Pulsed Laser Deposition Technique Research Articles

Multiple-Response Optimization of Aluminum Oxide Nanocoating Prepared by Pulsed Laser Deposition Using Taguchi Design

In this work, an aluminum oxide nanocoating was prepared using the pulsed laser deposition technique to study the properties of the coating and to find the optimal conditions to achieve the highest quality of the aluminum oxide nanocoating. The structural properties were studied using X-ray diffraction. The results showed that the aluminum oxide nanocoatings were alpha phase polycrystalline structures. The surface topography was studied using atomic force microscopy. The surface topography showed that the average surface roughness ranged from 1.26 nm to 7 nm. The optical properties were studied using a UV-VIS spectrometer. It showed the energy gap within the range 4.09 eV to 3.98 eV. The hardness of the aluminum oxide nanocoatings were calculated using the nanoindentation technique and found within the range of 32.79 GPa to 10.41 GPa. According to the present work, the effect of the input parameters represented by the pulse energy and the number of pulses on the responses represented by the energy gap, hardness, and surface roughness were studied. The experiments were designed based on the L9 orthogonal array with the Taguchi approach. A multiple responsive optimizations of Takeuchi's design was done using the desirability function.

Room-temperature multiferroicity in GaFeO3 thin film grown on (100)Si substrate

Room-temperature magnetoelectric multiferroicity has been observed in c-axis oriented GaFeO3 thin films (space group Pna21), grown on economic and technologically important (100)Si substrates by a pulsed laser deposition technique. Structural analysis and comprehensive mapping of the Ga:Fe ratio across a length scale range of 104 reveals coexistence of epitaxial and chemical strain. It induces formation of finer magnetic domains and large magnetoelectric coupling—a decrease in remanent polarization by ∼21% under ∼50 kOe. Magnetic force microscopy reveals the presence of both finer (<100 nm) and coarser (∼2 μm) magnetic domains. Strong multiferroicity in epitaxial GaFeO3 thin films, grown on a (100)Si substrate, brighten the prospect of their integration with Si-based electronics and could pave the way for development of economic and more efficient electromechanical, electrooptic, or magnetoelectric sensor devices.

Influence of annealing on structural, morphology, magnetic and optical properties of PLD deposited CuFe2O4 thin films

• Successfully produced of CuFe 2 O 4 nanoparticles and prepared thin films which is grown on a glass substrate by pulsed laser deposition (PLD) technique. • The detailed structural properties of films are studied using experimental (XRD, FE-SEM, VSM, and Optical properties). • The magnetization and remanence of prepared samples have decreased with increased annealing substrate temperatures. • As per report the thin films have direct band gap energy; it reduces with increasing annealing temperature, which is due to improve the crystallinity. In this work, copper-ferrite (CuFe 2 O 4 ) nano-crystallite was synthesized by the gel method and deposited on a microscope glass substrate using a pulse laser deposition (PLD) technique at room temperature. The obtained deposited thin films were annealed at four different temperatures (200 °C, 300 °C, 400 °C, and 500 °C) for 4 hours in an air atmosphere. The structural, morphological, thermal, magnetic, and optical properties of the thin film samples were characterized using an X-ray diffractometer (XRD), Field emission scan electron microscopy (FE-SEM), thermogravimetric and differential thermal analysis (TG-DTA), Vibrating sample magnetometer (VSM) and Ultraviolet-Visible spectrophotometer (UV-Vis). X-ray diffraction patterns of the unannealed and annealed films show the presence of the anti-ferromagnetic (α-Fe 2 O 4 ) phase along with the single-cubic spinel structure phase. The grain sizes were found to have low crystalline copper ferrite with a mixture magnetic and hematite crystalline phases. With the decrease of the grain size and increasing of annealing substrate temperatures, the ratio of hematite to magnetite phases increased, and reached to an impure magnetite phase for the 6.35 nm grain. The morphological images obtained by transmission electron microscopy technique showed that the particle size of copper ferrite nanoparticles gradually became smaller from 10 nm to 5 nm. Surface morphology of all fabricated samples investigated by field emission scan electron microscopy technique exhibiting different sizes, almost spherical grains and agglomerates, which may be depending upon preparation method and substrate temperature. The correlation between structure and thermal stability of prepared materials was studied by (TG-DTA). With increasing of annealing substrate temperature from room temperature to 500 °C, the saturation magnetization (M s ) value decreased from 8.79 emu/g to 2.12 emu/g while the coercivity (H c ) value increased from 52.22 Oe to 91.26 Oe. The lowest widening of optical band gap in the copper ferrite film was 1.57 eV. The magnetic and the optical parameters suggested that these films are potential candidates for gas sensor applications.

