Nanocrystalline Thin Films Research Articles

Thin film coatings material particles creation by pulsed methods in vacuum

Thin film materials particles creation pulsed methods such as magnetron sputtering HiPIMS, pulsed laser deposition PLD, vacuum arc pulsed discharge, high-intensity pulsed ion beam impact HIPIB, as well, were described. It was shown that the stream of material, created by means of an explosion action such as ablation, avalanche paired impacts and microsecond electrical disruption as well creates preconditions for nanocrystalline thin film coating manufacture.

Investigation of structure, morphology, photoluminescence, linear and third-order nonlinear optical properties of Sn1−xLaxO2 thin films for optical limiting applications

Transparent nano-crystalline thin films of Sn1−xLaxO2 (x = 0–0.1) were deposited on glass substrates using the cost-effective chemical spray pyrolysis method. The influence of La3+ concentration on the structural, morphological, linear and third-order nonlinear optical properties of the films were analysed. All the films possessed tetragonal crystalline structure, having a preferred (1 1 0) plane orientation irrespective of the doping content. Till a doping of 3 at%, the crystallite size showed a decreasing tendency. The fibrous morphology exhibited by the pure film got transformed into dense spherical microstructures at lower La doping levels. The films with lower doping content showed above 60% of transmittance in the visible wavelength region. The modification in the energy band gaps of the films were observed due to variations in the La concentration. The presence of various defects identified in the deposits by photoluminescence (PL) spectra analysis in the ultraviolet and visible region. Near white light emission was noticed in the films due to these defects. All the films exhibited third-order optical nonlinearity with an observed switching between reverse saturable absorption (RSA) and saturable absorption (SA). The films exhibited self-focussing and defocussing nature due to variation in the doping level. Sn0.94La0.06O2 film was identified as suitable for optical limiting application due to its least limiting threshold value. Hence, these spray pyrolyzed La doped films can be used in optical and nonlinear optical devices.

Phase transformation and enhanced blue photoluminescence of zirconium oxide poly-crystalline thin film induced by Ni ion beam irradiation

Swift heavy ions (SHI) irradiation of Nickel (Ni) beam with different ions fluence bring the modifications in the functional properties of radio frequency (RF) grown zirconium oxide (ZrO2) nanocrystalline thin films. X-ray diffraction analysis affirms the monoclinic to tetragonal phase transformation and diminishing of peak at higher fluence 1 × 1014 and 2 × 1014 ions/cm2 induced by electronic excitation caused by SHI. Zirconium oxide thin films exhibit the same thickness (195 nm) of virgin and irradiated samples and whereas the nanocrystalline thin films have the elemental composition in proper stoichiometry (1:2) as analyzed by rutherford backscattering spectroscopy (RBS). Photoluminescence measurements confirm the blue emission of virgin and irradiated sample recorded at excitation wavelength 270 to 310 nm. The intensity of obtained emission bands varies with fluence which is interpreted in terms of generation and annihilation of defect centers. The characteristic Ag and Bg Raman modes of monoclinic and tetragonal ZrO2 are obtained at different positions. Moreover, the nanocrystalline ZrO2 thin films exhibits the most prominent absorption phenomenon in the visible range and the irradiation cause significant decrease in band gap to 3.69 eV compare to the virgin ZrO2 sample (3.86 eV). XPS analysis indicates the shifting of the core levels Zr 3d and O 1s towards higher binding energy and spin—orbit splitting of different states. The findings in this research justify that the irradiated thin films can be a potential candidate for designing of new materials, intense radiation environments, nuclear reactors, nuclear waste systems, clean energy sources.

