Pulsed Excimer Laser Deposition Research Articles

Preparation of superconducting multilayer structure for power electronic devices

Multi-step KrF excimer pulsed laser deposition (MSPLD) technique has been developed to fabricate high-quality micrometer thick superconducting YBa 2Cu 3O 7−X (YBCO) films. As has been shown, a crystallization of YBCO at the initial stage of deposition crucially affects on thick YBCO film performance. Smooth, c-axis oriented 1- μm thick YBCO films with the critical temperature of T c(zero)=89.5 K and the overall critical current density of J c(77 K)=10 5 A/cm 2 have been prepared on the single crystal MgO substrate in three-step process by monitoring the laser fluence, laser repetition rate and substrate temperature. Micrometer thick YBCO films on the single crystal LaAlO 3 substrate show T c(zero)=85.7 K and J c(77 K)=10 3 A/cm 2, indicating that optimization of MSPLD processing conditions is much more critical for substrates with a small substrate/film lattice mismatch. Furthermore, Pb(Zr,Ti)O 3(PZT)/YBa 2Cu 3O 7−X/MgO heterostructures have been prepared by MSPLD technique with the critical temperature of T c(zero)=82.0 K in superconducting YBCO layer.

Development of buffer layers for high quality Tl-Pb-Sr-Ba-Ca-Cu-O thick films on flexible metal substrates

Previous work has demonstrated the ability to grow extremely high quality Tl/sub 0.5/Pb/sub 0.5/Sr/sub 1.6/Ba/sub 0.4/Ca/sub 2/Cu/sub 3/O/sub x/ epitaxial films up to 15 /spl mu/m thick using melt growth techniques on single crystal LaAlO/sub 3/ substrates. This melt growth process is an ideal candidate for producing high quality superconducting films on flexible metal substrates with textured buffer layers; however, the textured buffer layer of choice, cubic yttria stabilized zirconia (YSZ), appears to be incompatible with the melt growth of TI-Pb-Sr-Ba-Ca-Cu-O films. In this work, we investigate textured buffer layers which are compatible with the epitaxial growth of Tl/sub 0.5/Pb/sub 0.5/Sr/sub 1.6/Ba/sub 0.4/Ca/sub 2/Cu/sub 3/O/sub x/ films. Crucial properties for the successful development of a suitable buffer layer are lattice matching, chemical stability and texture. Buffer layer materials investigated are CeO/sub 2/ and LaAlO/sub 3/ grown using a UV (248 nm) pulsed excimer laser deposition system equipped with multiple targets and a controlled ambient. Influence of substrate temperature and ambient gas pressure and flow on buffer growth are analyzed via XRD characterization. Highly textured buffer layers have been fabricated.

Pulsed excimer laser deposition of Pb(Zr,Ti)O3 thin films on simox substrates

In this paper we report the fabrication of ferroelectric Pb(Zr,Ti)O3 (PZT) thin films on Pt-coated SIMOX (Separated-by-IMplanted-OXygen) substrates by pulsed excimer laser deposition combined with rapid thermal annealing. Based on the structural and interfacial characteristics analysis by X-ray diffraction, Rutherford backscattering spectroscopy and transmission electron microscopy, the thin films were revealed to be of polycrystalline perovskite structure with mainly <100> and <110> orientations; the crystallite size and the structure are dependent on the annealing time and temperature. The ferroelectric behaviour of the films was measured

Applications of Pulsed Excimer Laser Deposition with a Frozen Nitrogen Target to Deposition of NbN and BN Films

NbN and/or BN films were deposited by pulsed laser deposition (PLD) with a frozen nitrogen target. This novel method makes it possible to prepare active nitrogen species such as atomic nitrogen and it is expected to be useful for synthesis of nitride films. The usefulness of this method is confirmed by comparison with films formed by conventional ambient-controlled PLD. The deposited films were characterized by X-ray diffraction measurements, X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red (FT-IR) absorption spectroscopy. It was confirmed that the concentration of nitrogen in the films fabricated by PLD with a frozen nitrogen target increases and the nitriding process is enhanced.

