Crystallite Size Of Films Research Articles

Fabrication of nanostructured MgO:Fe as NO2 gas sensor prepared by spray pyrolysis technique

Nanostructured MgO:Fe was fabricated by spray Pyrolysis technique (SPT). XRD verifies MgO's cubic structure. The MgO thin film's crystallite size increased to 10.7–15.41 nm due to doping. SEM pictures display The surface becomes rougher and the grain size increases with concentration. The ideal MgO's average transmission value in the visible spectrum was 70%. The Tauc relation was used to calculate Eg, which decreased for MgO:Fe doping at 4%wt concentration from 362.1 to 3.52 eV. Resistance change as a measure of film sensitivity to gas indicates that MgO is a p-type semiconductor, with the maximum resistance being shown by MgO:Fe at 4%wt. The sensitivity of MgO films to NO2 diminishes as Fe content increases.

Opto-electronic properties of copper-zinc-sulfide thin films grown via metalorganic-chemical vapor deposition technique at different flow rates

In this work, copper zinc sulfide (CZS) ternary thin films were prepared from the pyrolysis of a Bis-(morpholinodithiato-s,s’)-Cu-Zn precursor using metal-organic chemical vapor deposition technique maintained at 450 °C in ambient nitrogen as the carrier gas. The deposition flow rate was varied to study its effect on the optoelectronic properties of CZS films. The particle-induced x-ray emission technique (PIXE) of the prepared single solid source precursor shows the presence of copper, zinc, and sulfur. The Fourier transform infrared spectrophotometer of the precursor reveals the metal-metal bond attachment to the ligand at a very low wavenumber. The XRD spectra reveal the formation of the hexagonal closed-packed structure of CZS films with a preferred orientation along the [111] direction. The film crystallite size is found to increase from 10.4 to 12.2 nm as the flow rate increases, while the dislocation density and stress decrease as the deposition flow rate increases. The SEM analysis revealed an improvement in the growth rate of the grains as the flow rate increased. The transmittance of the deposited CZS films was found to increase from 58% to 84.2% in the infrared region with an increase in band gap from 3.08–3.64 eV as the flow rate increased. The deposited film shows ohmic properties and an increase in conductivity from 0.243 to 0.847 ( while the resistivity decreases as the flow rate increases. These observations provide room for the deposited CZS film to serve as a potential material for optoelectronics and window layer solar cell devices.

Physical properties of Cu2MgSnS4 thin films prepared by chemical spray pyrolysis technique: The effect of thiourea concentration

In this work, chemical spray pyrolysis is employed to prepare Cu2MgSnS4 thin films using different concentrations of thiourea (0.14, 0.16, 0.18, 0.20, 0.22, 0.24) M at a substrate temperature of 400 ℃ and thickness of (300±10) nm. The XRD results displayed that all thin films are polycrystalline with tetragonal structure and favorite orientation along the (112) plane. The crystallite size of films is estimated by Scherrer's equation and it was found that it increases with increasing thiourea concentration up to 0.20 M and then it decreases with further increase in thiourea concentration. The FESEM result exhibited the appearance of nanostructures with different particle sizes and shapes. The band gap was estimated using Tauc's relationship and it was found that the value of the band gap increases with increasing thiourea concentration from 1.68 eV at 0.14 M to 1.83 eV at 0.20 M and then it decreases to 1.60 eV at 0.24 M. Raman spectroscopy investigation confirms the purity of the sample formation phase. The main peak for all films is located at about 330 cm-1 . The broadening of this peak in solid solutions can be attributed to the disturbance effects related to the locations of the metal and sulfur atoms in the tetrahedral lattice due to chemical substitutions in the crystalline positions. Hall effect results showed that all films are P-type. The increase in carrier concentration and its motility with increasing thiourea concentrations leads to a decrease in the resistance of the films.

