iMechanica - flexible electronics - Comments

Dear Xiaodong,

Xue Feng — Wed, 29 Oct 2008 04:55:56 -0400

Dear Xiaodong,

Many thanks for your comments. Your method is powerful to investigate the detailed information of the interface between PET and films at the micro and nano scale. I will consider for it in our future work.

xue

Bending of Inorganic Electronic Materials on Plastic Substrates

Xiaodong Li — Mon, 13 Oct 2008 11:19:00 -0400

This is a nice paper. The multilayered systems with hard and soft materials are of interest to the community. Experimental approaches are still challenging. Our group has published a paper using AFM/DIC technqiues. Your comments and suggestions are welcome. Thanks.

Xiaodong Li, Weijie Xu, Michael A. Sutton, and Michael Mello, "Nanoscale Deformation and Cracking Studies of Advanced Metal Evaporated Magnetic Tapes Using Atomic Force Microscopy and Digital Image Correlation Techniques," Materials Science and Technology, 22 (2006) 835-844.

slides for delamination of islands uploaded

Zhigang Suo — Sat, 17 Nov 2007 20:33:47 -0500

Rui: Slides for the right talk are uploaded now. Thank you. Zhigang

another talk

Rui Huang — Sat, 17 Nov 2007 16:22:52 -0500

Zhigang,

I appreciate your sharing slides and will follow up with my slides too. The files you attached here however are for a different talk.

No debonding observed in undeformed specimens

Nanshu Lu — Tue, 09 Oct 2007 22:25:18 -0400

To answer your question in another point of view we used FIB to cut undeformed specimens as well and observed no debonding at all. Hence we believe that FIB will not cause metal film debonding from the substrate.

Initial stress

Nanshu Lu — Tue, 09 Oct 2007 16:18:30 -0400

This is what we are working on actually. We did not deal with stress-strain in this submitted paper. You must already know that an ordinary way to determine the residual stress is to do curvature measurment of the specimen.

thanks

Rongmei niu — Mon, 08 Oct 2007 21:56:43 -0400

Hi, Nanshu, thanks for your telling me the method. hehe, comparing with your advanced method, my method is too backward. At the beginning, I kept eye on the Keithley source meter and recorded the value at once, and when one test finish, my hand is already too tired to raise.

Resistance measurement

Nanshu Lu — Mon, 08 Oct 2007 13:34:08 -0400

Hi, Rongmei,

Thanks for your interests on our work. To determine the initial resistance we measured the sample with a Keithley multimeter and then subtracted the system resistance which was obtained by contacting the two probes of the multimeter. We recorded in-situ resistance during tension by connecting the multimeter to the computer with a well-known software named LabView . Of course there's a little programing to do.

Regards,

Nanshu

thank you

Rongmei niu — Sun, 07 Oct 2007 10:44:32 -0400

Dear Xi , thanks. I want to make cross-section specimen of Cu films on PI all the time, but failed due to PI substrates. so I will learn from you, thanks again.

Re: FIB induced damage

Xi Wang — Sat, 06 Oct 2007 17:05:27 -0400

Hi Rongmei, thanks for being interested in our work. The milling process from the ion impact can cause some damages to the sample, including surface amorphization and contamination. MRS bulletin May 2007 actually has a very good review article about FIB milling process. The cut in Fig.5(b) was made by several steps, including fine polish steps with very low beam current. It is unlikely the feature is due to the FIB process.

Another question

Rongmei niu — Fri, 05 Oct 2007 19:27:05 -0400

Nan shu, I have another question want to consult you.

How about the initial stress before your tension?

Thank!

Best Regards

Rongmei

Could FIB damage the Cu film?

Rongmei niu — Fri, 05 Oct 2007 19:13:38 -0400

FIB are eupensive, so I have no chance to do it. while other students in my group did FIB observation by the way for me. unfortunately, there are mang damage on the surface of Cu film. accordingly, could the debonding of Fig. 5 (b) in your paper result from FIB?

How about the resistance

Rongmei niu — Fri, 05 Oct 2007 19:05:25 -0400

Nan shu, Thanks very much for your citing my work! and sharing your excellent work the paper.

I have a very primary question to consult you, how much the inital resistance? how did you monitor the resistance, all the time?

Thanks a lot

Reply to Teng

Nanshu Lu — Thu, 27 Sep 2007 11:41:55 -0400

Teng, thanks for your encouragement.

It is hard to characterize the grain boundray strength at this stage and we don't know for sure whether it is enhanced or not after the heat treatment. But you are right that transgranular cracking is dominant for our annealed films (with large grains). It appears that such failure is quite similar to single crystal cracking although our Cu film is polycrystalline.

We have run tensile tests of as-depostied films as well and we are going to complete and report it soon. One of the interesting observations is that there seems to have stress-induced grain growth for such fine-grained films. Therefore strains tend to localize at the large grain regions. We do have observed co-evolution of local thinning and debonding as well.

Effect of grain size on metal film ductility

Teng Li — Wed, 26 Sep 2007 22:44:03 -0400

Nanshu,

Excellent experiments! This is the first direct observation of the co-evolution of film necking and interface debonding.

One question about the effect of grain size on the rupture strain. It seems in the annealed samples with large grains (several microns), there is no appreciable grain boundary cracking even at large elongation. Do you think the huge ductility of such films results from the stronger grain boundaries or it's just due to the larger grain size. I'm wondering if you have done the experiments of stretching the as-deposited Cu films (like the one in Fig. 1a) to a large strain. In this case, the metal films with small grains (of tens of nanometer) may show both film necking and grain boundary cracking, as observed in previous experiments.