Blog posts
Question about dislocation nucleation sites in strained silicon-on-insulator
Electronic active device is built on the strained silicon-on-insulator (sSOI), e.g. strained Si layer on oxide, which in turn is bonded on bulk silicon wafer. Because no misfit dislocation can exist in strained silicon layer any more, will the dislocation be generated during later processing and operation? If there are still lots of dislocations in the strained silicon layer, where do they come from? Is there any experimental work to discover the dislocation nucleation sites? I guess they will nucleate from the triple junctions of gate-sSOI-cap, because the stress is singular in the triple junction. But I am not sure. So I want to know something about the experimental observations.
McMat 2007 Applied Mechanics and Materials Conference
My research work
I use this blog entry to upload my research work, then I have links for my publications in my resume. Otherwise, I don't have any links for my preprints.
If people can upload any files without writing a blog entry, that will be great.
Saturated voids in interconnect lines due to thermal strains and electromigration
Zhen Zhang, Zhigang Suo, Jun He
Thermal strains and electromigration can cause voids to grow in conductor lines on semiconductor chips. This long-standing failure mode is exacerbated by the recent introduction of low-permittivity dielectrics. We describe a method to calculate the volume of a saturated void (VSV), attained in a steady state when each point in a conductor line is in a state of hydrostatic pressure, and the gradient of the pressure along the conductor line balances the electron wind. We show that the VSV will either increase or decrease when the coefficient of thermal expansion of the dielectric increases, and will increase when the elastic modulus of the dielectric decreases. The VSV will also increase when porous dielectrics and ultrathin liners are used. At operation conditions, both thermal strains and electromigration make significant contributions to the VSV. We discuss these results in the context of interconnect design.
This has been published and the related references are listed here:
- Z. Zhang, Z. Suo, and J. He, J. Appl. Physics, 98, 074501 (2005). link
- J. He, Z. Suo, T.N. Marieb, and J.A. Maiz, Appl. Phys. Lett. 85, 4639 (2004). link
Ninth U.S. National Congress on Computational Mechanics
USNCCM IX, July 22 - 26, 2007
Pre- & Post-Congress Short Courses, July 22 & 26, 2007
Hyatt Regency San Francisco
San Francisco, California
BACKGROUND AND SCOPE
From their inception in 1991, the biennial congresses of the United States Association for Computational Mechanics have become major scientific events, drawing computational engineers and scientists worldwide from government, academia, and industry. The Ninth U.S. National Congress on Computational Mechanics (USNCCM IX), hosted by the University of California, Berkeley, will feature the latest developments in all aspects of computational mechanics, and will broaden the definition of the discipline to include many other computation-oriented areas in engineering and sciences. From applications in nanotechnology and bioengineering, to recent advances in numerical methods and high-performance computing, the technical program will reflect the Congress theme of "Interdisciplinary Computation''. In addition to plenary lectures and minisymposia that highlight the latest trends in computational mechanics, pre- and post-conference short courses addressing advances in multiscale and multiphysics methods, as well as other topics, will be held. Numerous vendor exhibits from Bay Area and national companies and organizations are also planned. Detailed information on USNCCM IX can be found at:
http://me.berkeley.edu/compmat/USACM/main.html
George Rankine Irwin (26 February 1907 - 9 October 1998)
Dr George Rankine Irwin (26 February 1907 - 9 October 1998) was an American scientist in the field of fracture mechanics and strength of materials. He was internationally known for his study of fracture of materials. Read more...
Also see his acceptance speech upon receiving the Timoshenko Medal.
Innovation Hall of Fame, University of Maryland.
Brain Storm and Carbon Nanotubes
Last year, I attended the course ES139/239 in Division of Engineering and Applied Sciences, Harvard University, the innovation in science and technology. The final project of my group was about carbon nanotube (CNT). In the stage of popping up ideas, we did not consider any feasibility issues, and just used our imagination to create fancy ideas. I was inspired by other guys a lot, felt too excited after the evening brainstorm session, and wrote down the ideas I coined up. Some of them are not nonsense, e.g. replacing Cu by CNT as conductor in integrated circuit (IC). Later on, I find a piece of news in nanotoday (Dec. 2005) that the company Arrowhead Research was to provide $680,000 over two years to Duke University to develop technology for IC based on CNTs. Of course, I am not the first one to come up with this idea. But this means the random imaginative idea is very helpful and sometimes feasible. Another point I learned from this course is to write down at least one idea per day. Keep doing this, then you have a large pool of ideas. One year later, you have 365 ideas. Don’t expect every idea to be useful. Even if just one or two of them are great, it is worthy doing. Imagine that if the future technology originated from one of your ideas, you will contribute the society and feel fullness of ecstasy. If you can realize your idea, you can be a millionaire or billionaire, and then lie on the beach of Caribbean to enjoy the sunshine.
The long tail of papers
(Initially posted in Applied Mechanics News on 25 July 2006)
In an entry on pay per paper, I alluded to Chris Anderson's new book, The Long Tail. It should be straightforward to collect page views or down loads or citations of individual papers in a journal. You can plot the numbers of hits of individual papers against the rankings of the papers. Here is the curve for articles in Slate. (Not sure why data stopped at top 500 hits. Why not go further to see a really long tail?) Hope someone in Applied Mechanics will show the same data for JMPS, IJSS, MOM, etc. It will be fun.
Here is the gist of Anderson's observation: If you care about the total sale, as a publisher might, then what matters is the area under the curve; the contribution of the tail may rival that of the head. This much is objective, and should not be controversial.
Now allow me to play a variation of the theme, which is admittedly subjective and possibly controversial. Let's say the net contribution of a journal to new knowledge is proportional to the area under the curve (the subjective part). Then numerous less cited papers may make a significant contribution comparable to the contribution made by the best cited papers.
If you are interested in this argument, you might as well generalize the analysis from a single journal to all journals in a field, or to all journals in science, engineering and medicine. I'm not sure if such a curve has ever been plotted, but the job should not be too hard.
Now, if you are an individual author, surely you'd like to have a lot of hits for your own papers, just as Anderson is celebrating his book becoming a best seller. However, if your job is to increase the total knowledge, as the NSF is set up to do, then you might as well pay as much attention to the long tail as to the tall head.