Preparation and characterization of structural and optical properties of CdS thin film spin coating prepared

In this paper, a Cadmium sulphide (CdS) nanocrystal thin film has been prepared on glass substrate using the sol-gel method. As deposit and effect annealing films at an annealing temperature of 500°C for 1hour were investigated and characterized. The characterization of prepared films included, structural properties using X-ray diffraction (XRD), Scanning electron microscope (SEM), Atomic force microscope (AFM), and optical Properties using UV-Visible measurement. based on XRD results the annealing reason increase in peak intensity due to the improvement in the crystallinity and the crystalline size decreased with increasing the annealing temperature in regrading of preferred diffraction peak (111) at 2 θ =26 to be fourth more, this indicated a formation of cubic structure of the CdS nanocrystalline thin films as the predominant phase. When the dislocation density and strain initially decreased with increasing the annealing temperature due to the improvement of crystallization. SEM images revealed that the films have Nano sphere-based or cluster-like shape and the structure uniformly grown on the substrate have been observed with annealing temperature. Besides, the roughness, root mean square(RMS), and average diameter. decreased while the grain size increased with annealing temperature. The optical properties showed that the films have low absorption over the visible region and it’s decreasing the annealing temperature which makes the CdS is a promising material for optoelectronic application. The energy gap increases with a decrease in the size of the crystallites, while an energy gap value is somewhat larger than the typical value of bulk CdS. This may be due to the quantum confinement effect due to the nanometer crystallite size of the cadmium sulphide thin film. The first section in your paper.

Radiations hardness of nanocrystalline nickel under 450 keV protons

This contribution reports on the effects of 450 keV proton irradiation within the 1015–1017H+/cm2 fluence range on nano-crystalline Ni thin films. The surface and in-volume induced damages were investigated by grazing incidence X-rays diffraction, atomic force microscopy, Rutherford backscattering as well as four-point probe resistivity measurements. Within such a type of H+ irradiation, a significant surface roughening and amorphization of the external parts of the Ni crystallites for the lowest fluence (1015 H+/cm2 and a re-crystalization for higher fluences (1016–1017 H+/cm2) was observed.

Compliance method to measure crack length and crack closure for automated fatigue crack propagation test of nanocrystalline nickel film

Experimental techniques for measuring the crack length and crack closure behavior of single edge crack tension [SE(T)] specimens with fixed ends were developed with compliance method employing a high-resolution laser displacement meter together with data processing for noise elimination. Then, an automatic force-shedding fatigue crack propagation test system was developed. Using this system, we measured the crack length and crack closure behavior of thin films with a thickness of 5 or 10 µm and width of 10 mm, with which the accuracy of crack length measurement was better than 0.46 mm. The crack closure behavior could also be identified by the compliance method. The relationship between the crack propagation rate da/dN and the stress intensity factor range ΔK for nanocrystalline (NC) and ultrafine-grained (UFG) thin film was independent of the force ratio, and the relationship for the 10 µm-thick film was almost identical to that for the 5 µm thick film. No crack closure was observed in the UFG and NC thin films, whereas it occurred in the medium-size-grained (MG) thin film. The da/dN–ΔKeff relationships for thin films were independent of the force ratio and film thickness. In the Paris law region, da/dN for the MG film was higher than that for an MG plate at comparable ΔKeff, showing that crack closure could not account for the thickness effect. However, no difference in ΔKeff,th was observed for both the MG film and the MG plate. In the Paris law region (Region B), no effect of grain size on the da/dN–ΔK relationship was observed for the 10-µm-thick film; however, the crack propagation rate was higher for a film with smaller grain size and thickness from 100 to 180 µm. For NC and UFG films, the crack propagation rate of the 100-µm-thick film was higher than that of the 10-µm-thick film, but it was almost identical for MG films; however, the rate for a thin film was higher than that for a bulk plate. The threshold stress intensity factor range was always lower for a film with smaller grain size.

