| Recent research in the field of nanometer-scale electronic devices, nanoelectronics, has focused on two fundamental issues: the operating principles of these devices, and the requisite technologies needed to realize as well as integrate them into useful circuits. It is entirely possible that at the forefront of this new field, a technology will emerge based on the properties of some molecules that act as electronic components. This technology is Molecular Electronics.; Here, we report on a reproducible method for the measurement of I-V characteristics on duplex lambda-DNA molecules labeled with disulfide end groups in two configurations; namely, with the disulfides either on the same single strand or on opposite strands of the duplex. No difference in I-V characteristics was concluded between the two configurations. We infer that charge transport in DNA is insensitive to which strand is contacted. The method is also employed toward a comparison of electronic transport through nicked and repaired lambda-DNA molecules. The repaired DNA double helices show a close-to-linear I-V characteristics, and a d.c. conductivity estimated at ∼1 x 10-3 S cm-1. In contrast, the nicked DNA shows pronouncedly nonlinear and rectifying behavior, with a conductivity gap of ∼3 eV. The low-field conductivity of the nicked DNA is approximately a factor 20 lower than that of the repaired DNA. The different I-V characteristics point to the promise of the use of DNA as a molecular wire in nanoscale devices. Also, an overview is presented of the theory of single electronics and realization of Single Electron Transistors (SET) via different approaches. First, the Step Edge Cut Off (SECO) process is employed as a possibility for the fabrication of high-temperature metal-based single electron devices with relaxed technological requirements. Then, lithographically defined constrictions are used to realize tunneling barriers either through the local oxidation of thin Al lines; or depleting the two-dimensional electron system (2-DES) of an InAs/GaSb heterostructure. The major problems that apply to the different methods are addressed and potential solutions given. Finally, some interesting mesoscopic effects achieved with the InAs/GaSb samples are presented. |
