Properties Of Thin Films Research Articles

Tuning of structure, surface morphology and optical properties of spray-coated nickel tin oxide thin films by heat treatment

In this work, nickel tin oxide (NiSnO3) in a 1:1 ratio was synthesized using a simple spray pyrolysis technique followed by annealing at 450 °C for different time durations. The X-ray diffraction (XRD) revealed the polycrystalline nature with perovskite structure of NiSnO3 without the formation of any secondary phases. Annealing improved the crystallinity of the films. The annealed films exhibited a preference for orientation along the (310) plane. The largest crystallite size was obtained for 4 h of annealed film. The scanning electron microscopy (SEM) images of the films distinctly illustrate enhanced crystallinity following the annealing process. Energy-dispersive X-ray spectroscopy (EDS or EDX) indicates that the film possesses a near-stoichiometric composition. All the films resulted in more than 70 % transmittance in the visible region except for 8 h annealed. The gradual reduction of energy bandgap was observed for the sample. The four peaks at 358 nm, 415 nm, 436 nm, and 460 nm were observed in photoluminescence (PL) spectra corresponding to near band emission and defects related emissions respectively. The determined optical parameters from the present study indicate that the 4-h annealed film holds promise as a favourable option for optoelectronic and photonic devices.

Role of Annealing with Electric Field Toward Improvement of Ferroelectric and Electroactive Properties of PVDF Copolymer and Terpolymer Thin Films.

The present study elucidates the role of annealing with electric field on lamellar crystalline structure and molecular orientation of polymer chains in ferroelectric copolymer (P(VDF-TrFE)) and ferroelectric terpolymer (P(VDF-TrFE-CFE)) spin-coated thin films. The ferroelectric polymer thin films annealed under an electric field support the growth of nanostructure with an "edge-on" lamellar crystalline structure having in-plane molecular chain orientation. The poled P(VDF-TrFE) thin films have higher remnant polarization (Pr) ≈6.2µCcm-2 and saturation polarization (Ps) ≈8.2µCcm-2 at an applied electric field of 250 MV/m compared to unpoled thin films having Pr ≈4.7 and Ps ≈6.2µCcm-2. Also, poled P(VDF-TrFE) thin films show lower coercive field (Ec) ≈94 MV/m compared to an unpoled thin film having Ec ≈105 MV/m. Similarly, poled PVDF-TrFE-CFE thin film shows better ferroelectric properties having Pr ≈0.4 and Ps ≈5.7µCcm-2 at an applied electric field of 200 MVm-1 compared to unpoled thin films having Pr ≈0.4 and Ps ≈4.1µCcm-2. The storage energy efficiency of unpoled and poled P(VDF-TrFE-CFE) thin films is measured to be ≈75% and 80%. Annealing of ferroelectric P(VDF-TrFE) polymer thin films under an electric field demonstrates improved ferroelectric and electroactive properties.

Indirect Enhancement of ALD Thin-Film Properties Induced by the ECAP Modification of an As-Extruded Mg-Ca Alloy.

The purpose of this study is to investigate the indirect effects on the properties of ZrO2 films deposited by atomic layer deposition (ALD) when an Mg-Ca alloy is modified through equal-channel angular pressing (ECAP) following extrusion. The study aims to understand how the increase in CaO content in the native oxide layer of the Mg-Ca alloy influences the crystallinity and defect density of the ZrO2 film. Consequently, the corrosion protection performance of the ZrO2 film is enhanced by 1.2 to 1.5 times. A reduction in the anti-scratch property of the ZrO2 film was also observed, with a critical load reduction of 34 μN. This research provides a detailed analysis of the modifications induced by ECAP on the as-extruded Mg-Ca alloy and its subsequent impact on the properties of the ZrO2 film.

Oxidation characteristics of copper oxide thin films deposited by direct current sputtering under substrate temperature and post-deposition copper-ion implantation

