Showing papers on "Pulsed laser deposition published in 2000"
TL;DR: In this article, β-Ga2O3 with an energy band gap of 4.9 eV was prepared on silica glass substrates by a pulsed-laser deposition method, and the resulting internal transmittance at the wavelength (248 nm) of the KrF excimer laser exceeded 50% for the 100-nm-thick film.
Abstract: Thin films of β-Ga2O3 with an energy band gap of 4.9 eV were prepared on silica glass substrates by a pulsed-laser deposition method. N-type conductivity up to ∼1 S cm−1 was obtained by Sn-ion doping and deposition under low O2 partial pressure (∼10−5 Pa) at substrate temperatures above 800 °C. The resulting internal transmittance at the wavelength (248 nm) of the KrF excimer laser exceeded 50% for the 100-nm-thick film, making this the most ultraviolet-transparent conductive oxide thin film to date and opening up prospects for applications such as ultraviolet transparent antistatic electric films in ultraviolet lithography.
797 citations
TL;DR: In this article, the authors outline the fundamental physics involved and go on to discuss recent experimental findings of pulsed laser deposition, as an alternative to chemical vapor deposition or molecular beam epitaxy.
Abstract: Photons have many advantages for vaporizing condensed systems, and laser vaporization sources have a flexibility not available with other methods. These sources are applied to making thin films in the well-known technique of pulsed laser deposition (PLD). The vaporized material may be further processed through a pulsed secondary gas, lending the source additional degrees of freedom. Such pulsed-gas sources have long been exploited for fundamental studies, and they are very promising for film deposition, as an alternative to chemical vapor deposition or molecular beam epitaxy. The authors outline the fundamental physics involved and go on to discuss recent experimental findings.
722 citations
TL;DR: An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p–n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO using conventional photolithography with the aid of reactive ion etching to fabricate the LED device.
Abstract: An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p–n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Multilayered films prepared by a pulsed-laser deposition technique were processed by conventional photolithography with the aid of reactive ion etching to fabricate the LED device. A rather sharp emission band centered at 382 nm was generated when a forward bias voltage exceeding the turn-on voltage of 3 V was applied to the junction. The emission may be attributed to a transition associated with the electron–hole plasma of ZnO.
515 citations
TL;DR: In this article, the violet photoluminescence was achieved at room temperature (RT) from ZnO films grown on sapphire (001) substrate by pulsed laser deposition (PLD).
482 citations
TL;DR: In this paper, aluminum-doped zinc oxide (AZO) thin films with low electrical resistivity and high optical transparency have been grown by pulsed-laser deposition on glass substrates without a postdeposition anneal.
Abstract: Aluminum-doped zinc oxide (AZO) thin films (∼3000 A) with low electrical resistivity and high optical transparency have been grown by pulsed-laser deposition on glass substrates without a postdeposition anneal. Films were deposited at substrate temperatures ranging from room temperature to 400 °C in O2 partial pressures ranging from 0.1 to 50 mTorr. For 3000-A-thick AZO films grown at room temperature in an oxygen pressure of 5 mTorr, the electrical resistivity was 8.7×10−4 Ω cm and the average optical transmittance was 86% in the visible range (400–700 nm). For 3000-A-thick AZO films deposited at 200 °C in 5 mTorr of oxygen, the resistivity was 3.8×10−4 Ω cm and the average optical transmittance in the visible range was 91%. AZO films grown at 200 °C were used as an anode contact for organic light-emitting diodes. The external quantum efficiency measured from these devices was about 0.3% at a current density of 100 A/m2.
440 citations
TL;DR: In this paper, electrical and optical properties of CuAlO2, a p-type conducting transparent oxide, were examined for the thin films prepared by the pulsed laser deposition technique, and the indirect and direct allowed optical band gaps were evaluated to be ∼1.8 and ∼3.5 eV, respectively.
