Phonon Response in the Infrared Region to Thickness of Oxide Films Formed by Atomic Layer Deposition

Abstract

Experimental transmission infrared spectra of gamma-Al(2)O(3) and ZnO films are collected from heat-treated thin oxide films deposited with uniform thickness on Si(100) using atomic layer deposition. We show that the Berreman thickness, i.e. the upper limit for a linear relationship between oxide film thickness and phonon absorbance in the infrared region in transmission configuration, is a concept that applies to both transverse and longitudinal optical phonons. We find that for aluminum oxide films the Berreman thickness is 125 nm, and we estimate that it is around approximately 435 nm for zinc oxide films. Combining experiment and simulation, we also show that the Berreman thickness is the maximum distance allowed between interfaces for Snell's law and Fresnel's formulas to determine the optical properties in the infrared region and in transmission configuration for a layer system including an oxide film. Below the Berreman thickness, a Taylor series expansion of the absorbance coefficient determines the linear relationship between phonon absorbance and oxide film thickness t, so that as t --> 0 absorption A(p) is proportional to 4pi omega(ph)t, where omega(ph) indicates optical phonon frequency. Above the Berreman thickness, field boundary conditions at the air/oxide film interface effectively contribute with a single interface in explaining optical phonon absorbance. Preliminary infrared spectra in reflection configuration for gamma-Al(2)O(3)/Si(100) are discussed, and the obtained data support the conclusions reported for the transmission configuration.

Synthesis and Antibacterial Properties of ZnO:Ag Films Prepared from a TritonMR Containing Solution

“…These properties makes ZnO attractive in places where high hygiene it´s necessary [14]. Therefore, several methods were used to prepare ZnO films such as: radio frequency (RF) sputtering process [15], CVD methods [16], pulsed laser deposition [17], spray pyrolisis [18], atomic layer deposition [19], chemical bath deposition [20] or electrodeposition [ 21 ]. However, these techniques usually require expensive and complicated equipment setup.…”

Polariton Evaporation: The Blackbody Radiation Nature of the Low-Frequency Radiation Emitted by Radiative Polaritons to the Surrounding Space

“…Radiative polaritons (RPs) were discovered in the late sixties [1]- [3] and recently gained attention due to their ability to explain optical and thermal properties of thin oxide films or crystals [4]- [11]. Radiative polaritons form upon the absorption of photons from infrared (IR) radiation by phonons in thin oxide films or crystals.…”

Effects of Metallic, Semiconducting, and Insulating Substrates on the Coupling Involving Radiative Polaritons in Thin Oxide Films

“…The effects of the chemistry and conductivity of the oxide film substrate on the interaction between IR radiation and planar thin oxide films have been discussed in the literature only to a limited extent. Authors have studied films on metal substrates, [8][9][10][11][12][13] semiconducting substrates, [14][15][16][17][18][19] and insulating substrates. [20][21][22] A comparison of the effects of the conductivity of different metal substrates can also be found.…”