Dispersion Of Thin Films Research Articles

Surface Plasmon Resonance Spectrometer in the Double Prism Configuration: Fast Characterization of the Thickness and Dielectric Constant Dispersion of Thin Films

Surface Plasmon Resonance Spectrometer in the Double Prism Configuration: Fast Characterization of the Thickness and Dielectric Constant Dispersion of Thin Films

Confined magnon dispersion in ferromagnetic and antiferromagnetic thin films in a second quantization approach: The case of Fe and NiO

We present a methodology based on the calculation of the inelastic scattering from magnons via the spin-scattering function in confined geometries such as thin films using a second quantization formalism, for both ferromagnetic and antiferromagnetic materials. The case studies are chosen with an aim to demonstrate the effects of film thickness and crystal orientation on magnon modes, using bcc Fe(100) and NiO with (100) and (111) crystallographic orientations as prototypical systems. Due to the quantization of the quasimomentum, we observe a granularity in the inelastic spectra in the reciprocal space path reflecting the orientation of the thin film. This approach also allows for the capture of softer modes that appear due to the partial interaction of magnetic moments close to the surface in a thin film geometry, in addition to bulk modes. The softer modes are also affected by crystallographic orientation, as illustrated by the different surface-related peaks of the NiO magnon density of states at approximately ∼65meV for (100) and ∼42meV for a (111)-oriented film. Additionally, we explore the role of anisotropy, revealing that anisotropy increases the overall hardness of the magnon modes. The introduction of a surface anisotropy produces a shift of the surface-related magnon DOS peak to higher energies with increased surface anisotropy, and in some cases leads to a surface-confined mode. Published by the American Physical Society 2024

Electronic structure of the highly conductive perovskite oxide SrMoO3

We use angle-resolved photoemission to map the Fermi surface and quasiparticle dispersion of bulklike thin films of ${\mathrm{SrMoO}}_{3}$ grown by pulsed laser deposition. The electronic self-energy deduced from our data reveals weak to moderate correlations in ${\mathrm{SrMoO}}_{3}$, consistent with our observation of well-defined electronic states over the entire occupied bandwidth. We further introduce spectral function calculations that combine dynamical mean-field theory with an unfolding procedure of density functional calculations and demonstrate good agreement of this approach with our experiments.

Optical properties of LMBE grown c-axis oriented GaN thin films using Surface Plasmon Resonance technique

Present work reports the growth and optimisation of thin films of Gallium nitride (GaN) with preferred c-axis (0002) orientation on Si (111) substrate using the Laser Molecular Beam Epitaxy technique. For the development of optically efficient GaN thin film, the nitrogen gas flow during film deposition has been optimised and film properties are measured using the highly sensitive Surface Plasmon Resonance (SPR) technique in OTTO configuration. Structural, morphological and optical properties of the GaN thin films were studied using XRD, AFM, PL and FTIR spectroscopy. Varying the deposition gas flow from 1.3 sccm to 4 sccm led to a decrease in refractive index values from 2.77 to 2.21. By using the SPR technique, the refractive index (n) dispersion of GaN thin films was also analysed with the incident radiated wavelength.

Dielectric and ferroelectric properties of multilayer BaTiO3/NiFe2O4 thin films prepared by solution deposition technique

In this work different lead-free multilayered structures, composed of perovskite BaTiO3 and spinel NiFe2O4 thin layers, were obtained by solution deposition method. Structural characterization of the sintered thin films confirmed the well-defined layered structure with overall thickness from 160 to 600 nm, crystalline nature of perovskite BaTiO3 and spinel NiFe2O4 phases without secondary phases (after sintering below 900 °C) and grains on nanometer scale. Dielectric properties of the multiferroic multilayer BaTiO3/NiFe2O4 thin films were analyzed in temperature and frequency range from 30 °C to 200 °C and 100 Hz to 1 MHz, respectively. In comparison to the pure BaTiO3 films, the introduction of ferrite layer reduces dielectric response and increases low frequency permittivity dispersion of the multilayer thin films. The multilayer samples have shown relatively low dielectric loss with stronger contribution of conductivity at higher temperatures, and characteristic broad peak representing “relaxation” of the interface charge accumulation.

Taylor dispersion in thin liquid films of volatile mixtures: A quantitative model for Marangoni contraction

Marangoni contraction describes the apparent dewetting behavior of certain volatile mixtures from high-energy surfaces due to Marangoni flows. These flows also lead to strong mixing in the droplets. Here we demonstrate that this process is fully captured in the lubrication approximation if one accounts for Taylor dispersion. We derive the dimensionally reduced form of the advection-diffusion problem of bulk mixtures in thin films, showing that Taylor dispersion is required to establish consistent orders in the long-wave expansion.