Abstract: Electrical and optical properties of CuAlO2, a p-type conducting transparent oxide, were examined for the thin films prepared by the pulsed laser deposition technique. The indirect and direct allowed optical band gaps were evaluated to be ∼1.8 and ∼3.5 eV, respectively. The conductivity at 300 K was ∼3×10−1 S cm−1 and its temperature dependence is of the thermal-activation type (activation energy ≈0.2 eV) at temperatures >220 K but is of the variable-range hopping type (log σ∝T−1/4) at <220 K. It was inferred that an admixed state of Cu 3d and O 2p primarily constitutes the upper valence band, which controls transport of positive holes, from a combined information on ultraviolet photoemission spectrum with x-ray photoemission spectrum. An energy band calculation by full-potential linearized augmented plane wave method substantiated the experimental findings. The present results gave a solid basis for our working hypothesis [Nature (London) 389, 939 (1997)] for chemical design of p-type conducting transpar...
406 citations
Journal Article•
TL;DR: In this paper, the result of the PtSi nanometer thin film based on silicon prepared by the pulsed laser deposition was described and the physical principle, unique characteristics and the proceeding of the study were introduced briefly.
Abstract: The pulsed laser deposition is a new technique for the growth of thin films,which has been attended generally by people recently The physical principle, unique characteristics and the proceeding of the study were introduced briefly In addation, the result of the PtSi nanometer thin film based on silicon prepared by the pulsed laser deposition was describedPULS
392 citations
TL;DR: In this paper, a 30 keV Ga+ focused ion beam assisted deposition using a aromatic hydrocarbon precursor was performed by a transmission microscope and Raman spectra, which indicated that the deposition film is a diamond-like amorphous carbon.
Abstract: Three-dimensional nanostructure fabrication has been demonstrated by 30 keV Ga+ focused ion beam assisted deposition using a aromatic hydrocarbon precursor. The characterization of deposited film on a silicon substrate was performed by a transmission microscope and Raman spectra. This result indicates that the deposition film is a diamondlike amorphous carbon. Production of three-dimensional nanostructure is discussed. Microcoil, drill, and bellows with 0.1 μm dimension were fabricated as parts of the microsystem. Furthermore, microstructure plastic arts is advocated as a new field using microbeam technology, presenting one example of a microwine glass with 2.75 μm external diameter and 12 μm height.
390 citations
TL;DR: In this article, the structural, electrical and optical properties of transparent conducting aluminum-doped zinc oxide (AZO) thin films have been investigated as a function of Al-doping amount (0 − 4 wt%) in the target.
331 citations
TL;DR: In this article, the results of field-emission scanning electron microscopy and TEM investigations showed that the GaAs nanowires are produced in >90% yield, are single crystals with 〈111〉 growth axes, and have diameters varying from three to tens of nanometers.
Abstract: Gallium arsenide (GaAs) nanowires have been synthesized in bulk quantities and high purity by laser-assisted catalytic growth. Field-emission scanning electron microscopy and transmission electron microscopy investigations show that the GaAs nanowires are produced in >90% yield, are single crystals with 〈111〉 growth axes, and have diameters varying from three to tens of nanometers, and lengths extending to tens of micrometers. Photoluminescence (PL) measurements made on individual GaAs nanowires show large blueshifts in the PL peak position compared to bulk GaAs, and are consistent with strong quantum confinement. The implications of these results are discussed.
305 citations
TL;DR: In this paper, it was shown that the photoluminescence (PL) intensity of ultra-violet (UV) luminescence strongly depends on the stoichiometry in the ZnO film rather than the micro-structural quality of the crystal.
Abstract: ZnO thin film has been deposited on a sapphire (001) at a temperature of 400°C using a pulsed laser deposition (PLD) with oxygen pressures of 50, 200, 300 and 500 mTorr. As the oxygen pressure for the thin film deposition increases, the crystallinity of the samples degrades as measured by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). In contrast, the photoluminescence (PL) intensity of ultra-violet (UV) luminescence increases as the oxygen pressure increases up to 300 mTorr. This is probably because the stoichiometry of oxygen-deficient ZnO film is improved by increasing oxygen pressure. According to the results from Hall measurements, the oxygen vacancy as a native donor defect in the ZnO decreases in concentration as the pressure increases. It is concluded that the UV luminescence intensity strongly depends on the stoichiometry in the ZnO film rather than the micro-structural quality of the crystal.
TL;DR: In this paper, transparent conducting indium tin oxide (ITO) thin films were grown by pulsed laser deposition on amorphous substrates and the structural, electrical, and optical properties of these films were investigated.
