Molecular Nanoelectronics

Fundamental physical restrictions, and the cost of device fabrication, might impede further progress in “down-sizing” currently present electronic devices. One area with great potential is the field of molecular electronics. So far several devices have been fabricated, however, fundamental questions, such as: “What is the nature of transport through these systems, and can we employ their electrical properties for new kind of devices?” have not been answered yet. Part of the problem lies in the fact that if we want to perform reliable electronic transport measurements on a molecular system we have to make a well controlled electrical contact between the molecule and the nanometer scale electrodes used in the measurements. This connection can influence intrinsic properties of the molecules. I propose to study, control and manipulate the electronic properties of conjugated molecules, in particular, the so-called photocromic molecular switches. The plan is to study electron transport through individual photochromic molecular switches which consist of conducting conjugated units, separated by switching units, which allow the electron transport to be turned on-and-off reversibly by exposure to light with specific frequencies. It is proposed to study the electronic transport through individual switches directly, by attaching these to metallic electrodes with controlled spacing in the nanometer range. In order to obtain complementary information three different experimental techniques will be used: mechanically controllable break junction (MCBJ) technique, scanning tunneling microscopy, and molecular field-effect transistor.