UC Berkeley researchers conducted several experiments at Argonne
As electronic devicesare becoming smaller, the materials from which they are made must be thinner. So scientists are looking for materials that retain special electronic properties even when they are ultra-thin.
They pay special attention to ferroelectrics,which reduce the power consumed by ultra-small electronic devices. This is the electrical analogue of ferromagnets, a special class of materials in which some of the atoms are located off-center. Because of this, a spontaneous internal electrical charge or polarization occurs. It can change direction when scientists subject the material to external stress. This opens up new prospects for ultra-low-power microelectronics.
The problem is that conventional ferroelectricmaterials lose internal polarization below a few nanometers in thickness. This means they are incompatible with modern silicon technologies. This prevents the integration of ferroelectrics into microelectronics.
In a new study, scientists decidedproblem. They discovered stable ferroelectricity in an ultrathin layer of zirconium dioxide only half a nanometer thick. That's the size of a single atomic building block, about 200,000 times thinner than a human hair. The team grew this material directly on silicon. They discovered that ferroelectricity appears in zirconia—a typically non-ferroelectric material—when it becomes very thin, about 1-2 nanometers in thickness.
The researchers also switched the polarization toultra-thin material in both directions using a slight voltage. This is how they demonstrated the thinnest working memory ever created for silicon.
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On the cover: what a two-dimensional ferroelectric material might look like.
Credit: UC Berkeley/Suraj Cheema