PLD Technique Research Articles

Microstructure and selected mechanical and electrical property analysis of Sr-doped LaCoO3 perovskite thin films deposited by the PLD technique

Abstract This work presents the results concerning microstructural, mechanical property and electrical resistance investigations of La1- x Sr x CoO3 thin films produced by the laser ablation (PLD – Pulsed Laser Deposition) method on Si and MgO single crystal substrates with (001) orientation. The microstructure and chemical/phase composition analysis of the deposited films was carried out using scanning/transmission electron microscopy, X-ray diffraction and atomic force microscopy. Additionally, adhesion and nanohardness tests were performed. The investigations allowed verification of the quality of the prepared La1- x Sr x CoO3 thin films and show that implementing the PLD technique makes it possible to obtain smooth and dense films with nanocrystalline structures, while preserving the composition of the bulk target. Research studies showed that by properly selecting the parameters for the PLD process it is possible to deposit films with a significantly lower amount and smaller size of undesirable nanoparticles. A specialized measuring station was used to determine the response of thin films to an oxidizing gas atmosphere. The observed decrease in resistance of the thin films in the presence of 50 ppm of NO2 oxidizing gas is typical for p-type semiconductors. This indicates that all of the produced films exhibit a sensitivity to this gas and could be used as NO2 sensors.

Effect of the AgO content on the surface morphology and electrical properties of SnO2 thin films prepared by PLD technique

Tin dioxide doped silver oxide thin films with different x content (0, 0.03, 0.05, 0.07) have been prepared by pulse laser deposition technique (PLD) at room temperatures (RT). The effect of doping concentration on the structural and electrical properties of the films were studied. Atomic Force Measurement (AFM) measurements found that the average value of grain size for all films at RT decrease with increasing of AgO content. While an average roughness values increase with increasing x content. The electrical properties of these films were studied with different x content. The D.C conductivity for all films increases with increasing x content. Also, it found that activation energies decrease with increasing of AgO content for all films. Hall measurements confirmed that all the intrinsic films are n-type charge carriers. The variation of carriers concentration increase with increasing x content. Hall mobility decreasing with increasing x content for all films. Also the variation of Drift velocity, carrier life time and free mean path decrease with increasing of x content.

Correlation between surface scaling behavior and surface plasmon resonance properties of semitransparent nanostructured Cu thin films deposited via PLD.

The surface scaling behavior of nanostructured Cu thin films, grown on glass substrates by the pulsed laser deposition technique, as a function of the deposition time has been studied using height–height correlation function analysis from atomic force microscopy (AFM) images. The scaling exponents α, β, 1/z and γ of the films were determined from AFM images. The local roughness exponent, α, was found to be ∼0.86 in the early stage of growth of Cu films deposited for 10 minutes while it increased to 0.95 with a longer time of deposition of 20 minutes and beyond this, it was nearly constant. Interface width w (rms roughness) scales with depositing time (t) as ∼ tβ, with the value of the growth exponent, β, of 1.07 ± 0.11 and lateral correlation length ξ following ξ = t1/z and the value of 1/z = 0.70 ± 0.10. These exponent values convey that the growth dynamics of PLD Cu films can be best described by a combination of local and non-local models under a shadowing mechanism and under highly sticking substrate conditions. From the scaling exponents and power spectral density function, it is concluded that the films follow a mound like growth mechanism which becomes prominent at longer deposition times. All the Cu films exhibited SPR properties where the SPR peak shifts towards red with increasing correlation length (ξ) whereas bandwidth increases initially with ξ and thereafter decreases gradually with ξ.

Effect of Annealing on Some Properties of Zn2SnO4 Thin Films Prepared by PLD Technique

In this paper, the investigation of structural and optical properties of Zn2SnO4 thin films were studied. The films are performed on glass substrates by pulsed laser technique (PLD) using laser Nd: YAG at wavelength of 1064 nm with 800 mj laser energy using repetition rate of 6 Hz. and average 400 laser pulses at room temperature and annealing by tubular quartz furnace at temperature (573,773) K for 2 hours with air. XRD measurements showed that the structure for all samples is polycrystalline with a cubic nanostructure. Surface morphology was studied using scanning electron microscopy SEM and atomic force microscopy AFM. After annealing, the roughness of the surface and the mean grain size were increased. Optical properties as a function to wavelength in the range (300-1100 nm) have been studied. Absorption spectra of Zn2SnO4 thin films showed that absorption decreases with increasing annealing temperature. Direct energy gap for a Zn2SnO4 thin film was increases with increasing temperature for all samples due to crystal growth. The optical properties such as extinction coefficient, refractive index, and dielectric constant were also studied. .

