PLD System Research Articles

Large area pulsed laser deposition of memristive Pr0.7Ca0.3MnO3 heterostructures for neuromorphic computing

Heterostructures of the perovskite Pr0.7Ca0.3MnO3 (PCMO) and a tunnel oxide such as AlOx are highly interesting memristive devices for emulating synaptic properties in neuromorphic circuits. Future chip generations with these memristive elements requires PLD systems which enables PCMO growth on a full wafer. To address the issue of plume broadening in this study, a slit system was used to localize the deposition region, thereby eliminating the need for excessive scanning. This study investigates the effect of the slit system and process gas pressure on plume broadening. This investigation has been used to parameterize a simulation software to assess the effectiveness of different movement speeds and to develop strategies for homogeneous deposition, adjustable to a chosen film thickness in the order of twenty nanometers. We used these strategies to fabricate area dependent switching memory cells on a standard 4″ Si wafer using the material combination of Pr0.7Ca0.3MnO3 and AlOx. The influence of the aluminum oxide thickness on the switching shows that the IV loop starts to exhibit a hysteresis for AlOx thicknesses ≥ 3 nm. An increase in AlOx thickness leads to an increase in resistance and capacitive charging. An additional thermal treatment reduces the resistance and the switching voltage and increases the ratio between low resistive and high resistive state. Devices without thermal treatment of the PCMO are compatible for back end of line processing of standard CMOS technology.

Homo-epitaxial growth of LiNbO3 thin films by Pulsed Laser deposition

With the deployment of the 5th Generation of mobile applications (5G), the performances of radio-frequency (RF) filters are pushed to their limits. Highly crystalline piezoelectric materials with an electromechanical coupling coefficient higher than aluminium nitride are of high interest. Lithium niobate (LiNbO3), with an electromechanical coupling coefficient from 5 % to 45 % for bulk waves, appears to be a promising candidate for a next generation of RF filters. However, despite decades of research, the growth of single-phased, stoichiometric and highly crystalline LiNbO3 thin films is still very challenging.In the present work, 200 nm-thick LiNbO3 films have been grown by pulsed laser deposition on congruent LiNbO3 substrates with various crystalline orientations: X-cut (i.e. (110)), Y-cut (i.e. (100)) and Z-cut (i.e. (001)). The influence of the substrate’s crystal cut on the physical and chemical properties of the LiNbO3 films is investigated. A High-Resolution X-ray Diffraction methodology is developed to characterize the crystalline properties of the homoepitaxial layers. In all cases, single-phased and epitaxial LiNbO3 thin films are obtained. These results indicate that a standard wafer-based PLD system can be used to grow LiNbO3 thin films with a crystalline quality and a stoichiometry very close to a LiNbO3 monocrystalline substrate.

High-quality BaTiO3 epitaxial growth on GaAs (001) substrate by novel SrTiO3/Ti2.5O3 buffer layers

Perovskite ferroelectric BaTiO3 material showed promising application in the photovoltaic field due to its positive polarization enhanced open voltage with ferroelectric modulation. Achieving perfect interfaces between the multi-layers based on BTO film was still unresolved. Therefore, we developed the bottom buffer layers SrTiO3/Ti[Formula: see text]O3 films deposited on GaAs for reducing the lattice mismatch between the epitaxial oxide (BTO) GaAs via PLD system. The out-of-plane epitaxial relationship of this heterostructure was [110]BaTiO3//[110]SrTiO3//[010]Ti[Formula: see text]O3//[001]GaAs and the in-plane epitaxial relationship was determined to be [110]BaTiO3//[110]SrTiO3//[100]Ti[Formula: see text]O3//[110]GaAs from RHEED and XRD results. In addition, we found that the inter-diffusions of Ga and As atoms from GaAs substrate to oxides films were prevented greatly by the SrTiO3/Ti[Formula: see text]O3 passivation layer. Using the Gibbs free energies of formations equations, we explained that the Ga atoms couldn’t diffuse through Ti-oxides at Ti[Formula: see text]O3/GaAs interface. Our work provided an effective measurement to develop the BTO application in the photovoltaic field.