Studies on SiC film deposited by pulsed XeCl excimer laser sputtering method

Thin films of SiC were grown by pulsed excimer laser deposition (PLD). The quality and structure of the films were examined by AES, XPS, TEM, SEM, XRD and IR. The deposited films were dense and uniform and stuck tightly to the substrates. The compositions of the films were quite uniform and the ratio of silicon to carbon atomic in the films was nearly 1:1, with slight excess carbon. The films contained less than 10% oxide contamination. The basic stage of the chemical valence in the films was the SiC covalent bond. The valence electrons density in the films was 94.4% of that in single crystal SiC. The structure of the films was the polycrystalline nHSiC ( n = 4, 6 or both) hexagonal system.

Influence of in-process copper incorporation on the quality of diamond-like carbon films deposited by pulsed laser deposition technique

Copper-incorporated carbon films have been prepared on Si(100) and Corning (7059) glass substrates by the pulsed excimer laser deposition technique using KrF radiation (λ = 248 nm). Cold-pressed composite pellets, having compositions from 2 at. % to 11 at. % copper in carbon, were used as targets for ablation. Good quality, scratch-proof films were obtained at a laser energy density of 2−3 J/cm2 and a substrate temperature of 50 °C. The films were characterized by x-ray diffraction (XRD), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), UV-visible spectrometry, ellipsometry, and four-point probe resistivity measurements. Under similar deposition conditions, films obtained from composite targets of lower copper concentration are seen to have better diamond-like character as compared to those obtained from a pure graphite target. At such low concentrations, copper is seen to cluster in the form of nanoparticles. As the copper concentration increases in the films, they tend to acquire disordered graphitic network with degraded DLC characteristics, and the size of copper agglomerates increases from about 5 nm (for the 2 at. % case) to 85 nm (for the 11 at. % case). It is seen that an increase in the copper content leads to modifications in the carbon network, additional interband transitions, and reduction of the band gap.

Sequential Deposition of NbN/MgO Film on Si(100) Using Pulsed KrF Excimer Laser Deposition Method with Different Ambiences

Sequential formation of NbN/MgO bilayers on Si(100) using pulsed KrF excimer laser deposition with different ambiences of oxygen and nitrogen has been performed. The effects of nitrogen ambience on the NbN formation in this sequential process are examined. The deposited films are characterized by X-ray ( Cu-Kα) diffraction, X-ray photoelectron spectroscopy and measurement of the critical temperature of superconducting transition. The concentration of nitrogen in the NbN film increases with the ambient pressure up to 9×10-2 Torr and superconducting transition is observed at ∼12.7 K. However, the plume distribution became broader with increasing N2 gas pressure and non- negligible oxidation of the NbN films occurred. The reasons for the oxidation problem are related to the enhancement due to the multiple collisions between the ablated particles and oxygen impurity, which is mainly generated by resputtering from the surfaces of both the previously deposited MgO film substrate and its holder.

MgO(200) Highly Oriented Films on Si(100) Synthesized by Ambient-Controlled Pulsed KrF Excimer Laser Deposition Method

MgO film growth on Si(100) using the ambient-controlled pulsed KrF excimer laser deposition method has been performed under a wide range of synthesis conditions: oxygen pressure (P O2 ) of 10-6–10-3 Torr, substrate temperature (T sub) of 100–300° C, and laser irradiation energy density on Mg metal target of 0.6–2.0 J/cm2. MgO(200) pole figures of MgO films are measured by the X-ray ( CuKα) diffraction method using Schulz's reflection attachment. Almost all MgO films have strong (200)-preferred orientation and rather weak (220)-preferred orientation. The crystallographic relation of the former case is MgO(200)//Si(100) and MgO[01*BAR*1*BAR*]//Si[01*BAR*1*BAR*]. MgO film with the highest degree of (200)-preferred orientation was fabricated under the optimized conditions of T sub=300° C, energy density= 1.5 J/cm2, and P O2 =1×10-4 Torr.

Pulsed laser deposition and characterization of ferroelectric Pb(Zr, Ti)O 3 thin films on silicon-on-insulator substrates

Ferroelectric Pb(Zr, Ti)O3 thin films were prepared by pulsed excimer laser deposition on silicon-on-insulator and Pt-coated silicon-on-insulator substrates, and rapid thermal annealing was performed to crystallize the films. Based on the analysis by x-ray diffraction, Rutherford backscattering spectroscopy and measurements of electrical properties, the films were revealed to be polycrystalline perovskite structure with mainly (100) and (110) orientations, and their crystallization was found to be dependent on annealing temperature and annealing time. The films show good ferroelectricity, with Pr = 15 μC/cm2, Ec = 50 kV/cm, high resistivity and high dielectric constant.

