Standard Pulsed Laser Deposition Research Articles

Pulsed Laser Deposition of Carbon-Based Materials: A Focused Review of Methods and Results

Pulsed Laser Deposition (PLD) is a highly flexible experimental methodology for the growth of thin films of a broad variety of materials, based on the generation of laser-induced plasmas (LIP) with material ablated from a solid target and on the transfer of the ablated material to a substrate. This review is focused on carbon-based materials—specifically, diamond-like carbon (DLC), graphene and carbyne—and will both discuss the influence of the most critical experimental parameters on the obtained materials and present the experimental developments proposed in the recent literature to tailor the properties of the deposited films and optimize the standard PLD technique for production of various carbon-based materials.

Transient liquid assisted growth of superconducting YBa2Cu3O7−x films based on pulsed laser deposition

We investigated the integration of transient liquid-assisted growth (TLAG) approach for epitaxial YBa2Cu3O7−x (YBCO) films by physical deposition methodologies (pulsed laser deposition (PLD)), as an additional opportunity for high-throughput growth of YBCO. As a prerequisite, highly flat and amorphous YBCO precursor films were deposited by PLD at temperatures below 400 °C on single-crystalline SrTiO3 (STO) and LaMnO3 (LMO)/STO, as well as industrial coated conductor architectures. Contrary to TLAG based on chemical solution deposition, where BaCO3 elimination is a key factor for the YBCO growth, TLAG-PLD growth is controlled by the transformation of Ba–Cu–O (s) to a transient liquid. High-quality c-axis YBCO films were successfully grown on different substrates, as demonstrated by high-resolution x-ray diffraction and transmission electron microscopy. In-situ resistance measurements revealed that the growth rates around 1000 nm s−1 can be achieved, outperforming the capabilities of standard PLD growth of REBa2Cu3O7 films by few orders of magnitude. Experimental conditions such as temperature, oxygen partial pressure, and heating ramp, were optimized to obtain critical temperature (T c) values up to 90 K. Critical current densities of 15 MA cm−2 at 5 K and 1.7 MA cm−2 at 77 K were obtained for YBCO films of 450 nm on LMO/STO.

High optical quality cellulose thin films grown from raw natural cotton by pulsed laser deposition

Raw natural cotton harvested in the fields of Thessaly, Central Greece, was used to grow high optical quality, highly durable cellulose thin films by pulsed laser deposition, using 193 nm ArF laser pulses. Standard pulsed laser deposition conditions at room temperature were applied and raw, unprocessed, natural cotton targets were used. The semi-crystalline cellulose of natural cotton converts to very durable solid films that are fully transparent in the visible wavelength range and exhibit amorphous structure. Thin film quality and surface morphology are parametrically investigated and show a strong dependence on laser fluence. Films deposited at the lowest fluence levels ~ 5 mJ/cm2 on target, close to the observed ablation threshold, exhibit roughness of ~ 1.7 nm rms. The high optical quality of the grown biocompatible cellulose materials proves the unique capacities of laser deposition and processing methods and promise novel biophotonics and other interdisciplinary applications for the health and safety of the citizen.

What’s new in laser based nanofabrication for the fast uptake in industrial application

Laser based efficient new nanofabrication methods with technical feasibility for the fast uptake in industrial application are of significant global demand. A recent simplest approach in this way is the standard pulsed laser deposition (PLD), used since 1960s after the development of high power lasers. Over all, PLD is a fit method towards the preparation of a variety of nanomaterials only for research purpose. Nevertheless, the method is relatively slow and could not adopted in industrial scale application. A recent new-fangled development in this direction is the atmospheric-PLD (APLD), where ablation of the target by a laser pulse occurs at atmospheric gas pressure and the ablated material is delivered to the substrate using a flowing medium such as gas or atmospheric plasma. With this method, a variety of nanomaterials such as plasmonic metal NP film could be produced for practical ap

Combinatorial Material Science and Strain Engineering Enabled by Pulsed Laser Deposition Using Radially Segmented Targets.

