Structure Of Thin Films Research Articles

Tin doped ZnFe2O4 thin film based ethanol sensor

In this work, tin doped ZnFe2O4 film was deposited onto microscope glass substrates by spray pyrolysis process followed by subsequent calcinations. The morphology and structure of the as-prepared thin films have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Temperature dependent current measurements were performed by two-probe method to analyze electrical properties, and electrical conductivity at room temperature. The effect of the tin component in ZnFe2O4 thin films on the gas sensing properties has been evaluated by the responses to ethanol vapor. The results have showed that the ZnFe2O4 thin films containing 2.5 wt% tin exhibit the best sensing properties to ethanol vapor. The response and recovery time are about 10 and 24 s, respectively. In addition, the as-prepared sensors exhibit excellent selectivity and stability. These results indicate that tin doped ZnFe2O4 thin films can be used in fabricating high performance gas sensors.

Structure and Thermal Conductivity of Thin Films of the Si$${}_{{1-x}}$$Ge$${}_{{x}}$$ Alloy Formed by Electrochemical Deposition of Germanium into Porous Silicon

Structure and Thermal Conductivity of Thin Films of the Si$${}_{{1-x}}$$Ge$${}_{{x}}$$ Alloy Formed by Electrochemical Deposition of Germanium into Porous Silicon

Structural and optical characteristics of Cu-doped CdS composite thin films

In this paper spin-coating method is used to create copper doped CdS composite thin films on glass substrates. Prepared Cux (CdS)1-x composite thin films, where x=1, 3 and 5 wt% Cu doped, have been characterised using an X-ray Diffractometer (XRD), scanning electron microscope (SEM) and UV-Visible spectrometer. These measurements provide the structural, morphological and optical properties of both pure and Cu doped CdS. The XRD pattern was used to examine the crystal structure and grain size of the CdS thin film. The optical spectra show absorption and band gap values of prepared samples. The band gap values have been found between 2.41 to 1.71. The photoluminescence (PL) spect rum emitted a strong peak approximately 430 nm which shows better optical quality for many applications.

Hydrogen Influence on Electrical and Photoelectrical Properties of InP/Pd Thin-Film Structures Obtained by Sol-Gel Method

Hydrogen Influence on Electrical and Photoelectrical Properties of InP/Pd Thin-Film Structures Obtained by Sol-Gel Method

Comparative investigation of the structure and mechanical properties of AlCrN and AlCrVYN thin films deposited by dcMS, HiPIMS, and hybrid dcMS/HiPIMS

AlCrN and AlCrVYN thin films were deposited by physical vapor deposition using dcMS, HiPIMS and hybrid dcMS/HiPIMS processes. Although all the thin films were produced using the same time-average power and show only slight differences in the chemical composition, significant differences regarding their structure, morphology, and mechanical properties were identified. Both dcMS-AlCrN and dcMS-AlCrVYN thin films show a column-like structure of sharply defined grains with large crystallites having size of 168 nm and 133 nm and exhibit a low hardness of (6.7 ± 1.3) GPa and (8.9 ± 1.0) GPa, respectively. In contrast, HiPIMS thin films, despite their lower deposition rate (especially evident in HiPIMS-AlCrVYN, which exhibited the lowest deposition rate among all examined films), show a denser structure predominantly composed of fcc-CrN and, in the case of HiPIMS- and dcMS/HiPIMS-AlCrN, small amounts of hcp-AlN. Consequently, the HiPIMS-AlCrN and HiPIMS-AlCrVYN thin films showed higher hardness values of 28.0 ± 2.1 GPa and 30.7 ± 1.9 GPa, respectively. Combining the two methods by using one cathode in dcMS mode and one in HiPIMS mode results in films with similar hardness values (26.9 ± 1.6 GPa for AlCrN and 28.7 ± 2.2 GPa for AlCrVYN) and morphologies comparable to the pure HiPIMS thin films, but with an increase in the deposition rate. This demonstrates the advantage of combining the two methods, especially for the AlCrVYN thin film production. In comparison to AlCrN, the AlCrVYN thin films generally exhibit higher hardness demonstrating the advantage of adding larger atoms into the thin film structure.

