The effects of the atmosphere on the surface modification of alumina by pulsed-laser-irradiation

1997 ◽  
Vol 12 (7) ◽  
pp. 1747-1754 ◽  
Author(s):  
Siqi Cao ◽  
A. J. Pedraza ◽  
L. F. Allard ◽  
D. H. Lowndes
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Thin Layer ◽  
Amorphous Phase ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Pulses ◽  
Near Surface ◽  
Metallic Particles ◽  
Cellular Microstructure

A near-surface thin layer is melted when alumina is pulsed-laser-irradiated in an Ar–4% H2 atmosphere or in air. A thin layer of amorphous phase forms when the substrates are irradiated in Ar–4% H2 at 1 to 1.3 J/cm2 with multiple laser pulses. Amorphous phase is also found in samples laser-irradiated in air and oxygen. After a laser pulse at an energy density of 1.6 J/cm2 or higher the melt solidifies epitaxially from the unmelted substrate with a cellular microstructure. There is a decrease in the cooling rate of the melt as the laser energy density is increased because more heat must be dissipated. The amorphous phase forms when the heat input due to the laser pulse produces a superheated melt that cools down sufficiently fast to avoid crystallization. Very small particles of aluminum in the laser-melted and subsequently solidified layer are observed only in samples laser-irradiated in an Ar–4% H2 atmosphere. In this reducing atmosphere, the alumina is possibly reduced to metallic aluminum which is mixed into the melt by the turbulence provoked by the laser pulses. The effects of these metallic particles on copper deposition when the irradiated substrates are immersed in an electroless bath are discussed.

Laser Encapsulation of Metallic Films in SiO2

1995 ◽  
Vol 397 ◽  
Author(s):  
A. J. Pedraza ◽  
S. Cao ◽  
D. H. Lowndes ◽  
L. F. Allard
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Laser Energy ◽  
Substrate Material ◽  
Laser Energy Density ◽  
Cross Sectional ◽  
Metallic Particles ◽  
Transmission Electron ◽  
Encapsulation Process ◽  
Deposited Film

ABSTRACTThin films of gold, copper and iron deposited on silica were driven into the substrate by a laser pulse. This transport takes place only when the irradiation is performed at a laser energy density of 0.7 J/cm2 or lower. Cross sectional transmission electron microscopy (TEM) of the irradiated specimens reveals two distinctive stages in the encapsulation process. In the first, the film melts and clusters into small particles and in the second one the particles are driven into the substrate by the laser pulse. The particle size of encapsulated metal varies from 5 to 50 nm. Selected area diffraction of the large particles and lattice fringe images of the smaller particles reveal pure metals, e.g., gold, copper or iron. Titanium films laser irradiated are not encapsulated in silica; instead, these films react with silica forming an amorphous compound. Apparently, one of the conditions required for encapsulation is that the metal should not react with the substrate material. On subsequent irradiation at a laser energy density of 1.5 J/cm2, ablation of silica partially exposes the metallic particles. Strong bonding between a new film deposited after irradiation and the substrate is obtained because these particles anchor the freshly deposited film. Anchoring is clearly revealed by cross sectional TEM. The mechanisms of encapsulation are discussed using results from TEM and adhesion testing.

Formation of polytype microstructure in pulsed-laser-irradiated sapphire substrates

1995 ◽  
Vol 53 ◽  
pp. 344-345
Author(s):  
Siqi Cao ◽  
A. J. Pedraza ◽  
L. F. Allard ◽  
D. H. Lowndes
Keyword(s):  
Energy Density ◽  
Laser Irradiation ◽  
Electroless Deposition ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Surface Modifications ◽  
Near Surface ◽  
Sapphire Substrates ◽  
Hcp Structure ◽  
Pulsed Laser Irradiation

Surface modifications of wide-gap materials are produced by pulsed laser irradiation. Under given conditions, these near-surface modifications can promote adhesion enhancement of deposited thin film materials, and activation for electroless deposition. AIN decomposes during laser irradiation leaving a metallic film on the surface. High density dislocations were observed in the surface layer of AIN that was laser melted but not decomposed. The laser melted alumina becomes amorphous at a laser energy density of ~1J/cm2. In sapphire, γ-alumina is formed when the sample is laser irradiated in Ar/4%H2. Here, we report the formation of a new structure in laser-irradiated sapphire.Optically polished c-axis sapphire substrates were laser-irradiated in an Ar/4%H2 atmosphere at 4J/cm2 energy density, using a 308 nm-wavelength laser with a pulse duration of ~40 ns. Sapphire (A12O3) has a space group R 3 c and can be described as an hcp structure having oxygen and aluminum layers alternately stacking along the c-axis.