Vertical composition gradients of ternary alloy thin films find applications in numerous device structures. Up to now such gradients along the growth direction have not been realized by standard pulsed laser deposition (PLD) systems. In this study, we propose an approach based on a single elliptically segmented PLD target suited for the epitaxial growth of vertically graded layers. The composition of the thin films can be varied by a simple adjustment of the position of the PLD laser spot on the target surface. We demonstrate this principle for the Mg xZn1- xO alloy system. Such vertically composition-graded Mg xZn1- xO thin films exhibit high optical quality and a well-defined Mg-content for each layer. No signs of interdiffusion of Mg-atoms between the layers have been found. Further, this method is capable to deposit homogeneous thin films with any desired, well-defined cation composition having the same high optical and structural quality as films grown by conventional PLD.

Nanostructuring the Er3+ distribution in PbO–Nb2O5–GeO2 thin film glasses

Nanostructured thin film glasses with a controlled concentration and in-depth distribution of Er3+ have been produced by alternate pulsed laser deposition (PLD) from host (PbO–Nb2O5–GeO2) and dopant (Er) targets (in-situ doping). Their photoluminescence (PL) response is compared to that of doped films grown by standard PLD using Er3+-doped glass targets (ex-situ doping), by studying the characteristic Er3+ emission at 1.53μm. PL intensity of in-situ doped films is maximized for in-depth separation between Er-doped layers ⩾5nm, whereas their lifetime is always longer in the case of nanostructured films having a separation between Er3+ ions similar to that of ex-situ doped films. These results stem from the different distribution of Er3+ ions in the host glass: isotropic 3D for ex-situ doped films or planar 2D for nanostructured films. Thus, the number of neighbor Er3+ ions is larger in the first case, which favors the increase of nonradiative deexcitation due to concentration quenching.

Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

High Curie temperature for La0.7Sr0.3MnO3 thin films deposited on CeO2 /YSZ-based buffered silicon substrates

Two kinds of epitaxial structures were grown by standard pulsed laser deposition on (001) Si, namelyLa0.7Sr0.3MnO3/Bi4Ti3O12/CeO2 /YSZ/Si(BTO-based), and La0.7Sr0.3MnO3/SrTiO3/CeO2 /YSZ/Si (STO-based) multilayers. The samples were investigated by means of x-ray diffraction,transmission electron microscopy, magnetic and transport measurements. The Curie temperatureTC of the BTO-based samples was found to be higher (360 K) thanfor the typical reference epitaxial LSMO film grown on (001)SrTiO3 single crystal (345 K), due to high compressive in-plane strain. TheSTO-based samples show high structural quality, low roughness and highTC (350 K), making them interesting candidates for use in innovative LSMO-based bolometersor spintronic devices operating at room temperature.

Heteroepitaxial film growth of layered compounds with the ZrCuSiAs-type and ThCr 2Si 2-type structures: From Cu-based semiconductors to Fe-based superconductors

FeAs-based layered superconductors such as F-doped LaFeAsO have recently been investigated intensively because of their high superconducting transition temperatures. Epitaxial films of these compounds are important to examine their intrinsic materials properties as well as to transfer them to device applications. In this review, we first present our research route from transparent p-type oxides semiconductors to the Fe-based superconductors. Then we review growth of epitaxial thin films for the layered oxychalcogenides and oxypnictides. Reactive solid-phase epitaxy technique was inevitable to prepare epitaxial thin films of the oxychalcogenides and Zn-based oxypnictides. On the other hand, epitaxial thin films of Mn-based oxypnictides were grown by standard pulsed laser deposition. These techniques, however, did not grow epitaxial thin films for LaFeAsO. Thus, we developed a modified pulsed laser deposition process and succeeded in obtaining epitaxial thin films of FeAs-based superconductors, LaFeAsO and cobalt-doped SrFe 2As 2.