Study on the effect of sputtering pressure on the physical properties of InN films on ITO substrate and the dependence of carrier transport characteristics of Li-doped p-NiO/n-InN heterojunction on the environmental temperature

The exceptional performance of ITO substrate has made it possible to use indium nitride (InN) material in a variety of applications. The combination of lithium-doped NiO and n-type InN in a heterojunction shows great potential as a material for optoelectronic devices. This study investigates the influence of sputtering pressure on the crystal structure, surface morphology, optical properties, and electrical characteristics of InN thin films prepared on ITO substrates through magnetron sputtering. The research findings indicate that the InN films grow preferentially along the (002) crystal plane, with the best crystalline quality observed under a sputtering pressure of 1.5 Pa. Subsequently, the changes in the optical bandgap, transmittance, and reflectance of the InN films with varying sputtering pressure were discussed. The study also discusses a comprehensive analysis of the trends in the electrical characteristics of the InN films with sputtering pressure and environmental temperature, demonstrating their excellent thermal stability at high temperatures. Additionally, Li-doped p-NiO/n-InN heterojunction devices were fabricated and analyzed to determine the influence of environmental temperature on the carrier transport characteristics of the devices, revealing their favorable electrical properties at different temperatures. This research enriches the field of InN material studies and opens up new prospects for the performance and practical applications of InN optoelectronic devices.

A thin film resistive humidity sensor based on polymer and carbon black nanoparticle composites

This paper proposes a resistive humidity sensor that uses a carbon-black and polyvinyl alcohol composites thin film, fabricated with a unique film coating method for thinner thickness and higher sensitivity. Improving the sensitivity of sensing films is still of great importance in the research field of gas sensors. The humidity sensor devices with thin composite film and microelectrode structure are fabricated on the glass substrate for a low cost and a simple fabrication process. The sensor gives a rapid response for humidity levels from 10.9% relative humidity (RH) to 73.7% RH, and the response time is about 5.77 s. Experimental results reveal that the sensor has good sensitivity, reproducibility, fast reaction time, and wide range. In addition to humidity, the sensor also responds well to gases such as ethanol. The proposed gas sensor in this paper can be applied to the other combinations of polymers and nanoparticles to form new gas sensors, which have the potential to be used as a gas sensor array for detecting the composition of complex gases such as volatile organic components.

Role of a capping layer on the crystalline structure of Sn thin films grown at cryogenic temperatures on InSb substrates

Metal deposition with cryogenic cooling is a common technique in the condensed matter community for producing ultra-thin epitaxial superconducting layers on semiconductors. However, a significant challenge arises when these films return to room temperature, as they tend to undergo dewetting. This issue can be mitigated by capping the films with an amorphous layer. In this study, we investigate the influence of different in situ fabricated caps on the structural characteristics of Sn thin films deposited at 80 K on InSb substrates. Regardless of the type of capping, we consistently observe that the films remain smooth upon returning to room temperature and exhibit epitaxy on InSb in the cubic Sn (α-Sn) phase. Notably, we identify a correlation between alumina capping using an electron beam evaporator and an increased presence of tetragonal Sn (β-Sn) grains. This suggests that heating from the alumina source may induce a partial phase transition in the Sn layer. The existence of the β-Sn phase induces superconducting behavior of the films by percolation effect. This study highlights the potential for tailoring the structural properties of cryogenic Sn thin films through in situ capping. This development opens avenues for precise control in the production of superconducting Sn films, facilitating their integration into quantum computing platforms.

Revealing Unusual Bandgap Shifts with Temperature and Bandgap Renormalization Effect in Phase‐Stabilized Metal Halide Perovskite Thin Films

AbstractHybrid organic–inorganic metal halide perovskites are emerging materials in photovoltaics, whose bandgap is one of the most crucial parameters governing their light‐harvesting performance. This work presents the temperature and photocarrier density dependence of the bandgap in two phase‐stabilized perovskite thin films (MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3) using photoluminescence and absorption spectroscopy. Contrasting bandgap shifts with temperature are observed between the two perovskites. Using X‐ray diffraction and in situ high‐pressure photoluminescence spectroscopy, it is shown that thermal expansion plays only a minor role in the large bandgap blueshift, which is attributed to the enhanced structural stability of the samples. The first‐principles calculations further demonstrate the significant impact of thermally induced lattice distortions on the bandgap widening. It is proposed that the anomalous trends are caused by the competition between static and dynamic distortions. Additionally, both the bandgap renormalization and band‐filling effects are directly observed for the first time in fluence‐dependent photoluminescence measurements and are employed to estimate the exciton effective mass. The results provide new insights into the basic understanding of thermal and charge‐accumulation effects on the band structure of hybrid perovskite thin films.

