Optical Properties Of Multilayer Films Research Articles

Influence of point defects on phase transformation and optical properties of TiO2 thin films via multilayering deposition technique

Thin anatase TiO2 films with preferential (004) orientation were successfully fabricated via multilayering technique, growth and stop repeatedly, using DC-magnetron sputtering and annealed at a relatively low temperature. The multilayering deposition technique suppressed the number of oxygen vacancy defects in TiO2 films without interrupting the columnar growth. The main columnar structure oriented along (101) plane and along (004) plane. Confirmed by the texture coefficient, the preferential (004) orientation of TiO2 films increased with increasing number of compact layers and the highest value was observed for post-annealed films at 200 °C. The surface morphology analysis indicated that the increase of surface roughness with increasing number of compact layers was related to the promotion of crystallization. The optical properties of multilayer films revealed that high number of compact layers greatly enhanced their absorption in the entire visible region, expanded energy band gap and increased refractive index.

Cover Feature: Steady‐State and Time‐Resolved Optical Properties of Multilayer Film of Titanium Dioxide Sandwiched by Gold Nanoparticles and Gold Thin Film (ChemNanoMat 8/2019)

Cover Feature: Steady‐State and Time‐Resolved Optical Properties of Multilayer Film of Titanium Dioxide Sandwiched by Gold Nanoparticles and Gold Thin Film (ChemNanoMat 8/2019)

Steady‐State and Time‐Resolved Optical Properties of Multilayer Film of Titanium Dioxide Sandwiched by Gold Nanoparticles and Gold Thin Film

AbstractWe proposed metal‐insulator (MI) and metal‐insulator‐metal (MIM) structures of titanium dioxide (TiO2) sandwiched by gold nanoparticles (AuNPs) layer and gold sputtered thin film (only for the MIM film) to couple localized plasmon mode of AuNP with multi‐reflection mode and/or cavity resonator mode of TiO2. The optical extinctions of MI and MIM with differing TiO2 thickness were studied theoretically by finite‐element method simulation and experimentally by optical spectrometry. The extinction peaks of MI and MIM shifted by exchanging the surrounding medium from air to TiO2. The interference of TiO2 in MI structure also affected the extinction spectra showing the oscillation along the spectrum of AuNP in TiO2. Then, the extinction degree of MIM was higher than that of MI because of the coupling between cavity resonance mode with localized plasmon mode and interband transition in AuNPs. In addition, the cross section of MI and MIM films were observed by scanning electron microscopy. The surface of thinner film was rough because TiO2 heterogeneously grew from AuNP. The irregular growth of TiO2 might have induced the wide‐range extinction in 300–2500 nm after Au thin film deposition. The transient absorption spectra using a femtosecond laser were also carried out under the condition of 800 nm for excitation laser and 950 nm for probe laser. The long‐lived electron (∼1 ns) was observed in thick MIM film as a result of hot electron transfer from the gold nanostructure in the film.

Optical properties of multilayer films of nanocomposites based on WS2 nanotubes decorated with gold nanoparticles

Multilayer films of WS2 nanotubes decorated with gold nanoparticles are prepared for the first time using nanocomposite assemblage on the water-heptane interface and film transition onto optically transparent or semiconducting surfaces. The film morphology resembles a mosaic structure of 10-25 square micron areas with in-plane textured nanotubes. Optical properties demonstrate several features around 490, 545, and 675 nm connected either with excitonic transitions or scattering guided by high anisotropy of the nanotubes and their texturing peculiarities in the films.

Characterization of SnO2/Cu/SnO2 multilayers for high performance transparent conducting electrodes

In order to improve the transparency and durability of the Cu films, SnO2/Cu/SnO2 layered composite structures have been investigated. The SnO2/Cu/SnO2 multilayer films have much lower sheet resistance compared with a single-layered SnO2 film. In our work, SnO2/Cu/SnO2 multilayer films were deposited on quartz glass substrates by RF and DC magnetron sputtering. We investigated the structural, electrical and optical properties of multilayer films at various Cu thicknesses and substrate temperatures. The highest conductivity of multilayer films was obtained with a carrier concentration of 2.3×1022cm−3 and a resistivity of 6.5×10−5Ω·cm at the optimum copper layer thickness and substrate temperature. The peak transmittance, photopic averaged transmittance, and figure of merit are 80%, 72%, and 8.3×10−3Ω−1, respectively.

Orientation, mechanical, and optical properties of poly (lactic acid) nanoclay composite films

AbstractIn this study, the orientation, mechanical as well as the optical properties of multilayer films of nanoclay filled poly (lactic acid) (PLA) as the core layer and polyethylene (PE) as the skin layer obtained from the film blowing process were investigated. The effect of nanoclay content in the range of 1–7.5 wt% was considered. The orientation of the polymers crystal unit cells, alignment of clay platelets as well as the extent of intercalation and exfoliation were studied using wide angle X‐ray diffraction (WAXD). The measurement of d‐spacing of the 001 plane (normal to platelets plane) of the clay tactoids indicated intercalation of the silicate layers in the PLA nanocomposite multilayer films. The Young modulus and tear resistance along the machine and transverse directions (MD and TD, respectively) improved significantly with the presence of the nanoparticles and percentage of nanofiller studied. The haze of the nanocomposite films decreased with clay concentration up to 5 wt% and increased by further addition of the nanoclay. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Optical properties of multilayer structures

The possibility of using the ellipsometry method for investigation of the optical properties of multilayer films and structures is shown. The optical properties of structures HfO2/SiO2/Si, HfO2/Si, ZrO2/Si, Ta2O5/Si, and Al2O3/Si are studied. It is found that a layer of hafnium silicate is formed at the interface between the HfO2 film and Si. Annealing of the structures in oxygen shows that oxides studied are oxygen-permeable and that the thickness of SiO2 at the film-substrate interface increases. The growth rate of SiO2 layers depends on the chemical nature of an oxide. Al2O3 films are impermeable for oxygen diffusion. The production of layers of alloys (Al2O3) x (HfO2)1 − x is optimized, which allows one to obtain layers with a homogeneous distribution of elements over the thickness.

