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Photovoltaic devices are expected to display peak performance if fabricated with perfect single crystals. Since surfaces break the periodicity of a single crystal, there are regions of defects, which give rise to states inside the forbidden energy gap. In polycrystalline thin films, the main structural defect is the grain boundary. The presence of grain boundaries affects the optical absorption, carrier mobility and lifetime of the semiconductor. This review focuses on grain boundary passivation in thin film photovoltaic devices based on copper chalcogenides. Achieving enhanced performance in copper chalcogenide thin film Photovoltaic devices requires effective grain boundary passivation. This approach aims to mitigate the adverse effects of grain boundaries on the optoelectronic properties of the material, leading to improved efficiency and stability in Photovoltaic devices. The abstract discusses recent developments, methodologies and outcomes related to grain boundary passivation strategies, shedding light on their significance in advancing the performance of copper chalcogenide thin film Photovoltaic devices. The exploration of grain boundary passivation in this context contributes valuable insights to the ongoing efforts in optimizing the performance of thin film Photovoltaic technologies.

Transparent sols of crystalline gadolinium doped zirconia particles with the general formula Zr_{1 - x}Gd_xO_{2 - x/2} (where x = 0–0.20), were prepared by a hydrothermal sol-gel method using cheap inorganic precursors. The composition, structure, crystallite size and lattice parameters of the crystalline dried sol particles and heated powders were studied. Thin films were deposited on quartz substrates using a simple dipping process and the structure, composition and crystallite size found to be identical to the powders with respect to the variation in temperature. Spectral transmittance studies showed that the films were transparent in the region between 400 and 1100 nm. The refractive index increased with the increase in annealing temperature, varying between 1.56 and 1.74. Optical band gap calculations gave band of 5.52 to 5.55 eV. Refractive indices and optical band gaps were compared with those of films containing other lanthanide dopants previously reported in the literature.

We present calculations of the electronic and magnetic structure of thin films of Ni, using the recursion technique based on the tight-binding linearized muffin-tin orbitals basis. We find that the surface layers of free standing Ni thin films do carry enhanced magnetic moment.

Cadmium sulfide (CdS) thin films (d=0.15–1.15 μm) were deposited onto glass substrates by the quasi-closed volume technique under vacuum. The investigations shown that the films are polycrystalline and have a hexagonal structure. It was experimentally established that the films with stable structure can be obtained if they are submitted to a heat treatment, consisting of several succesive heating/cooling cycles within a given temperature range (ΔT=300–600 K), the temperature dependence of the electrical conductivity becomes reversible. For heat-treated samples, the values of thermal activation energy calculated from the temperature dependence of the electrical conductivity, ranged between 2.30–2.45 eV. The spectral dependences of the transmission and absorption coefficients were studied in the range 500–1400 nm. The influence of heat treatment on the shape of the absorption spectra and dispersion index of refraction is studied for samples with different thickness. Optical energy gap, calculated from the absorption spectra was in the range 2.30–2.5 eV.

The theory of Green's functions (GF) for thin films was formulated, where site indices were different also along the direction of broken symmetry. This approach results in the layer dependence of correlation functions in films, which did not appear in the previous investigations of thin films. The magnetizations of three layer thin ferromagnetic (FM) and four layer thin ferroelectric (FE) films were investigated using the GFs found in this way. It was shown that the transition temperature varies from layer to layer, which is the obvious consequence of the generalization of the formalism of the GF calculation for films.

In our studies we observed a self-doping effect in Bi 2212 epitaxial thin films, totally covered by a protective golden layer, after the irradiation of these films with heavy ions. The irradiation with heavy ions was made in order to create columnar defects in the samples. We studied Bi 2212 thin films having various oxygen contents before irradiation and we observed for all of them an increase of the oxygen content in the films due to this self-doping effect caused by irradiation.

The epitaxial, single phase (100) Ba_0.5Sr_0.5TiO₃ (BST) films with thin interfacial layer of BST (x=0.4) were deposited on LAO (100) substrates using Pulse Laser Deposition (PLD). These films were characterized in terms of their phase formation and structural growth characteristics using X-ray diffraction and Atomic Force Microscopy respectively. The dielectric properties are strongly affected by the substrate type, post deposition annealing time, and temperature. In order to verify all these properties, thin interfacial-buffer layers of BST (10, 20, 50 nm) were introduced to relieve the stress induced between the film and the substrate. The variations of dielectric constant and ferroelectric properties of as deposited films are discussed in detail. The high tunability, low dielectric loss and low leakage current of these films make them attractive candidates for fabricating tunable dielectric devices. The observed dielectric properties of the BST-films are attributed to homo-epitaxial interfacial layer, which is responsible for the increase in the dielectric constant and tunability.

