Super High-<i>k</i> Unit-Cell-Thick α-CaCr<sub>2</sub>O<sub>4</sub> Crystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 39466643.
- Also identified by DOI 10.1021/acsnano.4c07032.
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Abstract
High-dielectric-constant (high-<i>k</i>) insulators are indispensable components to integrate semiconductors into metal-oxide-semiconductor field-effect transistors with sub-10 nm channel length, where the equivalent oxide thickness (EOT) of high-<i>k</i> insulator needs to be decreased to subnanometer scale. The traditional insulators, including Al<sub>2</sub>O<sub>3</sub>, SiO<sub>2</sub>, and HfO<sub>2</sub>, fit well with the existing silicon industry but suffer from serious degeneration of insulating properties, such as large leakage currents caused by high-density borders and interface traps, when their thicknesses are reduced to a few nanometers. Here, we synthesize a high-quality nonlayered ultrathin α-CaCr<sub>2</sub>O<sub>4</sub> crystal down to unit-cell thickness (∼1.2 nm) by an elements slow-supply chemical vapor deposition (CVD) method. The unit-cell-thick α-CaCr<sub>2</sub>O<sub>4</sub> crystals show a super high dielectric constant of 87.34, which is over 20 times higher than that of well-known layered insulator <i>h</i>-BN and corresponds to an EOT below 1 nm. Furthermore, it has a high breaking strength (39 GPa) and excellent stability. This strategy can also be used to fabricate other ultrathin ternary oxides, such as high-<i>k</i> ultrathin FeNb<sub>2</sub>O<sub>6</sub> crystals, demonstrating the universality of the CVD method.