Direct synthesis of few atomic layer MoS 2 films on a plastic substrate by pulsed laser deposition technique

Direct synthesis of few atomic layer MoS ₂ films on a plastic substrate by pulsed laser deposition technique

Laser Processed Hybrid Lead-Free Thin Films for SAW Sensors

In this study we report the specific interaction of various gases on the modified surface of acoustic wave devices for gas sensor applications, using the piezoelectric ceramic material BaSrTiO3 (BST), with different concentrations of Sr. For enhancing the sensitivity of the sensor, the conductive polymer polyethylenimine (PEI) was deposited on top of BST thin films. Thin films of BST were deposited by pulsed laser deposition (PLD) technique and integrated into a test heterostructure with PEI thin films deposited by matrix assisted pulsed laser evaporation (MAPLE) and interdigital Au electrodes (IDT). Further on, the layered heterostructures were incorporated into surface acoustic wave (SAW) devices, in order to measure the frequency response to various gases (N2, CO2 and O2). The frequency responses of the sensors based on thin films of the piezoelectric material deposited at different pressures were compared with layered structures of PEI/BST, in order to observe differences in the frequency shifts between sensors. The SAW tests performed at room temperature revealed different results based on deposition condition (pressure of oxygen and the percent of strontium in BatiO3 structure). Frequency shift responses were obtained for all the tested sensors in the case of a concentration of Sr x = 0.75, for all the analysed gases. The best frequency shifts among all sensors studied was obtained in the case of BST50 polymer sensor for CO2 detection.

Ameliorating the stability of erbium-doped fiber laser using saturable absorber fabricated by the pulsed laser deposition technique

In this paper, we present the performance and stability of an erbium-doped fiber laser (EDFL) based on ZnO saturable-absorber (SA) prepared using two schemes: solution method (SM) and pulsed laser deposition technique (PLDT). It was observed that EDFL with ZnO-SA prepared using SM emits at 1561.25 nm under a pump power of 230 mW. As the pump power is increased from 22.2 mW to 75.3 mW, the pulse duration decreases from 24.91 to 10.69 µs, and the pulse repetition rates increase from 11.59 to 40.91 kHz. Besides at pump power of 75.3 mW, the peak power, pulse energy, and average output power are measured as 0.327 mW, 2.86 nJ, and 0.18 mW, respectively. However, when PLDT-based SA was incorporated into the ring cavity, the emission wavelength is noticed at 1568.21 nm at a pump power of 230 mW. With the increase in pump power from 22.2 mW to 418 mW, the pulse repetition rates increase from 10.79 to 79.37 kHz and the pulse width decreases from 23.58 to 5.6 µs. Furthermore, the peak power, pulse energy, and average output power are observed to be 10.9 mW, 74 nJ, and 5.35 mW, respectively. The stability of EDFL based on SAs prepared using SM and PLDT has also been investigated. To the best of the author's knowledge, it is the first comparison of performance and long-term stability of EDFL based on two experimental techniques SM and PLDT-based SAs. These findings suggest that PLDT-based SAs provides optimum stability over a long period and enhanced the performance of fiber lasers compared to the SAs prepared using the conventional SM technique. This study paves the way for the development of ultra-stable SAs for their potential applications in pulsed laser sources and photonic devices.