Thermomechanic behavior of epitaxial GeTe ferroelectric films

A key development toward new electronic devices integrating memory and processing capabilities could be based on the electric control of the spin texture of charge carriers in semiconductors. In that respect, GeTe has been recently recognized as a promising ferroelectric Rashba semiconductor, with giant spin splitting of the band structure, due to the inversion symmetry breaking arising from ferroelectric polarization. Here, we address the temperature dependence of the ferroelectric structure of GeTe thin films grown on Si(111). We demonstrate the hysteretic behavior of the ferroelectric domain density upon heating/cooling cycles by low energy electron microscopy. This behavior is associated with an abnormal evolution of the GeTe lattice parameter as shown by x-ray diffraction. We explain these thermomechanical phenomena by a large difference of thermal expansion coefficients between the film and the substrate and to the pinning of the GeTe/Si interface. The accumulated elastic energy by the GeTe thin film during sample cooling is released by the formation of a-nanodomains with in-plane ferroelectric polarization components.

PECVD and PEALD on polymer substrates (part II): Understanding and tuning of barrier and membrane properties of thin films

AbstractThis feature article presents insights concerning the correlation of plasma‐enhanced chemical vapor deposition and plasma‐enhanced atomic layer deposition thin film structures with their barrier or membrane properties. While in principle similar precursor gases and processes can be applied, the adjustment of deposition parameters for different polymer substrates can lead to either an effective diffusion barrier or selective permeabilities. In both cases, the understanding of the film growth and the analysis of the pore size distribution and the pore surface chemistry is of utmost importance for the understanding of the related transport properties of small molecules. In this regard, the article presents both concepts of thin film engineering and analytical as well as theoretical approaches leading to a comprehensive description of the state of the art in this field. Perspectives of future relevant research in this area, exploiting the presented correlation of film structure and molecular transport properties, are presented.

Role of vacuum annealing on the structural, optical properties and Dc conductivity of titanium (IV) phthalocyanine dichloride thin films

The present work elucidates the significant alterations in several physical characteristics of thermally evaporated TiPcCl2 thin films resulting from vacuum annealing at 373 and 473 K. The structure, surface morphologies, and molecular structure of TiPcCl2 thin films were studied using x-ray Diffraction (XRD), Transmission Electron Microscope (TEM), Field-Emission Scanning Electron Microscope (FESEM), and Fourier Transform Infrared (FT-IR). Results confirmed nanostructure attributes of as-deposited and annealed films, as well as the phase transition in TiPcCl2 was observed during annealing. The optical constants of as-deposited and annealed films in the wavelength range of 200–2500 nm were determined using spectrophotometric techniques. The indirect optical energy gap was observed to diminish with increasing annealing temperature due to enhanced crystallinity of thin films. Using the single oscillator model, the dispersion of the refractive index at normal dispersion was investigated. The third-order nonlinear susceptibility, χ(3), the nonlinear refractive index n2 and the nonlinear absorption coefficient, βc, were calculated and then discussed for both the as-deposited and annealed films. The electrical conductivity of TiPcCl2 exhibited increased as the temperature increased, suggesting its characteristic as a conventional organic semiconductor. The parameters of Mott’s model were obtained and discussed under low-temperature conditions afterward. Conclusions derived from this research indicate that the unique properties of vacuum annealing TiPcCl2 have great promise for future use in optoelectronic systems.

Development of trimetallic cobalt-nickel-vanadium oxide anticorrosion coatings for the protection of AA2024 Al alloy specimens against sodium chloride solutions

Trimetallic cobalt-nickel-vanadium oxide (CoNiVOx) thin films were fabricated on aerospace grade AA2024 Al alloy specimens to investigate their behavior as anticorrosion coatings in a sodium chloride (NaCl) medium. Compact and homogenous nanostructured CoNiVOx coatings were developed using aerosol-assisted chemical vapor deposition by varying the deposition duration from 45 to 150 min at a constant temperature (475 °C). The structure and composition of the trimetallic CoNiVOx thin films were comprehensively investigated using X-ray diffraction, transmission electron microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, which demonstrated the successful synthesis of CoO/NiO/VO composite materials. The electrochemical corrosion properties of the trimetallic CoNiVOx films in a 3.5 % NaCl solution were determined using Tafel extrapolation and impedance spectroscopic tests, whereas the electrochemical stability and localized corrosion characteristics were determined using scanning electrochemical microscopic analyses. This study demonstrates that the trimetallic CoNiVOx oxide layer fabricated for 150 min exhibited an effective barrier protection performance on Al surfaces against corrosive attack in NaCl media.