Annealing effects on optical and structural properties of chromium oxide thin film deposited by PLD technique

Optical properties of chromium oxide (Cr2O3) thin films which were prepared by pulse laser deposition method, onto glass substrates. Different laser energy (500-900) mJ were used to obtain Cr2O3 thin films with thickness ranging from 177.3 to 372.4 nm were measured using Tolansky method. Then films were annealed at temperature equal to 300 °C. Absorption spectra were used to determine the absorption coefficient of the films, and the effects of the annealing temperature on the absorption coefficient were investigated. The absorption edge shifted to red range of wavelength, and the optical constants of Cr2O3 films increases as the annealing temperature increased to 300 °C. X-ray diffraction (XRD) study reveals that Cr2O3 thin films are amorphous; while the crystal structure of annealed Cr2O3 films is rhombohedral after annealing at 300 °C for two hour. AFM studies of Cr2O3 thin films exhibit a smooth and well dispersed on the surface.

Structural, Optical, Electrical and Magnetic Studies of PANI/Ferrite Nanocomposites Synthesized by PLD Technique

In the present work PANI, 90%PANI/10%Ni0.8Zn0.2Fe2O4 and 90%PANI/10% Ni0.2Zn0.8Fe2O4 thin films were deposited successfully on the p-type Si-substrates by employing pulsed laser deposition technique (PLD), while the ferrite nanoparticles were synthesized by gel method. The interaction between ferrite nano powders and polyaniline has been studied by using X-ray diffraction (XRD), scanning electron microscope (SEM), UV–Vis spectrum, I–V characteristics and vibration sample micrometer (VSM). X-ray diffraction confirmed the presence of PANI and ferrite phases in the thin film nanocomposites. The average crystalline size value of 90%PANI/10%Ni0.8Zn0.2Fe2O4 and 90%PANI/10%Ni0.2Zn0.8Fe2O4 nanocomposite was estimated by utilizing Scherrer’s formula, they were found 20 nm and 25 nm, respectively. SEM images of the PANI and PANI/ferrite showed dense and inhomogeneous film morphology. The versatile optical properties of PANI/ferrite thin film nanocomposites are important for solar cell application. The obtained optical band gap for 90%PANI/10%Ni0.8Zn0.2Fe2O4 (2.45 eV) is less than pure PANI (2.8 eV) thin film. The lowering in the band gap value of 90%PANI/10%Ni0.8Zn0.2Fe2O4 nanocomposite film could be assigned to band edge bending phenomena. The light sensing behavior of the polyaniline/ferrite nanocomposites were examined at room temperature and showed higher response as compared to pure PANI film. Temperature dependence resistance characteristic was investigated in range between 25 and 100 °C under air atmosphere. The results showed that the dc resistance gradually decreases with the temperature increases and showing the semiconductor behavior of the prepared samples. The measured electrical resistance and band gap energy strongly suggest that the film with composition 90%PANI/10%Ni0.8Zn0.2Fe2O4 is a suitable candidate to be used in solar cell applications.

Improved white light emission from ZnS:Mn/ZnO/GaN core-shell nanorods array

By depositing ZnS:Mn films using PLD technique to coat ZnO nanorods which were grown on GaN substrate using hydrothermal method, high quality ZnS:Mn/ZnO/GaN core-shell nanorods array was prepared. The PL spectrum of ZnS:Mn/ZnO/GaN core-shell array ranges from blue-violet light to red light (400–700 nm). It consists of four luminous bands: UV light at 375 nm originating from the free exciton emission of ZnO, a blue light emission at 450 nm from GaN, an orange light emission at 590 nm mainly from ZnO nanorods and Mn2+ in ZnS, and a green light emission at about 530 nm related to ZnS:Mn/ZnO interface. The mechanism of green light emission is analyzed in detail. The color coordinate of ZnS:Mn/ZnO/GaN core-shell array is (0.3347, 0.318), and the color temperature is 5375 K, much closer to the standard white light when compared with other systems.