Investigating optical, structural and morphological properties of polycrystalline CdTe thin-film deposited by RF magnetron sputtering

In this work, optimization of the physical properties of cadmium telluride (CdTe) thin films has been carried out to improve its performance by the influence of RF power. CdTe Nanocrystalline thin films were characterized by using various techniques such as atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). XRD study revealed that CdTe films are polycrystalline and have preferential growth in (111) direction. FESEM images showed a continuous and dense morphology of CdTe films on glass substrates. The AFM result shows that the surface roughness of films increases with annealing. Optical properties were investigated with the help of the UV–visible absorption spectrum which showed that the bandgap decreases with an increase in Radio-frequency power. Further, density functional theory (DFT) calculations showed that the optimum bandgap i.e. 1.57 eV for CdTe films deposited at 100 W RF power with 2% N2 is in good agreement with the experimental result. This study showed that CdTe films deposited at 100 W RF power with 2% N2 can be used as an excellent absorbing material for the application of optoelectronic devices solar cells.

A systematic investigation on structural and optical properties of sol–gel spin coating fabricated CdS nanocrystalline thin films: effect of Ni doping

In the present work, we have successfully fabricated undoped and Ni-doped nanocrystalline CdS thin film on an ultrasonically cleaned glass substrate employing the sol–gel spin coating technique. The structural and spectroscopic properties of the films were investigated using XRD spectra, UV–Vis spectroscopy and photoluminescence spectra, respectively. The X-ray diffraction spectra revealed the polycrystalline nature of films with cubic structure and (111) as preferred orientation. The average crystallite size evaluated by the Debye–Scherrer formula lying in the range of 6–12 nm for the deposited films. According to UV–VIS Spectroscopy, the average transmittance of films in the visible region varies between 70–90%. The optical band gap of CdS thin film was evaluated from absorption spectra. The bandgap of the deposited films is in the range of 2.48–2.70 eV which is higher than that of bulk CdS (2.42 eV). This verifies the blue shifting in band edge of CdS nanocrystalline thin films due to the quantum confinement effect. Photoluminescence spectra of the thin film showed that the fundamental band edge emission peak centred at 485 nm also called blue band emission. It is observed that the low temperature resistivity of the films was in the range of 107–103 Ω cm and also found to decrease with increasing Ni concentration, as a result from dc two probe measurements.

Tuning of Optical Band Gap: Genesis of Thickness Regulated Al Doped ZnO Nano-Crystalline Thin Films Formulated by Sol–Gel Spin Coating Approach

Tuning of Optical Band Gap: Genesis of Thickness Regulated Al Doped ZnO Nano-Crystalline Thin Films Formulated by Sol–Gel Spin Coating Approach

Enhancement of multifunctional optoelectronic and spintronic applications of nanostructured Cr-doped SnO2 thin films by conducting microstructural, optical, and magnetic measurements

A chemical synthesis method was used to produce Cr-doped SnO2 nanoparticles. By using the TEM technique, the nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) nanopowder was confirmed. With different Cr concentrations, the electron beam deposition technique was used to deposit a series of Sn1-xCrxO2 nanocrystalline thin films on a silica substrate. X-ray diffraction (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and vibrating sample magnetometry (VSM) techniques were used to examine the physical properties of the deposited films. The nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) thin film was confirmed by XRD and AFM morphology measurements. The XRD spectrum of the Sn1-xCrxO2 nanocrystalline film demonstrated a tetragonal crystal structure with no detectable extra phases. The optical measurements showed that as the Cr content increases, the direct optical energy gap Eg decreases without any sign of solubility limit up to x ≤ 0.1. The decrease in Eg is attributed to the sp-d exchange interaction. Also, the spectral behavior of the refractive index dispersion of the Cr-doped SnO2 indicates that as the Cr dopant increases, the refractive index of the deposited film also increases, which is attributed to the increase in the polarizability. Moreover, as the Cr content raises the atomic number, the density of the deposited film increases from 1.43 × 1022 cm−3 for SnO2 to 1.57 × 1022 cm−3 for Sn0·9Cr0·1O2. Further, the behavior of the refractive index dispersion of the deposited film was revealed using a single oscillator model proposed by Wemple-DiDomenico (WDD). Our calculations revealed that as the Cr concentration increases, the value of oscillator energy Eo decreases owing to the decrease in Eg, whereas the value of dispersion energy Ed increases because of the chemical structural changes such as the lattice parameters. Finally, the magnetic studies revealed that incorporating a small fraction of Cr into SnO2 produces room temperature ferromagnetism in the film, which is gradually suppressed by a further increase in Cr doping. These findings indicate that the Cr-doped SnO2 film can be recommended for optoelectronic and spintronic device applications.