Online perception on the performance of YBCO tapes via intelligent video-aided PLD system

Second generation HTS tape has entered the stage of mass production. The biggest bottleneck in stable production and consistently high-quality superconducting coatings lies in the control of deposition temperature during superconducting coatings. It is very challenging to effectively monitor the temperature in the dynamic process of roll-to-roll coating. Through observation, it is found that the color of superconducting surface is very sensitive to the change of coating temperature. In this study, a real-time video analysis technology has been developed to obtain the grayness scale of the surface of the superconducting layer during coating. The relationship between grayness scale, temperature and the final critical current of superconducting tape has been established through short sample experiments. These relationships are also clearly demonstrated in the long tape production process, which can significantly detect any abnormal trends of tape products by capturing the surface temperatures through grayness scale. The region of interest was tracked, by dividing it into three parts and calculating the average grayness level of each part. The results obtained can be used to determine PLD temperature setting and provide a reference for the subsequent slitting of superconducting tapes. This work also provides a potential quality improvement technique for superconducting tape production.

Voltage-regulated magnetization reversal in BNTFC/LSMO composite thin film

In order to investigate the electromagnetic effect in nanoscale, a multiferroic BNTFC/LSMO composite thin film was fabricated on (0 0 l) oriented LAO single crystal substrate employing a PLD system. Structural characterization showed that the LSMO layer is pseudo-cubic but the BNTFC presents a four-layer perovskite structure. Tests of physical properties indicated that such a composite thin film exhibits a good ferroelectricity, the Pr and EC are 5.04 μC·cm−3 and 587.12 kV·cm−1, respectively. And the ferromagnetism of the BNTFC system has been improved effectively with the introduction of LSMO lamina, the MS and HC are promoted to 68.13 emu·g−1 and 0.35 kOe. In the meantime, the dynamic process of the structure and movement of the out-of-plane ferromagnetic domains at different voltages using MFM innovatively was studied. It suggested that an applied voltage does change the distribution of ferromagnetic domains of the sample — voltage-regulated magnetization reversal.

Magnetocapacitance of magnetically strained multilayered thin films

Abstract We studied on magnetoelectric behaviors of magnetically strained magnetostrictive materials-ferroelectric materials-magnetostrictive materials sandwich-type multilayered thin films. The sandwich-type multilayered thin films were deposited on Pt substrates by PLD system with a KrF excimer laser (λ = 248 nm). In particular, thin films were studied for their crystal structure and surface/interface microstructure as well as magnetic and electrical properties. The experimentally measured results have proved that saturated magnetizations (Ms) of CoFe2O4 (20 nm, 20 nm, 200 nm)/BaTiO3 (200 nm, 100 nm, 200 nm)/CoFe2O4 (20 nm, 20 nm, 200 nm) sandwich-type multilayered thin films are measured as 23.58 emu/cm3, 38.52 emu/cm3, 103.71 emu/cm3 and the capacitance of those increased more under the magnetic field (1000 Oe) than zero field by 2.4%, 7.8%, 11.5% respectively. Our work suggests the possibility of enhanced magnetocapacitance under magnetic field by controlling the interfacial compressive/tensile stress of thin film. As a results we have compared the experimental and theoretical values depending on the parameters such as thickness and potential distribution of magnetostrictive materials through the simulation program COMSOL physics.

Light, shadows and surface characteristics: the multispectral Portable Light Dome

A multispectral, multidirectional, portable and dome-shaped acquisition system is developed within the framework of the research projects RICH (KU Leuven) and EES (RMAH, Brussels) in collaboration with the ESAT–VISICS research group (KU Leuven). The multispectral Portable Light Dome (MS PLD) consists of a hemispherical structure, an overhead camera and LEDs emitting in five parts of the electromagnetic spectrum regularly covering the dome’s inside surface. With the associated software solution, virtual relighting and enhancements can be applied in a real-time, interactive manner. The system extracts genuine 3D and shading information based on a photometric stereo algorithm. This innovative approach allows for instantaneous alternations between the computations in the infrared, red, green, blue and ultraviolet spectra. The MS PLD system has been tested for research ranging from medieval manuscript illuminations to ancient Egyptian artefacts. Preliminary results have shown that it documents and measures the 3D surface structure of objects, re-visualises underdrawings, faded pigments and inscriptions, and examines the MS results in combination with the actual relief characteristics of the physical object. Newly developed features are reflection maps and histograms, analytic visualisations of the reflection properties of all separate LEDs or selected areas. In its capacity as imaging technology, the system acts as a tool for the analysis of surface materials (e.g. identification of blue pigments, gold and metallic surfaces). Besides offering support in answering questions of attribution and monitoring changes and decay of materials, the PLD also contributes to the identification of materials, all essential factors when making decisions in the conservation protocol.

