This paper presents a study on plasma enhanced atomic layer deposition (ALD) of TiO2 and WO3 films on silicon substrates. At low temperatures, ALD processes, which are not feasible at high temperatures, could be possible. For example, temperatures at 180 °C and above allow no WO3 ALD process with WF6 as a precursor because etching processes hinder film growth. Further low temperature deposition techniques are needed to coat temperature sensitive materials. For the deposition, WF6 and TiCl4 are used as metal precursors and O2 and H2O as oxygen sources. The depositions were accomplished in the temperature range of 30 °C up to 180 °C for both metal oxides. Spectroscopic ellipsometry, x-ray reflection, and grazing incidence diffraction were used to investigate the deposited ALD thin films. Film growth, density, crystallinity, and roughness are discussed as functions of temperature after ensuring the ALD requirement of self-saturating adsorption. Growth rates and measured material properties are in good agreement with literature data.

The field of molecular electronics has progressed in recent years and demonstrated functionalities such as singlemolecule switches, [1,2] field emitters, [3] and even gateable structures. [4,5] Variations of the overall conductance of all these structures in nominally identical junctions were, however, large. Differences in conductance between these junctions were identified by recording conductance histograms of all measured junctions. Large conductance variations could be demonstrated between highand low-conductance states by using quantum interference effects [5] or by changing the molecular structures in a controlled way. [6] To be able to use molecules as future components in electronic applications, it would be useful not only to have binary, high and low, conductance states available, but also a range of possible modifications to fine-tune the exact properties of the circuit. Metallorganic components lend themselves for this purpose because of the broad palette of ions, promising also a broad range of achievable conductance properties. The influence of metal ions incorporated into porphyrin molecules has already been investigated, showing a decrease in conductance due to destabilization of the π-system by metalThe creation of molecular components for use as electronic devices has made enormous progress. In order to advance the field further toward realistic electronic concepts, methods for the controlled modification of the conducting properties of the molecules contacted by metallic electrodes need to be further developed. Here a comprehensive study of charge transport in a class of molecules that allows modifications by introducing metal centers into organic structures is presented. Single molecules are electrically contacted and characterized in order to understand the role of the metal centers in the conductance mechanism through the molecular junctions. It is shown that the presence of single metal ions modifies the energy levels and the coupling of the molecules to the electrical contacts, and that these modifications lead to systematic variations in the statistical behavior of transport properties of the molecular junctions. A rigorous statistical analysis of thousands of junctions is performed to reveal this correlation. The understanding of the role of the metal ion in the resulting conductance properties is an essential step toward the development of molecular electronic circuits.

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