Effect of Different Polyethylene Glycol (PEG) and Ethyl Cellulose on Impedance Spectroscopy of CuGaO2 Film

Delafossite materials (CuIMIIIO2) are p-type metal oxides which can be used as hole transport layers in a wide range of heterojunction solar cells. These materials are interesting because of their crystal structure that can facilitate hole diffusion through the valance band. Maximizing the interfacial capacitance within porous nanocrystalline films of CuGaO2 is a primary goal for enhancing their performance in solar cells. The electrochemistry of CuGaO2 can reveal much information about the capacitance of the material and therefore the electronic density of valance band states. Here we have investigated the structural and electrochemical properties of CuGaO2 nanocrystalline thin films in acetonitrile solution with LiClO4 electrolyte. Nanocrystalline films are produced by dispersion of CuGaO2 nanocrystals in a polymer solution designed to control the porosity of the resulting film. We have used different molecular weights of polyethylene glycol and two different chain lengths of ethyl cellulose polymers to understand their impact on film morphology. As the film capacitance is related to surface area, a more porous film is expected to increase the film capacitance. In addition, we have also varied the CuGaO2 : polymer ratio to find the optimum condition for enhanced film capacitance. The films were characterized by powder XRD where peak ratios for (003)/(006) and (012)/(006) planes were calculated to understand the orientation of nanocrystals within the film. Electrochemical Impedance Spectroscopy (EIS) was used to probe the electrochemical behavior and capacitance of the films. We are particularly observing the Creal values at low frequency for comparative study of various films. These studies find that Creal is maximized for the ethyl cellulose polymers and a 2:1 ratio of CuGaO2 : polymer mixture.

Studies structure, surface morphology, linear and nonlinear optical properties of nanocrystalline thin films of manganese (III) phthalocyanine chloride for photodetectors application

Manganese (III) Phthalocyanine Chloride (MnClPc) thin films were deposited over glass substrates through the thermal evaporation technique. The structural characteristics of MnClPc films at various thicknesses have been studied using X-ray diffraction (XRD), which revealed an amorphous structure. The atomic force microscope (AFM) investigates the surface morphology of MnClPc thin films and demonstrates that films have nanostructure with a size of 58 nm for thickness 55 nm and slightly increased with increasing film thickness. Spectrophotometer analyses of MnClPc thin films obtained over the wavelength range of 300−2500 nm were used to determine the linear and nonlinear optical parameters. Results indicate that the optical energy gap of MnClPc films was slightly changed due to thickness. The parameters of the optical dispersion were considered using a single-oscillator model. Also, the nonlinear refractive index and susceptibility were determined by the concepts of linear refractive index dispersion. The optical limiting characteristics by using two different types of laser showed a considerable reduction in the laser output power by increasing the film thickness. This intensive result for MnClPc will probably implement in an industrial approach in the field of photodetectors and optoelectronic devices.