Optical and microstructural characterization of nanocrystalline Cu doped ZnO diluted magnetic semiconductor thin film for optoelectronic applications

A series of Zn 1-x Cu x O nanocrystalline films were deposited on a silica substrate using e-beam evaporation technology. The physical properties of the deposited film were closely examined using x-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). The deposited film's structure revealed the formation of a hexagonal wurtzite structure, with no extra phases found. According to AFM analysis, the deposited Zn 1-x Cu x O (x = 0.0, 0.04, 0.08, 0.12, 0.16, and 0.2) film has nanocrystalline characteristics. The present findings show that increasing Cu content up to x ≤ 0.2 reduces the direct optical energy gap E g from 3.286 eV (x = 0) to 2.934 eV (x = 0.2), which can be attributed to the sp-d exchange coupling. The refractive index dispersion extracted from SE analysis for Cu-doped ZnO thin films increased as the Cu dopant increased. In addition, the refractive index dispersion of the deposited film was studied using a single oscillator model proposed by Wemple-DiDomenico (WDD). It was found that the oscillator energy E o decreases as the Cu concentration increases, while the dispersion energy E d increases. As a result of the improvement in the optical energy band gap and the tunability of the values of the dispersive oscillator parameters E o , E d , n 0 , ε 0 , M -1 , and M -3 with increasing Cu doping levels, Cu doped ZnO films are a good candidate for optoelectronic device applications. • E-beam techniques is used to deposit a series of thin film of Cu doped ZnO. • The deposited film's structure show the formation of a hexagonal wurtzite structure. • SE technique is used to obtained the direct energy gap and found that E g is reduced from 3.286eV to 2.934eV with Cu concentration increases from 0 up to 0.2. • The SE analysis reveal that refractive index dispersion of Cu-doped ZnO thin films has increased as the Cu dopant has increased.

Optical and electrical studies on MgTiO3– Ba5Nb4O15 composite thin films for integrated microwave circuit applications

A correlative study on optical and electrical properties of MgTiO3 (MTO) -Ba5Nb4O15 (BNO) composite thin films (MTBN) with respect to film thickness (260–450 nm) is reported. The optical bandgap energy of MTBN composite thin films (3.76 eV–3.65 eV) are found to be intermediate to MTO (3.44 eV) and BNO (3.85 eV) monoliths. Further, the optical dispersion in MTBN composite thin films can be defined by Cody-Lorentz dispersion law. Higher photoluminescence (PL) emission intensity and shorter carrier lifetime (0.8376 ns) ascribed to local symmetry break is observed for 450 nm film. Moreover, the Mott's variable range hopping mechanism was dominant conduction process in the MTBN composite films. Further, density of states near the Fermi level were found to be around 7.85×1018 eV−1cm−3 - 3.478×1019 eV−1cm−3 for 260 nm–450 nm MTBN films. The obtained optical and electrical properties prospect a potential application of the MTBN composite thin films in integrated microwave circuits.

Rayleigh analysis and dielectric dispersion in polycrystalline 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.2Ti0.8)O3 ferroelectric thin films by domain-wall pinning element modeling

We use impedance spectroscopy to investigate the dielectric response in polycrystalline, lead-free 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.2Ti0.8)O3 (BCZT) ferroelectric thin films as a function of amplitude E0 and frequency f of an applied ac electric field. Impedance spectra from f=10 Hz to 1 MHz were collected at different E0 on polycrystalline BCZT capacitor stacks, grown by pulsed laser deposition on platinized Si substrates and covered with Au electrodes. Deconvolution of the spectra is achieved by fitting the measured impedance to the impedance of an equivalent-circuit model of the capacitor stacks, including a recently proposed domain-wall pinning element ZDW. From an extended data analysis, we quantify the coupling strength between dielectric nonlinearity and frequency dispersion in the BCZT thin films, and we obtain a schematic diagram of the different domain-wall-motion regimes. Our results indicate that the presence of grain boundaries in BCZT reduces the coupling strength and suppresses the motion of internal domain-wall segments and also the irreversible center-of-mass motion of the domain walls.