Cadmium Telluride (CdTe) nanoparticles deposition on transparent conductive substrates via thermal evaporation

Cadmium telluride (CdTe) nanoparticles were deposited on glass substrates coated by indium tin oxide (ITO) and fluorine doped tin oxide (FTO) as transparent conducting films at 200 °C under pressure of 2×10-5 mbar. The thickness of the prepared films prepared was about 200 nm. The structure, optical, electrical, and morphological properties of the layers were analyzed by x-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, current-voltage (IV) characterization, and scanning electron microscopy (SEM), respectively. XRD patterns show the cubic structure of the deposited CdTe thin film on both ITO and FTO substrates. The preferred orientation of deposited films also changed from (111) for ITO substrate to (220) for FTO substrate. The crystallite size of films on ITO and FTO in these orientations were about 23.41 and 34.84 nm, respectively. The thin-film transmittance spectra were determined using UV-Vis spectroscopy in the wavelength range of 200-1200 nm. The optical energy bandgap of thin films on ITO and FTO substrates was calculated to be 1.60 and 1.63 eV, respectively. The I-V curve shows more electrical conductivity of the CdTe thin film on the FTO compared to the ITO. The surface morphology images show homogeneity and uniformity of the surface.

Growth and some surface characterization of tin Sulphide (SnS) thin film by two-electrode cell arrangement for photo absorption

This study presented deposition of tin sulphide (SnS) thin film using a two-electrode electrochemical cell arrangement. The bath electrolyte comprised tin sulphate (SnSO4 ), hydrated sodium thiosulphate (Na2S2O3∙5H2O) and sulphuric acid (H2SO4 ). The acid was used to adjust the pH of the bath. The deposited film was characterised using Surface Profilometer, X-Ray Diffractometer (XRD), Uv-Visible Spectrophotometer and four point probe technique. Surface profiling revealed that the film is continuous with thickness of about 60 nm. The XRD result showed that the film has orthorhombic crystal structure. Film's crystallite size was estimated as 0.61 nm and interplanar spacing as 0.29 nm. The Uv-visible Spectrophotometer result reveals that, the film has good absorbance but poor reflectance and transmittance in the visible light region. The film has direct allowed transition with energy band gap of 1.69 eV. Values of surface resistivity and conductivity were deduced from data obtained from Four-point probe studies as 5.12 x 10-4Ω-cm and 1.96 x 103Ω-1cm-1 respectively. The I-V characteristics curve of ITO/SnS/Ag structure is linear indicating an Ohmic contact between the substrate electrode and the deposited layer. It can therefore be suggested that the film can allow pathway for photoabsorption and also aid charge transfer in photovoltaic process.
 Keywords: tin sulphide, orthorhombic, electrochemical deposition, characterization, photovoltaic and surface resistivity.

Amorphization of thin supermalloy films Ni79Fe17Mo4 with oxygen during magnetron sputtering

Reactive sputtering of permalloy typically reduces crystallite size in films, if the concentration of reactive gas is low. This advances magnetic properties: decreases coercivity and increases good in-plane magnetic anisotropy. But oxygen is rarely applied for this purpose. Here, peculiar deposition conditions, including the geometry of the vacuum deposition system and large polymer substrate, allowed for the deposition of supermalloy with unusually high admixture of oxygen. Evolution of both static and dynamic magnetic properties with an increase in oxygen concentration proved to be dealt with the balance between grain size, surface structure, disordering of atomic structure and internal stresses. The critical concentration when supermalloy shows indications of oxidation is 5% of O2. Coercivity, resistivity, roughness and ferromagnetic resonance frequency are the parameters that are most sensitive to oxidation.

Effects of glass substrate coated by different-content buffer layer on the quality of poly-Si thin films

In this work, polycrystalline silicon (poly-Si) thin films were fabricated by aluminum induced crystallization (AIC) technique. SiNx, deposited as a function of NH3/SiH4 ratio, and AZO (Al-doped ZnO) films on glass were used as a buffer layer between glass and Si film. The effect of buffer layer content on the crystallinity of poly-Si thin films was studied by Raman analysis which shows that fully crystallization without stress was achieved for all samples. Moreover, the preferred crystalline orientation and crystallite size of films were deduced by X-ray diffraction (XRD) analysis. The preferred orientation is <100> as independent from the buffer layer content while the crystallite sizes increase up to 48.5 nm by increasing the amount of SiH4. The electrical properties of the films were carried out by four point probe and current–voltage (I–V) analysis. Both techniques demonstrated that the resistivity of the SiNx-based samples is around 0.1 Ωcm. The grain size analysis was accomplished by electron back scattering diffraction (EBSD) measurements. The grain size up to 25 µm was achieved as observed from EBSD images. The results show that the fabrication parameters of SiNx and AZO buffer layers have the great effects on the crystallography of poly-Si films.

