ECS Day 2: “Tantalizing” ZnO; cost-effective microfluidics; “Fox News flu”

by Michael A. Fury, Techcet Group

May 28, 2009 – Day 2 of the Spring 2009 meeting of The Electrochemical Society (ECS) kicked off with a standing-room-only keynote address in the Advanced Gate Stack New Materials symposium by Y. Nishii of Stanford University, entitled “Revolutionary Nanoelectronic Devices and Processes for Post 32nm CMOS.” Not surprisingly, heat is a primary motivator driving innovation (along with reducing power consumption), dealing with embedded non-volatile memory in the microprocessor, and developing on-chip interconnects that remain compatible as the device architecture evolves. In metal gate pairs, smaller crystal size is preferred. High-mobility channel materials are bringing us closer to the ever-future dawn of mainstream III-V materials. Carbon nanotube (CNT) research is very promising on a fundamental level, but CNT growth with consistent electrical properties and placement on the devices remain significant hurdles.

F. Lange of UCSB tantalized his audience with the use of aqueous synthesized ZnO as a future semiconductor material (though I thought one would require tantalum for that purpose). There have been a number of advances in deposition methods, doping control, and compatible device architectures that make this technology worth tracking as it emerges from university research labs.

B. Balu of Georgia Tech presented some clever work on cost-effective 2D microfluidic devices for applications outside well-equipped lab environments. Ordinary cellulose paper was treated to produce a super-hydrophobic surface, onto which normal hydrophobic dots and lines were printed by inkjet. The 1962 Furmidge equation for advancing and receding contact angles describes the ability of a liquid drop to roll down an inclined surface. By selecting the right combinations of printed hydrophobic feature size and liquid drop volume, the researchers were able to demonstrate the functions of drop storage, transfer, mixing, and sampling (partial transfer). These are the functions required in high-end analytical laboratory equipment to perform sophisticated analyses with small sample sizes. It appears that these same functions can be accomplished with a few pieces of special paper, which is what you need in a poor area with no electricity and people who need diagnosis and treatment.

E. Weber at Fraunhofer ISE is the latest recipient of the ECS Electronics and Photonics Division award for his work on metamorphic triple-junction solar cells. Their world-record efficiency solar cell tops out at 41.1% against a theoretical maximum of 61%. Closing that gap requires process technologies to deposit buffer layers that can better tolerate the lattice mismatch between the primary junction materials. In one example, a buffer with 8 transitional layers was able to reduce the top layer strain from 16% down to 7%. Thin films of GaAsN were incorporated to block defect propagation between layers. Unfortunately, in a room set up for over 300 people, only about 20 attendees were there to applaud these accomplishments.

B. Chu of the U. of Florida presented a AlGaN/GaN HEMT device structure modified to detect extremely low levels of botulinum toxin, the most toxic known substance to unvaccinated humans with an LD90 of 1ng/kg. In his detector, a 5nm Au film is deposited across the active gate area. Thioglycollic acid molecules bind to the Au at one end, and to botulinum antibodies at the other end. This antibody is quite specific to its matching toxin, and the presence of the toxin causes an electronegativity shift in the thioglycollic acid anchor that is detected as a current shift in the HEMT device. Levels as low as 0.1ng/ml were detected with sufficient signal-to-noise.

Last-minute cancellations continued to plague the ECS meeting. In one session, the announced reason for the speaker’s absence was not the economy, but the “Fox News flu.” Let us hope a cure can be found!

Michael A. Fury, Ph.D, is senior technology analyst at Techcet Group, LLC, P.O. Box 29, Del Mar, CA 92014; email [email protected].


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