Spectroscopic and Ion Probe Characterization of the Transport Process Following Laser Ablation of Yba2Cu3Ox

1990 ◽  
Vol 191 ◽  
Author(s):  
David B. Geohegan ◽  
Douglas N. Mashburn
Keyword(s):  
Laser Ablation ◽  
Ground State ◽  
Film Growth ◽  
Laser Energy ◽  
High Energy ◽  
Film Deposition ◽  
Oxygen Absorption ◽  
Total Charge ◽  
Laser Plume ◽  
Ion Probe

ABSTRACTSpatial and temporal measurements of the optical absorption, optical emission and ion probe response in the ablation plume formed following pulsed 248 nm irradiation of Y1Ba2Cu3Ox are reported over laser energy densities from near threshold into the film growth regime. Time of flight absorbance-velocity profiles in vacuum indicate the formation and acceleration of a plasma front, with ions leading neutrals on the edge of the expanding plume. Ion probe screening measurements show that the laser plume is a well-shielded plasma with Debye lengths <10 μm at film deposition distances. Velocity distributions and estimates of ground state Ba+, Ba, Y+, and Y densities indicate that the populations of the ions outnumber those of the neutrals at high energy densities in vacuum. Measurements of the slowing of the plasma front and attenuation of the total charge reaching the substrate are reported for laser ablation in background pressures of oxygen. Absorption by ground state YO and BaO in the region close to the pellet indicates oxide densities ˜5 × 1013 cm−3 close to the pellet.

scholarly journals Characterization of Ground State Neutral and Ion Transport During Laser Ablation of 1:2:3 Superconductors by Transient Optical Absorption Spectroscopy

1989 ◽  
Vol 169 ◽  
Author(s):  
David B. Geohegan ◽  
Douglas N. Mashburn
Keyword(s):  
Laser Ablation ◽  
Optical Absorption ◽  
Ground State ◽  
Velocity Component ◽  
Film Growth ◽  
Growth Conditions ◽  
Optical Absorption Spectroscopy ◽  
Low Velocity ◽  
Ion Probe ◽  
Order Of Magnitude

AbstractOptical absorption in the plume produced by excimer laser ablation of Y1Ba2Cu3O7‐x under film growth conditions has been observed for the first time and used to characterize the transport of ground state Y, Ba, and Cu neutrals as well as Y+ and Ba+ ions. Spatially and temporally resolved absorption measurements (0.6 mm, 20 ns resolution) indicate significant ground state number densities at times following the laser pulse that are up to an order of magnitude longer than the duration of fluorescence from excited states. Time‐of‐flight absorbance profiles result in velocity distributions that are broadened significantly toward lower velocities and reveal a low velocity component (<10 5 cm s_1) to the ablation process which is not observed using emission spectroscopy. Electric ion probe measurements of the time dependence of Y+ ions confirm the existence of the new, slow velocity component. Electron densities >1016 cm‐3 in the white plasma close to the pellet have been estimated using spectrally broadened emission lines. The effects of oxygen ambient pressures and the detection of YO, BaO, and CuO also are reported. This technique is applicable as an situ monitor of the kinetic energy of ablated species during low temperature deposition of epitaxial 1:2:3 superconducting thin films.

Synthesis of BiFeO3 Ceramic Targets and Thin Film Deposition by Laser Ablation

2006 ◽  
Vol 514-516 ◽  
pp. 328-332 ◽  
Author(s):  
Cezarina C. Mardare ◽  
Pedro B. Tavares ◽  
Andréi I. Mardare ◽  
Raluca Savu
Keyword(s):  
Laser Ablation ◽  
Laser Energy ◽  
Ferroelectric Properties ◽  
Hysteresis Loops ◽  
Combustion Method ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates

A dense ceramic target of BiFeO3 was synthesized by the urea combustion method. X-ray diffraction indicates that this target is composed of a mixture of phases, the main one is BiFeO3, but Bi46Fe2O72 and Bi2Fe4O9 are also present in small amounts. The BiFeO3 target was used for depositing thin films on Pt/Ti/SiO2/Si substrates by the laser ablation technique. The depositions were made in oxygen atmosphere at pressures in the range between 5x10-3 and 2x10-2mbar, using a KrF laser. The substrate temperatures were 450 or 500°C and the laser energy, the frequency and the distance between the target and the substrate were kept constant at 125mJ, 10Hz and 4cm, respectively. After a deposition time of 30minutes the thickness of the films was approximately 400nm. Some of the films were heat-treated in situ, in 100mbar O2 for 30minutes, at the same temperatures used for deposition. X-ray diffraction results show the BiFeO3 phase, as well as some Bi46Fe2O72 and Bi2Fe4O9. The films were crystallized without any preferential orientation, but the ones made at 2x10-2mbar and 450°C were partially amorphous. For measuring the ferroelectric hysteresis loops, either Al top electrodes were deposited by thermal evaporation or Pt, by sputtering. The distorted shapes of the hysteresis loops obtained indicated that the films exhibit weak ferroelectric properties and high leakage current values.

In Situ Growth of High Quality Epitaxial Yba2cu3O7‐X Thin Films at Moderate Temperatures by Pulsed Laser Ablation

1989 ◽  
Vol 169 ◽  
Author(s):  
Douglas H. Lowndes ◽  
David P. Norton ◽  
J. W. Mccamy ◽  
R. Feenstra ◽  
J. D. Budai ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Film Growth ◽  
Laser Energy ◽  
Thickness Variation ◽  
In Situ Growth ◽  
High Quality ◽  
Higher Temperature ◽  
Laser Beam Scanning ◽  
Rotating Target

AbstractPulsed KrF (248 nm) laser ablation has been used for in situ growth of smooth, high‐quality YBa2Cu3O7‐x epitaxial films of variable thickness on SrTiO3, KTaO3, LaGaO3, LaA1O3, cubic ZrO2, and MgO substrates, at temperatures of ∼60O‐730°C, without higher temperature post‐annealing. A rotating target pellet, fine focusing by a single cylindrical lens, laser‐beam scanning over the target, and laser energy densities ∼2.5‐3 J/cm2 can be combined to yield films of completely uniform composition and with ∼25% thickness variation over areas ∼8 cm2. The best films have Tc > 92 K and JC(H = 0, T = 77 K) > 2 MA/cm2. Film‐growth procedures are described, together with results of superconducting and normal‐state transport measurements.

Molecular-Dynamics Simulations of Laser-Ablation and Ionassisted Thin Film Deposition

1992 ◽  
Vol 285 ◽  
Author(s):  
H. Feil ◽  
J.S.C. Kools ◽  
J. Dieleman
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Laser Ablation ◽  
Molecular Dynamics Simulations ◽  
Film Growth ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Laser Fluences ◽  
Cu Thin Film ◽  
Dynamics Simulations

ABSTRACTMolecular dynamics simulations are performed of Cu thin film growth on Cu (111). Ion-Assisted Deposition is simulated by bombarding the substrate with Cu+ ions with a kinetic energy of 80 eV, while 1 eV Cu atoms are used for the simulation of Laser Ablation Deposition. It appears that Ion-Assisted Deposition leads to sputtering, enhanced surface mobility, surface disorder, mixing and rather deep damage. This is discussed in some detail. Laser Ablation Deposition, using laser fluences just above the ablation threshold, does not lead to damage and mixing. Sharper interfaces and more perfect heterostructures and superlattices can be produced using Laser Ablation Deposition.

High Intensity Laser Ablation of Titanium Target

2011 ◽  
Vol 227 ◽  
pp. 57-61 ◽  
Author(s):  
Kenza Yahiaoui ◽  
Tahar Kerdja ◽  
Smail Malek
Keyword(s):  
Laser Ablation ◽  
Laser Energy ◽  
Thin Film Deposition ◽  
Ablation Rate ◽  
Film Deposition ◽  
Laser Irradiance ◽  
Phase Explosion ◽  
Sem Images ◽  
Laser Breakdown ◽  
The Impact