The oxidation and structural, optical and morphological properties of copper oxide thin films deposited by direct current magnetron sputtering under different substrate temperatures and oxygen (O2) partial pressures, and subsequent 200 keV Cu ion implantation are investigated. The colour of the films progressively changed from yellowish brown to dark brown and oxide phase from Cu2O to Cu4O3 to CuO through mixed phases with increase in oxygen partial pressure from 20 to 90 % of the working pressure and substrate temperature from room temperature (27 °C) to 350 °C. The rate of oxidation and crystallinity of the films substantially increased with increase in substrate temperature. The ion implantation in the room temperature deposited films produced significant crystallization and decrystallization with respect to the ion fluence, and that in 350 °C substrate temperature deposited films instigated Cu-rich phase. The substrate temperature and ion implantation engendered distinctive red shift of the absorption edge and prevalent changes in the interference patterns in the optical spectra of the films. The calculated direct band gap values of the films are in the range of 1.7 to 2.42 eV, which decreased to the range of 1.65 to 2.17 eV on ion implantation. The indirect band gap of the films with predominant Cu4O3 and CuO phases are in the range of 1.23 to 1.49 eV. The refractive index and extinction coefficient of the films at 1100 nm are in the range of 2.1 to 2.5 and 0.03 to 0.12, which increased to the range of 3 to 7 and 0.2 to 0.45, respectively, on ion implantation. The films displayed agglomeration of the particles and directional growth of the agglomerates with respect to O2 partial pressure and substrates temperature, and increase in the size of the particles / agglomerates, and rough surface morphology on ion implantation.

Effect of deposition regime transition on the properties of Al:ZnO transparent conducting oxide layer by radio frequency magnetron sputtering system

High-quality zinc oxide thin films doped with aluminium adatoms have effectively been fabricated on pristine soda-lime silica glass substrates via radio frequency magnetron sputtering system. The deposition temperature was varied to explore the impact of deposition regime transition of as-deposited Al:ZnO thin films on their performance as transparent conducting oxide layers. In particular, the depositions were conducted at room temperature, 100 °C, 200 °C, and 300 °C, allowing for a comprehensive assessment of the resulting films. The Raman spectra depicted the modulation of Raman bands in correlation with the deposition regime transition, illustrating the impact of thermal induction on various properties of the as-deposited aluminium-doped zinc oxide thin films. Atomic force microscopy reveals the transformation from nearly spherical to elongated shape structure was obtained as the deposition process shifted from kinetic limited to thermodynamic limited regimes. The phase analysis and grazing incident of x-ray diffractometer disclose a single crystal orientation has been achieved at thermodynamic limited regime. However, two different crystal planes were predominant comparing between the surface and structural of as-deposited aluminium-doped zinc oxide thin films. It is also evident that a highly transparent with low lattice strain and better carrier concentrations of as-deposited aluminium-doped zinc oxide thin films were realized at thermodynamic limited regimes.

Tailoring the physicochemical and electrical properties of ZnO thin films by doping with light and heavy rare-earth element via wet chemical approach

Tailoring the physicochemical and electrical properties of ZnO thin films by doping with light and heavy rare-earth element via wet chemical approach

Na+ doped CuO: A new paradigm electrode material for high performance supercapacitors

This study investigates the influence of sodium doping on the properties of cupric oxide (CuO) thin films synthesized via spray pyrolysis. Comprehensive characterization was conducted using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Raman spectroscopy, Hall effect measurements, and electrochemical studies. All films exhibited p-type conductivity, with an optical band gap variation from 1.53 to 1.73 eV. XRD analysis confirmed the dominance of monoclinic CuO, with minor phases of Cu2O and Cu4O3. EDAX and XPS verified the incorporation of Cu, O, and Na elements. FESEM revealed a densely packed morphology with uniform particle distribution and rough surfaces in the electrically optimized film. The Raman spectra of doped samples showed increased intensity and sharpness, attributed to Na + ion-induced polarizability enhancement. Hall effect measurements indicated a tenfold decrease in carrier concentration and a more than tenfold increase in mobility upon sodium doping. Films doped with 4 at.% sodium exhibited the lowest resistivity. Additionally, Na doping enhanced the electrochemical performance of CuO. These findings demonstrate that sodium doping significantly enhances the electrical, optical and electrochemical properties of CuO thin films, making them suitable for applications in optoelectronic devices and supercapacitors.

Influence of calcination temperature on the 3D nanoscale topography of LaMnO3 thin films: A comprehensive surface analysis

In this paper, we present a comprehensive study on the 3D nanoscale topography of LaMnO3 thin films, focusing on the influence of calcination temperature on surface morphology. The study reveals significant structural, chemical, and morphological changes as a function of the calcination temperature. XRD analysis confirmed the formation of the orthorhombic LaMnO3 structure at 700 °C, 750 °C, and 800 °C, with increasing unit cell volume and crystallite size observed at higher temperatures. FTIR spectra identified characteristic functional groups associated with molecular vibrations, indicating the perovskite structure. SEM imaging showed grain growth with temperature, while EDS analysis confirmed compound formation and substrate interactions. AFM analysis revealed increased surface roughness with temperature, attributed to nucleation and crystal growth. Morphological and microtextural analyses further detailed changes in surface features, peaks, valleys, and voids. Fractal characterization highlighted variations in surface texture with temperature, with a decrease in dominant wavelength indicating changes in microtexture complexity. Overall, the findings provide insights into the temperature-dependent properties of LaMnO3 thin films, essential for optimizing growth conditions and understanding their potential applications in various fields.

