150 mm wafer
Allowed materials	almost any	almost any that does not degas. Note special carrier for III-V materials. See cross-contamination sheet.