Polymer electronics often enough use metallic or metal oxide conductors as contacting materials. This article at PNAS discloses a solvent annealing process to enhance the electrical conductivity of polymers like polyaniline to levels adequate to replace the metals. One can envision applying materials like these by means of ink-jet printing and solvent annealing, for example, eliminating masking and etching. It’s too soon to say whether the conductivity will be stable over long times.
Since my April 1 posting on graphene, I have found three interesting developments. In the first [arXiv:0912.5485], an international collaboration reports synthesis and roll-to-roll transfer of large area graphene. This marks a huge step forward in making graphene available for applications. In my opinion, the copper etch makes the method more expensive than it might otherwise appear. Considerable work remains here.
IBM reports [arXiv:1003.5702] a new technique for synthesizing electronically interesting graphene on SiC. In the conventional approach, silicon is sublimated from SiC(0001), leaving behind a monolayer of carbon which is covalently bonded to the substrate. IBM has found that subsequent treatment with oxygen at 250 C suffices to grow an oxide layer between the SiC substrate and the carbon layer. The carbon immediately rearranges its bonding to graphene.
IBM also reports [arXiv:0912.4794] on photocurrent response in bilayer and trilayer graphene field effect transistors all the way out to 40 GHz. While most research has been directed toward electronic applications, IBM points out that the photonic properties are every bit as interesting and technologically promising. Although they have so far demonstrated up to 40 GHz response,
[f]urther analysis suggests that the intrinsic bandwidth of such graphene FET based photodetectors may exceed 500 GHz. Most notably, the generation and transport of the photo-carriers in such graphene photodetectors are fundamentally different from those in currently known semiconductor photodetectors, leading to a remarkably high bandwidth, zero source-drain bias (hence zero dark current) operation, and good internal quantum efficiency.
The question “are there any bubbles trapped” has been asked many times of step-and-flash nanoimprinting. ASML was granted a U.S. patent on Tuesday, 6 April, with the title “Imprint lithography” [US7692771] The invention envisions a visible wavelength illumination and a scattering detector focussed on the template/resist interface. By watching the amount of light scattered from the interface, one can determine whether bubbles are present. The feedback loop permits real-time control of the delay between the template positioning and resist hardening steps, for example.
This patent has a sibling [US2007-0018360] which is ready to issue. Its allowed claims are more explicit, stating
the output providing an indication of whether or not the imprintable material has substantially fully flowed into a recess of the imprint template.
Under 35 U.S.C. 271(b) “[w]hoever actively induces infringement of a patent shall be liable as an infringer.” Previously, in order to meet the requirement that one “actively induces”, one generally must have knowledge of the patent in question.
The Court of Appeals for the Federal Circuit recently found (SEB S.A. v. Montgomery Ward & Co., PDF) that deliberate indifference to potential patent rights is equivalent of actual knowledge. To quote:
…a claim for inducement is viable even where the patentee has not produced direct evidence that the accused infringer actually knew of the patent-in-suit. This case shows such an instance. The record contains adequate evidence to support a conclusion that [one of the defendants] deliberately disregarded a known risk that SEB had a protective patent.
I wonder what this means if a company deliberately shields employees from knowledge of pre-existing patents.
[For further discussions see, for example, this link to IPWatchdog.]
As new materials go, graphene has generated enormous interest. The arXiv currently holds over 1000 papers with “graphene” appearing in the title. (See the graphic.)
Of these, 32 titles also contain the word “device”, while only three are concerned with patterning.
Interestingly, there are 14 publications at JVST B, of which three are concerned with patterning. I suppose we should conclude that, while this material is popular in the physics research community (due, no doubt, to its exotic properties [see also here]), it is still insufficiently understood and too difficult to manage in order to support more than preliminary attempts at making electronic devices.
IBM’s recent announcement notwithstanding, early applications of graphene may well be in bulk film applications such as photovoltaic contact layers. Even this may be a long road. Consider, pure graphene is a two-dimensional material. Being only one atom thick, it is exquisitely sensitive to surface contamination. In fact, most attempted applications use bilayer graphene, to decouple somewhat from the underlying substrate. Might it be that any “sandwich” application (like contact layers) would be forced to use a trilayer?
There are limits to going thicker of course. Graphene’s special properties disappear as the layer count increases. By 10 layers, we effectively have graphite, a rather uninteresting material for electronics.