In this study, we have investigated the structural, interfacial and ferroelectric properties of Sr_1-xCa_xBi₂Ta₂O₉ thin films grown on Pt/TiO₂/SiO₂/Si substrates using pulsed-laser-deposition technique. The decrease in lattice parameters with increasing Ca content was attributed to the smaller ionic radius of Ca. Atomic force microscopy shows that the average grain size and surface roughness of the films increases with the incorporation of Ca. Films with x=0.2 exhibited a maximum remanent polarization of ~23.8 μC/cm² with a coercive field of 175 kV/cm. The higher remanent polarization was attributed to the increased grain size and to the increase in the lattice mismatch between TaO₂ and SrO planes. The presence of metallic bismuth at the interface of the film and the substrates was confirmed using XPS depth profile analysis. The current transport property of the thin film capacitors suggests a bulk-limited dc-current conduction mechanism.

Magnetotransport data on MgB₂ thin films, fabricated on Al₂O₃ substrates using electron–bean deposition and Mg diffusion method are reported for applied magnetic fields up to 9 T. The upper critical field anisotropy, lower critical field and irreversibility field versus temperature are determined. The Hall coefficient is slightly temperature-dependent and positive in the normal state. Using the extracted data, the electronic mean free path, coherence length ξ₀, anisotropic coefficient γ and penetration depth λ are calculated.

The thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) of the as-deposited and electrochemically oxidized Hg₁Ba₂Ca₁Cu₂O_6+δ(Hg-1212) samples were carried out in air, flowing oxygen and nitrogen environment in order to estimate the thermal decomposition temperature and hence to maintain the annealing temperature and atmosphere. After annealing, electrochemically synthesized films showed an increase in T_c from 104.7 K to 119 K and J_c values from 1.43×10³ to 4.3×10³A/cm². Electrochemically oxidized Hg-1212 films in under-, optimally- and over-doped states were irradiated with a Red He–Ne laser (2mW) and the T_c was found to increase from 104.7 K to 106 K and J_c from 1.43×10³ to 1.89×10³A/cm². The effects of annealing and photo-irradiation on structural, microstructural and superconducting properties of electrochemically synthesized Hg-1212 films were investigated and discussed in detail in this paper.

The optical properties of metal-free phtalocyanine (H₂Pc) in thin film form is investigated. X-ray diffractograms of the (H₂Pc) powder show that it has a α-polycrystalline form with a monoclinic structure. The thermal evaporation of (H₂Pc) powder leads to α-polycrystalline films, oriented preferentially to the (001) plane. After annealing at 623 K for two hours, a mixture of α- and β-phases is formed on an amorphous background. The optical properties of (H₂Pc) thin films have been studied using spectrophotometeric measurements of transmittance and reflectance in the range 200–2200 nm for a different film thickness. The refractive index and the absorption index show independence on the film thickness. The refractive index shows anomalous dispersion in the region of the fundamental absorption edge. The absorption measurements show the characteristic splitting of the Q-band and ΔQ is obtained as 0.22 eV. The absorption coefficient in the absorption region reveals indirect transitions. The fundamental and the onset energy gap are determined as 2.74 eV and 1.55 eV, respectively.

Lead zirconate titanate (PZT) thin films of 5 μm thick were produced by a hydrothermal method on pure titanium substrates. ZrOCl₂-8H₂O, Pb(NO₃)₂ and TiO₂ were used as precursors and KOH as a promoter. The hydrothermal synthesis of PZT includes nucleation and crystal growth processes at 120°C or 140°C. The crystallization states were investigated by using scanning electron microscopy and X-Ray diffraction. Piezoelectric properties were evaluated from unimorph cantilever type actuators made of the films. The relationships between the deflection of the actuator due to piezoelectric transverse effect and applied electric field in the direction of thickness of the films showed good linearity. The output voltage from the films under cyclic compressive loading increased with increasing loading frequency, and is saturated at 10 Hz. The PZT films produced by the present methods are satisfactory as a smart material, and are better than the films produced using TiCl₄ as Ti precursor.

In this study, antimony-doped tin oxide (ATO) thin films were fabricated by the sol–gel dip coating process on glass substrates. After the deposition process, the films were treated by Argon–plasma (Ar-400 Watt). The effect of argon–plasma treatments on the electrical and optical properties of ATO thin films was then investigated as a function of the plasma treatment time. It was found that Ar–plasma treatment increased the electrical conductivity of ATO films, but it decreased the optical transmission of ATO thin films.

Nanostructured titanium aluminium nitride (TiAlN) thin films were prepared on Si (111) substrate by reactive DC magnetron sputtering technique for various N₂ flow rates. X-ray diffraction showed that the films are nanocrystalline and the grain size decreases from 14 nm to 5 nm as the N₂ flow rate is increased. The thermal properties are then studied by photoacoustic (PA) spectroscopy. The study revealed an increase in thermal diffusivity and conductivity with increasing N₂ flow rates, and the measured values of the thermal properties are significantly lower than those obtained with bulk materials which constitute TiAlN.

