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Quantum Wire Arrays in the Framework of ETS-4 and ETS-10

Onnaz Ozkanat, Jiangdong Deng and Al Sacco, Jr.

ETS-4 and ETS-10 crystals contain …Ti-O-Ti-O-Ti... (titania) chains isolated from each other by siliceous matrix. These one-atom thick titania chains are hypothesized to be “intrinsic” quantum wires where electrons or other carriers are confined in two dimensions. Therefore, ETS-4 and ETS-10 crystals can be considered as ”natural” quantum wire arrays. UV-vis spectroscopy of these crystals shows a significant blue shift suggesting possible quantum size effects resulting from these titania chains. To further determine if these chains are behaving as quantum wire arrays, electrical transport characteristics of these crystals were tested at room temperature, and will be tested at low temperatures. Individual ETS-4 crystals with the average dimensions of 10x200x20µm were embedded between the gold electrodes (Figure 1) utilizing standard nanofabrication methods.

Figure 1: Individual ETS-4 crystal embedded between the gold electrodes. Yilmaz et al., “Electrical Transport through Monatomic Titania Chains in Titanosilicate ETS-4”, Appl. Phys. Let. ,90, 152101 2007.

Current-voltage (I-V) curves obtained at room temperature (Figure 2) suggest that conduction occurs only through the monatomic titania chains in the framework of ETS-4 crystals. These curves show a non-Ohmic behavior at high bias voltage (>7 V). In addition, the I-V curves of consecutive measurements showed that the conductivity of ETS-4 crystals decreases after each measurement, suggesting deformation of the conducting medium. Currently, f ETS-4 crystals are being tested at low temperatures, at which quantized properties of carriers are expected to be observed. Also, ETS-10 crystals and their electrical transport measurements are being investigated. These crystals are thermally more stable than ETS-4 crystals, and are therefore expected to be more stable during repeated I-V testing. The results of these investigations may provide a basis for utilizing ETS-4 and ETS-10 crystals as quantum wire arrays in circuits.

Figure 2: Current-Voltage behavior of the ETS-4 crystal; inset demonstrates Current-Voltage behavior of Silicalite. Yilmaz et al., “Electrical Transport through Monatomic Titania Chains in Titanosilicate ETS-4”, Appl. Phys. Let. ,90, 152101 2007.