Effect of annealing temperature on the morphological, structural, and optical properties of zinc oxide nanostructures prepared by the sol–gel spin coating technique

ABSTRACT This study investigates the impact of different annealing temperatures on the properties of zinc oxide (ZnO) films, particularly at lower temperatures (150-550°C). The films were synthesized using the sol-gel technique, with zinc acetate dihydrate (ZAD) as the precursor and ethanolamine (MEA) as the stabilizing agent. Surface morphology, structural, and optical properties of the films were examined using various techniques. X-ray diffraction confirmed the (002) wurtzite crystal structure, while crystallite size, strain, stress, energy density model, and dislocation density are estimated using three models of Williamson-Hall (W-H) approach.Raman data indicated the hexagonal wurtzite structure of the film. Optical analysis showed good transmittance, with a bandgap estimated between 3.32 and 3.56 eV for all samples. SEM image analysis revealed a nanowall structure in the ZnO thin film annealed at 150°C. However, increasing the annealing temperature led to a more pronounced wrinkled morphology.

Studying the Crucial Physical Characteristics Related to Surface Roughness and Magnetic Domain Structure in CoFeSm Thin Films

This study investigated the effects of varying film thicknesses and annealing temperatures on the surface roughness and magnetic domain structure of CoFeSm thin films. The results revealed that as the film thickness increased, both the crystalline size and surface roughness decreased, leading to a reduction in coercivity (Hc) and improved magnetic contrast performance. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of cobalt (Co), iron (Fe), and samarium (Sm) within the thin films. Notably, the 40 nm Co40Fe40Sm20 thin film annealed at 200 °C exhibited lower sheet resistance (Rs) and resistivity (ρ), indicating higher conductivity and a relatively higher maximum magnetic susceptibility (χac) at 50 Hz. These findings suggest that these films are well suited for low-frequency magnetic components due to their increased spin sensitivity. The 40 nm Co40Fe40Sm20 thin film, subjected to annealing at 200 °C, displayed a distinct stripe domain structure characterized by prominently contrasting dark and bright patterns. It exhibited the lowest Hc and the highest saturation magnetization (Ms), leading to a significant improvement in their soft magnetic properties. It is proposed that the surface roughness of the CoFeSm thin films plays a crucial role in shaping the magnetic properties of these thin magnetic films.

Structural and spectroscopic features of naphthol green B integrated for improved light harvesting capability of organic/inorganic hybrid solar cells

Regarding the intensified interest in photovoltaic devices for a wide range of applications, here, we exploited a promising naphthol green organic dye for designing efficient organic/inorganic heterojunction for solar cell applications. The crystal and molecular structures of the spin-coated NGB thin films were inspected using XRD and FTIR techniques, respectively. A nanostructured polycrystalline film was obtained with a crystallite size of ∼76.2 nm with a stable molecular configuration. The optical properties of the films were analyzed using spectrophotometrically measured transmission and reflection. The prepared films showed high absorption over the UV–Vis–NIR regimes with a relatively small energy gap of ∼1.42 eV and a low refractive index of ∼1.48 which increased its suitability for photosensing applicability. The photovoltaic performance of the fabricated Ag/NGB/p-Si/Al heterojunction was evaluated in detail yielding promising photovoltaic characteristics with Voc ∼0.77 V, Jsc ∼18.64 mA/cm2, and PCE ∼6.49 %.

Plasmonic Titanium Nitride Nanohole Arrays for Refractometric Sensing.