Abstract: Transparent conducting indium tin oxide (ITO) thin films (40–870 nm) were grown by pulsed laser deposition on amorphous substrates and the structural, electrical, and optical properties of these films were investigated. Films were deposited using a KrF excimer laser (248 nm, 30 ns FWHM) at a fluence of 2 J/cm2, at substrate temperature of 300 °C and 10 mTorr of oxygen pressure. For ITO films (30–400 nm thickness) deposited at 300 °C in 10 mTorr of oxygen, a resistivity of 1.8–2.5×10−4 Ω cm was observed and the average transmission in the visible range (400–700 nm) was about 85%–90%. The Hall mobility and carrier density for ITO films (40–870 nm thickness) were observed to be in the range of 24–27 cm2/V s and 8–13×1020 cm−3, respectively. The ITO films have been used as the anode contact in organic light emitting diodes and the effect of ITO film thickness on the device performance has been studied. The optimum thickness of the ITO anode for the maximum device efficiency was observed to be about 60–100 nm....
TL;DR: In this paper, a strong correlation is observed between the structure and the microwave dielectric properties of epitaxial Ba0.5Sr0.3 (BST) thin films deposited onto MgO by pulsed laser deposition.
Abstract: A strong correlation is observed between the structure and the microwave dielectric properties of epitaxial Ba0.5Sr0.5TiO3 (BST) thin films deposited onto (001) MgO by pulsed laser deposition. Films were deposited at 750 °C in an oxygen pressure that was varied from 3 to 1000 mTorr. The tetragonal distortion (ratio of in-plane and surface normal lattice parameters, D=a/c) of the films depends on the oxygen deposition pressure. D varied from 0.996 at 3 mTorr to 1.003 at 800 mTorr. At microwave frequencies (1–20 GHz), BST films with low distortion have higher dielectric constants (e∼500), and lower dielectric loss (tan δ∼0.02) compared to films with higher distortion. The correlation of the microwave properties with the film structure can be attributed to stresses and polarizability in the film. The BST film grown at the oxygen deposition pressure of 50 mTorr exhibits a large dielectric constant change and a low dielectric loss at the same time, which corresponds to the film in low stress (D=1.0004). For tu...
Book•
01 Feb 2000
TL;DR: In this paper, the Kinetic Theory of Gases and its application in physical vapor deposition are discussed. And the principles of Sputtering Discharges are discussed as well as their application in film deposition.
Abstract: Introduction to Physical Vapor Deposition. The Kinetic Theory of Gases. Adsorption and Condensation. Principles of High Vacuum. Evaporation Sources. Principles of Sputtering Discharges. Sputtering. Film Deposition. Index.
TL;DR: In this paper, high electrically conductive indium-tin-oxide thin films were epitaxially grown on an extremely flat (100) surface of yttria-stabilized zirconia single-crystal substrates at a substrate temperature of 600 °C by a pulsed-laser deposition technique.
Abstract: Highly electrically conductive indium–tin–oxide thin films were epitaxially grown on an extremely flat (100) surface of yttria-stabilized zirconia single-crystal substrates at a substrate temperature of 600 °C by a pulsed-laser deposition technique. A resistivity down to 7.7×10−5 Ω cm was reproducibly obtained, maintaining optical transmission exceeding 85% at wavelengths from 340 to 780 nm. The carrier densities of the films were enhanced up to 1.9×1021 cm−3, while the Hall mobility showed a slight, almost linear, decrease from 55 to 40 cm2 V−1 s−1 with increasing SnO2 concentration. The low resistivity is most likely the result of the good crystal quality of the films.
TL;DR: In this paper, a series of heteroepitaxial Ba0.6Sr0.4TiO3 were grown on 0.29(LaAlO3):0.35(Sr2TaAlO6) substrates using pulsed-laser deposition.
Abstract: A series of heteroepitaxial Ba0.6Sr0.4TiO3 were grown on 0.29(LaAlO3):0.35(Sr2TaAlO6) substrates using pulsed-laser deposition. X-ray characterization revealed compressive in-plane stresses in the thinnest films, which were relaxed in a continuous fashion with increasing thickness. A theoretical treatment of the misfit strain was in good agreement with the measured out-of-plane lattice parameter. The low-frequency dielectric constant was measured to be significantly less than the bulk value and found to decrease rapidly for films less than 100 nm. A thermodynamic model was developed to understand the reduction in dielectric constant. By observing the microstructure using plan-view and cross-section transmission electron microscopy, we identified local strain associated with a threading dislocation density on the order of 1011 cm−2 as a possible mechanism for dielectric degradation in these films.