Diluted magnetic semiconducting properties of nanocrystalline Zn0.98X0.02O (X = Fe, Ga, Ni) thin films deposited by PLD technique for spintronic applications

Structural, optical and diluted magnetic semiconducting properties of pristine ZnO, Fe-doped (Zn0.98Fe0.02O), Ga-doped (Zn0.98Ga0.02O) and Ni-doped (Zn0.98Ni0.02O) ZnO thin films deposited by pulsed laser deposition technique have been studied. X-ray diffraction (XRD) studies reveal the nanocrystalline nature in single wurtzite phase of all the films. Optical bandgap of the films found to depend upon the transition/post-transition metal doping and has a maximum value (∼3.65 eV) for Zn0.98Ga0.02O film and lowest value (∼3.23 eV) for Zn0.98Ni0.02O film. SQUID-vibrating sample magnetometer studies confirm the ferromagnetic nature of all the films with well defined field dependent magnetization (M−H) curves and temperature dependent zero field cooled (ZFC) and field cooled (FC) curves. The origin of ferromagnetism in the present films has been analyzed under bound magnetic polarons (BMPs) and grain boundary specific area models. The present films are found to follow the grain boundary specific area model for the origin of ferromagnetism.

Synthesis of Cadmium Oxide/Si Heterostructure for Two-Band Sensor Application

Cadmium oxide on Si heterostructure device has been constructed using (111) oriented silicon substrate by reactive PLD technique. The deposition of CdO film was carried out by irradiating high-purity Cd target using Nd:YAG laser in the presence of reactive oxygen gas. The deposited tin films were characterized by the X-ray diffraction, scanning electron microscopy and AFM. The electrical properties of deposited films were investigated reaching to the optimum pressure of oxygen at which the device has been prepared. The films were polycrystalline in nature having high orientation along (111) (200) and (220) planes. The films are formed to give the lower value of the resistivity which was found to be 7.56 × 10−3 Ω cm at the ambient of oxygen pressure around 350 Torr and without using post-deposition heat treatment. The electrical properties such as current–voltage in dark and illumination and capacitance–voltage measurement were carried out and found to be directly related to the substrate temperature. Also, the detector parameters have been characterized by measuring responsivity and detectivity which are found to be 0.38 A/W and 3.9 × 1012 cm Hz1/2 W−1, respectively.

High temperature superconducting YBCO microwave filters

Epitaxial thin films of YBCO high temperature superconductor are widely used in telecommunication technology such as microwave filter, antenna, coupler and etc., due to their lower surface resistance and lower microwave loss than their normal conductor counterparts. Thin films of YBCO were fabricated by PLD technique on LAO substrate. Transition temperature and width were 88 K and 3 K, respectively. A filter pattern was designed and implemented by wet photolithography method on the films. Characterization of the filter at 77 K has been compared with the simulation results and the results for a made gold filter. Both YBCO and gold filters show high microwave loss. For YBCO filter, the reason may be due to the improper contacts on the feedlines and for gold filter, low thickness of the gold film has caused the loss increased.

The influences ofV and Gd dopants on the structures and electrical and magnetic properties of PbPdO2 thin films.

PbPdO2, PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 thin films with body-centered orthorhombic structure were prepared by PLD technique, respectively. Their structures, magnetic and electrical properties were measured by XRD, SEM, AFM, EDS, XPS and VSM, respectively. The experimental results indicate that the three samples all have the preferred orientation of (002), and room temperature ferromagnetism. From EDS and XPS results, we can deduce that there exist Pb vacancies in the three samples. Meanwhile, the valence states for Pb, Pd, O, Gd and V ions were found to be 2+, 2+, 2−, 3+ and mixed 4+ and 5+, respectively. It was also found that the magnetic moments of PbPdO2 and PbPd0.9Gd0.1O2 are least and largest, respectively. Moreover, the electrical characteristics analysis indicates that the electrical resistivity is enhanced by V ion substitution, but reduced by Gd ion substitution. In addition, the significant insulator–metal transition temperatures of PbPdO2, PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 were found to be about 385 K, 390 K and 430 K, respectively. Finally, according to the experimental facts of Pb vacancies in the three samples, the first-principles calculated models containing Pb vacancies were established. The calculated results explain well the magnetic origin of PbPdO2, and V and Gd doping roles on its electrical and magnetic properties.

