Investigation of the electronicstructures of single molecularjunctions from current voltage characteristics
Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Molecular electronics has lately shown significant progress due to rapid advances in investigative methods and is vital to the future of the electronic industry since the fundamental limits of the solid state transistors are closer than ever. To reach the application of using single molecules as electronic components, it is imperative to investigate the electronic structure of a single molecule connected to metal electrodes.
This research has focused on examining current voltage behavior to clarify the electronic structure using transition voltage spectroscopy (TVS) and a single level tunneling (SLT) model. In an approximate model, TVS can be used to determine the molecule frontier orbital-electrode energy gap (EF -ξ0) and in most cases prove molecular presence in the junction. The SLT model can be tted to experimental data to obtain molecule-electrode bond strength and molecule-electrode energy gap.
The measurement system prepared and tested was a mechanically controlled break junction. It has ability not only to test current voltage characteristics but also probe external magnetic and electric eld modulation eects. The current-voltage characteristics of benzenedithiol, hexanedithiol and a recently synthesized oligothiophene molecule with five thiophene rings were measured and analysed by using TVS and tting the SLT model. Most of the current-voltage characteristics could be tted using the SLT model. Analysis revealed that the variation in molecular conductance is mainly due to variation in molecule-electrode coupling strength and not due to the EF -ξ0 energy gap. Dierent EF -ξ0 were discovered for the three dierent molecules. It was shown that the transition voltage roughly approximates the EF -ξ0 energy gap by comparing the TVS results to the results obtained from fitting the SLT model.
Place, publisher, year, edition, pages
2013. , 89 p.
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-129288OAI: oai:DiVA.org:kth-129288DiVA: diva2:651335
Master of Science in Engineering - Microelectronics
Malm, Gunnar B, Professor