Crystallization of Thin PZT Films Deposited by Laser Ablation into Ferroelectric Perovskite Phase by Thermal Processing

Thin PZT films are deposited on Pt-metallized Si substrates by ArF excimer pulsed laser deposition. The structural phase transformation of the PZT films from the amorphous and /or pyrochlore phase to the desired perovskite phase caused by subsequent thermal processing at different temperatures and time durations is studied by X-ray diffraction (XRD), both for rapid thermal processing (RTP) and conventional annealing. It is found that in order to obtain excellent ferroelectric PZT thin films with as much perovskite phase as possible, the annealing temperature and time duration should be in the ranges of 600 to 750°C and 300 to 600 s, respectively.

Properties of Pulsed Laser Deposited CdSxTe1-x Films on Glass

AbstractInterdiffusion of sulfur and tellurium across the CdS/CdTe interface is fundamentally important in the operation of CdTe solar cells. However, the properties of the resulting alloy semiconductor, CdSxTe1-x, are not well understood. We have prepared films of this ternary material by pulsed excimer laser deposition (PLD) across the alloy range. These films were examined by x-ray diffraction, wavelength dispersive x-ray spectroscopy, optical absorption, and Raman scattering to determine the influence of sulfur content on the crystal structure, lattice constant, energy gap, and vibrational mode behavior.

Preparation of Pb(Zr0.52Ti484848)O3 thin films on silicon-on-insulator substrates by excimer laser deposition combined with rapid thermal annealing

In this paper we report the fabrication of ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films on Si-on-Insulator (SOI) substrates with and without an electrode by pulsed excimer laser deposition combined with rapid thermal annealing. Based on the structural and interfacial characteristics analysis by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and automatic spreading resistance measurement (ASR), the film structure and orientation were revealed to be dependent on the annealing time and annealing temperature as well as deposition temperature. From RBS spectra and XTEM observation it is shown that the PZT thin films did not interact with the top silicon layers of SOI and that the composition of the film was similar to the target. The ASR measurements showed that the electrical properties of PZT/SOI as well as PZT/Pt/SOI were abrupt, and that the electrical properties of the SOI substrates were still good after the PZT growth.

BaRuO 3 thin films prepared by pulsed laser deposition

High electrical conductive BaRuO 3 thin films with (110) perovskite orientation have been successfully fabricated on Si(100) substrates by pulsed ArF excimer laser deposition and post-annealing. The resistivity of the films at room temperature is in the range of 10 −2–10 −3Ω cm. Auger electron spectroscopy (AES) measurement shows that the compositions uniformly distributed throughout the film. Rutherford backscattering spectroscopy (RBS) analysis indicates that the chemical stoichiometric ratio is well consistent with the ideal one as in BaRuO 3.

Characterization of Pb(Zr,Ti)O3 thin films on SOI prepared by excimer laser deposition

Abstract Ferroelectric Pb(Zr,Ti)O3 (PZT) thin films were prepared by pulsed excimer laser deposition on Silicon-on-Insulator (SOI) substrates with and without an electrode. Their properties can be improved by rapid thermal annealing, based on the structural and interfacial characteristics analysis by X-ray diffraction, Rutherford backscattering spectroscopy and automatic spreading resistance measurements. The thin films were revealed of to be polycrystalline perovskite structure with mainly ⟨100⟩ and ⟨110⟩ orientations; the crystallite size and the structure are dependent on the annealing time. The PZT thin films did not interact with the top silicon layers of SOI, and the composition was on the tetragonal side of the morphotropic phase boundary in the PbTiO3-PbZrO3 phase diagram.