In thin film deposition by pulsed laser ablation (PLD), the mass ablation rate depends on laser energy, on the pulse duration and on the thermodynamic properties of the ablated materials. In order to optimize the PLD technique and the films quality, the evolution of the amount of the ejected materials with laser irradiance, the SEM images of the laser impacts on the target and the ion yield in the vapour plume, were used. This allows us to predict the different mechanisms that are responsible to mass ablation according to laser irradiance which was ranging from 1.5108W/cm2 to 5.51010 W/cm2. Three diagnostics devices have been used: A quartz microbalance placed in front of the target, where the maximum of materials ejection occurs, a Scanning Electron Microscope (SEM) was used to show the impact morphology evolution with the laser irradiance and a charge collector, biased at negative voltage, was used to measure the ions yield and ions kinetic energy. The results show the evolution from normal evaporation mechanism at moderate laser irradiance to phase explosion mechanism at higher laser irradiance. Laser irradiance threshold for phase explosion onset is well determined by microbalance measurement, SEM micrographic pictures and the laser breakdown in the vapour plume was determined by the charge collector.

scholarly journals Effect of Ambient Gas Pressure on Pulsed Laser Ablation Plume Dynamics and Znte Film Growth

1995 ◽  
Vol 397 ◽  
Author(s):  
CM. Rouleau ◽  
D.H. Lowndes ◽  
M.A. Strauss ◽  
S. Cao ◽  
A.J. Pedraza ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
High Energy ◽  
Gas Pressure ◽  
Ex Situ ◽  
Extended Defect ◽  
Ion Probe ◽  
Ambient Gas ◽  
Probe Measurements

ABSTRACTEpitaxial thin films of nitrogen-doped p-ZnTe were grown on single-crystal, semi-insulating GaAs substrates via pulsed laser ablation of a stoichiometric ZnTe target. Both low pressure nitrogen ambients and high vacuum were used. Results of in situ reflection high energy electron diffraction (RHEED) and time-resolved ion probe measurements have been compared with ex situ Hall effect and transmission electron microscopy (TEM) measurements. A strong correlation was observed between the nature of the film's surface during growth (2-D vs. 3-D, assessed via RHEED) and the ambient gas pressures employed during deposition. The extended defect content (assessed via cross-sectional TEM) in the region >150 nm from the film/substrate interface was found to increase with the ambient gas pressure during deposition, which could not be explained by lattice mismatch alone. At sufficiently high pressures, misoriented, columnar grains developed which were not only consistent with the RHEED observations but also were correlated with a marked decrease in Hall mobility and a slight decrease in hole concentration. Ion probe measurements, which monitored the attenuation and slowing of the ion current arriving at the substrate surface, indicated that for increasing nitrogen pressure the fast (vacuum) velocity-distribution splits into a distinct fast and two collisionally-slowed components or modes. Gas-controlled variations in these components mirrored trends in electrical properties and microstructural measurements.

RHEED Pole Figure Measurements of Biaxial Thin Film Growth Front Evolution

2011 ◽  
Vol 1308 ◽  
Author(s):  
Gwo-Ching Wang ◽  
Yu Liu ◽  
Churamani Gaire ◽  
Wen Yuan ◽  
Toh-Ming Lu
Keyword(s):  
Pole Figure ◽  
Film Growth ◽  
Texture Evolution ◽  
Growth Front ◽  
High Energy ◽  
Film Deposition ◽  
Oblique Angle Deposition ◽  
X Rays ◽  
Biaxial Texture ◽  
Figure Technique

ABSTRACTThe most frequently used characterization technique for biaxial texture formation in thin films is x-ray pole figure analysis. However, x-rays interact weakly with matter and can penetrate a few microns deep into the film. The texture obtained by x-rays is therefore an average texture from the entire thickness of the film. As the texture of a film often changes during growth, information on the basic mechanisms that control the final texture is often lost. In contrast electrons interact strongly with matter and they have very limited penetration and escape depths of a few nm. In this paper we will show how we can use our newly developed reflection high energy electron diffraction (RHEED) surface pole figure technique to probe the surface texture evolution of the growth front from the initial stage (nm thick) to the later stage. The RHEED pole figure technique is a surface-sensitive technique that allows us to obtain information on the dynamic behavior of texture evolution of the growth front during film deposition. We shall explain the principle, measurement, and construction of such RHEED surface pole figures. An example of the biaxial texture evolution of CaF2 due to the atomic shadowing effect during oblique angle deposition is described.

