Dielectric Properties Of Thin Films Research Articles

Optical, structural, and vibrational properties of In2S3 thin films by sputtering-RF for applications in optoelectronics devices

Abstract Experimental results on the crystalline orientation properties, energy band gap, and Raman vibrational modes of Indium Sulfide (In2S3) thin films grown by Sputtering in Radio Frequency mode are presented. The In2S3 thin films were grown at 25, 200, and 300°C; thereafter the samples were thermally annealed in air for 30 min at 450°C, in order to improve their crystalline and physical properties. Energy dispersive X-ray spectroscopy results showed that the β-In2S3 crystallographic phase became predominant as the substrate temperature increased. For the optical transmittance spectra, it was observed that the deposited In2S3 thin films at 300°C and with thermal annealing showed an increase in their band gap energy of nearly 60 meV. The direct energy band gap of In2S3 films varied in the range of 2.76–2.82 eV. The scanning electron microcopy image and elemental analysis shows a better morphology, and an increase in O and Sn when the In2S3 samples were subjected to thermal annealed and the substrate temperature increased, respectively. Photoluminescence spectra were obtained at room temperature and showed two emission bands around 1.75 (709 nm) and 2.35 eV (527 nm), one related to interstitial indium donor sites (Ini) and oxygen acceptor vacancies (OVs), and the second to an emission band corresponding to the transition sulfur donor-indium acceptor. As the substrate temperature increased and thermal annealing of In2S3 was performed, the 1.75 eV emission bands increased in intensity with respect to the 2.35 eV band. From the Raman measurements, it was observed that the vibrational peaks were better defined as the substrate temperature increased and In2S3 underwent thermal annealing. In addition, to study the spinel-like defect structure, the peaks corresponding to the five main vibrational modes of In2S3 were identified as the Alg mode, Eg mode, and three modes of the F2g.

In2S3 thin films with potential use as window layers in photovoltaic devices

In this study, we use the Haacke’s figure of Merit (FOMH) as a valuable parameter for determining suitable Indium Sulphide thin films among a set of samples processed with different deposition parameters, in order to use them as window layers in the usual configuration of photovoltaic devices. Two sets of In2S3 thin films were deposited by radiofrequency (RF) magnetron sputtering technique with an average thickness around 90 nm and using different deposition parameters. One set of samples was processed using different RF power in the range of 75–250 W at room temperature, the second set was obtained using different substrate temperatures 24 °C–350 °C keeping a constant RF power at 75 W. The FOMH consider optical and electrical properties of In2S3 thin films in order to evaluate the feasibility of the thin film to be used as a window layer in photovoltaics devices. The In2S3 thin films processed by RF-Sputtering were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Ultraviolet-Visible spectroscopy, Raman spectroscopy, x-ray diffraction (XRD) and four-probe method. The In2S3 thin films had a high optical transmittance of 84% and the energy band gap values of the films decreased from 2.48 to 2.38 with the increase in substrate temperature and deposition power. The estimated grain size decreasing from 65 to 45 nm as the RF power increased. Additionally, the crystallinity of the selected In2S3 thin films was analyzed by Raman and XRD and showing that the cubic and tetragonal β-In2S3 phases can coexist in the films. The In2S3 thin films showed resistivity vales around Higher values of FOMH were obtained for In2S3 thin films processed at 75 W, 250 W, 100 °C and 300 °C, therefore these layer are feasible candidates to be used as window layers in photovoltaic devices.

