James Im | Finding the Fundamentals of Silicon for Advanced Electronics

James Im
Professor of Materials Science and of
Applied Physics and Applied Mathematics
This profile is included in the publication Excellentia, which features current research of Columbia Engineering faculty members.
                                    Photo by Eileen Barroso

Silicon, the second most abundant element in the Earth’s crust, is the key material of the modern information age. Microelectronic chips use bulk-silicon wafers to power computers, and silicon is used for increasingly important electronic applications, such as inexpensive solar cells, high-resolution flat-panel displays, radio-frequency identification tags, and 3-D integrated chips. But manufacturers need high-quality crystalline silicon films in which atoms are nicely and periodically arranged.

While it’s easy to obtain amorphous silicon films, they are not well-suited for making these electronic devices. Developing efficient ways to generate high-quality silicon films is a key to the proliferation of these micro- and macro-electronic applications.

James Im’s process for developing high-quality silicon film is playing a crucial role in developing the latest generation of flat-screens for a wide array of electronic devices.

Im has done extensive research that investigates how silicon, solid thin films and nanoscale structures behave when these materials are rapidly heated by laser irradiation, melted, and then subsequently solidify. While his studies look primarily at the scientific and fundamental issues involved, the findings also have led to various technical approaches for realizing high-quality silicon films on various technologically important substrate materials such as glass or plastics.

These laser-induced and melt-mediated crystallization processes, which convert initially amorphous or defective silicon films into low-defect-density silicon films, take place at temperatures above 1400 degrees C. According to Im, understanding how silicon melts and solidifies under these extreme conditions is critical for understanding how the atoms are subsequently packed and positioned.

“Knowing the fundamental details of how Si melts and solidifies makes it a rather straight-forward exercise for us to come up with efficient and effective ways to generate useful materials with periodically arranged atoms that make good electronic devices,” said Im.

The fundamental findings and technical approaches generated at Columbia are powering the evolution of the field of thin Si-film based electronics. One method, called Sequential Lateral Solidification (SLS), is used to manufacture high-resolution LCDs, and has recently emerged as the leading method for the next generation of flat-panel TVs, which use organic LEDs.

Top display makers, including LG Display, Sharp, and Samsung, have already licensed this technology. The innovation is also applicable to smart cards, RFIDs, image sensors, and 3-D integrated circuit devices.

In addition to laser-based approaches, Im is also investigating other beam-induced crystallization techniques that could provide unconventional, yet effective solutions for various electronic devices and applications.

B.S., Cornell, 1984; Ph.D., Massachusetts Institute of Technology, 1989

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