Raman Measurements on Graphite Modified by High Power Laser Irradiation

1984 ◽  
Vol 35 ◽  
Author(s):  
J. Steinbeck ◽  
G. Braunstein ◽  
M.S. Dresselhaus ◽  
B.S. Elman ◽  
T. Venkatesan
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Laser Irradiation ◽  
High Power ◽  
Laser Energy ◽  
Laser Pulses ◽  
Laser Energy Density ◽  
High Power Laser ◽  
Power Laser ◽  
Raman Microprobe

AbstractThe behavior of highly anisotropic materials under short pulses of high power laser irradiation has been studied by irradiating highly oriented pyrolytic graphite (HOPG) with 30 nsec Ruby-laser pulses with energy densities between 0.1 and 5.0J/cm2. Raman spectroscopy has been used to investigate the laser-induced modifications to the crystalline structure as a function of laser energy density of the laser pulse. A Raman microprobe was used to investigate the spatial variations of these near-surface regions. The irradiation of HOPG with energy densities above ~ 0.6J/cm2 leads to the appearance of the ~ 1360 cm-1 disorder-induced line in the first order Raman spectrum. The intensity of the ~ 1360cm-1 line increases with increasing laser energy density. As the energy density of the laser pulse reaches about 1.0J/cm2, the ~ 1360cm-1 line and the ~ 1580cm-1 Raman-allowed mode broaden and coalesce into a broad asymmetric band, indicating the formation of a highly disordered region, consistent with RBS-channeling measurements. However, as the laser energy density of the laser pulses is further increased above 3.0J/cm2, the two Raman lines narrow and can again be resolved suggesting laser-induced crystallization. The Raman results are consistent with high resolution electron microscopy observations showing the formation of randomly oriented crystallites. Raman Microprobe spectra revealed three separate regions of behavior: (i) an outer unirradiated region where the material appears HOPG-like with a thin layer of material coating the surface, (ii) an inner irradiated region where the structure is uniform, but disordered, and (iii) an intermediate region between the other regions where the structure is highly disordered. The changes in structure of the inner region are consistent with the behavior observed with RBS and conventional Raman spectra. The identification of an amorphous carbon-like layer on the outer region is consistent with a large thermomechanical stress at the graphite surface, introduced by the high power laser pulse, and known to occur in metals.

scholarly journals IR Laser-Induced Changes to L-adrenaline-D-hydrogentartrate Incorporated in KBr Matrices

2002 ◽  
Vol 20 (2-4) ◽  
pp. 89-98
Author(s):  
Tatijana S. Jovanovic ◽  
Milica R. Bogavac ◽  
Bojan B. Radak ◽  
Milan S. Trtica
Keyword(s):  
Carbon Dioxide ◽  
Energy Density ◽  
Laser Energy ◽  
Laser Pulses ◽  
Laser Energy Density ◽  
Cooh Group ◽  
Temporal Shape ◽  
Ir Laser ◽  
Out Of Plane ◽  
Induced Changes

Changes in the pharmaceutical L-adrenaline-D-hydrogentartrate, incorporated in KBr matrices, induced by a pulsed carbon-dioxide Transversely Excited Atmospheric (TEA) laser, were observed. Modifications of the sample were monitored via infrared spectra. Special attention was devoted to the dependence of the sample changes on the laser energy density used. The irradiation of the pharmaceutical has been performed with two laser lines at wavelengths of about 10.6 µm. The laser lines coincide well with the absorption band of the pharmaceutical, which is assigned to the ring vibrations/out-of-plane OH deformation vibrations, within the carboxyl (COOH) group of L-adrenaline-D-hydrogentartrate. Laser energy densities of 1.20 and 1.70 J/cm2 modified the pharmaceutical/compound. It was found that this modification is in essence a thermal effect. The level of change showed a dependence on the laser energy density, number of accumulated laser pulses and temporal shape of the pulse.

The Shallow Implantation of Bismuth During the Growth of Bismuth Nanocrystals in Al2O3 by Pulsed Laser Deposition

2003 ◽  
Vol 780 ◽  
Author(s):  
A. Suárez-García ◽  
J-P. Barnes ◽  
R. Serna ◽  
A. K. Petford-Long ◽  
C. N. Afonso ◽  
...  
Keyword(s):  
Energy Density ◽  
Cross Section ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Laser Energy Density ◽  
X Ray ◽  
Continuous Layer ◽  
Transmission Electron ◽  
Order Of Magnitude

AbstractThe effect of the laser energy density used to deposit Bi onto amorphous aluminum oxide (a-Al2O3) on the growth of Bi nanocrystals has been investigated using transmission electron microscopy of cross section samples. The laser energy density on the Bi target was varied by one order of magnitude (0.4 to 5 J cm-2). Across the range of energy densities, in addition to the Bi nanocrystals nucleated on the a-Al2O3 surface, a dark and apparently continuous layer appears below the nanocrystals. Energy dispersive X-ray analysis on the layer have shown it is Bi rich. The separation from the Bi layer to the bottom of the nanocrystals on top is consistent with the implantation range of Bi species in a-Al2O3. As the laser energy density increases, the implantation range has been measured to increase. The early stages of the Bi growth have been analyzed in order to determine how the Bi implanted layer develops.

