Carbon-Based Transistors Ramp Up Speed and Memory for Mobile Devices

Tel Aviv University – Working with carbon molecules called C60 (buckyballs), Mentovich has successfully built a sophisticated memory transistor that can both transfer and store energy, eliminating the need for a capacitor.

This molecular memory transistor, which can be as small as one nanometer, stores and disseminates information at high speed — and it’s ready to be produced at existing high-tech fabrication facilities. Major companies in the memory industry have already expressed interest in the technology, says Mentovich, who was awarded first prize for his work at May’s European conference in the session on Novel Materials Approaches for Microelectronics of the Materials Research Society.

As many as 15 years ago, technology experts realized that the problem with shrinking electronics would be the physical size of the hardware needed to make them run. The idea of a sophisticated transistor, which could do the job of both the transistor and the capacitor, was a technological dream — until now.

In order to tackle this technology gap, Mentovich was inspired by the work of Israel Prize winner Prof. Avraham Nitzan of TAU’s Department of Chemistry, who proved that, due to its special structure, a molecule can store both an electric charge and information at the same time. To apply this finding to transistors, Mentovich used C60 molecules, made up of 60 carbon atoms, and put them in the channels of a transistor, creating a smaller-than-silicone, high-speed transistor that could also do the job of a capacitor.

The next step is to find a fabrication facility with the necessary materials to manufacture the transistors. According to Mentovich, the benefit of this product is that with the right equipment, which is standard in high-tech facilities, and his breakthroughs on how to put the transistors together, these molecular memories could be manufactured anywhere. “The distance to implementation is not far,” he says.

Applied Physics Letters – Post-complementary metal-oxide-semiconductor vertical and molecular transistors: A platform for molecular electronics (2011)

We demonstrate two types of post-complementary vertical-metal-insulator tunneling transistor in which a self-assembled monolayer is coupled to the channel of one of them. It is found that the properties of the molecular device are better than those of similar transistors in which these molecules are absent. The molecular transistor exhibits higher currents than the non-molecular device and shows negligible leakage currents, with clear features which are attributed to the properties of the molecules

ELad Mentovich PHD thesis was “Realization of the Molecular transistor Roadmap”

Even if Moore’s Law continues to hold, it will take 250 years to fill the performance gap between present-day computers and the ultimate computer determined from the laws of physics alone. Molecular nanostructures promise to occupy a prominent role in any attempt to extend charge based device technology beyond the projected limits of CMOS scaling. The aim of my PhD is to discuss the potential of molecular electronics and to identify and solve the fundamental knowledge gap for the successful introduction of molecule-enabled computing technology. Thus, an attempt is made to extend the performance of the current device technology beyond the classical limit and into the quantum regime in which the main characteristics are not only current and amplification but also the non-linear effects crucial for transistor operation. In doing so, new transport physics of molecular devices will be explored.

Results, Results, Results
In this part, a novel molecular transistor I developed is introduced and characterized. In these vertical devices the active part of the device is composed of a monolayer of molecules or protein yielding an active area of the transistor of only a few nanometers.

CMOS compatible transistor- The C-Gate MolVeT

Recently we have suggested and demonstrated a novel universal method in which a new type of nanometer-sized, ambipolar, vertical molecular transistor is fabricated in parallel fashion. This central-gate molecular vertical transistor (C-Gate MolVeT) is fabricated by a combination of conventional microlithography techniques and self-assembly methods.

The C-Gate MolVet fabrication procedure. (a) A network of gold electrodes is defined on top of a highly doped silicon wafer covered with 100 nm thick thermal oxide, followed by the deposition of a 70 nm layer of Si3N4 dielectric. (b) Arrays of microcavities, ranging from 800 nm to 1.5 micron in diameter are created by drilling holes through the entire layer to the highly doped silicon substrate, followed by mild etching of several nanometers of the gold electrode. This undercut in the electrode provides space for oxide growth. (c) A titanium column is evaporated followed by the definition of a larger cavity and oxidation of the titanium column to form the gate electrode. (d) Adsorption of the protein-based SAM on top of the exposed gold ring and definition of the upper electrode. (e) The final C-Gate MolVet structure is achieved by an indirect evaporation of palladium on top of the protein layer. (f, g) Tilted high-resolution scanning electron microscopy (HRSEM) images of a single device (f) and array (g) of transistors before molecular assembly. (h) Optical image of the transistor after stage (c). (i) HRSEM image featuring an array of C-Gate MolVet transistors.

Publications of the Mentovich research group

“Post CMOS transistors as a new platform for Molecular Electronics” has been submitted for publication.

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