Preparation of high-quality factor dielectric resonators for low-noise YBa[formula omitted]Cu[formula omitted]O[formula omitted] radio frequency superconducting quantum interference devices

Tank circuit (resonator) is essential for the operation of the radio frequency (rf) superconducting quantum interference device (SQUID) and the quality factor of the tank circuit has significant impact on the sensitivity of the rf SQUID. For high transition temperature (high-Tc) rf SQUID, dielectric resonator is presently one of the most practical tank circuits. By growing YBa2Cu3O7−δ (YBCO) superconducting thin film on (100) SrTiO3 substrate with a pulsed-laser deposition technique and then patterning the YBCO thin film into flux concentrator with a washer structure, a series of dielectric resonators with unloaded quality factor Q0 ranging from 200 to 6000 has been prepared. Surface morphology and electrical transport measurements have been carried out to investigate the dependence of Q0 on the property of the YBCO thin film, which suggests that it is effective to boost the Q0 of the resonator through improvements in both the crystalline quality and the superconductivity of the thin film. By integrating the resonators with the same SQUID chip, a set of YBCO rf SQUIDs has been assembled to explore the influence of Q0 of the resonator on the performance of the rf SQUID. It is observed that the white noise of the device decreases substantially with the increase of Q0, in accordance with the theoretical suggestion. Moreover, as Q0 rises, the low frequency noise of the device is shown to reduce as well, revealing the importance of the high-Q0 resonator in depressing the noise of the high-Tc rf SQUID over the entire frequency range. With the resonator of Q0=6000, the YBCO rf SQUID at 77 K exhibits a field sensitivity of 50 fT/Hz1/2 in the white noise region, 58 fT/Hz1/2 and 110 fT/Hz1/2 at 10 Hz and 1 Hz respectively, suggesting its potential in applications such as magnetoencephalography in biomagnetism which have critical requirements on field sensitivity of the high-Tc SQUID especially at low frequencies.

Epitaxial Growth of β-Ga2O3 Thin Films on Si with YSZ Buffer Layer.

We report the epitaxial growth of (2̅01)-oriented β-Ga2O3 thin films on a (001) Si substrate using the pulsed laser deposition technique employing epitaxial yttria-stabilized zirconia (YSZ) buffer layers. Epitaxial β-Ga2O3 thin films possess a biaxial compressive strain on YSZ single-crystal substrates while they exhibit a biaxial tensile strain on YSZ-buffered Si substrates. Post-annealing improves the crystalline quality of β-Ga2O3 thin films. High-resolution X-ray diffraction analyses reveal that the epitaxial (2̅01) β-Ga2O3 thin films on Si have eight in-plane domain variants to accommodate the large difference in the crystal structure between monoclinic β-Ga2O3 and cubic YSZ. The results provide a pathway to integrate epitaxial β-Ga2O3 thin films on a Si gold standard substrate, which will expand the application scope beyond high-power electronics.

Ultra-fast dynamic deposition of EuBa2Cu3O7−δ-BaHfO3 nanocomposite films: Self-assembly structure modulation and flux pinning behaviors

Structure modulation of rare-earth barium cuperates (REBCO) superconducting films plays an essential role in the flux pinning behaviors. In this paper, nano-composite EuBa2Cu3O7−δ-BaHfO3 (EuBCO/BHO) films were deposited by the ultra-fast pulsed laser deposition technique. All nano-composite films exhibited high-quality orientation under the growth rates up to 100 nm/s. TEM cross-sectional analysis reveals that the EuBCO/BHO films have a distinct lamellar structure, which is related to the periodic change of growth conditions during the multi-turn dynamic deposition. In addition, the morphology of BHO varies with dopant content, which suggests a strong correlation between dopant content and the BHO self-assembly mechanism. Consequently, the vortex behavior shifts from giant-flux creep to vortex-glass formation at the thermally activated flux flow region as the dopant content increases. The primary flux pinning behaviors change from random to correlated pinning with the increase of dopant content at 4.2 K. Due to the larger contribution of the correlated pinning machinimas, the 8% BHO-doped EuBCO film exhibits the highest Jc value at 4.2 K, with moderate fields (below 8 T) among all the three films. At 4.2 K and 14 T, the 6% BHO doped EuBCO film has the highest Fp value attributing to the predominate random pinning mechanism.