A novel time-integral type laser energy meter based on anisotropic Seebeck effect

We have posed the design of a time-integral type laser energy meter based on anisotropic Seebeck effect for the first time. Anisotropic Seebeck effect is responsible for the laser-induced thermoelectric voltage effect in high temperature superconductor (HTSC) cuprates and colossal magnetoresistance (CMR) manganites thin films grown on tilted single crystal substrates. In this study, for an example, an epitaxial La 2/3Ca 1/3MnO 3 thin film prepared on a tilted LaAlO 3 substrate by standard pulsed-laser deposition (PLD) method is tested with a 1064-nm Q-switched Nd:YAG laser and its 2nd (532 nm), 3rd (355 nm), and 4th (266 nm) harmonics from room temperature to 16 K. The integral of the voltage signal with time shows a good linear relation with the laser energy per pulse in the measured wavelength and temperature range, which confirms the theoretical analysis given in this letter and can be used to design a time-integral type laser energy meter. The sensitivity increases as the film thickness increases or as the thermal diffusion constant decreases, which makes the time-integral type laser energy meter low cost as compared with the peak-voltage type. It operates with fast (nanosecond range) and broad-spectrum (from infrared to ultraviolet) response in wide temperature range (from room temperature to 10s K), and can be useful replacements for pyroelectric power/energy meters.

Enhanced dielectric properties in single crystal-like BiFeO3 thin films grown by flux-mediated epitaxy

We have fabricated single crystal-like BiFeO3 (BFO) thin films by flux-mediated epitaxy using pulsed laser deposition (PLD). The Bi–Cu–O flux composition and its thickness were optimized using composition spread, thickness gradient, and temperature gradient libraries. The optimized BFO thin films grown with this technique showed larger grain size of ∼2μm and higher dielectric constant in the range of 260–340 than those for standard PLD grown films. In addition, the leakage current density of the films was reduced by two orders of magnitude compared to that of standard PLD grown films.

${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7}$ Coated Conductor Grown by Hybrid Liquid Phase Epitaxy

The hybrid liquid phase epitaxy (HLPE) approach has the potential to be a high rate-low cost process. This deposition process is used to grow epitaxial YBa2Cu3O7 (YBCO) films in the presence of a thin (100 to 500 nm) liquid BaO-CuO flux layer. Despite the presence of the molten flux, YBCO growth is found to be feasible on technical substrates because of the limited dissolution of the buffer layer in the thin flux layer. The high atom mobility at the growing interface under the liquid flux enables high growth rates (demonstrated to be greater than 10 nmldrs-1 in a wide temperature regime and predicted to be up to ~5 nmldrs-1). We report results on HLPE YBCO films grown on (100) strontium titanate and textured technical substrates such as rolling-assisted biaxially textured substrates (RABiTS) and ion-beam-assisted-deposited (IBAD) MgO. High values of the critical temperature above 90 K and critical current ~400 A per cm width for 3 mum thick films on single crystal substrates and promising high values on technical substrates are obtained. Furthermore, there is potential for making thicker films of the same quality since film density is maintained with thickness. Angular-dependent transport critical current as a function of applied field for these films, as well as microstructural measurements by transmission electron microscopy are also reported. The angular and field dependence of critical current density are similar to standard PLD (pulsed laser deposition) films. Although the films are of high epitaxial quality they contain yttria precipitates which are possible sources of flux pinning centers.

Comparative studies of nanostructural and morphological evolution ofCeO2 thin films induced by high-temperature annealing

High-temperature annealing performed at∼1000 °C orhigher in an oxidizing atmosphere is a simple technique to significantly modify the as-grown nanostructuresof CeO2 films, which are typically granular with high surface roughness.We evaluated the effect of high-temperature annealing on variousCeO2 films deposited by three deposition methods, namely standard pulsed laser deposition (PLD),large-area pulsed laser deposition, and electron-beam evaporation. High-temperature annealingpromotes high epitaxy and crystallinity, as well as stabilization of the flat (001) surfaces ofCeO2. This is most commonly observed on the annealedCeO2 film grown by standard PLD, which is usually atomically smooth and pore-free. In contrast,CeO2 films grown by large-area PLD and electron-beam evaporation are characterized bysimilarly flat surfaces but are discontinuous due to the presence of pores. Depending on thelength of the annealing time, the pores range from small-sized nanopores with widths of∼30–100 nm anddepths of ∼3–5 nm, up to relatively large-sized pores with widths of∼100–500 nm anddepths of ∼10–20 nm. The differences in the nanostructural and morphological evolution of theCeO2 films are further correlated to their as-grown properties, including grain size, orientation,and possibly the initial porosity of the film.