Influence of nanocrystalline size on optical band gap in CdSe thin films prepared by DC sputtering

Cadmium selenide CdSe thin films have been deposited on glass substrate by using plasma sputtering at room temperature with different times of sputtering. The CdSe thin films are characterized using XRD. The crystallite size of the film is calculated from XRD data, which is found as 12.65nm as-deposited. It is also found that crystallite size of CdSe thin films increased with thin films thickness. The optical properties concerning the absorption spectra were studied for the prepared thin films. The energy band gaps were found to be in the range of 2.21eV to 1.8eV. On varying the film thickness in the range of 350nm to 600nm, it was found that the optical band gap increased due to the nanocrystalline size of the CdSe thin films decreased.

Variation of Structural and Surface Properties of RF Sputtered Aluminum Oxide (Al2O3) Thin Films Due to the Influence of Annealing Temperature and Time

Aluminum oxide (Al2O3) thin films were deposited on Si (111) substrates by using RF magnetron sputtering of Al2O3 target in Ar atmosphere. The synthesized films were annealed in the temperature range of 200 to 600°C in nitrogen (N2) environment for 2 and 4 hours. Variations in these structural and surface properties of the films were investigated using X-ray diffraction (XRD) and atomic force microscope (AFM). XRD analysis reveals that the synthesized films are in polycrystalline form with preferential orientation along (111) plane. By increasing the annealing temperature, the crystallite size of films was found to increase, whereas the micro-strain and dislocation density were decreased. The decrease in micro-strain and dislocation density was ascribed to the reduction in the lattice strain. The surface roughness of the films was increased with the increase of the annealing temperature, which was attributed to the films’ grains growth and also with the increase in RF sputtering power.

Effect of heat-treatment on the structural and optical properties of Cu2S thin films deposited by CBD method

Semiconducting Cu2S thin films were successfully deposited on glass substrate under three different conditions such as as-deposited, post heat-treated and pre heated precursor solution by chemical bath deposition technique. Structural and optical properties of the films were characterized by X-ray diffraction (XRD), scanning electron microscope, energy dispersive X-ray (EDX) analysis and UV–Visible spectrophotometer. The XRD spectra showed the amorphous nature of thin films with hexagonal structure. The d value and micro strain increased and the average crystallite size decreased from 1.9 to 1.4 and 1.3 nm respectively when the as-deposited film was subjected to post heat-treatment and the precursor solution temperature was elevated. The presence of more nucleation centers and fast reaction rate decreased the average crystallite size in films grown with pre heated precursor solution. The noticed blue shift in energy gap and the shift of XRD peak position towards the lower 2θ side by heat-treatment could be considered as a sign of the quantum confined effect due to the formation of the nano-sized Cu2S crystals on the surface. The transmittance of heat-treated Cu2S films in the visible region matched the phototropic vision of human eye (~600 nm) which makes them suitable for solar control coatings on architectural windows and automobiles in the regions with warm climates. Low transmittance behaviour of pre heated Cu2S films could be used for anti dazzling coatings for car windscreens and driving mirrors to reduce the dazzling effects of light at night. EDX spectra showed the chemical purity of the films. The observed broad absorption and blue shift in band gap of the heat-treated films were due to quantum confinement effect. Fourier transform infrared studies were also carried out and the results are presented.

Study on the correlation between crystallite size and optical gap energy of doped ZnO thin film

In the present paper, we have studied a new approach to the description of correlation between the optical and structural properties of ZnO thin films with doping levels of Al, Co, and In. The doped zinc oxide thin films were deposited using ultrasonic spray technique on a glass substrate at 350°C. The correlation between structural and optical properties with doping level suggests that the crystallite size of the films is predominantly estimated by the bandgap energy and the concentration of Al, Co, and In. Also, the gap energy of doped films was estimated by the crystallite size and doping level. The measurement in the crystallite size and optical gap energy of doped films with correlation is equal to the experimental data. The minimum error value was estimated in doped ZnO thin films with indium and cobalt. Thus, results indicate that such Co-doped ZnO thin films are chemically purer and have many fewer defects and less disorder, owing to an almost complete chemical decomposition.

Electrochemically Deposited Thermoelectric Bismuth-Telluride Films

Thermoelectric bismuth-telluride films were successfully prepared from nitric acid aqueous solution with ethylene glycol on Ti-sputtered silicon substrates by electrochemical deposition techniques. Cyclic voltammograms (CV), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used to investigate nucleation process, the crystal structures, morphologies and compositions of the bismuth-telluride films. The results show that the materials are Bi-rich, exhibiting preferred (110) orientation with rhombohedral structure. The crystallite size of films was calculated based on Scherrer’s equation and found to be 18-20 nm.

