Final Report Summary - INVISIBLE (Advanced Amorphous Multicomponent Oxides for Transparent Electronics) Transparent electronics is today one of the most advanced topics for a wide range of device applications, where the key component are wide band gap semiconductors, where oxides of different origin play an important role, not only as passive component but also as an active component similar to what we observe in conventional semiconductors. As passive components they include the use of these materials as dielectrics for a wide range of electronic devices and also as transparent electrical conductors for used in several optoelectronic applications, such as liquid crystal displays, organic light emitting diodes, solar cells, optical sensors, etc. As active material, they exploit the use of truly electronic semiconductors where the main emphasis is been put on transparent thin film transistors; light emitting diodes, lasers, uv sensors, integrated circuits among others. Oxide semiconductors are a promising class for thin film transistors (TFT) that have made an impressive progress especially in display applications in a relatively short time, challenging silicon not only in conventional applications but specially opening doors to completely new and disruptive areas like paper electronics.The INVISIBLE project was a focused interdisciplinary research project aiming to develop this new class of multicomponent passive and active oxide semiconductors (n- and p-types) and dielectrics (low and high k), to fabricate the novel generation of full transparent electronic devices and integrated circuits, either using rigid or flexible substrates. We have already achieved the production of oxide based thin film transistors (n and p-TFTs) and integrated circuits like inverters, C-MOS like devices, ring oscillators and ISFETs for DNA/RNA/proteins detection.All the developments have been done using the conventional PVD like techniques like rf magnetron sputtering at room temperature, compatible with the use of low cost and flexible substrates (polymers, cellulose paper, among others). These facilitate a migration away from tradition “silicon like” fab based batch processing to large area, roll to roll manufacturing technology which will offer a significant advantage in terms of reduced cost with increased throughput due to less steps. Nevertheless other competitive and low cost technologies like “printed electronics” is today an emerging disruptive technology which has made impressive progress specially in the last 10 years, in particular for field-effect mobility of solution-processed, organic TFTs has increased to levels exceeding that of thin-film amorphous silicon TFTs (~1 cm2 V-1 s-1). Ink-jet of inorganic materials for making active devices was relatively rare compared to organic materials, mainly due to the difficulty in preparing ink-jet printable precursors. This is also one of the objectives of INVISIBLE project, and we achieved already to produce by solution-process oxide based TFTs.Another goal of the INVISIBLE project was to use cellulose paper as an electronic material, and besides the already proof of concept done in 2008 with the first TFT produced in the world using a cellulose paper as dielectric layer, we have succeed now to produce a paper-CMOS using n- and p-type TFTs developed within the project. However, there are significant challenges to overcome to enable this ambitious frontier research vision. The technology barriers to be overcome are at least at two levels; materials and processing. The materials challenge is the development of radically new materials which can offer the electronic, mechanical and optical properties required and to facilitate low cost processing and manufacture strategies. The processing challenge is the development of novel deposition techniques, which enable low temperature, large area processing on flexible/low cost substrates. These achievements have positioned CENIMAT as one of the internationally leading groups in the field of Transparent Electronics and the leading group in Paper Electronics.
