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Prefabricated OFET Test Chips, High Density

OFET high density substrate

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Alternatives include our high density platinum OFET test chips and our platinum FET test chips (optimised for 2D materials).

We use silicon/silicon oxide substrates with thermally evaporated gold electrodes. Our standard prefabricated substrates are supplied in batches of ten and fabricated using our High Density OFET system; see schematics below for details.

The prefabricated high-density OFET test chips are recommended for the collection of statistical data after the experimental parameters have been optimised. Create up to 20 OFETs from a single thin film. Simply spin on your semiconductor and quickly wipe between the devices to isolate them before testing with our high-density OFET test board.

A surface passivation treatment is recommended in order to achieve the best results with these bottom-contact, bottom-gate devices. There is a surface treatment procedure detailed in the User Manual for your convenience.

All devices are made to order, so the lead time is up to 2 weeks for standard devices. We can also fabricate the patterns onto other substrate materials for your individual research requirements, so please contact us to discuss your needs.

If you are uncertain about which range of specifications best suits your needs, please contact us to speak to one of our technical support team.

Product code Channel geometry Channel width Channel length OTS/PFBT treatment Quantity Price
S221 Linear 1 mm 30 μm No 10 £500
S223 Linear 1 mm 30 μm variable No 10 £500
S233* Interdigitated 18 mm 50 μm No 10 £500

*S233 yield of working devices is 90% (18/20) per substrate and 95% total (190/200). 


Ossila's High Density Substrates feature 20 OFETs which can benefit your research in a number of ways. Firstly, production cost is reduced as a result of a higher volume of OFETs per substrate compared to the low density equivalents. This can help to stretch your budget to allow you to produce and test larger numbers of OFETs.

Secondly, producing OFETs is a far faster and less laborious process. Fabrication time is reduced by up to 50% when using prefabricated high density OFETs, freeing up more time to test the devices. As a result of this, greater volumes of statistics can be produced which in turn can provide more robust and reliable research.

High density FET substrate diagram with semiconductor processed on to it, ready to measure.
Diagram of a high-density FET substrate made from thermally evaporated gold electrodes on top of a silicon/silicon oxide substrate with semiconductor processed on to it, ready to measure. 20 OFETs per substrate.

Furthermore, OFET variability is reduced since a larger number of OFETs are produced with each fabrication. At Ossila we have optimised the fabrication process in order to produce consistently high quality substrates. In this respect, using our prefabricated substrates rather than fabricating your own can help you to gather more reliable data to benefit your research project.

Prefabricated high density substrates are ideal for mobility testing as they enable swift, efficient testing of high volumes of OFETs. The Ossila high-density OFET test board has been designed for this purpose. 

Rather than using a mechanical probe station to test OFETs, which is a delicate and time-consuming process, the high density test board allows testing of multiple OFETs at one time; simply drop the substrate into the test slot, secure the push-fit lid and connect the board via its BNC connectors to an array of test equipment.

The board has been intelligently designed to reduce external noise, leakage current and stray capacitance in order to provide reliable and precise low-current testing.

High density FET mobility test board
The Ossila High Density OFET Test Board, designed for rapid, reliable testing of multiple OFETs.


We fabricate p-doped silicon substrates with an insulating 300 nm silicon oxide top layer. Gold is then thermally evaporated on top to produce gate electrodes which also cover the conductive edge of the substrate. It is therefore essential that the edge of the substrate is conductive and not covered with the silicon oxide layer. If not, the silicon oxide must be scratched off the sides of the substrates before it can be used.

Prefabricated OFET: gate electrode details
Structure of our prefabricated silicon/silicon oxide substrates.

At Ossila we have optimised the fabricating process to ensure that the edges are conductive and the substrates are immediately ready to use.

We fabricate our high-density substrates with 1-2 nm chromium and 60-70 nm gold. The chromium acts as an adhesion layer to ensure the gold remains firmly attached to the silicon substrate.

One of the most difficult parts of substrate preparation is the OTS treatment; a small amount of moisture must be present to create a smooth monolayer, but too much moisture can result in a rough surface. After extensive research we have optimised this process in our labs and can therefore offer substrates pre-treated with OTS to accelerate your research program even further.

For individual details and dimension drawings of each substrate type see below.

Linear 1 mm x 30 µm constant channel length substrate (S221)

Geometry Linear
Arrangement 20 identical OFETs
Channel width 1 mm
Channel length 30 µm
30 micron channel High Density FET schematic
Dimension drawing of 1 mm x 30 µm substrate.

Linear 1mm x 30 µm variable channel length substrate (S223)

Geometry Linear
Arrangement 20 OFETs, 5 channel widths (4 of each width)
Channel width 1 mm
Channel length 30, 40, 50, 60 and 80 µm
30 micron variable channel High Density FET schematic
Dimension drawing of 1 mm x 30 µm variable substrate.

Interdigitated 18 mm x 50 µm constant channel length substrate (S233)

Geometry Interdigitated
Arrangement 20 identical OFETs
Channel width 18 mm
Channel length 50 µm
interdigitated 50 micron channel HD FET schematic
Dimension drawing of one of the 18 mm x 50 µm devices on the high density substrate.

To the best of our knowledge the information provided here is accurate. The values provided are typical at the time of manufacture and may vary over time and from batch to batch. Products may have minor cosmetic differences (e.g. to the branding) compared to the photos on our website. All products are for laboratory and research and development use only.

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