Substrate Temperature Impact on the Structural, Optical and Photo-Catalytic Activity of Sputtered Cu-Doped ZnO Thin Films

Herein, I describe a study on the impact of substrate temperature on the structural, optical and photo-catalytic activity of sputtered Cu-doped ZnO thin films. Cu-doped ZnO nanocrystalline thin films of 10 wt.% Cu were first prepared at different substrate temperatures by radio frequency magnetron sputtering. Energy-dispersive X-ray spectroscopy was used to verify the percentage of Cu-doping. Both the structural and optical changes for the deposited thin films were measured by different characterization techniques. The nature of the deposited films was measured by X-ray diffraction analysis (XRD) that showed four characteristic peaks (002), (103), (100), and (111) related to ZnO. The intensity of the XRD peaks was affected by Cu-doping and increasing the substrate temperatures. The surface morphology and roughness for the prepared thin films were measured by atomic force microscopy. The calculated optical band gap of the prepared thin films deceased from 3.16 eV for the pure ZnO to 2.74 eV, 2.71 eV, 2.69 eV and 2.66 eV for the 10 wt.% Cu-doped ZnO thin film deposited at room temperature, 100°C, 200°C, and 300°C, respectively. The photoluminescence (PL) spectra for the prepared thin films were recorded to examine the impact of Cu-doping and the effect of increasing the substrate temperatures. As a photo-catalyst, the deposited thin films demonstrated high efficiency and stability concerning the degradation of methylene blue organic dye under a 500 W visible lamp and reusability for photo-catalytic experiments without much loss.

Surface and displacement damage engineering on CdSe nanocrystalline thin film by swift heavy Ag ions: A theoretical investigation by SRIM/TRIM package

Engineering of surface and structural properties of a sample by ion beam technology has got tremendous attention in recent times. Here, surface modification in CdSe nanocrystalline thin film due to 120 MeV Ag swift heavy ions (SHI) irradiation has been studied through Stopping and Range of Ions in Matter (SRIM)/Transport of ions in matter (TRIM) package in terms of sputtering yield and average surface binding energy. From this study, average range has been obtained as 1.6 μm and average surface binding energy as 1.7 eV. SHI deposits huge energy to the atomic lattice and that displaces the lattice atoms from their original positions, which has been utilized here to obtain displacement damage. The damage profile has been studied as a function of dpa, which shows that the maximum displacement damage peaks is at 1.5 μm for CdSe due to 120 Mev Ag ions irradiation.

Influence of current density on the physical properties of electroplated NiFeP nano thin films for MEMS applications

Nanocrystalline thin films of NiFeP have been synthesized through electroplating technique on Copper substrate by varying the current densities from 5 to 20 mA/cm2 at constant bath temperature. The chemical composition of the NiFeP thin films and their corresponding surface features have been studied using energy dispersion X-ray analysis and scanning electron microscopy, respectively. Surface roughness was assessed using atomic force microscopic technique and X-ray diffraction (XRD) was used to study the nature and structure of the nano-crystalline material. The magnetic activity of NiFeP thin films was analyzed using a vibrating sample magnetometer (VSM). The surface analysis indicates that the coatings are smooth and free from cracks while the XRD data reveal the crystalline nature and the average crystalline dimensions of the nano thin films. The thickness of the NiFeP thin films measured at various current density values were observed to be in the range of 26–58 nm. VSM test shows higher magnetization values along with low coercivity for NiFeP thin films. A maximum saturation magnetization of 71.36 × 10–3 emu with a coercivity of 301 Gauss is also found to be exhibited by the NiFeP thin films that are coated at higher current densities. The adhesion of coated NiFeP thin films and their corresponding micro hardness have been also studied. Owing to their observed mechanical stability and magnetic nature, the prepared NiFeP thin films has a potential to be exploited for device applications for Micro-Electro-Mechanical Systems (MEMS).