Amorphous-cathode-route towards low temperature SOFC

Amorphous cathode films deposited by PLD technique have higher oxygen diffusivity compared with the material in a crystalline state.

Synthesis and characterizations of (δ-Bi2O3)0.93(TiO2)0.07 thin films grown by PLD technique for optoelectronics

In this work (δ-Bi2O3)0.93(TiO2)0.07 nanocomposite thin films were synthesized by pulsed laser technique (PLD) onto glass substrate, XRD analysis revealed that the films have polycrystalline structure of cubic δ-Bi2O3 with preferred orientations, the chemical compositions were studied by FTIR which confirmed the presence of Bi-O-Ti and Ti-O-Bi vibration modes, AFM analysis showed the films were free of voids and cracks with RMS roughness of 10.3nm and average grain size 55.27nm, the optical properties indicated that the films have high transmittance (> 80%) in visible and NIR regions with high optical band gap of 3.8166eV, these novel characteristics of this nanocomposite make it a promising optical material for optoelectronic applications.

Dielectric properties of Mn doped Bismuth Barium Titanate based ceramic thin films prepared by PLD technique

In this article, the effect of Mn doping on the permittivity and dielectric loss in 0.67BiFeO(3)-0.33BaTiO(3) (BF-BT) based film bulk acoustic resonator test structures has been investigated. BF-BT thin films were deposited on the fused silica substrates with Pt/TiO2/Ti as bottom electrode. During the study of the BF-BT based parallel-plate structures, it has been revealed that BF-BT is in the ferroelectric state at room temperature. Higher permittivity (epsilon) is observed at a growth temperature of 600 degrees C and lower dielectric loss is achieved at 0.3 wt% Mn doping contents. These results show that the proposed BF-BT based FBAR test structure has a great potential for applications in tunable thin Film Bulk Acoustic Resonator (FBAR) devices. Comparison of the measured and simulation results has been made by utilizing the Mason equivalent circuit.

Microstructure and properties of VN/Ag composite films with various silver content

The VN/Ag composite films with various silver content were prepared by PLD technique, and the microstructures, mechanical and tribological properties at elevated temperature to 900 °C of films were investigated, respectively. The results show that the films were composed of the fcc VN and Ag nano-crystalline grains. With the increase of silver content from 8.2 to 56.1 at.%, the grain size increased and the surface morphology deteriorated gradually, the hardness and elastic modulus of the films decreased from 18.6 GPa, 226.3 GPa–8.1 GPa, 126.6 GPa, respectively. Only appropriate silver addition could improve the lubricity of the VN/Ag films. The film with 16.6 at.% Ag were found to be optimized for lubrication from RT to 900 °C. At low temperatures, the lubricant property of the film relied on the metal silver heavily. At elevated temperatures, a series of Magnéli phase (vanadium oxides) and the layered structure silver vanadates (such as Ag3VO4, AgVO3) formed by tribochemical reactions in the contact area played a critical role in improving lubrication properties. A synergy of the lubricating Ag at low temperatures and the new lubrication phases generated at high temperatures could be responsible to the excellent lubricity of the VN/Ag films in wide temperature range.

Fabrication of pulsed laser deposited Ge doped CZTSSe thin film based solar cells: Influence of selenization treatment

In the present work, Ge doped CZTGeS thin films are pulsed laser deposited followed by annealing treatment in selenium environment. The influence of selenization condition on the structural, morphological, optical and electrical properties of the absorber thin films are investigated. The thin films characterized using X-ray diffraction (XRD) and Raman spectroscopy techniques confirm the formation of Kesterite CZTGeSSe thin film compound with dominant A1 mode vibration. The morphological and optical studies of the thin films reveal the formation of compact and void free microstructure with optimal band gap in the range of 1–1.2eV. The impact of selenization temperature on the quality of thin films has been studied and thin film solar cells are fabricated with CZTGeSSe absorbers grown at various annealing temperatures from 525 to 575℃ to evaluate the performance of devices as a function of an annealing temperature. The elemental Ge and Sn losses from the absorber compound confirmed from X-ray fluorescence spectroscopy (XRF) depended on the annealing temperature and linearly increased with increasing temperature affecting the optical, compositional and microstructural properties of the thin films. Compositional non uniformity is one of the factors that limit the performance of solar cell device. PLD technique due to its advantage of achieving precise stoichiometry control combined with optimized selenization conditions can potentially address the issue. Compared to solar cell fabricated from absorber compound annealed at 525 and 575℃, the solar cell fabricated from the absorber annealed at 550℃ exhibited the best conversion efficiency of 3.82% with Voc 434mV, Jsc 18.33mA/cm2, FF 47.0% and retained nearly 90% power conversion efficiency (PCE) stability after time period of 60 days.

