Process temperature-dependent interface quality and Maxwell–Wagner interfacial polarization in atomic layer deposited Al₂O₃/TiO₂ nanolaminates for energy storage applications

Abstract

Considering excellent tunability of electrical and dielectric properties in binary metal oxide based multi-layered nanolaminate structures, a thermal atomic layer deposition system is carefully optimized towards the synthesis of device...

Alumina-Titania Nanolaminate Condensers for Hot Programmable Catalysis

“…Despite the complexity of their deconvolution, the binding energies for both peaks do shift slightly to higher energies as the deposition temperature increases. Since the binding energies for Ti 3+ are lower (2p 3/2 : 458.07 eV, 2p 1/2 : 463.70 eV) than for Ti 4+ (2i 3/2 : 459.39 eV, 2p 1/2 : 465.17 eV), [21] the shift suggests a higher concentration of Ti 3+ and corresponding oxygen vacancies when deposition is conducted at higher temperatures. Therefore, the XPS result is consistent with the larger capacitance at higher deposition temperatures, due to a higher defect concentration in the TiO 2 sublayers.…”

“…Alternatively, nanolaminate films consisting of alternating amorphous, sub-nanometer titania and alumina layers have been fabricated via atomic layer deposition or pulsed layer deposition, resulting in composite films with dielectric constants of 100 to 1,000, [10,11,12] that have been extensively evaluated. [13,14,15,16,17,18,19,20,21] The high dielectric constants of alumina-titania nanolaminates (ATO) are attributed to the presence of oxygen vacancies in TiO 2 and charge accumulation at the interface of the alternating Al 2 O 3 and TiO 2 layers due to their different conductivities, an effect known as Maxwell-Wagner relaxation. [10,11,12] This dielectric mechanism resembles the internal barrier layer capacitor structure in CaCu 3 Ti 4 O 12 ceramics, where the high capacitance arises from grain boundaries rather than the intrinsic properties of the material.…”

Versatile Landscape of Low-k Polyimide: Theories, Synthesis, Synergistic Properties, and Industrial Integration

“…Because there are numerous phase interfaces, defects, and cracks inside the composite material, substantial charge will be concentrated at the interface in the electric field, forming a macroscopic dipole moment to produce interfacial polarization . Particularly, the interfacial polarization intensity of dielectric materials containing conductive fillers is much higher than other polarization types. − The researchers realized early on the significant influence of P int on the dielectric properties of materials. , Currently, one of the most prominent models for analyzing interfacial polarization is the Maxwell–Wagner double-layer dielectric capacitor model. , The model is composed primarily of two parallel dielectric films. The charge polarization at the interface is mainly due to the spatial discontinuity of the permittivity and conductivity, which causes charge redistribution in space.…”

Tunable Nanobattery Effect and Negative Differential Resistance Characteristics in Interfacial Polarization-Dominated Al2O3/TiO2 Nanolaminates

“…From these measured spectra, depicted in Figure 2a−c, the high-frequency shift of the curves with an increase in temperature and the shrinkage of high-k plateau with decreasing t s indicate a strong correlation between the temperature and frequency behavior of the dielectric parameters, which can be exclusively described by the activation energy (E a ) of the charge carriers. 10,12 At the M−W relaxation peak position (H; i.e., f = f p ), the relaxation time for interface charge carriers is known to follow the Arrhenius relationship and take the form 13…”

“…Interestingly, when t s is reduced from 1.41 to 0.48 nm, an increasing trend of E a values, from 0.34 to 0.47 eV, is observed, which is in the range of the ion-jumping activation energy (0.2−1 eV) and close to the polaron relaxation processes observed in M−W interfacial-polarization-dominated materials. 10,14 The mechanism underlying this abnormal trend of E a in these NLs is supposed to arise from the characteristics of major polarization charge carriers, i.e., electrons, because their tiny masses make them sensitive to the quantum size effects. In the case of ATA NLs, the large conduction band offset across Al 2 O 3 /TiO 2 interfaces can lead to a potential well structure, where the titania and alumina sublayers act as quantum wells (QWs) and barrier layers, respectively.…”