The Wear Mechanisms Description Of Multilayer Coatings, Performed By Transmission Electron Microscopy – An Overview Of The Own Research Work

Abstract The aim of the presented paper was to describe the wear mechanisms operating at the small length scale in multilayer coatings subjected to a mechanical testing. A hybrid PLD system (Pulsed Laser Deposition connected with magnetron sputtering) was used for the multi-layer coating deposition. Coatings were subjected to indentation, ball-on disc wear and scratch adhesion tests. Microstructure of the as-deposited coating and after mechanical tests was studied using the Scanning (SEM) and the Transmission (TEM) Electron Microscopes. The research work revealed that application of innovative multilayer coatings may allow to predict their life time and to steer their properties.

Study of La-Incorporated HfO2 MIM Structure Fabricated Using PLD System for Analog/Mixed Signal Applications

Metal-insulator-metal (MIM) capacitors with Al/HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Al structure were fabricated using pulse laser deposition for the first time and were further investigated for their electrical and morphological properties. The MIM capacitors for future applications in analog/mixed signal circuits need further improvement in their electrical characteristics. We have fabricated MIM capacitors having low leakage current density of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math>$\sim 9.6 \times 10^{-9}$</tex-math></inline-formula> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at −1 V and high-capacitance density ∼20.8 fF/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 3.5 V for 100-Hz frequency. The frequency dispersion effect of these MIM capacitors is observed to be quite small. We have also obtained an improved voltage coefficient of capacitance of ∼101 ppm/V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 1 MHz along with improved dielectric constant which is one of the most important parameters for next generation MIM capacitors. The physical thickness of HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> dielectric film stack is found to be 13 nm in cross-section TEM. This value of physical thickness is consistent with the low EOT ∼1.66-nm estimated using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C–V</i> curve. Morphological studies of having nanostructured film morphology with low roughness are consistent with the electrical characteristics of MIM capacitors. Further improvement in electrical properties like lower leakage current density, etc., has been obtained in post metallic annealed MIM capacitors. We have observed Schottky emission as the dominant current conduction mechanism for these MIM capacitors.

Nano-crystalline Ag–PbTe thermoelectric thin films by a multi-target PLD system

It has been evaluated the ability of ArF pulsed laser ablation to grow nano-crystalline thin films of high temperature PbTe thermoelectric material, and to obtain a uniform and controlled Ag blending, through the entire thickness of the film, using a multi-target system in vacuum. The substrate used was a mirror polished technical alumina slab. The increasing atomic percentage of Ag effect on physical–chemical and electronic properties was evaluated in the range 300–575K. The stoichiometry and the distribution of the Ag component, over the whole thickness of the samples deposited, have been studied by XPS (X-ray photoelectron spectroscopy) and corresponding depth profiles. The crystallographic structure of the film was analyzed by grazing incidence X-ray diffraction (GI-XRD) system. Scherrer analysis for crystallite size shows the presence of nano-structures, of the order of 30–35nm. Electrical resistivity of the samples, studied by the four point probe method, as a function of increasing Ag content, shows a typical semi-conductor behavior. From conductivity values, carrier concentration and Seebeck parameter determination, the power factor of deposited films was calculated. Both XPS, Hall mobility and Seebeck analysis seem to indicate a limit value to the Ag solubility of the order of 5%, for thin films of ∼200nm thickness, deposited at 350°C. These data resulted to be comparable to theoretical evaluation for thin films but order of magnitude lower than the corresponding bulk materials.

Interrelation of epitaxial strain and oxygen deficiency in La 0.7 Ca 0.3 MnO 3−δ thin films

The interrelation between the epitaxial strain and oxygen deficiency in La0.7Ca0.3MnO3-{\delta} thin films was studied in terms of structural and functional properties. The films with a thickness of 1000{\AA} were prepared using a PLD system equipped with a RHEED facility and a pyrometric film temperature control. The epitaxial strain and the oxygen deficiency in the samples were systematically modified using three different substrates: SrTiO3, (LaAlO3)0.3-(Sr2AlTaO6)0.7 and LaSrAlO4, and four different oxygen pressures during film growth ranging from 0.27mbar to 0.1mbar. It could be demonstrated that the oxygen incorporation depends on the epitaxial strain: oxygen vacancies were induced to accommodate tensile strain whereas the compressive strain suppressed the generation of oxygen vacancies.

