An argue with CalTech. Chemistry Grad.

Anant Babu Marahatta
Ph.D. student
Tohoku University
(ananta037@gmail.com)

Theme of this article is: “Knowing English is not enough to present Chemistry but one must know Chemistry in English.”
(some thing about Amphidynamic Crystal)

In order to strengthen and enhance the education and research functions of graduate schools of Japanese universities, Ministry of Education, Culture, Sports, Science and Technology (MEXT) introduced the “Global COE (Centers of Excellence) Program in some of the top universities of Japan on 2002. Another main objective is to foster highly creative young researchers who will become world’s leaders in their respective fields through experiencing and practicing research of the highest world standard.Molecular complex Chemistry is one of the fields covered by the GCOE.

Being one of the Chemistry doctoral students of the nation’s high tech. university [Tohoku University] with the nation’s largest chemistry department, I also belong to the network of GCOE program. One of the annual events of the Tohoku Univ. sponsored by this program is to provide a chance for the doctoral students to lead a week long Int’l conference. Including the key speakers and the chairpersons of each section, every participant must be the Ph.D. candidate of Chemistry. The professors only act as a facilitator. He/she never interferes the students’ leadership.

One of the key speakers of the program was from California institute of Technology (CalTech). He was presenting his research work related to coordination chemistry and was chanting the effects of ligands to synthesize the Supramolecules with the metal ions. He was also claiming that his research output is fabulous and praiseworthy. One of the major parts of that molecule was the phenylene ring encapsulated into the cage that can create enough free space for undergoing smooth rotation. He was calling this ring as a “spacer” because the surrounding spokes can control the space around the phenylene. Any way, we around 200 students were listening his interesting speech. Being a chair person of this section, I was feeling that he was pretending some hidden facts behind his research area even though he was very bold and smart guy. He presented well and wrapped his talk by thanking his collaborators.

Then, it’s my time to open the floor for the discussion. I asked the participants for the comments and the queries. Some students asked about the effects of the coordinating efficiency of ligands’ and some other related stuffs. A Tohoku professor was suggesting him about the possibility of changing properties of that supramolecule by changing central metal ions.

Before announcing the next speaker, I raised my query about that spacer so called phenylene ring. I am/ was very much familiar with such molecules having central rotating part encased into the static part. I also knew that such type of molecular crystals with rotating part and static part in a same molecule are called Amphidynamic crystal, but this is a very new type which I encountered while reading a paper published on 2002. My question was “does your molecular crystal belong to Amphidynamic crystal?” But that guy did not understand the last term and instead asked me for the clarification. I just clarified him by reminding the term “Amphibia” and then called the next speaker.

Immediately after this session, the same guy approached and said to me “Knowing English is not enough to present chemistry but one must know chemistry in English.” Excellent understanding!!!! isn’t it?

Small Science Vs. Large Science

Anant　Babu Marahatta
Ph.D. student in chemistry
Tohoku University, Japan

Science carried out by individuals or small teams of investigators is said to be “small science” and the science carried out for large scientific data gathering programs is said to be “large science”.

Research done by individuals or small teams of investigators has been crucial for many of the important discoveries made in all branches of science. The individual or small group research work has been the first step for bringing up the revolutionary changes in the world. Such type of research facilitates the researcher to concentrate in the particular problem and hence increases the thinking level of the researchers as well. It has been found that the research work performed by the individuals or by the small teams is more accurate and reproducible. Since every branch of science needs accuracy which in fact catalyses the rate of tailoring and building up the new inventions and discoveries. These discoveries provide the fundamental basis for the application of scientific knowledge to national economic and societal goals.

Small science helps to define the goals and directions of large scientific data gathering projects [so called large science]. In turn, these data feed and are often best synthesized and interpreted by the long-term efforts of the small science community. In small science, the rate of manipulation of data is almost nil due to the accuracy which perfectly orients into the solutions of the problems.

Are Carbon Nanotubes the Future of VLSI Interconnections?

Original paper is published by-
K. Banerjee and N. Srivastava
University of California


Summarised by Anant

What is VLSI?
• Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistor-based circuits into a single chip.
• VLSI began in the 1970s when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device.
New wiring solutions…!
• Metallic carbon nanotubes (CNTs) are promising candidates that can potentially address the challenges faced by copper and thereby extend the lifetime of electrical interconnects.
• carbon nanotubes (CNTs) have aroused a tremendous amount of interest in their use as building blocks of future integrated circuits due to their outstanding electrical properties

CNT based interconnects can potentially offer significant advantages over copper.
• CNTs exhibit extraordinary strength and unique electrical properties are efficient conductors of heat and are metallic in nature.
•SWCNTs are a very important variety of CNT because they exhibit important electric properties that are not shared by MWCNTs. The remarkable properties of SWCNTs stem from the symmetry and unusual electronic structure of grapheme [one atom thick sheet of graphite].

∙An isolated CNT can carry current densities in excess of 1010 A/cm2 without any signs of
damage even at an elevated temperature of 250 0C. However, the high resistance associated with an isolated CNT (greater than 6.45 KΩ) necessitates the use of a bundle (rope) of CNTs conducting current in parallel to form an interconnection. CNT bundle interconnects have superior performance compared to Cu.

∙For short CNT bundle with small length (L), [especially for L < λCNT], resistance is higher than that of a Cu interconnect because the large contact resistance dominates the overall CNT resistance. However, for long interconnect lengths; i.e. long CNT bundle interconnects have smaller resistance than their Cu counterparts [ L>λCNT].
∙The interconnect delay can be reduced considerably by using densely packed CNT bundle interconnects, so that large power savings can be achieved. CNT bundle interconnects can reduce intermediate level interconnect delay by more than 60% due to their lower resistance.

Reliability and Thermal Analysis
∙Due to strong sp2 bonding, carbon nanotubes are much less susceptible to electro-migration (EM) problems [that plague copper interconnects] and can carry very high current densities. Metallic single-walled CNT bundles have been shown to be able to carry extremely high current densities of the order of 109 A/cm2. Cu interconnects = 106 A/cm2 due to EM.
∙A 100 x 50 nm2 cross-section Cu interconnect can carry current up to 50 μA, whereas a 1 nm diameter CNT can carry upto 20-25 uA current. Hence, from a reliability perspective, a few CNTs are enough to match the current carrying capacity of a typical Cu interconnect.
However, the need to reduce interconnect resistance (and hence delay) makes it necessary to pack several thousands of CNTs in a bundle.
Conclusion
∙There is no any experimental work or theoretical analysis yet about the nature of electromagnetic interactions between non-isolated (or tangled) nanotubes. So the authors have not considered their mutual effect during conduction, however they highlighted that this challengeable investigation should be done before using them in a circuit though these challenges are not expected to cause any fundamental problems.