Effect of cobalt substitution on the structural, ferroelectric, and magnetic properties of bismuth ferrite thin films

Epitaxial films of multiferroic BiFe1−xCoxO3 (BFCO) with 0≤x≤0.35 are grown on (001)-oriented SrTiO3 and SrRuO3 buffered SrTiO3 substrates using the pulsed laser deposition technique. The effect of structural transformation from rhombohedral to tetragonal phase with increasing cobalt substitution on the magnetic, electrical, and piezo-/ferroelectric properties is investigated. Piezoresponse force microscopy is used to quantify the coercive voltage from the phase hysteresis loops for different thickness films to investigate the semi-empirical Kay–Dunn scaling law with varying cobalt concentrations. For the rhombohedral structure, a reduction of the coercive voltage is observed with increasing substitution of Fe by Co. The coercive voltage of a 10 nm BFCO (x=0.35) film is found to be 0.63 V, which is 67% lower than that of a pure BiFeO3 (BFO) (1.9 V) film of the same thickness. Cobalt substitution also leads to changes in the magnetic and electrical properties due to modification of spin ordering and reduction of the bandgap, respectively. Further, to validate the experimental results, we have performed theoretical calculations using density functional theory. The theoretical results indicate a reduction in unit cell volume and enhancement in net magnetization can be achieved with cobalt substitution, in agreement with experimental results. Partial Co substitution can, thus, provide a pathway to realize BFO-based nonvolatile magnetoelectric devices with reduced operating voltage.

Boron doping of diamond-like carbon films by pulsed laser deposition technique for photovoltaic application

Diamond-like carbon (DLC) films were deposited by pulsed laser deposition technique using a glassy carbon disc as carbon source material. Boron doping in DLC films was carried out by ablating boron disc sequentially during the synthesis of DLC films. Field emission scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and Raman measurements were utilized to characterize the films. Hot-probe study indicated the films to be p-type. Core level XPS spectra of B1s appeared at ∼ 189.5 eV and indicated that boron atoms are in form of B-C network connect. Raman studies indicated a dilatation of host lattice with the incorporation of boron in DLC matrix favouring graphitization. Band gap of the thin films decreased from ∼2.0 eV (pure DLC) to ∼1.76 eV with increased incorporation of boron. A photovoltaic cell structure (glass/indium tin oxide)/B:DLC/ZnO/Ag) conceived here, indicated an open circuit voltage ∼110 mV, short circuit current density ∼7.5 mA/cm2 with a fill factor ∼0.3, and a low conversion efficiency (η) ∼ 0.23%.

Effect of growth condition on the electrical behavior of BiFeO3/Si thin film devices

BiFeO3 thin films were deposited onto single crystalline Si (100) substrate using Pulsed Laser Deposition technique. The effect of different oxygen partial pressure on the BiFeO3 film growth, structural and transport properties has been investigated. Structural characterization shows that film growth under lower partial pressure exhibits a minor impurity phase which gets suppressed under higher oxygen partial pressure (OP2). The effect of OP2 during the deposition on the leakage current and the role of oxygen vacancies have been understood in the context of various charge transport mechanism. RBS study confirms the presence of oxygen content in the film studied which are responsible for the modification in the Electrical behavior of BFO/Si thin film devices.

Impact of laser energy on resistive switching properties of BiFeO3 thin films

In this report, BFO thin film samples were deposited using Pulsed Laser Deposition (PLD) technique by altering the PLD laser energy from 150 to 250 mJ, to study the role of laser energy on resistance switching property of pure BFO thin film. Efficient resistive switching properties are essentially required for realization of a memristor device. An appreciably high resistance ratio (∼100) between HRS i.e. high resistance state (“OFF” state) and LRS i.e. low resistance state (“ON” state) was obtained for the sample fabricated at 200 mJ PLD laser energy with a stable retention period of 106 s with reproducible endurance cycles of 108. From the study of charge transport mechanism, it has been observed that the Ohmic conduction is the dominating mechanism in the lower applied biased region while space charge limited conduction (SCLC) and Child's law are the dominating mechanisms in the higher applied biased region for all the deposited BFO thin film samples. Current study extends the application of multiferroic BFO thin films for memory devices.

