Nanostructuring of GeTiO amorphous films by pulsed laser irradiation

Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10–30 mJ/cm2. The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm) of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 °C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm2 and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the segregation of Ge atoms in the GeTiO matrix. The nanostructuring effects induced by the laser irradiation can be used in functionalizing the surface of the films.

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Electron and scanning probe microscopies in the study of YBa2Cu3O7 thin-film growth

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010017178x ◽

1994 ◽

Vol 52 ◽

pp. 810-811

Author(s):

M. Grant Norton ◽

Rand R. Biggers ◽

Iman Maartense ◽

E. K. Moser ◽

Jeff L. Brown

Keyword(s):

Thin Films ◽

Laser Irradiation ◽

Film Growth ◽

Film Surface ◽

Scanning Probe ◽

Spherical Particles ◽

Target Figure ◽

Atomic Force ◽

Deposition Parameters ◽

Microscopic Features

Electron and scanning probe microscopies are used to examine the microstructure and surface topography of YBa2Cu3O7 (YBCO) thin films formed by pulsed-laser deposition (PLD). A major emphasis of this work has been the correlation of the observed microstructural features and the deposition parameters.The formation of microscopic features on the surface of thin films deposited by PLD seems to be an undesirable and almost unavoidable feature of this process. One such feature is often associated with microstructural changes produced in the target during laser irradiation. These are apparently spherical particles with diameters ranging from 0.1 to 10μm. These particles are produced by melting of the target and the subsequent solidification of the molten ejecta. Particles may also be produced as a result of changes in the surface morphology of the target during laser irradiation. However, notall surface features observed on the films deposited by PLD are due to ejecta from the target. Figure 1 shows an atomic force microscope (AFM) image of a YBCO film grown on a (100)-oriented LaAlO3 substrate. Usually films grown with our typical deposition conditions on (100)-oriented LaAlO3 substrates arepredominantly c-axis oriented. The film is approximately 150 nm thick. Different types of outgrowth are visible on the film surface.

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Mechanism of Laser-Assisted Evaporation of II-VI Semiconductors

MRS Proceedings ◽

10.1557/proc-29-301 ◽

1983 ◽

Vol 29 ◽

Cited By ~ 20

Author(s):

J. T. Cheung

Keyword(s):

Thin Films ◽

Laser Irradiation ◽

Mass Spectroscopy ◽

High Power ◽

Nd:Yag Laser ◽

Thermal Evaporation ◽

Laser Pulses ◽

High Power Laser ◽

Power Laser ◽

Evaporation Mechanism

ABSTRACTThe evaporation mechanism of CdTe, HgTe and HgO.7CdO.3Te under high power laser irradiation was investigated using mass spectroscopy. Results were compared to thermal evaporation. Thermal evaporation yields Te molecules and Cd(Hg) atoms. In the case of HgTe and Hgo.7Cdo.3Te, the evaporation is noncongruent. Evaporation induced by the irradiation of 1.06 μm Nd:YAG laser pulses evolves atomic Hg, Cd and Te congruently. The dissociative and congruent nature of this process makes it a very attractive technique for depositing thin films.

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Metastable Phase Formation in Laser Processed Al-Ge Thin Films

MRS Proceedings ◽

10.1557/proc-74-223 ◽

1986 ◽

Vol 74 ◽

Author(s):

F. Catalina ◽

C. N. Afonso ◽

C. Ortiz

Keyword(s):

Thin Films ◽

Laser Pulse ◽

Comparative Study ◽

Laser Irradiation ◽

Eutectic Composition ◽

Metastable Phase ◽

Pulse Length ◽

Free Standing ◽

Metastable Phase Formation ◽

Laser Pulse Length

AbstractThis paper presents a comparative study of the microstructures formed in Al.59Ge.41and Al.70Ge.30 (eutectic composition) free standing films under laser irradiation. An hexagonal metastable phase located between Allamella, can be formed depending on the film composition and the laser pulse length.

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Growth and Microstructure of SrBi2Ta2O9 thin films

MRS Proceedings ◽

10.1557/proc-574-131 ◽

1999 ◽

Vol 574 ◽

Author(s):

S. Srinivas ◽

Ram S. Katiyar ◽

Won-Jeong Kim ◽

Steven W. Kircohefer ◽

James S. Horwitz ◽

...

Keyword(s):

Thin Films ◽

Surface Roughness ◽

Laser Pulse ◽

Laser Fluence ◽

Laser Energy ◽

Film Surface ◽

Tangent Loss ◽

Homogeneous Surface ◽

X Ray ◽

Average Grain Size

AbstractSingle phase, (001) oriented SrBi2Ta2O9(SBT) thin films have been deposited on (100) MgO substrates using pulsed laser deposition(PLD) technique. In order to study the influence of the growth conditions on the microstructure and stoichiometry, SBT film growth was carried out under different deposition conditions, using an Kr:F excimer laser (248 nm, 30 ns FWHM). Effect of laser fluence(0.75–2 J/cm2), frequency of the laser pulse (4–10 Hz), substrate temperature (700–850°C), oxygen partial pressure(150–450 mTorr) have been studied using X-ray diff-raction(XRD), Scanning Electron Microscope(SEM), X-ray energy dispersive analysis (EDAX), atomic force microscopy(AFM). It was found that small variation in growth temperature and oxygen pressure has a large influence on the average grain size (50–180 nm) and surface roughness (0.14–0.3 nm) respectively. Outgrowths on the film surface were observed at high substrate temperatures, high laser energy and with higher frequencies (>6) of the laser pulse. Highly c-axis oriented SBT thin films with homogeneous surface morphology and with an average surface roughness of 0.14 nm were deposited at 750 °C, 260 mTorr O2 pressure and 1.25 J/cm2 laser fluence. These films have a tangent loss around 0.05 and dielectric constant around 417 with a tunability of 4% in the microwave frequency region (1–20 GHz).