Formation of Q-carbon by adjusting sp3 content in diamond-like carbon films and laser energy density of pulsed laser annealing

Carbon ◽  
2020 ◽  
Vol 167 ◽  
pp. 504-511 ◽  
Author(s):  
Hiroki Yoshinaka ◽  
Seiko Inubushi ◽  
Takanori Wakita ◽  
Takayoshi Yokoya ◽  
Yuji Muraoka
Keyword(s):  
Energy Density ◽  
Laser Annealing ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Carbon Films ◽  
Laser Energy Density ◽  
Diamond Like Carbon ◽  
Pulsed Laser Annealing

Er-Doping in Silicon by Pulsed Laser Irradiation

1993 ◽  
Vol 301 ◽  
Author(s):  
Kenshiro Nakashima
Keyword(s):  
Energy Density ◽  
Laser Irradiation ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Energy Density ◽  
Er Doping ◽  
Erbium Ions ◽  
State Regime ◽  
Er Doped ◽  
Pulsed Laser Irradiation

ABSTRACTErbium ions were successfully doped in silicon by pulsed laser irradiation above the threshold laser energy density. Photoluminescence peaks at 1.54, 1.59 and 1.64 µm from Er-optical centers were observed after annealing of Er-doped samples. The intensity of the 1.54 µm Er-emission band increased upon increase in the laser energy density, and then gradually decreased after reaching the maximum, due to the laser sputtering of the silicon substrate. Oxygen atoms, which were unintentionally codoped with Er-ions, were found to be distributed in the same region as in Er-ions, and were suggested to play roles to activate Er-optical centers. The maximum concentration of Er-ions doped in the solid state regime were estimated to be the order of 1018 cm−3 by the Rutherford backscattering measurements.

Bilayer Structures Obtained by Pulsed Laser Quenching of Binary Systems

1988 ◽  
Vol 100 ◽  
Author(s):  
P. Baeri ◽  
G. Foti ◽  
M. G. Grimaldi ◽  
F. Priolo ◽  
R. Reitano ◽  
...  
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Binary Systems ◽  
Pulsed Laser ◽  
Epitaxial Layers ◽  
Silicon Substrates ◽  
High Fluence ◽  
Laser Quenching ◽  
Ion Implanted

ABSTRACTNiSi and Ni2Si layers on silicon substrates as well as high fluence Si(As) ion implanted layers,have been rapidly melted by 30 ns Nd laser pulse irradiation.The energy density ranged between 0.4 and 1.2 J/cm2. Bilayer structures have been observed when the energy density has been chosen properly.Buried epitaxial layers together with an amorphous or a policrystalline layer on top,have been detected by RBS and TEM measurements.

Laser Energy Dependent Structure of Pulsed Laser Deposited Barium Dititanate Films

2009 ◽  
Vol 66 ◽  
pp. 183-186
Author(s):  
L. Li ◽  
Chuan Bin Wang ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Energy Density ◽  
Surface Morphology ◽  
Pulsed Laser Deposition ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Preferred Orientation ◽  
Laser Deposition ◽  
Laser Energy Density ◽  
Energy Dependent ◽  
Deposited Films

Barium dititanate (BaTi2O5) films were prepared on MgO (100) substrate by pulsed laser deposition under various laser energy densities. The effect of laser energy on crystallinity, orientation and surface morphology was investigated. The preferred orientation of the as-deposited films changes from (710) to (020) with decreasing laser energy, and the surface morphology is different depending on laser energy too. The b-axis oriented BaTi2O5 film could be obtained at the laser energy density of 2J/cm2, where the film shows a dense surface with an elongated granular texture.

Time-resolved optical studies of oxide-encapsulated silicon during pulsed laser melting

1988 ◽  
Vol 3 (3) ◽  
pp. 498-505 ◽  
Author(s):  
G. E. Jellison ◽  
D. H. Lowndes ◽  
J. W. Sharp
Keyword(s):  
Laser Annealing ◽  
Laser Energy ◽  
Threshold Energy ◽  
Pulsed Laser ◽  
Silicon Layer ◽  
Oxide Thickness ◽  
Time Resolved ◽  
Model Calculations ◽  
Near Surface ◽  
Surface Profiling

Nanosecond time-resolved reflectivity and ellipsometry experiments have been performed on (100) Si wafers encapsulated by 5.5–76.2 nm thick thermal oxides, using pulsed KrF (248 nm) laser energy densities sufficient to melt the Si beneath the oxide. Post-irradiation nulling ellipsometry, optical microphotography, and surface profiling measurements were carried out. It was found that the threshold energy density required to melt the Si varies with oxide thickness; this is explained primarily by the reflective properties of the oxide overlayer. The time-resolved reflectivity and ellipsometry measurements show that rippling of the SiO2 layer occurs on the 20–40 ns timescale and results in a decrease in specular reflectivity of the rippled silicon surface beneath. Optical model calculations suggest that pulsed laser annealing through a thick oxide layer results in a damaged near-surface silicon layer (∼ 30 nm thick); this layer contains defects that are probably responsible for the degraded performance of devices.

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