Electron tunneling studies of Mn₁₂-Acetate /
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| Other Authors: | |
| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2008]
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Abstract: | We used self-assembling tunnel junctions (SATJs) to study the electron transport through films of the molecular magnets, Mn₁₂₋Acetate. Pulse laser deposition (PLD) was used to deposit two monolayers of Mn₁₂₋Acetate on thin Pt wires (diameter 0.001 in). The electron tunneling current was measured with typical bias voltages from -1 to 1 V at liquid helium temperature, 4.2 K. I, dI/dV , and d²I/dV² signals were directly acquired with the aid of a current amplifier and two lock-in-amplifiers. Results show that the differential conductance is approximately 10⁻⁶ S for bias voltages 0.04 V <̲ V <̲ 1 V and exhibits a strong voltage dependence. In the region V <̲ 0.04 V, we find a zero-bias feature (ZBF) in which the differential conductance is suppressed. In some samples, we observe I - V staircases which we attribute to electrons"hopping" between the electrodes and the molecules. The observed hysteresis was attributed to the slow relaxation of molecules re-orienting within the junction. Abrupt conductance jumps at a bias voltage of -0.12 V were also observed and may indicate state transitions in the Mn₁₂₋Acetate molecules. Furthermore, we observed that the zero bias feature (ZBF) can switch from an enhancement to a suppression of the differential conductance. A dip and dry (DAD) method was also used to form films of Mn₁₂₋Acetate on Al and Pt wires. Although the conductances were similar to those obtained using the PLD method, there were some subtle differences. In particular, we did not observe the I - V staircases and the state jumps were more ambiguous. The differential conductance for the Mn₁₂₋Acetate films on Al wires were typically 10⁻⁷ S, which we attributed to the oxide layer on Al surfaces. We have also found substantial changes in the I - V characteristics when the Pt wires coated with the Mn₁₂₋Acetate films were stored in 10⁻² Torr for 6 months. In particular, we observed many new features such as peaks in the conductance as a function as the bias voltage. We believe that these effects may be caused by the slow oxidation of the Mn₁₂₋Acetate molecules. |
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| Item Description: | "Major Subject: Physics" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Electronic resource. |
| Format: | Mode of access: World Wide Web. System requirements: World Wide Web access and Adobe Acrobat Reader. |
| Bibliography: | Includes bibliographical references. |