The work reported here demonstrates the feasibility of controlling the dielectric properties—high dielectric constant (k) and substantially extended relaxation frequency—of thin film nanolaminates (NLs) consisting of alternating TiOx and Al2O3 sublayers with various sublayer thicknesses grown by atomic layer deposition. For 150 nm thick TiOx/Al2O3 NLs with sub-nanometer thick sublayers, few Angstrom change in sublayer thickness dramatically increases relaxation cut-off frequency by more than 3 orders of magnitude with high dielectric constant (k > 800). This unusual phenomenon is discussed in the framework of two-phase Maxwell-Wagner relaxation.
We report on the fundamentals for the synthesis of Al2O3/TiOx nanolaminates (NLs) with an Al2O3 interfacial layer at the electrode/nanolaminate interface, resulting in exceptionally high dielectric constant (k > 550 up to 0.1 MHz), very low losses (tan δ ≤ 0.04 up to 10 kHz), and leakage current density (≤10−8 A/cm2 at 1.0 V). The high k is attributed to the Maxwell-Wagner relaxation between semiconducting TiOx and insulating Al2O3 nanolayers, while low losses and leakage current densities are due to blockage of charged carriers transport through the Al2O3 interfacial layer. Additionally, a high-capacitance capacitor based on the Al2O3/TiOx NL structure is demonstrated on 16 μm deep Si trenches, which can be used to enable the next generation of nanoscale energy storage and memory devices.
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