Transparent microelectronics using low temperature deposition of transparent conducting oxides on flexible substrates
The emerging industry, often described as organic, printed or large area electronics, encompasses a wide range of semiconductor material sets – both organic and inorganic – and fabrication techniques, which span a variety of printing and other deposition methods.
Metal oxides are a promising group of materials in the portfolio of large-area electronics, including both p- and n-type semiconductors, dielectrics and transparent conductors. The ability to make these components from metal oxide materials compatible with a low-cost deposition process opens up further applications such as smart packaging, disposable diagnostics for healthcare, RFID, security tagging and even low-cost solar cells.
Small Grant funding from CIKC enabled Dr Andrew Flewitt to undertake a short project with UK SME Plasma Quest to use the company’s HiTUS sputtering tool for metal oxide deposition. The machine combines enhanced control of deposition while retaining the inherent simplicity of sputter coating and is compatible with low-temperature processing for fabrication of electronics on plastic substrates. With further CIKC support a HiTUS tool was purchased from Plasma Quest to enable Flewitt’s team to develop a portfolio of electronic-grade metal oxide semiconductor materials within the HiPZOT project.
Flewitt explains: ‘We’ve been working recently on transparent electronics using a class of materials called metal oxides which have properties that allow you to make from them conductors, semiconductors and dielectrics – all the things that you need to make a basic logic device. But the material itself is optically transparent so you can make electronics that you can see straight through.’
Within HiPZOT, high performance n-type and p-type semiconductors, dielectrics and transparent conductive oxides were demonstrated. With further work, other applications are possible, such as low cost solar cells on plastic by integration of cuprous metal oxide and zinc oxide.
Though Plasma Quest’s HiTUS sputtering tool has been successfully put to use for making optical coatings, the HiPZOT project proved the machine’s compatibility for fabricating large area electronics on plastic films, de-risking the subsequent transition high volume R2R production environments.
HiPZOT has led to two TSB funded projects, FIREBIRD and FlexIC, where the University of Cambridge is working with industrial partners to bring to market printed metal oxide electronics. In FlexIC, project partner PragmatIC Printing, which is located in Cambridge, and has been using facilities and expertise at the University to further its technology development. It is now producing electronics made from metal oxides on a new pilot line installed at the Printable Electronics Technology Centre within the Centre for Process Innovation.
Along with the other partners on FlexIC, which include Plasma Quest, PragmatIC Printing is establishing a printed logic supply chain. In 2013, PragmatIC Printing’s pilot line will begin production of its printed logic devices in small volumes for select applications developed with commercial partners.
Flewitt says: ‘One of the big successes of CIKC is that it provides a flexible funding mechanism, enabling short, collaborative projects with industry to open up bigger opportunities. Small Grants are particularly effective, as within a matter of weeks projects can be started up and the next steps for research towards commercial application can be identified.’
The UK has an internationally leading research base in large area electronics that has developed over the last 20 years; the work at the University of Cambridge, supported with the CIKC funding for the HiPZOT project, helps expand the portfolio of materials suitable for large area electronic devices and products. For example, Flewitt’s team has developed a promising high k dielectric material.
By working collaboratively with commercial partners such as PragmatIC Printing, as well as suppliers of production tools, a new value chain that could benefit UK manufacturing is in the process of being established.