Effect of bias voltage on the structure and properties of CoCrFeNi high entropy alloy thin films prepared by magnetron sputtering

In this study, CoCrFeNi high entropy alloy thin films were prepared on 304 stainless steel and single crystal Si substrates using the direct-current magnetron sputtering process under different bias voltages. The effects of these bias voltages on the film micrographs, phase structure, surface roughness, corrosion resistance, and mechanical characteristics of thin films were studied by a scanning electron microscope, transmission electron microscope, X-ray diffractometer, atomic force microscope, electrochemical workstation and nanoindentation tester, respectively. The results indicated that all films exhibited equiaxed nano-scale grains and developed a columnar structure. Fe, Co, Cr, and Ni were uniformly dispersed in all films and all films displayed face centered cubic solid solution (FCC). At a bias voltage of 0 V, the CoCrFeNi HEAs film formed a FCC single phase. With increasing bias voltage, the crystallinity decreased and then increased, reaching the worst crystalline state at bias voltage of −200 V due to the fact that the structure of the film was composed of FCC nanocrystalline and amorphous biphasic structure. Meanwhile, the surfaces of the film prepared at bias voltage of −200 V exhibited the densest structures and the least roughness, with grain sizes reaching a minimum value of approximately 10 nm. In addition, columnar grains of the film prepared at a bias voltage of −200 V displayed the densest state and had the least size, thus this film displayed the best corrosion resistance of a minimum value 1.51 × 10−7 A/cm2, a maximum hardness of approximately 11.18 ± 0.2 GPa and a maximum elastic modulus of approximately 193 ± 2.8 GPa. The passivation films of CoCrFeNi HEAs films were mainly composed of Cr2O3.

Environmentally friendly p-type CTS-based thin-film thermoelectric generator

Cu-based sulphides are promising materials for environmentally friendly Te-free thermoelectric generators (TEGs). Cu2SnS3 (CTS) stands out for its electronic properties, stemming from its conductive Cu–S networks, especially in fully disordered cubic structural form. While wet chemical techniques are the most utilized for CTS synthesis, they introduce organic contaminants that reduce electronic connectivity between grains, limiting their performance as in-plane thin-film TEGs. We present a new method to improve the electronic properties of CTS thin films for thermoelectric applications involving three-step dry route synthesis of ball milling, thermal evaporation, and sulfurization of Cu2–Sn metallic precursors. Via this method, charge carrier concentration increased significantly, as estimated by Hall effect analysis, which was attributed to the Cu-poor stoichiometry, also confirmed via energy-dispersive X-ray spectroscopy (EDXS). Microstructural analysis by scanning electron microscopy (SEM) revealed micrometre-sized grains composed of even smaller crystalline domains, which X-ray diffraction (XRD) showed to be ~ 50 nm in diameter. When compared with literature results, our procedure leads to a fourfold enhancement in the thermoelectric power factor (PF=S2σ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$PF={S}^{2} \\sigma$$\\end{document}), determined through the Seebeck coefficient measurements (S\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S$$\\end{document}) and electronic conductivity (σ) estimated by the van der Pauw technique. The CTS TEG has a power volume density of 2.3 μW K−1 cm−3, measured by a custom current–voltage–power (I–V–P) setup with varying load resistance. Results present a 100% increase in performance compared to ink-based techniques and were reproducible across three different batches. This strategy, improving the density of the CTS thin films, offers a new way to enhance Cu-based thin-film TEGs.

Exploring the effect of thin film thicknesses on linear and nonlinear optical properties of MoO3 thin film

The structural, morphological, linear, and nonlinear optical properties of MoO3 thin films deposited by thermal deposition were measured. The effect of various thicknesses of films was studied. The structural and morphological parameters of films, determined by x-ray diffraction, field emission scanning electron microscopy, and AFM images, are compared to the linear and nonlinear optical characteristics of these media. The bandgap of the prepared thin films was obtained from the diffuse reflectance spectroscopy spectra. The electron’s effective mass (me*/m0), linear refractive index (n0), and optical static and high frequency dielectric constant (ɛ0, ɛ∞) values were calculated by using the bandgap energy values. Increasing the thicknesses of thin films decreased the bandgap, increased the root mean square, and increased the size of nanoparticles and the nonlinear response of thin films. The high magnitude of n2 and β was because of MoO3 (300 nm-thickness), which were of the order of 10−5 cm2/W and 10−1 cm/W, respectively. The fluctuations in nonlinear responses observed at different thicknesses are attributed to d–d transitions and intraband scattering of equilibrium electrons influenced by laser radiation, as indicated by the nonlinearity data. The considerably elevated refractive nonlinearity values in the analyzed film materials suggest their potential for practical application in optoelectronic devices.