TL;DR: In this article, the authors synthesize ZnO films on GaAs substrates at different growth conditions by pulse laser deposition and show that the bound exciton peaks located between 3.37 and 3.35 eV are very strong.
Abstract: ZnO films were synthesized on GaAs substrates at different growth conditions by pulse laser deposition. High-purity (99.999%) oxygen was used as the ambient gas. The pressure of the ambient oxygen gas for ZnO film growth was varied from 20 to 50 mTorr, and the growth temperature from 300 to 450 °C. ZnO films showed very strong bound exciton peaks located between 3.37 and 3.35 eV. The full width at half maximum of the bound exciton peak is less than 5 meV. These results indicate ZnO films on GaAs substrates can be used for optical devices such as light-emitting diodes. The other significant properties of textured ZnO films on GaAs substrates are described.
TL;DR: In this paper, epitaxial Ba0.4Sr0.6TiO3 (BST) films via laser ablation were deposited on MgO and LaAlO3 substrates for tunable microwave devices.
Abstract: We deposited epitaxial Ba0.4Sr0.6TiO3 (BST) films via laser ablation on MgO and LaAlO3 (LAO) substrates for tunable microwave devices. Postdeposition anneals (∼1100 °C in O2) improved the morphology and overall dielectric properties of films on both substrates, but shifted the temperature of maximum dielectric constant (Tmax) up for BST/LAO and down for BST/MgO. These substrate-dependent Tmax shifts had opposite effects on the room-temperature dielectric properties. Overall, BST films on MgO had the larger maximum dielectric constant (e/e0⩾6000) and tunability (Δe/e⩾65%), but these maxima occurred at 227 K. 30 GHz phase shifters made from similar films had figures of merit (ratio of maximum phase shift to insertion loss) of ∼45°/dB and phase shifts of ∼400° under 500 V (∼13 V/μm) bias, illustrating their utility for many frequency-agile microwave devices.
TL;DR: The observed ion acceleration suggests that formation in the plume of a high-energetic electron tail due to absorption of laser radiation is responsible for the development of a double layer in laser-induced plasma plumes.
Abstract: Charge-collector probe measurements have been performed to elucidate ion acceleration in laser-induced plasma plumes over a range of laser fluences important for pulsed laser deposition. The fundamental (1064 nm) or second (532 nm) harmonics of a Nd:YAG laser were used for ablation. The evolution of the time-of-flight ion signal from single-peaked to double-peaked and again to single-peaked with increasing laser fluence in the range of $2--25 {\mathrm{J}/\mathrm{c}\mathrm{m}}^{2}$ has been followed. The analysis of the ion velocity distributions shows that increasing laser fluence results in the appearance of a portion of accelerated ions that can be recognized as an additional fast peak in the time-of-flight distribution. The dependencies of the ion signal on the target-to-collector distance, the background pressure, and the wavelength of laser radiation have been studied. The results are discussed from the viewpoint of the generation of a self-consistent ambipolar electric field (so-called double layer). The observed ion acceleration suggests that formation in the plume of a high-energetic electron tail due to absorption of laser radiation is responsible for the development of a double layer.
Patent•
12 May 2000
TL;DR: In this article, an improved ALD apparatus is disclosed as having multiple deposition regions in which individual monolayer species are deposited on a substrate under different processing conditions in each region, each deposition region is chemically separated from an adjacent deposition region.
Abstract: An improved ALD apparatus is disclosed as having multiple deposition regions in which individual monolayer species are deposited on a substrate under different processing conditions in each region. Each deposition region is chemically separated from an adjacent deposition region. A loading assembly is programmed to follow pre-defined transfer sequences for moving semiconductor substrates into and out of the respective adjacent deposition regions. According to the number of deposition regions provided, a multitude of substrates could be simultaneously processed and run through the cycle of deposition regions until a desired thickness of deposited solid film is obtained.