Laser induced thermoelectric voltage effect in La0.67Pb0.33MnO3 thin films doped with Ag

The La0.67Pb0.33MnO3 (LPMO) thin films doped with Ag on vicinal-cut LaAlO3 substrates were prepared using standard pulsed laser deposition technique, in which laser induced thermoelectric voltage (LITV) effect was found. With Ag doping level x (x is defined as,x=massAg/massLPMO) increasing from 0.00 to 0.10, the response time of LITV signals in LPMO thin films firstly decreases (reaching minimum at 0.06), and then increases (still less than that with zero Ag doping). Further, an optimal film thickness was found, at which the peak voltage and response time of LITV signals to reaches maximum and minimum, respectively. The response time of LITV in the LPMO thin films are substantially smaller than that of La0.67Ca0.33MnO3 thin films at the same Ag doping level.

The effects of annealing step-edges on SrTiO/sub 3/ and MgO single-crystal substrates on YBa/sub 2/Cu/sub 3/O/sub 7/ Josephson junctions

The effect of annealing step-edges on SrTiO/sub 3/ and MgO single-crystal substrates on Josephson junctions of YBa/sub 2/Cu/sub 3/O/sub 7/, has been studied. The step-edge was fabricated by argon-ion milling technique and was annealed at 1050/spl deg/C in oxygen atmosphere. YBa/sub 2/Cu/sub 3/O/sub 7/ thin film was deposited on the annealed step-edge by a standard pulsed laser deposition. The effect of annealing the step-edge on the junction was characterized by AFM and current-voltage (I-V)characteristic. The annealed step-edge on SrTiO/sub 3/ and MgO substrates showed that the surface of the substrates was smoother and I-V characteristic of Josephson junction improved.

A new approach in layer-by-layer growth of oxide materials by pulsed laser deposition

Pulsed laser deposition (PLD) has become thin film deposition technique with increasing prominence. One of the advantages above other techniques is the possibility to growth at relative high background pressures, with a large freedom in choosing the kind of gas. An example is oxygen in the case of high Tc superconductors and giant magnetic resistors. However, the advantage of relative high pressures hinders the use of a number of diagnostics and monitor techniques, like reflective high energy electron diffraction (RHEED). With the introduction of the possibility to use RHEED at standard PLD pressures, it became possible to study the growth of oxide materials under different oxygen and temperature conditions. In this paper we employed this technique on SrTiO3, which can be grown in different growth modes depending on growth temperature and oxygen pressure during deposition. Applying a modified etch treatment on SrTiO3 single crystals, a real 2D growth mode could be observed by the homo-epitaxial growth of SrTiO3, as indicated by RHEED oscillations. In addition to the RHEED oscillations another phenomenon is observed, typical for PLD. The pulsed way of deposition leads to discontinuities in the intensity of the diffracted pattern. This is caused by the mobility of the deposited material from a disordered distribution till an ordered one and leads to a characteristic exponential slope with characteristic relaxation time constants. These time constants give extra information about relaxation, crystallization, and nucleation of the deposited material during growth. Finally, a new approach to deposit these complex oxide materials will be introduced. This, so-called interval deposition, is based upon the results obtained from the intensity oscillations as well as relaxations. The basic idea is to deposit an equivalent of one unit cell of material in such a short time that no coalescence in larger islands can occur, followed by a relaxation time before the next unit cell layer is deposited. This interval deposition leads to an imposed layer by layer growth.

In-situ monitoring during PLD of YBa/sub 2/Cu/sub 3/O/sub 7-δ/ using RHEED at high oxygen pressure

The surface morphology and initial growth of YBa/sub 2/Cu/sub 3/O/sub u-/spl delta//, using Pulsed Laser Deposition (PLD), have been subject to in many studies. Both, Scanning Probe Microscopy (SPM) as well as Reflection High Energy Electron Diffraction (RHEED) have been applied. The latter is mostly operated using modified deposition parameters, like a reduced oxygen pressure. Here, we have studied the initial growth using a PLD-RHEED system at standard PLD pressures. In this system, in-situ RHEED can be applied in a background pressure of oxygen up to 50 Pa. The initial growth of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// on SrTiO/sub 3/ substrates is studied. The influence of the substrate termination, i.e., SrO or TiO/sub 2/, on the growth will be discussed.