Simultaneous normal – Anomalous dielectric dispersion and room temperature ferroelectricity in CBD perovskite BaTiO3 thin films

Chemical bath deposition (CBD) method, being an electroless technique, is used to prepare phase pure barium titanate (BaTiO3) thin films using glass as substrate. Molarity of the solution is varied from 0.1 to 1.2 M, whereas, solution temperature is kept constant at 78 °C. XRD analyses show formation of perovskite tetragonal phase of BaTiO3 at all the molarities when films are annealed at 300 °C. Strengthening in perovskite tetragonal phase is observed with increase in solution molarity. Ellipsometric results show high transmission (∼ 83 %) in the visible region for thin films prepared with 1.2 M solution. Variation in direct band gap, 3.31–3.61 eV, is observed for annealed thin films. High dielectric constant (∼ 539.26 at log f = 3) and low tangent loss is obtained for 1.2 M based thin films. Thin films prepared under all the conditions show normal and anomalous / U-shaped frequency dependent dielectric response (i.e. ∼ 2754.24 at log f = 1.5 and ∼ 2004.73 at log f = 7.5). Maximum spontaneous polarization of ∼ 14.78 μC/cm2 and remnant polarization of ∼ 6.94 μC/cm2 are observed for 1.2 M sample. It is important to mention here that U-shaped high dielectric and good ferroelectric properties of BaTiO3 are observed in current study with no change in perovskite structure of tetragonal phase making it a potential candidate for storage devices at low and high frequencies.

Influence of vacuum annealing on the dispersion of thin double niobium-copper films deposited onto oxide materials

The kinetics of dispersion of thin niobium-copper films deposited onto leucosapphire, alumina and zirconia ceramics and annealed in vacuum at temperatures up to 1100 °C with different exposition times at each temperature (from 5 up to 20 min) was studied. The double films consisted of two layers: the first metallization layer was 150 nm niobium nanofilm deposited onto the oxide surface, and the second copper layer 1,5 mm thick deposited over the first one as a solder was used for joining of metallized oxide samples. It was found that these films remain rather dense during heating up to 1050 °C; and after annealing at 1100 °C they decompose into individual fragments covering about 80% the area of the ceramic substrates even after annealing during 20 min. The kinetic curves for the dispersion of these films were plotted.

Optical Responses of Localized and Extended Modes in a Mesoporous Layer on Plasmonic Array to Isopropanol Vapor.

Mesoporous silica features open and accessible pores that can intake substances from the outside. The combination of mesoporous silica with plasmonic nanostructures represents an interesting platform for an optical sensor based on the dependence of plasmonic modes on the refractive index of the medium in which metallic nanoparticles are embedded. However, so far only a limited number of plasmonic nanostructures are combined with mesoporous silica, including random dispersion of metallic nanoparticles and flat metallic thin films. In this study, we make a mesoporous silica layer on an aluminum nanocylinder array. Such plasmonic arrangements support both localized surface plasmon resonances (LSPRs) and extended modes which are the result of the hybridization of LSPRs and photonic modes extending into the mesoporous layer. We investigate in situ optical reflectance of this system under controlled pressure of isopropanol vapor. Upon exposure, the capillary condensation in the mesopores results in a gradual spectral shift of the reflectance. Our analysis demonstrates that such shifts depend largely on the nature of the modes; that is, the extended modes show larger shifts compared to localized ones. Our materials represent a useful platform for the field of environmental sensing.

Dielectric dispersion and superior thermal characteristics in isotope-enriched hexagonal boron nitride thin films: evaluation as thermally self-dissipating dielectrics for GaN transistors

The isotope-enriched h-BN films exhibited a dielectrics dispersion with low dielectric loss, below 1.3%. Their optical band gaps depend on isotopic composition (5.54 to 5.79 eV). Thermal conductivity of pure B10/11N are enhanced by around 231%.

Kinetics of Dispersion During Annealing in Vacuum of Thin Double Nickel-Silver Films Deposited onto Oxide Materials

The kinetics of dispersion of thin nickel-silver films deposited onto alumina and zirconia ceramics and annealed in vacuum at temperatures up to 1000 °C with different exposition times at each temperature (from 5 up to 20 min) was studied. The double films consisted of two layers: the first metallization layer was 150 nm nickel nanofilm deposited onto the oxide surface, and the second silver layer 1.5 mm thick deposited over the first one as a solder was used for joining of metallized oxide samples. It was found that these films remain rather dense during short-term heating up to 900 °C; and, after annealing at 950 °C and 1000 °C, they decompose immediately into individual droplets covering more than half the area of the ceramic substrates. The kinetic curves for the dispersion of these films were plotted.

Dielectric dispersion in thin LiNbO3 films

The comparative study of dielectric dispersion in thin LiNbO3 films deposited by radio-frequency (RF) magnetron sputtering and laser ablation on Si substrates was carried out. It was found that the dielectric permittivity of the lithium niobate films prepared by the various methods had the significant dispersion due to the barrier effects arising at the ferroelectric/semiconductor interface. The structure of LiNbO3 films deposited by the laser ablation was more imperfective in a comparison to the LiNbO3 films deposited by the RF magnetron sputtering.