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Investigation of propagation dynamics of material deformations caused by laser pulse action

Journal of Physics Conference Series ◽

10.1088/1742-6596/2144/1/012008 ◽

2021 ◽

Vol 2144 (1) ◽

pp. 012008

Author(s):

A F Banishev

Keyword(s):

Spatial Distribution ◽

Laser Pulse ◽

Laser Pulses ◽

Pulse Action ◽

Mechanical Stresses ◽

Powerful Laser ◽

Phosphor Powder ◽

Glow Intensity ◽

Evolution Dynamics ◽

Laser Pulse Action

Abstract The mechanoluminescent materials attract increasing attention of scientists due to their capability of visualizing the mechanical stresses and deformations experienced by them. The deformations of materials arising under the action of powerful laser pulses were studied. The composite mechanoluminescent materials based on the polymer and phosphor powder were used for visualization and registration of deformation evolution dynamics. The mechanoluminescent materials were deposited on the surface of the materials under study. It has been shown that the spatial distribution of glow intensity of the mechanoluminescent layer and the rate of its change make possible judging the value and rate of material deformation under laser pulses.

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Reversible 100 mA Current Switching in a VO2/Al2O3-Based Two-Terminal Device Using Focused Far-Infrared Laser Pulses

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.18905 ◽

2021 ◽

Vol 21 (3) ◽

pp. 1862-1868

Author(s):

Jihoon Kim ◽

Sungwook Choi ◽

Seul-Lee Lee ◽

Do Kyung Kim ◽

Min Seok Kim ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Heat Dissipation ◽

Film Surface ◽

Far Infrared ◽

Laser Pulses ◽

Deposition Condition ◽

Current Switching ◽

Terminal Device ◽

Switched Current

In this study, we implemented reversible current switching (RCS) of 100 mA in a two-terminal device based on a vanadium dioxide (VO2) thin film, which could be controlled by far-infrared (FIR) laser pulses. The VO2 thin films used for fabrication of two-terminal devices were grown on sapphire (Al2O3) substrates using a pulsed laser deposition method. An optimal deposition condition was determined by analyzing the resistance-temperature curves of deposited VO2 thin films and the current–voltage characteristics of two-terminal devices based on these films, which were suggested in our previous works. The film surface of the VO2-based device was directly irradiated using focused CO2 laser pulses, and the insulator-metal transition or metal-insulator transition of the VO2 thin film could be triggered depending on laser irradiation. Consequently, RCS of up to 100 mA could be accomplished. This on-state current is close to the upper limit of the current flowing through our VO2 device. The switching contrast, defined as the ratio between on-state and off-state currents, was evaluated and found to be ˜11,962. The average rising and falling times of the switched current were found to be ˜29.2 and ˜71.7 ms, respectively. In comparison with our previous work, the improved heat dissipation structure and the high-quality thin film could maintain the switching contrast at a similar level, although the on-state current was increased by about two times.

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Raman Measurements on Graphite Modified by High Power Laser Irradiation

MRS Proceedings ◽

10.1557/proc-35-219 ◽

1984 ◽

Vol 35 ◽

Cited By ~ 2

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.

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Surface Structures Formed on AISI 420 Stainless Steel by Pulsed Laser Irradiation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.494.309 ◽

2005 ◽

Vol 494 ◽

pp. 309-314 ◽

Cited By ~ 3

Author(s):

B. Gaković ◽

M. Trtica ◽

S. Petrović ◽

P. Panjan ◽

M. Čekada ◽

...

Keyword(s):

Stainless Steel ◽

Laser Pulse ◽

Laser Energy ◽

Central Zone ◽

Target Surface ◽

Laser Pulses ◽

Ablation Rate ◽

Pulse Action ◽

Surface Structures ◽

Aisi 420

The effects of TEA CO2 laser radiation on AISI 420 stainless steel and formed surface structures are studied. The laser energy density of 45.0 J/cm2 has modified the target surface. Qualitatively, the modifications of AISI 420 steel can be summarized as follows: change of color after action of one laser pulse; central zone of interaction in crater like form and periphery zone of interaction (for more than 10 laser pulses); appearance of grainy features and ablation rate of near 4 nm per laser pulse (action of 400 laser pulses); hydrodynamical effects like resolidified rim and droplets.

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Crystallization of Amorphous Titanium Oxide Thin Films by Pulsed UV-Laser Irradiation

MRS Proceedings ◽

10.1557/proc-397-447 ◽

1995 ◽

Vol 397 ◽

Author(s):

Yo Ichikawa ◽

Hideaki Ada Chi ◽

Kentaro Setsune ◽

Syun-Ichiro Kawashima ◽

Koichi Kugimiya

Keyword(s):

Crystal Structure ◽

Thin Films ◽

Laser Irradiation ◽

Optical Transmission ◽

Laser Pulses ◽

Uv Laser ◽

Before And After ◽

Krf Excimer Laser ◽

Quartz Substrates ◽

Local Crystal Structure

ABSTRACTEffects of ultraviolet (UV) laser irradiation on the local crystal structure have been investigated for amorphous Ti-O thin films sputtered on ST-cut quartz substrates. The irradiation was conducted with a pulsed KrF excimer laser of 248nm in wavelength. There were few changes in the optical transmission spectra of the films before and after the irradiation. The crystal structure of the films was characterized by electron diffraction, XPS and EXAFS analyses. The results obtained from these analyses suggest the films gradually crystallize to a TiO2 crystal with the rutile type structure by the increasing of the laser pulses.

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