PLD of transparent and conductive AZO thin films

The pulsed laser deposition (PLD) of aluminium (2 wt %) doped with zinc oxide (98 wt %) (AZO) on glass substrates showed structures and morphology in the nanoscale. The deposition of the AZO thin films was completed at chosen substrate temperatures and low partial pressure of 20 mTorr. The laser energy density fixed at 4 J/cm2 appeared suitable for the ablation of bulk AZO and reduced the probable arrival of droplets onto the substrates. Moreover, the AZO films were deposited at a target-to-substrate distance of 5.78 cm, and the calculated crystallite size ranged from 31.1 to 45.4 nm. The lowest film resistivity of 6.8 × 10−5 Ω cm at an average optical transmittance of 83 % in the UV–vis–NIR region confirms the effect and relevance of the preparation procedure. These observations confirm the AZO thin film crystallinity with an average bandgap energy of 3.36 eV extrapolated relative to the photon energy. Thus, the PLD technique ensures a more significant avenue toward the growth of crack-free and reliable thin films with improved electrical and optical properties.

Synthesis of Silver, Gold, and Platinum Doped Zinc Oxide Nanoparticles by Pulsed Laser Ablation in Water.

In this paper, we propose a simple two-step method for the synthesis of Ag, Au, and Pt-doped ZnO nanoparticles. The method is based on the fabrication of targets using the pulsed laser deposition (PLD) technique where thin layers of metals (Ag, Pt, Au) have been deposited on a metal-oxide bulk substrate (ZnO). Such formed structures were used as a target for the production of doped nanoparticles (ZnO: Ag, ZnO: Au, and ZnO: Pt) by laser ablation in water. The influence of Ag, Au, and Pt doping on the optical properties, structure and composition, sizing, and morphology was studied using UV-Visible (UV-Vis) and photoluminescence (PL) spectroscopies, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The band-gap energy decreased to 3.06, 3.08, and 3.15 for silver, gold, and platinum-doped ZnO compared to the pure ZnO (3.2 eV). PL spectra showed a decrease in the recombination rate of the electrons and holes in the case of doped ZnO. SEM, TEM, and AFM images showed spherical-shaped nanoparticles with a relatively smooth surface. The XRD patterns confirm that Ag, Au, and Pt were well incorporated inside the ZnO lattice and maintained a hexagonal wurtzite structure. This work could provide a new way for synthesizing various doped materials.

The impact of annealing on the electrical properties of ITO/n-CdSe Schottky junctions deposited by pulsed laser deposition technique

The impact of annealing on the electrical properties of ITO/n-CdSe Schottky junctions deposited by pulsed laser deposition technique

Effect of Different Parameters on Raman Scattering Released from Nb2O5 Nanostructures Prepared via PLD Technique

Due to the significance of Nb2O5 as a promising industrial and biomedical material and the importance of Raman analyses to identify nanostructural molecular responsivity for various applications, this study aims to investigate Nb2O5 molecular bands that emerged under the impact of the Raman scattering phenomenon. Besides other advantages, Raman scattering analyses can provide a further investigation of the nanostructural polycrystalline phases supporting the XRD analyses. A pulsed laser was selected as the deposition technique for Nb2O5 thin films prepared with four different parameters. The selection of the pulsed laser deposition (PLD) method was due to the insufficient studies and investigations of Nb2O5 nanostructures prepared via this method. The deposition parameters included the laser energy per pulse, substrate temperature, laser wavelength, and the number of laser pulses. Each preparation parameter was studied in a range, and one obtained value was optimized or selected for investigating the next parameter. Q-switched Nd:YAG pulsed laser was employed for this purpose. Orthorhombic (T-Nb2O5) and monoclinic (H-Nb2O5) were obtained and investigated. XRD analysis was incorporated to confirm the resulting Nb2O5 phases. Previous studies and observations of Niobium (V) oxide molecular Raman scattering bands were also listed for comparison purposes. The results of this study were well-agreed with the previously obtained results.

