Introduction to the IGM
Since the inception of the "Laboratory for Display Technology" in 1991, the market for LCDs with active matrices based on amorphous silicon has grown into a billion-dollar industry with a high level of technogical maturity. As a result, the activities at the IGM have shifted towards new processes and materials for applications in display technologies. Foremost among these new technologies are the activities in the field of organic light emitting diodes (OLEDs). In addition to the actual processing of the light emitting layer and its encapsulation to protect the sensitive organic materials from oxygen and moisture, the IGM's research is focused on the development of active matrix backplanes suited to the special demands of OLED displays. The IGM has had successes with processes in both poly-crystalline silicon and with micro-crystalline or polymorphous silicon technologies. The combination of IGM developed processes and long years of experience in display control allow the IGM to realize complete active matrix OLED displays in-house. Research into metal oxide semiconductors, especially Indium-Gallium-Zinc-Oxide offer a new alternative to amorphous or poly-crystalline silicon and allow the IGM to process active matrices based on these new materials as well.
The use of organic semiconductors and carbon nano tubes in thin film transistors is another field of activities at the IGM. These technologies could offer cheaper future industrial process than silicon based TFT technologies as they can avoid complex vacuum systems. Furthermore, these materials can be processed at lower temperatures, allowing the use flexible substrates such as plastic foils in the display processes. The same technologies can be used for liquid crystal displays.
Moving beyond the technologies for flat panel display, the IGM also engages in research into optical signal processing. One focus is on the synthesis of optical filters that are important in communication technology.
On the side of teaching, Professor Frühauf offers lectures on filter synthesis, optical signal processing, thin film technology and flat panel technology. Several lab courses allow for students to gain some hands-on experience complementing the lectures. Special mention goes to the lab course for flat panel technology, where students get to build a complete seven-segment liquid crystal display for a digital alarm clock, providing a good overview over the processes essential to display technology. One of the most important components is the independent research by students in projects and final bachelor, reasearch, or master theses. The IGM supervises between 15 and 20 such projects each year.
The IGM's many activities in research and teaching are supported by the team of highly-qualified and reliable staff.
History of the Institute
The story of electrical engineering at the Stuttgart University begins in 1882 with the first lectures by Wilhelm Dietrich (1852-1930), soon followed by the first chair for electrical engineering at the then-Polytechnikum Stuttgart, at the time still a part of the (mechanical) engineering department.
In 1921 Fritz Emde (1873-1951) succeeded Prof. Dietrich, founding the "Institute for Theoretical Electrical Engineering". The research focus was on electric fields. Wilhelm Bader (1900-1984) succeeded Professor Emde in 1939, adding the "Theory of electric networks" to the activities at the Institute. Bader himself pioneered many methods for the synthesis of electric networks.
When Professor Bader retired, the activities were separated into two new institutes. Günther Lehner succeeded at the "Institute for the Theory of Electrical Engineering" (today ISS), continuing the activities in field theory while Ernst Lüder founded the new "Institute for Network and System Theory", adding system theory (the mathematical description of time and frequence dependent properties of linear systems) to the already established network theory.
In 1971 a laboratory for thin and thick film technologies was build to enable the institute to implement and test electric networks. The original focus on sensors was supplemented in 1978 by thin film transistors (TFTs) on glass substrates. The development of thin film technologies already had a well-established practical application since liquid crystal displays had their first commercial break through with the invention of the TN-cell in the 1970s. The use of TFTs enabled active matrix liquid crystal displays with high resolution and an improved image quality. One good indication for the importance of thin film transistors in display technology is the synonymous use of the term "TFT" for "active matrix LCDs".
The research into thin film transistors lead the "Institute for Network and System Theory" to display technologies, soon expanding beyond the TFTs themselves into other technologies required for displays. The first AM-LCD at the institure was built in 1982.
In the 1980s the impact of LCD flat panels and their multitude of applications plus their future economic impact was becoming apparent. The Federal Ministry for Research and Technology (BMFT) and the state of Baden-Württemberg decided in 1988 to build a research lab for display technologies specifically for investigating industrial grade production techniques and commercial applications. This newly founded "Laboratory for Display Technologies" was attached to the "Institute for Network and System Theory" under Professor Ernst Lüder at the Stuttgart Unversity. The laboratory opened in 1991 at the Stuttgart-Vaihingen campus. At its core is the 480 m2 clean room. The "Laboratory for Display Technologies" has always been focused on application-oriented research and portability to industrial grade production. Therefore, the lab was designed to build complete active matrix LCDs on glass substrates of up to 16 inches squared. This capability to process such (relatively, for a research facility) large substrates gives the laboratory a unique position in all of Europe. The research activities at the laboratory included displays with active matrices of amorphous and poly-crystalline silicon or CdSe and displays with MIM-addressing. A number of different liquid crystal effects was investigated and realized. Research included less common concepts such as PDLSs and Guest-Host cells or bistabile displays with cholesteric or ferromagnetic liquid crystals in addition to the more common TN and VA-cells. The laboratory enjoys world wide recognition and can point to numerous research successes.
Most research activities are third party funded. In addition to federal and European research grants, close cooperations with numerous industrial partners in Germany, Europe, but also in North America and Asia are important sources for funding and projects. Especially German companies profit from the extensive research activities at the "Laboratory for Display Technologies", allowing them to build their own know-how in the field of flat panel displays in a field that is otherwise dominated by companies from Asia.
After the retirement of Professor Lüder in 1999 the "Institute for Network and System Theory" was renamed to "Institute for System Theory and Display Technologies" and the activitie were separated into two chairs. In 2001 Prof. Dr.-Ing. Bin Yang received the call to the chair for "System Theory and Signal Processing" , while Prof. Dr.-Ing. Norbert Frühauf took over the activities at "Chair for Display Technologies".
As large area microelectronics were gaining in importance, in addition to the display technologies for example also in printed organic circuits, the newly independent "Institute for Large Area Microelectronics" was split off from the "Institute for System Theory and Display Technologies". The laboratory for display technologies was placed under this new institute and continues the activities in flat panel technologies. The new institute's activities were expanded by additional applications of large area microelectronics, such as adaptive optical systems, spatially distributed sensor and modulator systems, and printed electronic systems.