In2S3 Thin Films via Open‐Air Chemical Vapor Deposition Using Indium‐Diethyldithiocarbamate: Deposition and Characterization

Cadmium‐free materials for the buffer layer of thin‐film solar cells and their low‐cost manufacturing methods have been of great interest in the solar industry. In this study, diindium trisulfide (In2S3) is investigated as an alternative buffer layer material: In2S3 thin film was deposited at atmospheric pressure utilizing open‐air chemical vapor deposition (CVD). Indium‐diethyldithiocarbamate (In‐DDTC) is used as the only solid precursor. The deposition conditions, crystal structure, optical properties, and electrical properties of In2S3 thin films are studied. The solid source temperature is found to affect the morphology, whereas the substrate temperature affected the growth rate and the sulfur‐to‐indium ratio of the films. X‐Ray diffraction and Raman scattering measurements suggested that the prepared films consist of β‐In2S3 and show a strong (103)‐plane orientation under suitable deposition conditions. The films exhibited indirect and direct transitions around 2.0 eV and 2.7–2.8 eV, respectively. The thin films showed n‐type conduction, with the lowest resistivity of 28.6 Ω cm. Overall, In2S3 thin films prepared via open‐air CVD are promising alternative buffer layer materials, which are expected to contribute to the realization of low‐cost and environmentally friendly thin‐film solar cells.

Variable Temperature Spectroscopic Ellipsometry as a Tool for Insight into the Optical Order in the P3HT:PC70BM and PC70BM Layers.

Two combined ellipsometric techniques-variable angle spectroscopic ellipsometry (VASE) and variable temperature spectroscopic ellipsometry (VTSE)-were used as tools to study the surface order and dielectric properties of thin films of a poly(3-hexylthiophene-2,5-diyl) (P3HT) mixture with a fullerene derivative (6,6-phenyl-C71-butyric acid methyl ester) (PC70BM). Under the influence of annealing, a layer of the ordered PC70BM phase was formed on the surface of the blend films. The dielectric function of the ordered PC70BM was determined for the first time and used in the ellipsometric modeling of the physical properties of the P3HT:PC70BM blend films, such as their dielectric function and thickness. The applied ellipsometric optical model of the polymer-fullerene blend treats the components of the blend as a mixture of optically ordered and disordered phases, using the effective medium approximation for this purpose. The results obtained using the constructed model showed that a layer of the ordered PC70BM phase was formed on the surface of the layer of the polymer and fullerene mixture. Namely, as a result of thermal annealing, the thickness of the layer of the ordered fullerene phase increased, while the thickness of the underlying material layer decreased.

Effect of different dopants on the structural and physical properties of In2S3 thin films: a review

Effect of different dopants on the structural and physical properties of In2S3 thin films: a review

Influence of La3+ doping on nebulizer spray pyrolysed In2S3 thin film for enhanced photodetector performance

In recent years, the photodetectors gained much attention due to their wide range of applications and fabrication of high-performance, cost-effective devices using environmentally friendly material is always challenging. In this work we report the fabrication of Lanthanum -doped indium sulfide thin films (In2S3:La) using a low-cost nebulizer spray pyrolysis method. La-doping concentration is varied from 0 to 5 wt% and the effect of doping on the properties of In2S3 thin films are investigated using X-ray diffraction (XRD), energy dispersive x-ray analysis (EDX), field emission scanning electron microscope (FESEM), UV–Vis spectroscopy, photoluminescence spectra. Incorporation of 3 wt% of La3+ in In2S3 lattice has substantially improved the crystallinity, surface morphology and optical properties of the thin films suitable for the device fabrication. Moderate doping of La3+ in the crystal lattice of β-In2S3 led to a red-shift in the absorption edge, which benefited utilization of wider light spectrum. Photodetectors are fabricated using In2S3:La (0–5 wt%) films and photodetector performance parameters are evaluated using I-V characteristics and current–time characterization. The In2S3 film with 3% La dopant concentration showed high photodetector performance with estimated detectivity (D*), photoresponsivity (R), and external quantum efficiency (EQE) of 1.11 × 1011 Jones, 5.05 × 10-1 AW−1, 118% respectively. For the same sample, the rise and fall time calculated from transient photo-response analysis is found to be 0.4 s and 0.3 s respectively. These optimally doped In2S3:La 3wt% thin film samples could be useful for the fabrication of photosensor based optoelectronic devices.