A spin-2 system consisting of two layers of Bethe lattices each with a branching ratio of q Ising spins was analyzed by the use of the exact recursion relations in a pairwise approach. The upper layer interacting with nearest-neighbor (NN) bilinear interaction J₁ is laid over the top of the lower layer interacting with bilinear NN interaction J₂, and the two layers are tied together via the bilinear interaction between the vertically aligned adjacent NN spins denoted as J₃. The study of the ground state phase diagrams on the (J₂/|J₃|, J₁/|J₃|) plane with J₃>0 and J₃<0 and on the (J₂/J₁, J₃/q J₁) plane with J₁>0 has yielded five distinct ground state configurations. The temperature dependent phase diagrams are obtained for the case with intralayer coupling constants of the two layers with ferromagnetic type J₁ and J₂>0, and the interlayer coupling constant of the layers with either ferromagnetic J₃>0 or antiferromagnetic type J₃<0 on the (kT/J₁, J₃/J₁) planes for given values of the J₂/J₁ for various values of the coordination numbers. As a result, we have found that the model presents both second- and first-order phase transitions, therefore, tricritical points.

In this work, the heat capacity in dimensionally quantized semiconductor thin films with Kane's dispersion law is investigated. Under certain conditions, quantum size effect occurs, depending on the thickness of the thin film, the concentration of conductive electrons, and the non-parabolicity parameters. In thin films having non-parabolic energy spectrum in degenerate electron gas, the film thickness depends on the subband number and the concentration. Therefore, heat capacity takes the form of the saw toothwise and changes as non-monotonous.

Hydrogen-free diamond-like carbon (DLC) thin films were prepared at different repetition rates of laser pulses by pulsed laser ablation of graphite target at room temperature. The microstructure of the thin films was characterized by Raman spectroscopy. Raman measurements showed that sp³ bonded carbon fraction is reduced with increase of repetition rates of laser pulses from 5 to 20 Hz. Optical properties, namely photoluminescence (PL), optical absorption, extinction coefficient (k), and refractive index (n), were measured by fluorescence spectrophotometer, scanning spectrophotometer, and spectroscopic ellipsometer. By changing the repetition rates of laser pulses from 5 to 20 Hz, the PL and optical absorption were gradually increased, while the deposition rate and optical band gap of the films decreased strictly with the increase of repetition rate. The extinction coefficient (k) and refractive index (n) were found to be in the range of 0.468–0.938 and 1.92–2.27, respectively. These results indicate that repetition rate of laser pulses has a strong influence on the microstructure and optical properties of the films. Based on the experimental results, a possible causation about the effect of repetition rate on PL was proposed.

Giant magnetostrictive (Tb_0.28Dy_0.72)Fe_1.90 thin films were deposited on Si (111) substrates at room temperature by pulsed laser deposition (PLD). The crystalline state and the magnetic properties of the samples were investigated in relation to the different annealing temperatures T_a, which varied between 623K and 923K. X-ray diffraction results indicated the films are in amorphous state after annealing at T_a = 623K-823K for 1h, and were partially crystallized at T_a = 923K for 1h. Meanwhile, the annealing treatment showed a great influence on the magnetic anisotropy. The orientation of the magnetic easy axis of the as-deposited films changed from perpendicular to parallel to the film plane after annealing treatment. The mechanism of the transformation of the magnetic easy axis was explained in terms of the tensile stress which is formed due to the difference in the thermal expansion coefficients of the thin film and substrate.

The magnetic coupling in pseudomorphic overlayer and sandwich structures of 2ML magnetic ultrathin films on Cu(001) substrate is investigated by using spin-polarized density functional theory. The 2ML magnetic overlayers have significant magnetic moment except CrNi overlayer for which magnetic moment is very small (0.004 μ_B/atom). The overlayers having one layer of Cr turn out to be antiferromagnetically coupled except CrNi/Cu overlayer which has ferromagnetic coupling. All other overlayers have ferromagnetic coupling. In contrast to ferromagnetic MnMn/Cu overlayer, the Cu/MnMn/Cu sandwich has antiferromagnetic coupling. Similar to CrFe/Cu overlayer, the Cu/CrFe/Cu sandwich has antiferromagnetic coupling, while all other sandwiches have ferromagnetic coupling. The sandwiched structures have reduced magnetic moment as compared to their overlayer counterparts. The MnMn, MnFe, and MnCo sandwiches have highly reduced magnetic moment as compared to their overlayer counterparts.

Laser ablation has attracted special interest for the formation of thin films compared with other formation technique. A distinctive feature of laser ablation is that it allows high quality and stoichiometry of films of even very complex element material. In this presentation, laser ablation of AgInSe₂ chalcopyrite semiconductor will be discussed in which it is difficult to maintain stoichiometry by conventional method. High Quality AgInSe₂ (AIS) films were grown on Glass substrates by the ultra-high-vacuum pulsed laser deposition technique from the AIS target synthesized from high-purity materials. The X-ray diffraction studies of the films show that films are textured in (112) direction. The substrate temperature appears to influence the properties of films. Increase in substrate temperature results in a more ordered structure. Compositional analysis has been carried out by EDAX. It is observed that compositional stoichiometry is maintained to a greater extent by PLD technique than other traditional methods like thermal evaporation. The optical studies of the films show that the optical band gap is about 1.20 eV.