Voltage Induced Molecular Motors Constitute the Smallest Self‐Assembled Molecular Electronic Counter

Abstract

These transistors occupy limited space in the chip and as predicted by Gordon Moore the size of the transistors have shrunk to the extent that the number of these transistors in the chip has almost doubled roughly in every two years. [6] The shrinking size of the transistor leads to issues such as non-reliable performance of the devices, overheating due to extensive contact resistances, [7,8] and increase of leakage current [9] to name some of them. An alternate method to circumvent the problems is to follow the slow but efficient natural computing method, which is being followed by all the living organisms. The benefit is that the scale of computation is massive, but it is impossible to achieve this with the traditional methods. One of the closest approaches to the natural computing process is to use synthetic molecules which are primarily consisting of carbon atoms and replicate the physical phenomena by using a self-assembled structure where the molecules will be allowed to interact with each other till they reach the minimum energy configuration. Some of the well-known molecules which can be potentially used for this purpose are 2,3,5,6-Tetramethyl-1,4-benzoquinone (DRQ), Rose Bengal, DDQ. The common structural and functional attributes of these molecules are their redox behavior owing to the presence of some redox active groups, [10-12] which alleviate the impossibility of using these molecules for large scale computation. Moreover, these molecules have multiple conformational states [13] with each state having different conductance, which will be useful for assigning different logic states in a group of self-assembled molecules. So, achieving a self-assembled structure for these molecules, one needs the perfect condition for the molecules to come together. Usually, self-assembly is a process to minimize the surface energy of the system. [14] There are multiple reports of achieving selfassembly of organic molecules in a scanning tunneling microscope (STM), [15-21] but the application of these self-assembled structures is limited. [22-24] In a Ultra-High Vacuum (UHV) STM, single molecules have been observed routinely and are manipulated using various techniques. They have been studied as molecular motors by the application of an external stimulus such as electric field, [25,26] optical signal, [27-31] mechanical forces, [32-38] etc. One such exciting process is the change in An electronic counter is an integral component in an analog to digital (A/D) or digital to analog signal conversion circuit. The number of flip-flops (n) in these devices decides the quality of the conversion as the output is proportional to 2 n. Since each flip-flop is a combination of transistors, and each transistor occupies some space, there is a limitation in the quality of conversion. The smallest 4-bit asynchronous counter is built by using a self-assembled redox-active organic molecule 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), where each DDQ molecule is acting as an individual flip-flop which is the building block of a coun...