TL;DR: In this article, an epitaxial Ba1−xSrxTiO3 (BST) thin films have been deposited onto (100) MgO and LaAlO3 substrates using pulsed-laser deposition.
Abstract: Epitaxial Ba1−xSrxTiO3 (BST) thin films have been deposited onto (100)MgO and LaAlO3 substrates using pulsed-laser deposition. Thick (>1 μm) Ag interdigitated capacitors capped with a thin protective layer of Au have been deposited on top of the BST films using electron-beam deposition. The capacitance (C) and dielectric quality factor (Q=1/tan δ) of the structure has been measured at microwave frequencies (1–20 GHz) as a function of electric field (E⩽67 kV/cm) at room temperature. In epitaxial BST films, either high dielectric tuning (4:1), which is defined as {[C(0)−C(E)]/C(0)}×100, or high dielectric Q (∼100–250) was observed but not both at the same time. Film strain was observed by x-ray diffraction and is closely related to the dielectric properties as limiting the ability to obtain both high tuning and high dielectric Q in epitaxial BST thin films. A thin BST buffer layer was used to relieve the strain in the films. In strain-relieved films, both dielectric tuning and dielectric Q were increased af...
TL;DR: In this paper, the surface layer of the grown films contained an additional phase with Ba atoms in a different chemical state, which was homogeneously mixed with the BST phase up to several nm depth, while UVPLD grown films exhibited a much thinner (∼ 1 nm) and continuous layer.
Abstract: Ba0.5Sr0.5TiO3 (BST) thin films grown on Si by an in situ ultraviolet-assisted pulsed laser deposition (UVPLD) technique exhibited significantly higher dielectric constant and refractive index values and lower leakage current densities than films grown by conventional PLD under similar conditions. X-ray photoelectron spectroscopy (XPS) investigations have shown that the surface layer of the grown films contained, besides the usual BST perovskite phase, an additional phase with Ba atoms in a different chemical state. PLD grown films always exhibited larger amounts of this phase, which was homogeneously mixed with the BST phase up to several nm depth, while UVPLD grown films exhibited a much thinner (∼1 nm) and continuous layer. The relative fraction of this phase was not correlated with the amount of C atoms present on the surface. Fourier transform infrared spectroscopy did not find any BaCO3 contamination layer, which was believed to be related to this new phase. X-ray diffraction measurement showed that...
TL;DR: In this article, a narrow potential well has been formed on the surface of the ZnO thin films due to high density of surface states and negatively biasing the thin films during STS measurement.
Abstract: ZnO thin films were grown on silicon (100) by pulsed laser deposition. Highly textured crystalline ZnO thin films can be grown at 600 °C. The films were then annealed at 600 °C in oxygen. The effects of annealing on chemical composition of the ZnO films were investigated by x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XPS spectra indicate that water has been adsorbed and then dissociated into H and OH groups. The surface properties of ZnO were studied both by scanning tunneling microscopy and scanning tunneling spectroscopy (STS). A narrow potential well has been formed on the surface of the ZnO thin films due to high density of surface states and negatively biasing the ZnO thin films during STS measurement. The discrete energy levels can be measured by STS.
TL;DR: In this paper, the microstructure and dielectric properties of barium strontium titanate, Ba1−xSrxTiO3, films grown by laser ablation on LaAlO3 substrates, where x=0.1, were investigated.
Abstract: We report a systematic study of the microstructure and dielectric properties of barium strontium titanate, Ba1−xSrxTiO3, films grown by laser ablation on LaAlO3 substrates, where x=0.1–0.9 at an interval of 0.1. X-ray diffraction analysis shows that when x 0.4, compared with the peak temperatures of the bulk Ba1−xSrxTiO3. At room temperature, the dielectric constant and tunability are relatively high when x⩽0.4 but start to decrease rapidly as x increases.
TL;DR: In this paper, an Anatase-structured TiO2 thin films were deposited on window glass by CVD, and the photocatalytic dissociation rates of benzene with CVD-grown TiO 2 under UV exposure were characterized.
Patent•
28 Sep 2000TL;DR: In this article, a source of pulsed laser energy, a receiving substrate, and a target substrate are placed in relation to the target substrate so that the transferred material in the desorbed coating can be deposited at a defined location on the receiving substrate.