Influence of a thin dielectric layer on resonance frequencies of square SRR metasurface operating in THz band

Abstract This article investigates the effect of an additional thin dielectric layer on the top of the metasurface (MS), on the transmission of electromagnetic waves in the terahertz band. For this purpose, the split ring resonator-based MS was designed and analyzed in the terahertz band. The influence of permittivity, film thickness, and suspension height on S 21 transmission coefficient characteristics was studied. For this purpose, a numerical model was created and solved using the finite element method. The conducted study can be helpful in three cases. First, changing the suspension height of the dielectric layer may allow tunable MSs using MEMS structures. Also, this research can be used to determine the effect of applying an additional layer of protection when using the MS as a sensor to test substances that can damage it. In addition, there is an opportunity to study the dielectric properties of thin films using the proposed MS.

PVDF/RGO based piezoelectric nanocomposite films for enhanced mechanical and dielectric properties

Polymer nanocomposites are dominating today in the global scenario due to their diverse applications. The study involves the investigation of the role of Reduced graphene oxide (RGO) as nanofiller on mechanical and dielectric properties of Polyvinylidene difluoride (PVDF). Flexible piezoelectric thin films of PVDF loaded with RGO nanofillers were synthesized using a solvent casting technique. The crystal structure of neat PVDF and RGO loaded PVDF films were analysed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Tensile strength and Young’s modulus of polymer nanocomposite films were analysed by performing tensile testing on a universal testing machine (UTM). The results showed an improvement in elastic modulus up to a certain nanofiller percentage (2 wt% RGO). Measurement of dielectric properties of thin films was conducted using an impedance and material analyser (IMA). The dielectric constant of the film increases with increment in RGO loading. Thus, overall increment in piezoelectric properties take place. This nanocomposite can be used for developing flexible and highly sensitive sensors and actuators.

Chemical bath deposition of petal-shaped In2S3 microspheres and their photoelectrochemical properties

In this paper, In2S3 thin films were prepared by chemical bath deposition. The photoelectric properties of In2S3 thin films were optimized by controlling the amount of acetic acid. The structural characteristics of In2S3 were characterized by X-ray diffraction (XRD). The morphologies of In2S3 thin films were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The bandgaps of In2S3 thin films were measured by UV–Vis-NIR spectra. PEC measurements indicated that when 0.4 M CH3CO2H was added, the PEC property of In2S3 was the best, and highest photocurrent density was 41.93 μA/cm2.

Impact of annealing on electric and elastic properties of 10-nm Hf0.5Zr0.5O2 films prepared on Si by sputtering

HfO2-based films are important materials used in broad range of electronic applications from high-performance transistors and memory cells, to thermoelectric and energy harvesting elements. By employing scanning probe methods, we made nanoscale comparison of chemical composition, surface morphology, the elastic modulus and the surface potential of bare 10-nm thick Hf0.5Zr0.5O2 films prepared on Si by a carbon-free sputtering process. The composition mapping confirmed uniform distribution of Hf and Zr in the film along wafer size. Suppression of the monoclinic phase in films annealed at 600 - 800 °C had strong impact on spatial variations of film properties. Small surface roughness, large electric domain sizes (50–200 nm at 700 °C) and small fluctuations of the surface potential (40–50 meV) in Si coated with the films are appealing for gate-stack applications. Films annealed at 600-700 °C showed the elastic modulus of about 169 GPa and the ferroelectric polarization reversal at a field of ~1 MV/cm as observed by nanoscale poling with a Pt-coated scanning probe. In contrast, properties of films annealing at 800 °C were affected by growth of thick interfacial oxide layer. The presented nanoscale approach is beneficial in optimizing of physical and mechanical properties of thin dielectric films.