A fully automated pulsed laser deposition system for HTS multilayer devices

For the fabrication and development of high-temperature superconducting (HTS) thin film devices, which often require multiple layers, it is essential to have control over all parameters during growth. Until recently the overwhelming majority of film growth was controlled manually. We have found this can often lead to error and irreproducibility. To overcome these problems we have designed and constructed an automated multitarget excimer pulsed laser deposition (PLD) system. We identify key elements of the system that can be utilised to address many of the problems currently encountered in HTS film growth. Optimisation using Robust Design techniques has also been used in the identification of principal parameters in growth of films and multilayers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Heteroepitaxial growth of BaTiO3 films on Si by pulsed laser deposition

Dielectric BaTiO3 films were heteroepitaxially grown on Si (100) substrates in cube-on-cube manner by employing a conductive TiN buffer layer. An epitaxial TiN film was grown by KrF pulsed excimer laser deposition. BaTiO3 film was grown epitaxially on the TiN film at a substrate temperature higher than 600 °C and in an oxygen pressure less than 1 mTorr. This epitaxial BaTiO3/TiN layer on Si was observed to have sharp interfaces and little interdiffusion of constituent atoms by secondary ion mass spectrometry. The surface of the BaTiO3 film had a root-mean-square roughness less than 1 nm as observed by atomic force microscopy. A TiN/BaTiO3/TiN trilayer structure was formed and the dielectric property was measured for this metal-insulator-metal type capacitor. The BaTiO3 film showed a high relative dielectric constant of 803 at the frequency of 1 MHz and a low leakage current less than 10−8 A/cm2 at 2 V.

Formation and Characterization of Epitaxial TiO2 and BaTiO3/TiO2 Films on Si Substrate

Rutile-phase TiO2 films were epitaxially grown on Si(100) substrates by oxidizing epitaxial TiN films grown by KrF pulsed excimer laser deposition. The TiO2 film was (110)-oriented and composed of two domains perpendicular to each other in the plane. The electrical resistivity at 2.5 V and the dielectric constant at 1 MHz of the film were 1.1×1010 Ω· cm and 49, respectively. This film could be used as a buffer layer for the growth of epitaxial BaTiO3 film on Si. The BaTiO3 (260 nm)/TiO2 (230 nm) double-layered film showed a high dielectric constant (ε r=91) and a very low leakage current of 5×10-8 A/cm2 at 10 V.

Laser deposition of metallic alloys and multilayers

The characteristic behaviours of pulsed excimer laser deposition (at 248 nm) of metallic alloys and multilayers are: high deposition rates of up to 3 nm/s above an ablation threshold of about 5 J/cm 2, a nearly congruent transfer between target and film, droplets on the film surface, and a strong thickness dependence of the obtained films. Compared to sputtered or evaporated films the alloys obtained are characterized by similar structures in most cases, but often larger extensions of single-phase regions and enlarged lattice parameters in the growth direction, while multilayers sometimes have different textures, often a better alignment of the grains in the growth direction and in systems with a negative heat of mixing sometimes a different critical bilayer thickness for the formation of fully amorphous films. Therefore, the pulsed laser deposition is an attractive alternative thin-film technique for the deposition of metallic alloys and multilayers.

Afm Study of CeO2 Growth on Sapphire as a Buffer Layer for YBa2Cu3O7

AbstractThe structure of CeO2 films grown on (1102) sapphire and on YBCO thin films was investigated. The films reported on here were grown by pulsed excimer laser deposition and their surface structure was probed using atomic force microscopy. We found that CeO2 films grown on sapphire were epitaxial with a granular structure which is smooth on an atomic scale. We see evidence of a surface reconstruction on a very smooth CeO2 (100) oriented surface. At higher growth temperatures, three dimensional islands begin to form. When a CeO2 film is grown on top of a YBCO film, the growth mode is two dimensional. The steps in this layer by layer growth are a surprisingly large 2 nm. This is about equal to 4 times the CeO2 lattice constant. This step height appears to be temperature dependent.

In Situ Monitoring and Model Simulation of BaTiO3 Pulsed Laser Thin Film Deposition

AbstractWe have applied intensified Charge Coupled Detector (ICCD) imaging to real-time, in situ monitoring of excited vapor species emission during the pulsed excimer (248 nm wavelength) laser deposition (PLD) of BaTiO3 ferroelectric thin films. Molecular beam mass spectrometry (MS) was used for species identification and velocity distribution analysis. Gasdynamic model simulations of the plume formation and transport process are tested by comparison with the ICCD and MS results. Particular attention is given to the time scale during and immediately following the laser pulse (0 - 460 ns), and also to the effects of added 02. atomic oxygen was found to be the predominant species present at the leading edge of the vapor plume. Other, slower species found included neutral Ti, TiO, Ba, and BaO.