Annealing-dependent changes in the structural and electrical properties of NiO epitaxial films

NiO and Ni-cluster-embedded NiO epitaxial films grown on c-sapphire substrates using pulsed laser deposition technique are annealed at different temperatures in an oxygen environment. The structural, morphological, and electrical properties of these samples are investigated as functions of the annealing temperature. It is observed that, in all cases, the sample surface becomes smoother with the increase in annealing temperature. The resistivity of the Ni-cluster-free NiO epilayers is found to decrease with the increase in annealing temperature beyond ∼300 °C. Annealing at 450 °C results in about a two orders of magnitude decrease of resistivity from the highly insulating state of the as-grown. The resistivity shows a gradual increase when annealed at temperatures higher than 450 °C. A reduction of resistivity with annealing can be attributed to the enhancement of the density of Ni vacancies, which are known to act as shallow acceptors in NiO. The formation energy of the Ni vacancies, which has been estimated from the versus plot, comes out to be 623 meV. The density of 60° dislocations in these films increases sharply when annealed above 500 °C. A reduction of conductivity of films annealed above 500 °C can thus be explained in terms of the enhancement of the rate of scattering of carriers by these defects. The resistivity of the Ni-cluster-embedded highly conducting NiO epilayers is found to increase rapidly by more than several orders of magnitude beyond an annealing temperature of ∼200 °C. This has been ascribed to percolation-driven metal-to-insulator transition arising as a result of the reduction of the cluster density with annealing.

Preparation of ZnS-decorated MWCNTs/p-Si hybrid photodetector by pulsed laser deposition

In the present work, a zinc sulfide (ZnS) nanostructure film is deposited on multi-walled carbon nanotubes (MWCNTs) by means of pulsed laser deposition technique. The structural, morphological, and optical properties of ZnS-decorated MWCNTs are investigated. X-ray diffraction (XRD) studies showed the presence of peaks related to polycrystalline faced-center cubic ZnS and MWCNTs. The best crystallinity is found for ZnS/MWCNTs nanocomposite prepared at 5.3 J/cm2. Scanning electron microscope (SEM) investigation shows that the deposited ZnS films have a smooth structure with some spherical particles attached to the film surface. The SEM image of the ZnS-decorated MWCNTs confirms the formation of a nanocomposite morphology structure. The optical energy gap of ZnS film decreases from 4 to 3.85 eV as laser fluence increases from 5.3 to 6.5 J/cm2, and in addition, the energy gap of ZnS-decorated MWCNTs nanocomposite film is smaller than that of ZnS film. The current-voltage characteristics of ZnS/Si and ZnS-decorated MWCNTs/Si heterojunction photodetectors are measured in dark and illumination conditions. The responsivity of n-ZnS/p-Si and n-ZnS/MWCNTs/p-Si prepared at 6.5 J/cm2 was found to be as high as 0.35 at 710 nm and 0.674 A/W at 610 nm, respectively. The figures of merit of the ZnS/Si photodetectors, including external quantum efficiency and specific detectivity, were improved after being embedded with MWCNTs. The band lineup of n-ZnS-decorated MWCNTs/p-Si under illumination was constructed.

Room temperature tunability of ferroelectricity and dielectricity in La and Mn codoped BiFeO3 nanoflakes: Implications for electronic devices applications

This study sheds a light on the in-situ growth of nanoflakes structure in Bi0.9La0.1Fe0.5Mn0.5O3 (BLFMO) thin film. The BLFMO thin films of various thicknesses were grown on LaNiO3 (LNO) coated Si (100) substrates using pulsed laser deposition technique. A long-range crystal structure of the as prepared BLFMO thin films was studied by X-ray diffraction measurements, which shows that the LNO buffer layer allows growth for a specific orientation. The compact and densely packed nanoflake structures in BLFMO thin film samples were confirmed by surface morphological investigations. To measure the polarization versus electric field (p-E) loop of BLFMO chip samples, a standard bipolar sinusoidal waveform with its magnitude of 250 kV/cm was applied at the frequency of 1 kHz. The maximum saturation and remnant polarizations of 104.50 μC/cm2 and 86.24 μC/cm2 respectively were probed for a critical thickness (420 nm) of the BLFMO layer. The voltage polarity-dependent leakage current behavior of Ag/BLFMO/LNO thin-film capacitor is thoroughly explored in detail. The value of leakage current density was observed from 1.16 × 10−4 to 2.24 × 10−5 J/cm2 for BLFMO thin films at an external applied electric field of 300 kV/cm. The highest tunability ∼60.20% and minimum temperature capacitance coefficient ∼1.23 × 10−3 were also observed for the same critical thickness of proposed chip element. The present study may open up a new opportunity to fabricate thin film based ferroelectric memory devices.