Pulsed laser deposition of PbTe under monopulse and multipulse regime

The aim of this paper is to compare PLD technique with monopulse and multipulse nanosecond laser excitation. We show the feasibility of depositing nanometric layers of PbTe employing the regimes already mentioned. Each of the grown layers were characterized by XRD, EDXS, SEM, Spectroscopic Elipsometry, AFM and the thickness was measured by mechanic profilometry. We have conducted comparative experiments to show the advantages and drawbacks of making PLD with mono and multipulse nanosecond laser.

Contribution of Titanium, Chromium and Carbon Buffer Interlayers to Bio-Tribological Properties of Multilayer Composites

Abstract Research studies on bio-tribological protective coatings of titanium, chromium and carbon based have been performed. Thin films were fabricated by hybrid PLD technique (PLD supported by magnetron sputtering). Coatings consisted of two parts; the inner part (first from the substrate) in each case was formed by titanium or chromium/titanium nitride or chromium nitride (Ti/TiN or Cr/Cr2N). The outer part was formed by pure DLC or multilayer DLC/Ti or Cr. No delamination was found at the interface. Titanium or chromium metallic layer was deposited as a first layer directly on the metallic substrate to avoid delamination. All individual layers were built of columnar nano-crystallites. Mechanisms of the mechanical wear of analyzed systems were presented, focusing on the cracking propagation in ball-on-disc tests using an 1 N and 5 N applied loads for 5 000 cycles. Complex microstructure analysis of presented nano-multilayer coatings, before and after mechanical tests, were performed by means of transmission electron microscopy (TEM). The highest stress concentration during mechanical uploading was moved through the multilayer coating by breaking only one layer at the time. The microstructure characterization revealed that cracking propagating in the outer part of the coating was stopped at the interface. In the case of the inner part of the coating Ti/TiN; Cr/Cr2N, ceramic layers showed brittle cracking, while metallic (Ti or Cr) ones deformed plastically. Fabricated coatings were subjected under the analysis in the biomechanical system optimized to test for the direct contact with a human whole blood. The study considered physiological conditions mainly related to the temperature and humidity and the frequency of cyclic deformation of the artificial vessel into which the tested sample was introduced.

Growth and characterization of yttrium iron garnet films on Si substrates by Chemical Solution Deposition (CSD) technique

Yttrium Iron Garnet (YIG) films were prepared on Si substrates by Chemical Solution Deposition (CSD) technique using acetic acid and deionized water as solvents. Well-crystallized and crack-free YIG films were obtained when annealed at 750 °C and 850 °C respectively, showing a low surface roughness of several nanometers. When annealed at 750 °C for 30 min, the saturated magnetization (Ms) and coercive field (Hc) of YIG films were 0.121 emu/mm3 (4πMs = 1.52 kGs) and 7 Oe respectively, which were similar to that prepared by PLD technique. The peak-to-peak linewidth of ferromagnetic resonance (FMR) was 220 Oe at 9.10 GHz. The results demonstrated that CSD was an excellent technique to prepare high quality yttrium iron garnet (YIG) films on silicon, which could provide a lower-cost way for large-scale production on Si-based integrated devices.

Preparation of NanostructureTiO2 at Different Temperatures by Pulsed Laser Deposition as Solar Cell

Deposition of the Titanium oxide (TiO2) particles on glass and the Si substrates was materialized for a wide range of temperatures (100-400)°C; using PLD technique at constant laser energy 800 mJ of frequency doubled Nd: YAG laser wavelength of 532nm running at 10 Hz rate and 10ns duration pulses. UV-Vis spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM), Atomic Force Microscope(AFM), electrical conductivity (σdc), Hall coefficient (RH) and (I-V) and (C-V) measurements were employed to examine optical, morphological and electrical properties of the deposited films. 85% film transparency was accomplished with optical band gap of (3.25 – 3.64) eV.(I-V) characteristics showedan enhanced TiO2 p-n junction thin film solar cell efficiency by 1.6% at 400°C.