Effect of Heat Treatment on the Dispersion of the Magnetic Anisotropy of MnSb Nanoinclusions Embedded in Thin GaMnSb Films

We observed a temperature-controlled increase in the magnetic anisotropy and its dispersion in thin GaMnSb films with MnSb nanoinclusions obtained by pulsed laser deposition. The data of transmission electron microscopy indicate that in the samples, a transition of the crystalline structure of magnetic MnSb nanoinclusions from hexagonal (spatial group (sp. gr.) P63/mmc) to cubic (sp. gr. F-43m) takes place. Analysis of the temperature dependences of the magnetic moment m(T), measured using a SQUID magnetometer, obtained for both unannealed and annealed samples cooled in a zero magnetic field and a magnetic field of 10 kOe, indicates that this mechanism is not unique. In unannealed samples, the distribution of the magnetic anisotropy of MnSb nanoinclusions, determined from the dependences of m(T), is unimodal. In the annealed samples, the same dependence becomes multimodal. This means that several thermally activated processes occur in the samples during annealing, resulting in several “populations” of nanoinclusions present in the annealed thin films. The contribution to the increase in the magnetic anisotropy during annealing can result in the structural phase transition, the mismatch of the crystal lattices between MnSb and GaSb, an increase in the average volume of MnSb nanoinclusions, and a change in their stoichiometry.

Влияние термообработки на дисперсию магнитной анизотропии нановключений MnSb, внедренных в тонкие пленки GaMnSb

AbstractWe observed a temperature-controlled increase in the magnetic anisotropy and its dispersion in thin GaMnSb films with MnSb nanoinclusions obtained by pulsed laser deposition. The data of transmission electron microscopy indicate that in the samples, a transition of the crystalline structure of magnetic MnSb nanoinclusions from hexagonal (spatial group (sp. gr.) P 6_3/ mmc ) to cubic (sp. gr. F -43 m ) takes place. Analysis of the temperature dependences of the magnetic moment m ( T ), measured using a SQUID magnetometer, obtained for both unannealed and annealed samples cooled in a zero magnetic field and a magnetic field of 10 kOe, indicates that this mechanism is not unique. In unannealed samples, the distribution of the magnetic anisotropy of MnSb nanoinclusions, determined from the dependences of m ( T ), is unimodal. In the annealed samples, the same dependence becomes multimodal. This means that several thermally activated processes occur in the samples during annealing, resulting in several “populations” of nanoinclusions present in the annealed thin films. The contribution to the increase in the magnetic anisotropy during annealing can result in the structural phase transition, the mismatch of the crystal lattices between MnSb and GaSb, an increase in the average volume of MnSb nanoinclusions, and a change in their stoichiometry.

Magneto-optical study of anomalous magnetization reversal in the presence of anisotropy dispersion in CoPd thin films

Magneto-optical study of anomalous magnetization reversal in the presence of anisotropy dispersion in CoPd thin films

Analysis of Dispersion Characteristics of Rayleigh Waves in Nanostructured Thin Films

The present study aims to theoretically analyze the dispersion characteristics of Rayleigh waves and verify the results through experiments. Raleigh waves are generated by scanning acoustic microscope, which are used to evaluate the thickness of thin films and the material characteristics of the samples. The transfer matrix method was used in the theoretical analysis of Rayleigh wave dispersion in thin films with slow-on-fast and fast-on-slow structures. To verify the dispersion diagram derived from the analysis, the e-beam evaporation and plasma-enhanced chemical vapor deposition technique was applied to fabricate slow-on-fast and fast-on-slow thin films of varying thicknesses. Slow-on-fast structures were created by depositing nickel (Ni) films on silicon (Si) substrates; fast-on-slow structures were produced by depositing silicon nitride (Si₃N₄) on gallium arsenide (GaAs) substrates. The scanning acoustic microscope used V(z) curves to precisely measure the velocity of the Rayleigh waves. This was to evaluate their dispersion depending on the thickness of each film. A comparison of the measured velocities against the theoretical dispersion diagram resulted in an error rate of less than 6% in the slow-on-fast structure and less than 10% in the fast-on-slow structure. In conclusion, this study confirmed that the theoretically derived dispersion characteristics correspond well with those observed in actual thin films, thereby suggesting the potential use of theoretical dispersion diagrams in evaluating the thickness and material characteristics of thin films.

Influence of X-ray irradiation on the optical absorption edge and refractive index dispersion in Cu6PS5I-based thin films deposited using magnetron sputtering

Influence of X-ray irradiation on the optical absorption edge and refractive index dispersion in Cu6PS5I-based thin films deposited using magnetron sputtering