Author correction to “Enhanced property of thin cuprous oxide film prepared through green synthetic route”

This correction adds some information to our publication [Chin. J. Chem. Phys. 32, 365–372 (2019)] that we previously missed to include.

Structural control in atomic layer deposited hafnium oxide thin films through vertical cavity surface-emitting laser (VCSEL)-Based ultra-rapid heating

HfO2 thin films were formed by plasma-enhanced atomic layer deposition (PEALD) using TDMAHf precursor as a Hf source and oxygen plasma as an oxygen source. Rapid annealing assisted by a 980 nm wavelength vertical cavity surface-emitting laser (VCSEL) was employed to assess the dielectric properties of the HfO2 thin films, compared to furnace annealing. Operational power and time of VCSEL was precisely controlled by computational simulation. In addition to decreased thickness of the interfacial layer, rapid annealing enabled reduced leakage current density as annealing temperature increased due to suppression of crystallization, resulting from the extremely short time duration of 0.98 s–8.14 s. Cross-sectional microstructures exhibited incomplete grain boundary formation of the rapidly annealed HfO2 thin film. VCSEL-based rapid annealing was verified to be an efficient process to enhance the dielectric characteristics of high-k dielectric oxide films.

First-principles quantum analysis of structural, optoelectronic, and thermophysical properties of Co/Ni doped ceria Ce1−xTmxO2 (Tm=Co, Ni) for solar cell applications

The properties of CeO2 thin films, such as their memory store capabilities, visual transparency, chemical and thermal durability, adjustable energy band topologies, and high oxygen storage capacity have captured the attention of scientists. The energy band dispersions for Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) are calculated to get insight into the characteristics of the materials under investigation. The anticipated energy bandgaps for Ce1−xCoxO2 and Ce1−xNixO2 are 2.6 and 2.7 eV, respectively, in the spin ↑ channel. However, both compounds show metallic character in inspin ↓ channel. The phenomena of photon absorption/dispersion by the host materials can be elucidated using dielectric function εω of Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%). Significant photon absorption can be noted in UV and IR regions for Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) in spin ↑ and spin ↓ channels, respectively. Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) exhibits a minimal photon reflection, approximately 15%. Ce1−xNixO2 shows excellent thermoelectric characteristics as its ZT value is high (1.8 at 1000K) compared to Ce1−xCoxO2. Based on their thermodynamic properties, Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) are thermodynamically stable compounds.

Tailoring the opto-electronic properties of SnS thin films by indium doping and fabrication of heterojunction diodes

This study comprehensively investigates the effect of Indium (In) doping on the structural, morphological, and optoelectronic properties of tin mono-sulfide (SnS) thin films deposited using co-evaporation. X-ray diffraction studies identified the orthorhombic phase of SnS. Raman analysis confirmed the formation of SnS by co-evaporation. Morphological analysis revealed uniform coating of the films, a transition from rod-like to regular grain-like structures with increased In doping. A systematic reduction in Sn concentration, with the increase in In is observed in EDS, indicating the substitutional doping of In. The decrease in root mean square roughness with In incorporation suggests smoother film surfaces. The films demonstrated a pronounced improvement in optoelectronic properties, with a notable increase in the absorption coefficient and a bandgap reduction from 2.18 eV to 1.74 eV, resulting from In doping. A significant enhancement in electrical characteristics is observed, including a 140 % increase in conductivity and a systematic rise in carrier concentration with higher In doping levels. Heterojunction devices are fabricated with structure <FTO/Al:ZnO/In:SnS/Ag> having a series resistance of 29.9 Ω having an ideality factor of 2.8.