Hydrogenated Amorphous Silicon Thin-Film Deposition by Direct Photo-Enhanced Decomposition of Silane Using an Internal Hydrogen Discharge Lamp.

1986 ◽  
Vol 70 ◽  
Author(s):  
P. A. Robertson ◽  
W. I. Milne
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Film Growth ◽  
Hydrogenated Amorphous Silicon ◽  
Thin Film Deposition ◽  
High Energy ◽  
Film Deposition ◽  
Discharge Lamp ◽  
Hydrogen Discharge ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon (a-Si:H) thin films have been deposited from silane using a novel photo-enhanced decomposition technique. The system comprises a hydrogen discharge lamp contained within the reaction vessel; this unified approach allows high energy photon excitation of the silane molecules without absorption by window materials or the need for mercury sensitisation. The film growth rates (exceeding 4 Å/s) and material properties obtained are comparable to those of films produced by plasma-enhanced CVD techniques. The reduction of energetic charged particles in the film growth region should enable the fabrication of cleaner semiconductor/insulator interfaces in thin-film transistors.

Laser-Ablation of Various Oxide Materials Over Large Areas

1990 ◽  
Vol 191 ◽  
Author(s):  
James A. Greer ◽  
H. Jerrold Van Hook
Keyword(s):  
Laser Ablation ◽  
Physical Vapor Deposition ◽  
Film Growth ◽  
High Energy ◽  
Published Report ◽  
Device Applications ◽  
Novel Method ◽  
Reactive Gases ◽  
Infrared Materials

Laser-Ablation (LA) had received little attention prior to the first published report of depositing Y1Ba2Cu3O7-x) (YBCO) thin films with this novel method.[1] However, LA has been used to produce films of infrared materials for some time[2], and the recent discovery of 1-igh Temperature Superconductors (HITS) has sparked considerable interest in this relatively obscure Physical Vapor Deposition (PVD) technique. Over the past three years, a variety of in-situ LA processes for producing films of HTS compounds, as well as other materials, have been reported in the literature.[3,4,5,6,7] Like any other PVD technique, LA has its own unique advantages anid disadvantages. The main advantages of LA include: 1) its ability to accurately replicate the stoichiometry of the ablation target within the laser-deposited film; 2) the high energy of the ablated species which may enhance the quality of film growth; 3) it does not require hot filaments which allow a number of reactive gases to be present in the chamber during deposition; and 4) a wide array of complex chemical compounds can be deposited. Two of the main problems facing this emerging PVD technique have been: 1) it has been applied mostly to small area deposition (<6 cm2) with poor uniformity, and 2) the ablated films typically display a large number- of particles ranging in size from 0.5 μm to over 10 μm, whose presence may significantly hamper a number of microelectronic device applications.

High Damage Threshold Optical Films for Excimer Lasers

1991 ◽  
Vol 236 ◽  
Author(s):  
H. Ito ◽  
N. Kajita ◽  
Y. Minowa ◽  
H. Yoshida ◽  
T. Ina
Keyword(s):  
Current Density ◽  
Film Growth ◽  
Laser Energy ◽  
Ion Beam ◽  
Damage Threshold ◽  
High Energy ◽  
Sio2 Film ◽  
Ion Current ◽  
Optical Films ◽  
Ion Current Density

AbstractHigh damage threshold coating for high energy KrF excimer laser has been developed by the multiple ion beam deposition system, which contains a couple of the ionized cluster beam (ICB) sources and the ionized gas beam source. The damage threshold of low refractive SiO2, high refractive A12O3 and SiO2/A12O3 multilayer coatings is found to be more than 105 shots at 8J/cm2 laser energy. Oxidation is enhanced by ion bombardment during the film growth.The refractive indices of SiO2 and A1203 films were 1.46 and 1.62 at the ion current density of 0.8μA/cm2. The film density of SiOx approaches to the bulk SiO2 of 2.3Og/cm3 with increasing ion current density. The stress-free SiO2 film can be obtained at the ion current density of around 0.5 μA/cm2.

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