Abstract: An device for depositing a transfer material onto a receiving substrate includes a source of pulsed laser energy, a receiving substrate, and a target substrate. The target substrate comprises a laser transparent support having a back surface and a front surface. The front surface has a coating that comprises a mixture of the transfer material to be deposited and a matrix material. The matrix material is a material that has the property that, when it is exposed to pulsed laser energy, it is more volatile than the transfer material. The source of pulsed laser energy is be positioned in relation to the target substrate so that pulsed laser energy is directed through the back surface of the target substrate and through the laser-transparent support to strike the coating at a defined location with sufficient energy to volatilize the matrix material at the location, causing the coating to desorb from the location and be lifted from the surface of the support. The receiving substrate is positioned in a spaced relation to the target substrate so that the transfer material in the desorbed coating can be deposited at a defined location on the receiving substrate.
TL;DR: In this article, the converse piezoelectric effect using scanning force microscopy (SFM) combined with a lock-in technique was used to characterize at the nanoscale level ferroelectric SrBi2Ta2O9 and Bi4Ti3O12 thin films.
Abstract: The local polarization state and the electromechanical properties of ferroelectric thin films can be probed via the converse piezoelectric effect using scanning force microscopy (SFM) combined with a lock-in technique. This method, denominated as piezoresponse SFM, was used to characterize at the nanoscale level ferroelectric SrBi2Ta2O9 and Bi4Ti3O12 thin films, grown by pulsed laser deposition. Two types of samples were studied: polycrystalline films, with grains having random orientations, and epitaxial films, consisting of (100)orth- or (110)orth-oriented crystallites, 100 nm to 2 μm in lateral size, which are embedded into a (001)-oriented matrix. The ferroelectric domain structure was imaged and the piezoelectric response under different external conditions was locally measured for each type of sample. Different investigation procedures are described in order to study the ferroelectric properties via the electromechanical response. A distinct ferroelectric behavior was found for single grains of SrBi2Ta2O9 as small as 200 nm in lateral size, as well as for 1.2 μm×175 nm crystallites of Bi4Ti3O12. By probing separately the crystallites and the matrix the investigations have demonstrated at the nanoscale level that SrBi2Ta2O9 has no spontaneous polarization along its crystallographic c-axis, whereas Bi4Ti3O12 exhibits a piezoelectric behavior along both the a- and c-directions. The electrostriction coefficients were estimated to be 3×10-2 m4/C2 for polycrystalline SrBi2Ta2O9 and 7.7×10-3 m4/C2 for c-orientedBi4Ti3O12.
TL;DR: Despite PLDs ability to improve the crystal structure by incorporating water vapor into the deposition process, the characterization with EDX and XPS showed that coatings had different Ca/P ratios from that of the pure HA targets, which almost assured the presence of non-HA phases.
TL;DR: In this paper, the authors presented the first report of the production of a granular low-density carbon nano-foam with rich fraction of sp3 bonding, and the bulk density of various foam samples was in the range (2-10)×10-3 g/cm3, and specific surface area was 300-400 m2/g.
Abstract: High-repetition-rate laser ablation and deposition of carbon vapours results in the formation of quite different carbonaceous structures depending on the pressure of the ambient Ar gas in the chamber. Diamond-like carbon films form at a pressure below ≈0.1 Torr whereas a diamond-like carbon nano-foam is created above 0.1 Torr. Although laser-deposited amorphous carbon films have been extensively investigated in the past, here we present what, to our knowledge, is the first report of the production of a granular low-density carbon nano-foam with rich fraction of sp3 bonding. The bulk density of various foam samples was in the range (2–10)×10-3 g/cm3, and the specific surface area was 300–400 m2/g. The resistivity of the foam measured at low-voltage (±30 V) is (1–3)×109 Ohm cm at room temperature and (1–10)×1013 Ohm cm at 80 K. The dc conductivity of this low-density carbon foam and its temperature dependence appears to be very close to that of RF-sputtered solid amorphous diamond-like carbon films.
TL;DR: In this article, X-ray diffraction and Raman scattering results show that brookite is the main phase present in the titania thin film and has not previously been reported for pulsed laser-deposition thin films.