Software Design Based on PLD High-Speed Data Acquisition System

Data collection in the important position of modern industrial production and scientific research is increasingly outstanding, as well as the real-time collection, real-time transmission and real-time processing of high speed data acquisition requirements are constantly improve. In addition, for different occasions, the data acquisition system of data sampling parameters are different. PLD as a universal integrated circuit, its logic function according to user's programming on the device, this paper introduces the high-speed data acquisition system based on PLD, mainly expounds the software design of the system, this paper introduces a simple PLD system, using FPGA as the data acquisition chip, the main measure the infrared remote control code acquisition, based on EDA technology to design a core, using DMA access to data, to achieve high-speed system requirements.

Influence of ion bombardment on growth and properties of PLD created DLC films

A hybrid PLD system with ion bombardment of films was developed. Growing DLC films were modified during the laser deposition (10 J cm−2) by argon ions with energy in the range from 40 eV to 210 eV and cathode current of 0.15 A and 0.5 A. The content of sp2 “graphitic” and sp3 “diamond” bonds was measured using XPS. Sp3 bonds changed from 60 % to 81 %. We found the highest sp3 content for energy of 40 eV. Hardness (and reduced Young’s modulus) were determined by nanoindentation and reached 49 GPa (277 GPa). Film adhesion was studied using the scratch test and was up to 14 N for titanium substrates. Relations among deposition conditions and measured properties are presented.

In-depth analysis of the endogenous reference genes used in the quantitative PCR detection systems for rice

To standardize the rice-specific PCR detection methods, five previously reported rice (Oryza sativa) taxon-specific genes were compared and evaluated. The investigated genes included the rice root-specific gene (gos9), the ppiphosphofructokinase gene (ppi-PPF), the phospholipase D gene (PLD), the starch branching enzyme gene (RBE4) and the sucrose phosphate synthase gene (SPS). Sequencing analyses revealed that among the tested rice cultivars, single-nucleotide polymorphisms (SNPs) existed in the gos9, PLD, ppi-PPF and SPS amplicons, though no statistically significant effect on their Ct values was found. The ppi-PPF and PLD systems were found to produce amplicons in non-rice species, such as sugarcane and broomcorn. The quantitative real-time PCR results revealed that this cross-reaction led to an underestimate of the GM (genetically modified) rice content. With the exception of the aforementioned shortcomings, these five endogenous reference genes all have acceptable amplification efficiencies, which ranged from 98 to 108 %, and high sensitivity within the limit of detection (LOD) values, which ranged from 5 to 10 copies of the haploid genome. In estimating the GM content in blinded rice samples, these five systems produce relatively accurate quantitative results with deviations less than 15 %, but the RBE4 system produced the most accurate quantitative results. Therefore, we have determined that the RBE4 gene is the most suitable rice reference gene, and the gos9 and SPS genes can also be used as rice reference genes because they have good commutability with the RBE4 gene. Care should be taken when interpreting results based on the PLD and ppi-PPF genes owing to their cross-reaction with other species.

30 mm wide process of GdBCO PLD/clad-type textured metal substrates

Gd1Ba2Cu3Ox (GdBCO) coated conductors using bi-axially textured clad-type substrates have been developed for high temperatures superconducting (HTS) power cables. In this project, large amount of coated conductors (CCs) are necessary for the several tests of basic properties of HTS power cables and the fabrication of a 15m long 3-in-one HTS model cable. In order to ensure an adequate amount and properties of coated conductors, the stable manufacturing technology and the high production rate at each process are required.In this report, we have newly installed a high power laser of 300W for the PLD system, resulting in improvement of the manufacturing stability and the deposition rate for GdBCO film. In addition, we have optimized target–substrate distance in PLD process, and the uniformity of Ic distribution across 30mm wide tapes were remarkably improved. Furthermore, the surface morphology of buffer layers were enhanced by optimizing the deposition condition using electron beam (EB) evaporation method, and the maximum Ic value for a short sample has achieved 497A/cm at 77K in the self-field. Based on these progresses, we are currently developing the stable manufacturing process for long CCs with over 400A/cm.