Impact of substrate temperature on structural, morphological and optical properties of In2S3 thin films deposited on ITO/glass substrate by spray pyrolysis technique

Impact of substrate temperature on structural, morphological and optical properties of In2S3 thin films deposited on ITO/glass substrate by spray pyrolysis technique

Effect of Substrate Nature on the Structural, Optical and Electrical Properties of In2S3 Thin Films

Effect of Substrate Nature on the Structural, Optical and Electrical Properties of In2S3 Thin Films

On the Integration of Dielectrometry into Electrochemical Impedance Spectroscopy to Obtain Characteristic Properties of a Dielectric Thin Film

AbstractWe demonstrate a novel impedimetric approach providing unprecedented insight into characteristic properties of dielectric thin films covering electrode surfaces. The concept is based on the joint interpretation of electrochemical impedance spectroscopy (EIS) together with dielectrometry (DEM) whose informative value is mutually interconnected. The advantage lies in the synergistic compensation of individual shortcomings adversely affecting conventional impedimetric analysis strategies relying exclusively on either DEM or the traditional EIS approach, which in turn allows a reliable determination of thickness and permittivity values. The versatility of the method proposed is showcased by an in‐situ growth‐monitoring of a nanoporous, crystalline thin film (HKUST‐1) on an interdigitated electrode geometry.

Enhanced Ferroelectric, Dielectric Properties of Fe-Doped PMN-PT Thin Films

Fe-doped 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT) thin films were grown in Pt/Ti/SiO2/Si substrate by a chemical solution deposition method. Effects of the annealing temperature and doping concentration on the crystallinity, microstructure, ferroelectric and dielectric properties of thin film were investigated. High (111) preferred orientation and density columnar structure were achieved in the 2% Fe-doped PMN-PT thin film annealed at 650 °C. The preferred orientation was transferred to a random orientation as the doping concentration increased. A 2% Fe-doped PMN-PT thin film showed the effectively reduced leakage current density, which was due to the fact that the oxygen vacancies were effectively restricted and a transition of Ti4+ to Ti3+ was prevented. The optimal ferroelectric properties of 2% Fe-doped PMN-PT thin film annealed at 650 °C were identified with slim polarization-applied field loops, high saturation polarization (Ps = 78.8 µC/cm2), remanent polarization (Pr = 23.1 µC/cm2) and low coercive voltage (Ec = 100 kV/cm). Moreover, the 2% Fe-doped PMN-PT thin film annealed at 650 °C showed an excellent dielectric performance with a high dielectric constant (εr ~1300 at 1 kHz).

Tunable TTB strontium and tantalum based thin films: Influence of the deposition parameters on the structural and dielectric properties

Structural and dielectric properties of thin films produced by reactive radiofrequency sputtering of a (Sr2Ta2O7)100-x (La2Ti2O7)x target with x = 1.65 were studied. The chemical composition characterization shows Sr/Ta ratios ranging between 0.49 and 0.56, thus pointing out the deposition of strontium deficient films, belonging to the tetragonal tungsten bronze family. The highest permittivities and tunabilities, associated with the lowest dielectric losses, are obtained when films are pure and fully textured. This is achieved for a 900 nm-thick film deposited at TS = 850 °C: ε’ = 116, tanδ = 0.007 and tunability T = 14.5% at 340 kV/cm and 100 kHz.

Experimental studies and new theoretical modeling on the properties of In2S3 thin films

Indium sulfide (In2S3) is a material extensively used as an alternative buffer layer to that of cadmium sulphide (CdS) for thin film photovoltaic applications. In this work, In2S3 thin films were obtained over SiO2 glass with various substrate temperatures (Ts) using the vacuum thermal evaporation method. The effect of Ts which varies from 25 °C to 300 °C on structural, optical and morphological homestead are reported and discussed here. Our deposited In2S3 films are typified via X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and UV–Vis–NIR spectroscopy. XRD analysis reveals the amorphous nature of all samples. AFM graphics reveals that the deposited layers are smooth along relatively high surface roughness. The UV–Vis–NIR spectra show a high transmittance for all samples ranging from 75% to 90%, over the region extending from the UV–Vis to the near-infrared. The evaluated optical band gap energy showed a decrease from 2.60 eV to 2.12 eV with increasing Ts, which might be attributed to the presence of high concentration of defects, in the compound band structure. These experimental data were confirmed by theoretical predictions obtained by transfer matrix method (TMM) simulations.