Growth and Structural Characterization of Sr2TiO4: Chemical Control Over the Terminating SrTiO3 Surface.

AbstractThin films of Sr2TiO4 were grown using pulsed laser deposition (PLD) and laser-MBE on [100]-SrTiO3single crystal substrates. Films grown by standard PLD display only a single peak in the X-ray diffraction spectra, corresponding to the (006) peak of the K2NiF4 parent structure. Using a Laser-MBE, controlled two-dimensional growth and RHEED intensity oscillations can be routinely obtained. The period of the RHEED intensity oscillations was confirmed to correspond to the deposition of one-half the unit cell. In contrast to PLD-grown films, the (004) and (006) peaks are observed in XRD spectra for the Laser-MBE-grown films. The intensity of the (004) peak is discussed and modeled with respect to in-plane disorder arising from substrate step-edges and out-of-plane film-substrate structural mismatches. That a single, half unit-cell can be deposited allows one to "flip" the terminating surface of SrTiO3 in a controlled and simple manner from a pure TiO2 layer to a SrO layer. Experimental evidence of the importance of such surface control is given for the SrCuO2 structural stability.

In-situ monitoring by reflective high energy electron diffraction during pulsed laser deposition

Pulsed laser deposition (PLD) has developed during the past decade from a fast but limited preparation tool towards a competitive thin film deposition technique. One of the advantages above other techniques is the possibility of growth at relative high background pressure. There is a large freedom in choosing which kind of gas. Moreover, in a number of applications, the gaseous species in the background pressure are part of the elements to be grown, e.g., oxygen in the case of high T c superconductors. However, the advantage of relative high pressures leads to restrictions of using standard diagnostics and monitoring of the film growth, e.g., reflective high energy electron diffraction (RHEED). Here, a PLD chamber including an in-situ RHEED system is presented, which makes it possible to monitor and study the growth at standard PLD parameters. Using a two-stages differential pumped, magnetically shielded, extension tube mounted at the electron gun side and a special designed phosphor screen including CCD camera, real time monitoring by observation of RHEED oscillations could be established at pressures up to 50 Pa. In this paper the latest results on applying this technique on SrTiO 3 and YBa 2Cu 3O 7 will be presented. Additional to the usual diagnostics performed with RHEED, another phenomena can be observed. The pulsed way of deposition, characteristic for PLD, leads to relaxations in the intensity of the diffracted pattern due to the mobility of the deposited material. These relaxation times give extra information about relaxation, crystallization, and nucleation of the deposited material. The presented technique leads to a better understanding of the growth during pulsed laser deposition and, because of the possibility to monitor the growth, will make PLD competitive with other deposition techniques.

In-situ growth monitoring during PLD of oxides using RHEED at high oxygen pressure

In pulsed laser deposition (PLD) of oxides, usually high oxygen pressures are used to incorporate oxygen in the as-grown film at high substrate temperature and to prevent the growing film to be bombarded by high-energetic particles, originating from the plasma. Furthermore, the background pressure influences the shape and size of the plasma and, therefore, the deposition rate and homogeneity of the film and the energy of the ad-atoms on arrival. Reflection high energy electron diffraction (RHEED) is often used to monitor the growth of oxide thin films. In general, low background oxygen pressures are used. Because of the low oxidation power at low pressures, low substrate temperatures have to be used. This hampers, in general, the film crystallinity. We have developed a PLD-RHEED system for growth monitoring during the deposition of oxides at standard PLD conditions. Using a two-stage differential pumping system, clear diffraction patterns are observable up to 50 Pa. Therefore, monitoring and control of thin film growth by PLD on an atomic level is feasible, even in quite high background pressures. The influence of the substrate treatment, e.g. annealing and etching, on the growth of atomic layers of SrO and BaO, as well as the homo-epitaxial growth of SrTiO 3, will be discussed in this contribution.