Applied Physics

Patterning at a Distance

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Science  13 Oct 2006:
Vol. 314, Issue 5797, pp. 225
DOI: 10.1126/science.314.5797.225a

Recent experimental work has shown that a metallic, quasi-two-dimensional electron gas (q2-DEG) can be formed at the interface region of two insulators such as LaAlO3 and SrTiO3 when the thickness of the upper LaAlO3 layer reaches a critical value of four unit cells. Because other high-mobility two-dimensional electron gases can be engineered to display a range of functional characteristics such as superconductivity, magnetism, and ferroelectric and multiferroic behavior at low temperature, there is interest in developing these oxide interfaces with the expectation of pushing such effects to higher temperature. However, because of the thinness of the upper oxide layer, conventional lithographic patterning techniques have proved detrimental to the interface properties.

Schneider et al. achieve the critical thickness by lithographically patterning the q2-DEG without exposing or damaging the interface region during the process. They begin by depositing a LaAlO3 layer thinner than the critical threshold onto a SrTiO3 substrate, creating a temporarily insulating interface. Next they use a liftoff technique to add a thick patterned amorphous overlayer. LaAlO3 height in the gaps of the amorphous layer is then increased above the critical thickness to produce a patterned, high-quality metallic q2-DEG at the buried interface. — ISO

Appl. Phys. Lett. 89, 122101 (2006).

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