Condensed Matter Physics Seminar

2 p.m., Thursday, February 15, 2007
Room 1201, Physics Building

Controlled Fabrication and Imaging of Nano-Scale Devices

Douglas R. Strachan

(Departments of Physics & Astronomy and Materials Science & Engineering University of Pennsylvania)

Abstract: Molecular-scale three-terminal devices hold the potential for a wide range of electronic applications requiring new fundamental scientific understanding. One of the biggest challenges in developing molecular-scale devices is to fabricate precisely and monitor the formation of the nanometer-scale electrodes (nanogaps). Though techniques for controllably forming the required metallic nanogap tunnel-junctions and quantum point contacts (QPCs) have been developed over the last decade using mechanical break junctions, this earlier technique requires devices to be formed on flexible substrates, which is incompatible with device development. We have pioneered a technique for the controllable fabrication of nanogap junctions and QPCs on top of rigid supporting substrates (D. R. Strachan et al. Appl. Phys. Lett. 86, 043109 (2005)). Our technique employs an applied current with feedback to electromigrate and break down a nano-scale electrode to the quantum regime. Remarkably, this allows one to follow the electrode evolution into the quantum regime on a room temperature table-top setup -- showing conductance steps in multiples of 2e²/h, followed by a tunneling regime showing steps as the atoms are rearranged. We have extended this technique to permit the real-time high-resolution imaging of the nanogap formation in a transmission electron microscope (TEM). This TEM imaging allows us to monitor the dynamics of the device evolution, where the gaps remain ordered and clear of residue during the process. Our measurements have revealed the significant role of joule heating in the formation of electromigrated nanogaps and give important insight useful for nano-scale device development. I will finish by discussing our current progress towards utilizing our electrodes in device construction. Our advances in simultaneously controlling and imaging electromigrated nanogaps should have far reaching applications in the design and study of these extremely small devices.

Host: Anlage
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