Exact statistical solution for the hopping transport of trapped charge via finite Markov jump processes

In this study, we developed a discrete theory of the charge transport in thin dielectric films by trapped electrons or holes, that is applicable both for the case of countable and a large number of traps. It was shown that Shockley–Read–Hall-like transport equations, which describe the 1D transport through dielectric layers, might incorrectly describe the charge flow through ultra-thin layers with a countable number of traps, taking into account the injection from and extraction to electrodes (contacts). A comparison with other theoretical models shows a good agreement. The developed model can be applied to one-, two- and three-dimensional systems. The model, formulated in a system of linear algebraic equations, can be implemented in the computational code using different optimized libraries. We demonstrated that analytical solutions can be found for stationary cases for any trap distribution and for the dynamics of system evolution for special cases. These solutions can be used to test the code and for studying the charge transport properties of thin dielectric films.

Structural and optical properties of In2S3 thin films deposited by sulfurization assisted thermal evaporation method

Indium sulfide (In 2 S 3 ) films were deposited onto soda lime glass by sulfurization assisted thermal evaporation method at different sulfurization temperatures. These films are further annealed for 1 hr at 300 °C. The structural, morphology and optical properties of these films are studied using x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray analysis (EDAX), Raman and UV–Visible spectroscopy. Low angle-XRD analysis revealed that all films are polycrystalline in nature and confirmed the formation of only cubic phase of In 2 S 3 . The FE-SEM and EDAX analysis revealed significant change in the film morphology and composition upon sulfurization and annealing temperature. UV–Visible spectroscopy analysis showed that all films have strong absorption in visible region of the spectrum. With increase in sulfurization and annealing temperature the band gap increases and is found in the range 1.57–2.12 eV. However, band gap of In 2 S 3 thin films deposited at different sulfurization temperature are higher than those obtained after annealing of films.

Tunable Dielectric and Thermal Properties of Oxide Dielectrics via Substrate Biasing in Plasma-Enhanced Atomic Layer Deposition.

The ability to control the properties of dielectric thin films on demand is of fundamental interest in nanoscale devices. Here, we modulate plasma characteristics at the surface of a substrate to tune both dielectric constant and thermal conductivity of amorphous thin films grown using plasma-enhanced atomic layer deposition. Specifically, we apply a substrate bias ranging from 0 to ∼117 V and demonstrate the systematic tunability of various material parameters of Al2O3. As a function of the substrate bias, we find a nonmonotonical evolution of intrinsic properties, including density, dielectric constant, and thermal conductivity. A key observation is that the maximum values in dielectric constant and effective thermal conductivity emerge at different substrate biases. The impact of density on both thermal conductivity and dielectric constant is further examined using a differential effective medium theory and the Clausius-Mossotti model, respectively. We find that the peak value in the dielectric constant deviates from the Clausius-Mossotti model, indicating the change of oxygen fraction in our thin films as a function of substrate bias. This finding suggests that the increased local strength of plasma sheath not only enhances material density but also controls the dynamics of microstructural defect formation beyond what is possible with conventional approaches. Based on our experimental observations and modeling, we further build a phenomenological relation between dielectric constant and thermal conductivity. Our results pave invaluable avenues for optimizing dielectric thin films at the atomic scale for a wide range of applications in nanoelectronics and energy devices.

Design and Optimization Methodology of Coplanar Waveguide Test Structures for Dielectric Characterization of Thin Films

This paper describes an accurate design method of coplanar waveguide (CPW) test structures on characterizing dielectric properties of thin films with arbitrary thickness. Current CPW measurement method has difficulty in providing accurate dielectric properties of films with extremely small thickness. To address this issue, an optimized algorithm is presented to generate proper geometric parameters of CPW test structures for films with different thickness. To validate the accuracy of the proposed design methodology, various test cases of CPW structures with different dimensions have been designed and implemented, the extracted dielectric properties (e.g., dielectric constant and loss tangent) from the S-parameters of the different test cases are compared to the benchmark results simulated by accurate electromagnetic tool Ansys HFSS. It demonstrates the efficacy of the proposed optimized method on quickly producing correct dimensions of CPW test lines for accurate properties characterization of thin films.