Extraction–Pyrolytic Method for TiO2 Polymorphs Production

The unique properties and numerous applications of nanocrystalline titanium dioxide (TiO2) are stimulating research on improving the existing and developing new titanium dioxide synthesis methods. In this work, we demonstrate for the first time the possibilities of the extraction–pyrolytic method (EPM) for the production of nanocrystalline TiO2 powders. A titanium-containing precursor (extract) was prepared by liquid–liquid extraction using valeric acid C4H9COOH without diluent as an extractant. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA–DSC), as well as the Fourier-transform infrared (FTIR) spectroscopy were used to determine the temperature conditions to fabricate TiO2 powders free of organic impurities. The produced materials were also characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The results showed the possibility of the fabrication of storage-stable liquid titanium (IV)-containing precursor, which provided nanocrystalline TiO2 powders. It was established that the EPM permits the production of both monophase (anatase polymorph or rutile polymorph) and biphase (mixed anatase–rutile polymorphs), impurity-free nanocrystalline TiO2 powders. For comparison, TiO2 powders were also produced by the precipitation method. The results presented in this study could serve as a solid basis for further developing the EPM for the cheap and simple production of nanocrystalline TiO2-based materials in the form of doped nanocrystalline powders, thin films, and composite materials.

Multifunctional Nanocrystalline Cu–Ti Thin Films Enhance Survival and Induce Proliferation of Mouse Fibroblasts In Vitro

This paper describes the effect of a nanocrystalline thin film based on copper and titanium on mouse fibroblast cells. Cu–Ti coatings were prepared using magnetron sputtering. In their composition was 25 at.% Cu and 75 at.% Ti. The goal of the study was to evaluate the effect of the material on the survival, migration, and proliferative capabilities of mouse L929 fibroblasts. The Cu25Ti75 material had no effect on the induction of cell death and did not disturb the cell cycle phase. The study showed a unique effect of a Cu25Ti75 thin film on mouse fibroblast cells, and the results concerning mitochondrial activity, cell proliferation, and migration proved that the material is nontoxic and shows proliferative properties in a wound healing test. The possible biomedical applications of the new nanocrystalline thin film biomaterial with multifunctional properties are described.

Grain-size dependence of magnetic microstructure and high-frequency susceptibility of nanocrystalline thin films: A micromagnetic simulation study

The size of crystallites is one of the most important factors that determine the key characteristics of nanocrystalline thin magnetic films that make them very promising media for various applications. In this paper, using micromagnetic simulation, we study in detail the influence of the grain size on the magnetic microstructure of the films and its relation with high-frequency dynamics of magnetization. When the grain size exceeds some critical value Dcr, a sharp broadening and shift of the ferromagnetic resonance line are observed at certain frequencies of the alternating magnetic field. Using a two-magnon scattering model, it is shown that these effects are caused by the scattering of spin waves on the inhomogeneous stochastic magnetic structure—magnetization ripple. An expression for the determination of the critical size Dcr is obtained. The micromagnetic simulation results agree with the main conclusions of the static and dynamic theories of magnetization ripple and also confirmed by experimental data reported by other authors.

Synthesis, characterization and optical properties of Co2+ doped PbS nanocrystals

We present theoretical and experimental results in PbS nanocrystalline thin films systematically doped with Co2+ ions utilizing the green Chemical Bath Deposition technique at ∼90 °C. All growth parameters are kept constant by systematically adding different solution's volume containing the Co2+ ions. We apply the first-order chemical kinetic reaction model to investigate some physicochemical parameters. The crystalline phase is investigated by X-ray Diffraction, identifying the cubic phase in all samples. After dopping the PbS sample (PbSCo2+), the grain size decreases from ∼29.7 nm to ∼15.7 nm and dislocation density increases from ∼3.4 lines m−2 to ∼6.4 lines m−2. The absorbance and bandgap studies conducted in the Vis-UV region show the typical 1Se→1Sh and 1Se→1Ph electronic transitions and the excitonic bands located at ∼1.5 eV and ∼1.8 eV due to higher energy transitions from 1Dh→1De, and 1Fh→1Fe respectively in nanocrystals. Finally, we apply three theoretical models to elucidate the correlation associated with the crystal radius and the bandgap energy (Eg).

Retracted: Influence of L-Tryptophan on Growth and Optical Properties of PbS Nanocrystalline Thin Films

Retracted: Influence of L-Tryptophan on Growth and Optical Properties of PbS Nanocrystalline Thin Films