Fabrication of Antireflective Films Composed of High and Low Refractive Index Layers Using Layer-by-Layer Self-Assembly Method

We introduce a novel and versatile approach for controlling anti-reflective (AR) properties of multilayer films based on layer-by-layer (LbL) self-assembly (SA) method. For the fabrication of these films, blend (i.e., mixed) layers containing both polyanions (i.e., titanium precursor (TALH) and poly(sodium 4-styrenesulfonate) (PSS)) were assembled with polycation (i.e., poly(diallyldimethylammonium chloride) (PDAD)) for the formation of the high refractive index multilayers and on the other hand, the negatively charged silica particles with the diameter of about 100 nm were employed for low refractive index layer. The refractive index of TALH:PSS/PDAD multilayer was controlled by blending ratio and annealing temperature as TALH has the relatively high refractive index (n = 1.68) in comparison with that (n = 1.46) of conventional polyelectrolytes (PEs) at room temperature and furthermore these titanium precursors are partially changed into TiO2 with relatively high refractive indices (n = 1.50 ~ 1.81) at annealing temperature of 250 oC. In the case of silica particle layer used for low refractive index layer, the calculated refractive index was about 1.35 due to much vacancy among the adsorbed silica colloids although the inherent refractive index of silica material is about 1.45. As a result, the films composed of TALH:PSS/PDAD multilayers with tunable refractive index and silica colloidal layer can easily modulate the optical properties of multilayer films by blending ratio and heat treatment.

IMD—Software for modeling the optical properties of multilayer films

A computer program called IMD is described. IMD is used for modeling the optical properties (reflectance, transmittance, electric-field intensities, etc.) of multilayer films, i.e., films consisting of any number of layers of any thickness. IMD includes a full graphical user interface and affords modeling with up to eight simultaneous independent variables, as well as parameter estimation (including confidence interval generation) using nonlinear, least-squares curve fitting to user-supplied experimental optical data. The computation methods and user interface are described, and numerous examples are presented that illustrate some of IMD’s unique modeling, fitting, and visualization capabilities. © 1998 American Institute of Physics.

Optical properties of metallic multilayer films

Optical properties of multilayer films consisting of alternating layers of two different metals are studied on the basis of the Maxwell equations and the Boltzmann transport theory. The influence of free-electron scattering at the film external surface and at the interfaces is taken into account and considered as a function of the electromagnetic-field frequency and the structure modulation wavelength. Derived formulas for optical coefficients are valid at low frequencies, where the skin effect is nearly classical, as well as in the near-infrared, visible, and ultraviolet spectral ranges, where the skin effect has an anomalous nature. It is shown that the obtained results are apparently dependent on the values of scattering parameters. Also, the oscillatory nature of analyzed spectra is observed, where the two oscillation periods may appear on certain conditions. The oscillations result from the electron surface and interface scattering and their amplitudes and periods depend on the boundary conditions for free-electron scattering. Finally, an application of the interference phenomenon in dielectric layers is proposed to enhance nondistinct features, which can appear in optical spectra of metallic films.

Optical properties of amorphous multilayers a-Si:H/a-Si 3N 4:H with random well or barrier layer

The optical properties of multilayer films a-Si:H/a-Si 3N 4:H in which the thickness of well or barrier layers are randomly distributed have been studied. The reflectance anomaly observed in random multilayers with well layers thickness distribution disappear when the total film thickness become close to wavelength corresponding to a reflectance anomaly peak. The irregularity of the interference patterns in reflectance and transmittance spectra and the reflectance anomaly are also observed for random multilayers with barrier layers thickness distribution.

Optical properties of amorphous semiconductor multilayer films with random-thickness well layers

Abstract The optical properties of multilayer films in which the thicknesses of the well layers are randomly distributed have been studied. Two effects associated with randomness were observed in the optical spectra of these films. One of these is a distortion of the interference patterns in reflectance and transmittance spectra, and the other is a unique disorder-related reflection peak. The effects are discussed briefly.

Spectral selectivity of Al 2O 3-Cu-Al 2O 3 multilayer films

The optical properties of Al 2O 3/Cu/Al 2O 3 films are reported for different angles of incidence of light in the wavelength range 900-190 nm. The multilayer films exhibit > 90% reflectance in the wavelength range 900-600 nm and low visible transmittance (< 48%). The annealed films exhibit greater reflectance compared to unannealed films, and tend to be more stable on exposure to atmospheric conditions. The effect of diposition parameters on the optical properties of multilayer films is briefly reported.

Diffusion of miscible polymers in multilayer films

AbstractThermal and optical properties of multilayer films of miscible polyethyloxazoline (PEOx) and poly(styrene‐co‐acrylonitrile) have been studied as a function of time and temperature. Differential scanning calorimetry showed that the distinct, characteristic Tg's of the component polymers of the original films disappear after only short heating periods above Tg, and a single transition appears. The new transition region is broad at first, but narrows on subsequent heating. The measurement of light transmittance as a function of wavelength through the heat‐treated films also confirms the diffusion of the miscible polymers and gives results which are comparable to the thermal measurements. Films from immiscible polymers of polystyrene and PEOx retain their properties after various heat treatments. A qualitative discussion of the diffusion process as examined by the thermal measurements is presented.