Nanoscale Etching of Metallic Perovskites Using STM
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Nanoscale Etching of Metallic Perovskites Using STM Ø. Dahl1, S. Hallsteinsen2, J. K. Grepstad1, A. Borg2, and T. Tybell1 1 Department of Electronics and Telecommunication, Norwegian University of Science and Technology, N-7491 Trondheim, Norway 2 Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway ABSTRACT
In the present work we use a scanning tunneling microscope to modify the surface structure of epitaxial SrRuO3 thin films. Point and line etching experiments were carried out in ultra-high vacuum, using tungsten tips. The point etchings showed that pulses fired at small (< 4.5V) bias voltages did not bring about any physical modifications of the film surface, while voltages in excess of 4.5 V led to etched holes accompanied by mounds. Moreover, well-defined line etching was achieved with a typical depth of approximately two unit cells and linewidths as small as 5 nm. The experiments demonstrate that a scanning tunneling microscope can be used for nanometer-scale patterning of SrRuO3 thin film surfaces. INTRODUCTION
The persistent miniaturization of microelectronics makes lithography on the nanometer length scale an important challenge both with regard to continuous downscaling of classical topdown processes such as standard UV and e-beam lithography and to the development of novel bottom-up techniques based on nanometer-scale structured templates. Scanning probes offer the possibility to achieve surface modifications at the atomic level [1], and successful etching has been achieved in a variety of materials ranging from semiconductors [1] to high-temperature superconductors [2]. Based on such scanning probe techniques, devices such as single electron transistors [3] have been successfully realized. For electronic materials sensitive to composition and doping, such as the high-temperature superconductors and colossal magnetoresistors [4], scaling down the classical top-down processes to nanometer dimensions may adversely affect the physical properties of the mesastructures due to e.g. oxygen diffusion and a large surface-to-volume ratio. The development of nanoscale-engineered templates for the direct growth of epitaxial perovskite nanostructures is an exciting possibility in this context. In this paper, we report on using a scanning tunneling microscope (STM) to etch thin films of the metallic perovskite SrRuO3 (SRO), a chemically inert material [5] well lattice-matched for epitaxial growth of a number of perovskites and perovskite-related materials. The etching is performed in ultra-high vacuum (UHV), which makes this a promising technique for patterning of the above mentioned templates. We demonstrate the feasibility of structuring the SRO film surface, routinely etching lines with a controlled linewidth of 5 nm. Moreover, we present
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detailed data on the effects of writing voltage, tip-sample distance, and pulse length in this etching of epitaxial SRO thin films.
EXPERIMENTAL DETAILS
The samples investigated were ~500Å thin films of (110)-oriente
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