Study of the resonant frequencies of silicon microcantilevers coated with vanadium dioxide films during the insulator-to-metal transition

Vanadium dioxide (VO2) thin films were grown on silicon microcantilevers and companion test substrates by pulsed laser deposition followed by in situ annealing in an oxidizing atmosphere, with annealing times used to control crystallite sizes. Annealing times of 18 min produced VO2 films with average crystallite sizes of ∼10 nm or less, while those annealed for 35 min had crystallites of average size ∼90 nm, comparable to sample thickness. X-ray diffraction and x-ray photoelectron spectroscopy studies of the samples showed that films with crystallite sizes ∼40 nm or greater consisted of substoichiometric VO2 in its monoclinic phase, with preferential orientation with (011) planes parallel to the sample surface, while finer structured samples had a substantially similar composition, but showed no clear evidence of preferential orientation and were probably partially amorphous. Forced vibration experiments were performed with the cantilevers as they were thermally cycled through the VO2 insulator-to-metal transition (IMT). Very large reversible changes in the resonant frequencies of up to 5% (3.6 kHz) as well as hysteretic behavior were observed, which depend strongly on film crystallite size. The average value of Young’s modulus for VO2 films with crystallite sizes of ∼90 nm was estimated from the mechanical resonance data at room temperature to be ∼120 GPa, but the large tensile stresses which develop between film and substrate through the IMT impede a similar determination for the VO2 tetragonal phase, since the commonly used relationships for cantilever frequencies derived from elasticity theory are not applicable for strongly curved composite beams. The results presented show that VO2 thin films can be useful in novel microscale and nanoscale electromechanical resonators in which effective stiffness can be tuned thermally or optically. This response can provide additional functionality to VO2—based devices which take advantage of other property changes through the IMT.

Optical properties of semimagnetic semiconductors studied by thermoreflectance spectroscopy

The effect of introducing the magnetic elements Ni and Co into a II–VI host lattice, and their influence on the fundamental band gap energy, have been studied by means of thermoreflectance (TR) spectroscopy, following the evolution of the E0 transition at the Γ-point of the Brillouin zone, in terms of the magnetic ion concentration, and/or the film crystallite size. Two systems have been studied: (1) Cd1−xNixTe thin films grown by r.f. supttering onto Corning glass substrates with Ni concentrations in the range: 0 < x < 0.15. The films showed a nanocrystalline structure with the grain size decreasing as the film Ni content increases. From the TR spectra it was found that the band gap shifts to higher energies as the nanocrystalline size decreases, giving us evidence of a quantum-size effect due to electron confinement; (2) Cd1−xCoxSe crystals grown by the vapor phase chemical transport technique at a temperature of 950°C, for two concentration values: x = 0.01 and 0.05. As compared to a pure CdSe sample, the crystal with a Co concentration of 1 at% shows a shift of the E0 transition of about 70 meV to lower energies. For both samples, there appear additional oscillations in the low energy part of the TR spectrum which we interpret as due to the levels introduced by the Co-3d orbitals. The shifts of the E0-point are also discussed.

Large uniaxial anisotropy in permalloy films

Unusually large uniaxial anisotropies were observed when Permalloy films were prepared for microwave phonon generation. These films were formed on single-crystal quarts substrates. To investigate the origin of this anisotropy a number of Permalloy films having negative (92% Ni-8% Fe), near zero (83% Ni-17% Fe), and positive (70% Ni-30% Fe) magnetostriction were formed onto single-crystal quartz squares at substrate temperatures varying from room temperature to 398°C. The anisotropy increased with increasing substrate temperatures. The anisotropy constant (K) for the 92-8 and 70-30 compositions ranged from 6.0 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> erg/cc for room temperature films to 2.0 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> erg/cc for films evaporated at ~390°C. K for the 83-17 composition ranged from 4.0 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> erg/cc to 1.0 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> erg/cc for the same temperature. At first it was believed that the large anisotropy could be attributed to epitaxial growth of the Permalloy films onto the quarts. However, reflection electron diffraction showed the films to be completely randomly oriented. Furthermore, it was evident that the crystallite size in films evaporated onto glass and single-crystal quartz substrates were essentially the same for a given substrate temperature.