Helping circuits get enough oxygen

The microelectronics industry is on thin ice. There’s an oxygen-rich, insulating layer inside transistors that’s become dangerously thin as circuitry has shrunk. At risk is the steady pace of innovation that the industry has maintained for more than 40 years (SN: 3/25/00, p. 204: Looking for Mr. Goodoxide).

VACANT LOTS. A new electron microscopy method reveals an oxygen-deprived layer (top) in this strontium titanate sample. The yellow glow on and between ball-like strontium atoms shows where oxygen atoms are missing. Muller, et al./Nature

Seekers of alternative oxide layers have so far come up empty-handed. That’s because all of them, so far, have too many absent oxygen atoms. This can lead to unwanted charging of the material, says David A. Muller of Cornell University and Lucent Technologies’ Bell Labs in Murray Hill, N.J.

Now, Muller and his coworkers have devised an electron microscope technique capable of detecting even single missing oxygen atoms in nanoscale layers of the ceramic oxide strontium titanate. This could expedite the search for new oxides. In the past, oxide researchers have had to evaluate new candidate materials by incorporating them into transistors and testing those devices.

To develop the new technique, which is described in the Aug. 5 Nature, Muller and his coworkers grew strontium titanate layers with differing numbers of oxygen vacancies. Then, they spotted the voids by gauging the angles at which electrons ricocheted off atoms and how much energy electrons lost traversing the material.

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