Group IVB metal nitrides have attracted great interest as alternative plasmonic materials. Among them, titanium nitride (TiN) stands out due to the ease of deposition and relative abundance of Ti compared to those of Zr and Hf metals. Even though they do not have Au or Ag-like plasmonic characteristics, they offer many advantages, from high mechanical stability to refractory behavior and complementary metal oxide semiconductor-compatible fabrication to tunable electrical/optical properties. In this study, we utilized reactive RF magnetron sputtering to deposit plasmonic TiN thin films. The flow rate and ratio of Ar/N2 and oxygen scavenging methods were optimized to improve the plasmonic performance of TiN thin films. The stoichiometry and structure of the TiN thin films were thoroughly investigated to assess the viability of the optimized operation procedures. To assess the plasmonic performance of TiN thin films, periodic nanohole arrays were perforated on TiN thin films by using electron beam lithography and reactive ion etching methods. The resulting TiN periodic nanohole array with varying periods was investigated by using a custom microspectroscopy setup for both reflection and transmission characteristics in various media to underline the efficacy of TiN for refractometric sensing.

β-FeSi2: A high refractive index candidate material for infrared bandpass filters

Bandpass filters (BPFs) are optical filters with significantly high transmittance in a specific wavelength range and low transmittance on both sides. Infrared BPFs can reduce system losses and overheating caused by other light wavelengths owing to their ability to selectively transmit infrared light of the desired wavelength. This article discusses the potential of using a high refractive index material, β-FeSi2, in BPFs. To the best of our knowledge, no studies have applied β-FeSi2 to infrared BPFs. Simulation results showed that its high refractive index allows the excellent performance of the BPF to be achieved using a multilayer thin film structure with only three layers. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy results showed that the β-FeSi2 thin film exhibited the lowest absorptance of approximately 0 when the correct stoichiometry (Fe:Si = 1:2) was achieved through co-sputtering. Based on these findings, a β-FeSi2/SiO2/β-FeSi2 multilayer thin film was designed to fabricate the BPF. The fabricated BPF exhibited a narrow peak and achieved a peak transmittance exceeding 80%. This suggested that β-FeSi2 is a promising material for fabricating infrared BPFs. Utilizing these filters is expected to yield significant efficiency improvements and reduce losses across various applications, including thermophotovoltaics and infrared heaters.

Electrochemical growth of PAH-dendrimers supramolecular films. An integrated experimental-theoretical approach

The electrochemical oxidation of a polyphenylene-based dendrimer containing 96 sp2 carbon atoms (PPD) allows obtaining a more extended conjugated carbon framework, polymer PPD (pPPD), starting from the parent fused-benzene-based PPD. The structure and electronic properties of the polymeric thin film obtained by electrochemical oxidation have been characterized by Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy. Structural properties of the thin film formed upon electrochemical oxidation of PPD, are characterized by Matrix-Assisted Laser Desorption/Ionization (MALDI-TOF) and Gel-Permeation Chromatography (GPC) measurements. The degree of order of the layers as well as the virtual, and occupied, electronic states are addressed and exploited to obtain information on conjugation and oligomer size within the polymeric pPPD film. The experimental results are compared with DFT, B3LYP/6–31G(d), calculations. The overall results suggest that the thin film formed on the electrode surface is mainly formed by PPD dimer and trimer upon electrochemical oxidation.

Influence of thermal annealing on silicon negative ion implanted SiO2 thin films

SiO2 thin film of thickness 300 nm grown on p-type silicon substrate was implanted with 100 keV silicon negative ions with fluences varying from 5×1015 to 1×1017 ions cm−2. The implanted samples were annealed at the temperature of 500 °C under N2 ambient. Electron spin resonance (ESR), Fourier transform infrared (FTIR), Photoluminescence (PL), and glancing angle X-ray diffraction (GXRD) techniques have been used to investigate the implanted SiO2 thin film after thermal annealing. ESR studies revealed the absence of vacancy defects after thermal annealing. FTIR studies showed variations in the vibrational modes, attributed to the formation of new structures after annealing at 500 °C. PL studies showed the presence of a peak at 720 nm with an intensity higher than that observed for the unannealed SiO2 samples. This effect showed a decrease in the non-radiative defect centers with an increase in the radiative Si:SiO2 interface states after thermal annealing. The presence of an additional peak at 692 nm may be attributed to the radiative recombination centers associated with silicon nanoclusters formed after annealing at 500 °C. GXRD studies showed a decrease in the intensity of the spectra for the samples implanted with 1×1016 and 5×1016 ions cm−2 after thermal annealing at 500 °C. This result reveals the formation of new SiOx structures in SiO2 thin film.