Preparation and properties of Hydroxyapatite-Ti composite thin films by co-sputtering method for biocompatibility applications

In this paper, we report on enhancing the biocompatibility properties of Hydroxyapatite-Titanium (HA-Ti) thin films fabricated using the co-sputtering method. By adjusting the HA/Ti ratio through varying the sputtering power of Ti, we obtained HA-Ti thin films with different crystal structures, morphologies, and hydrophilic properties. HA-Ti thin films sputtered at different titanium powers of 80, 100, 120, 140, and 160 W will obtain thin films with larger grain sizes and poorer crystallinity, respectively. However, their hydrophilic properties increase as the contact angle decreases from 78° to 20° degrees. In vitro BHK cell tests indicated that the HA-Ti thin film had excellent biocompatibility. Therefore, this material is suitable for biological applications and has significant potential in medical implant technology.

Structural and Optical Properties of Magnetron-Sputtered Chromium Oxynitride Thin Films

Doping non-metal elements into Cr2O3 can tailor its properties, making it more efficient for applications like sensors or photocatalysis. For this purpose, the current research work presents the impact of nitrogen doping on the structural and optical properties of Cr2O3 thin films. Pure and N-doped Cr2O3 (Cr2O3−xNx) thin films were synthesized using the DC reactive magnetron sputtering approach. The stoichiometry was obtained by raising values of x, where x = 0, 0.125, 0.25, and 0.50. X-ray diffraction analysis confirmed the rhombohedral crystal structure without the presence of any other secondary phase in undoped and N-doped Cr2O3 thin films. Furthermore, crystallinity and average crystallite size have enhanced by doping. Field emission scanning electron micrographs disclosed that the surface morphology of the prepared samples changed considerably with doping. A thorough optical investigation was carried out by spectroscopic ellipsometry. Several optical properties significantly changed with dopant content. The reduction in the optical bandgap from 2.50 eV to 1.82 eV, with N-doping was observed. The study demonstrated that N-doping improves the structural and optical properties that make it a promising candidate for optoelectronic applications.

Evidence of topological surface states in Bi2Te3 thin film grown by electron beam evaporator through co-deposition technique

Topological insulators have drawn tremendous interest in current research for their exotic quantum phenomena and new-generation technological applications. In this literature, we have explored the topological properties of a 100 nm Bi2Te3 thin film, prepared by co-deposition technique through a custom-built electron-beam-evaporator. The detailed structural, compositional, and morphological analysis indicates the formation of a good-quality, well-stoichiometric, smooth film on Si (100) substrate. Our electrical-transport measurement exhibits three different types of temperature (T) dependency of resistance, where substrate Si-carrier dominates the transport at much higher-T (>250K), whereas a constant and logarithmic variation of filmʼs resistance are seen for below 250K and 25K, respectively. The logarithmic dependency is originated due to 2D electron-electron interaction, while the constant nature is arising from electron-phonon interaction. Finally, systematic temperature and angle-dependent magneto-conductance studies are performed. From which, we have found the existence of topological-surface-state in our Bi2Te3 film through the evidence of non-zero Berry phase (β = 0.66π), high phase-coherence-length (lϕ = 101.8 nm), and 2D coherency factor (α = −0.33).

Effect of substrates on the structural, surface chemical state, and optical properties of Ga-doped Al2O3 thin films

We report the stabilization of Ga-doped Al2O3 (GaAlO) thin films into rhombohedral structure (R 3‾ c space group). We used the target material of composition A11.5Ga0.5O3 (bulk) to deposit the films on Alumina (0001) and p-type Si (100) substrates by using the electron beam evaporation technique. X-ray diffraction pattern confirmed the formation of polycrystalline rhombohedral structure for the as-grown films on Alumina substrate, whereas the films grown on Si substrate showed amorphous structure. The post-heat treatment of as-grown films at 550 °C stabilized rhombohedral structure in all the films, irrespective of the substrates. X-ray photoelectron spectra confirmed modification in surface chemical state of the films depending on nature of the substrates. Optical bandgap of the GaAlO films was stabilized in the range of 3.44 eV–4.04 eV, which is substantially reduced in comparison to corundum structured α-Al2O3 having optical band gap in the range of 8–9 eV and α-Ga2O3 having optical band gap of 4.5–5.5 eV. The defect-induced electronic states and substrate induced interfacial diffusion contributed additional energy gap in the range of 1.50–2.92 eV for GaAlO films grown on Si substrate. The development of highly crystalline corundum structured α-(Al, Ga)2O3 alloyed thin films and engineering their band gap energy in a wide range (1.5–4 eV) is useful for applications of semiconductor metal oxides in high power and medium frequency opto-electronic devices.

Structural, Electronic Structure, and Electrical Properties of Pure and Vanadium-Doped CuCrO2 Thin Films

Structural, Electronic Structure, and Electrical Properties of Pure and Vanadium-Doped CuCrO2 Thin Films