ZnO 나노휘스커 소재를 이용한 MEMS가스센서의 소비전력과 메탄 감응 특성 연구

A low power gas sensor with microheater was fabricated by MEMS technology. In order to heat up the gas sensing material to a operating temperature, a platinum(Pt) micro heater was built on to the micromachined Si substrate. The width and gap of microheater were and , respectively. ZnO nanowhisker arrays were fabricated on a sensor device by hydrothermal method. The sensor device was deposited with ZnO seeds using PLD systems. A 200 ml aqueous solution of 0.1 mol zinc nitrate hexahydrate, 0.1 mol hexamethylenetetramine, and 0.02 mol polyethylenimine was used for growthing ZnO nanowhiskers. The power consumption to heat up the gas sensor to a operating temperature was measured and temperature distribution of sensor was analyzed by a Infrared Thermal Camera. The optimum temperature for highest sensitivity was found to be although relatively high(64 %) sensitivity was obtained even at as low as . The power consumption was 72 mW at and was only 25 mW at .

Oriented growth of CoPt nanoparticles by pulsed laser deposition

The magnetic nanoparticles of Fe/FeCo/FePt, in the past, in a PLD system were grown by us using argon ambient gas pressure of about 0.1–75.0 mbar, as the ambient gas pressure can be used to tune the energy of the incident plasma plume species, the expansion volume, the growth duration, etc. which can control the particle size. In present paper, we report the direct synthesis of small-sized nanoparticles even when no ambient gas was used, with the experiments being done in higher vacuum of about 10−5 mbar in PLD chamber. The deposition rate under vacuum condition is significantly higher than the deposition rate at high ambient pressure. The study of inplane and outplane magnetic properties, along with XRD results, confirmed that the as-deposited CoPt nanoparticles thin film has oriented growth. The as-deposited CoPt nanoparticles are in magnetically soft fcc phase and a post deposition annealing at 600°C resulted in phase transition to magnetically hard fct phase.

Ferromagnetism in ZnCoO thin films deposited by PLD

In the paper, we report the synthesis and characterization of bulk and thin films of cobalt doped ZnO. Doped ZnO thin films with (002) orientation were grown on sapphire substrates in different N2 pressures using a Nd:YAG laser based PLD system. XPS analysis of thin films confirmed the presence of Co+2 ions in the bulk target material and in thin film samples. PL measurements exhibited emission in the visible region only. M–H curves showed ferromagnetic nature of thin films which was found to change with the change in ambient nitrogen gas pressure. The surface morphology of thin films was also affected by ambient nitrogen gas pressure.

Remarkable progress in fabricating RE123 coated conductors by IBAD/PLD technique at Fujikura

Increase of production rate and improvement of quality for RE123 coated conductors have been tried. In-plane texturing of MgO was attempted by the IBAD system with the world largest ion source. As a result of optimizing condition in large deposition area, the dramatically high throughput of 1000 m / h was realized to obtain the IBAD-MgO with Δϕ < 10°. Furthermore, simple buffer structure was demonstrated. Well textured CeO2 layer with Δϕ of around 4° was obtained by directly deposited on IBAD-MgO layer in spite of large lattice mismatch of 28% between CeO2 and MgO. Several over 100 m buffer substrates with the architecture of / PLD-CeO2 (60 m / h) / IBAD-MgO (333~1000 m / h) / Y2O3 (500 m / h) / Al2O3 (150 m / h) / Hastelloy / were already prepared. On these production substrates, GdBCO layer was deposited by the large PLD system at high throughput. The 260 m long GdBCO tape with Ic > 600 A except some locations was obtained at the throughput of 15 m / h. In addition to the speed-up, the very high Ic of 1040 A was also achieved by the hot-wall heating PLD system.

Continuous Deposition of YBCO Films for Coated Conductor Using PLD Method

A reel-to-reel PLD system was set up for studying YBCO coated conductor. YBCO films could be continuously grown on the CeO2/YSZ/Y2O3 buffered Ni-5W tape. Some deposition parameters were investigated. XRD θ–2θ scans were employed to characterize the c-axis orientation and in-plane texture of YBCO films deposited with different laser repetition rates and tape moving speeds. We investigated the dependence of critical current Ic on laser repetition rates and tape moving speeds for YBCO films. It had been found that a-axis oriented grains appeared as YBCO layer thickness increased, which prevented the values of Ic improved.