Laser Induced Surface Chemical Epitaxy of II-VI Materials

1989 ◽  
Vol 158 ◽  
Author(s):  
Charter D. Stinespring ◽  
Andrew Freedman
Keyword(s):  
Surface Chemistry ◽  
Low Power ◽  
Epitaxial Film ◽  
Ultrahigh Vacuum ◽  
Laser Pulses ◽  
Subsequent Annealing ◽  
Surface Chemical ◽  
Efficient Conversion ◽  
193 Nm ◽  
Substrate Temperatures

ABSTRACTStudies of the thermal and photon-induced surface chemistry of dimethyl cadmium (DMCd) and dimethyl tellurium (DMTe) on GaAs(100) substrates under ultrahigh vacuum conditions have been performed for substrate temperatures in the range of 123 K to 473 K. Results indicate that extremely efficient conversion of admixtures of DMTe and DMCd to CdTe can be obtained using low power (5 - 10 mJ cm−2) 193 nm laser pulses at substrate temperatures of 123 K. Subsequent annealing at 473 K produces an epitaxial film.

Thermal and Photolytic Decomposition of Adsorbed Cadmium and Tellurium Alkyls

1988 ◽  
Vol 129 ◽  
Author(s):  
C.D. Stinespring ◽  
A. Freedman
Keyword(s):  
Surface Chemistry ◽  
Ultrahigh Vacuum ◽  
Photolytic Decomposition ◽  
Substrate Temperatures

ABSTRACTStudies of the thermal and photon-induced surface chemistry of dimethyl cadmium (DMCd) and dimethyl tellurium (DMTe) under ultrahigh vacuum conditions have been performed for substrate temperatures in the range of 133 K to 295 K. Results on GaAs(100) and Si(100) surfaces indicate that for DMTe, the predominant adspecies, dimethyl tellurium, can be photodissociated to a metal adspecies at both 193 and 248 nm. For DHCd, the major adspecies, monomethyl cadmium, is unreactive to photon stimulation.

Thermal and Photon-Induced Chemistry of Adsorbed Cadmium and Tellurium Alkyls

1987 ◽  
Vol 101 ◽  
Author(s):  
C.D. Stinespring ◽  
A. Freedman
Keyword(s):  
Surface Chemistry ◽  
Photoelectron Spectroscopy ◽  
Single Photon ◽  
Experimental Studies ◽  
Ultrahigh Vacuum ◽  
Dissociative Chemisorption ◽  
X Ray ◽  
Organometallic Molecules ◽  
Uv Photons ◽  
193 Nm

ABSTRACTExperimental studies of the thermal and photon-induced surface chemistry of two organometallic molecules, dimethyl cadmium and dimethyl tellurium, are reported for a variety of surfaces including Au, GaAs, Si, and SiO£. These studies followed ultrahigh vacuum compatible procedures and used x-ray photoelectron spectroscopy to characterize the chemical state and coverage of the adspecies formed at 295 K. The results showed considerable diversity in the thermal surface chemistry of the systems investigated. Depending on the substrate, physisorption and dissociative chemisorption to yield monomethyl and metal adspecies were observed. Irradiation of the physisorbed adspecies with 193 nm UV photons led to single photon photodecomposition and limited photodesorption. Similar irradiation of the monomethyl-adspecies caused only limited photodesorption.

Epitaxial Growth of Thin Ge Films on [001] Gaas by Laser Photochemical Vapor Deposition from GeH4

1987 ◽  
Vol 101 ◽  
Author(s):  
V. Tavitian ◽  
C. J. Kiely ◽  
J. G. Eden
Keyword(s):  
Growth Rate ◽  
Film Thickness ◽  
Vapor Deposition ◽  
Epitaxial Film ◽  
Film Growth ◽  
Cross Sectional ◽  
Parallel Geometry ◽  
193 Nm ◽  
Photochemical Vapor Deposition ◽  
Substrate Temperatures

ABSTRACTEpitaxial Ge films have been grown on [001] GaAs for substrate temperatures (Ts) as low as 285°C by photodissociating GeH4 at 193 nm in parallel geometry. For a laser fluence of ~15 mJ - cm-2, the film growth rate varies from 0.6 to ~5 nm - min-1, depending upon Ts and gas pressure. Plan and cross-sectional TEM studies of the Ge/GaAs bicrystal demonstrate that the 400–700 A thick Ge films are single crystal and epitaxial with the substrate. The present limitation on epitaxial film thickness appears to be imposed by reduced adatom mobility at the temperatures investigated.

scholarly journals Surface Chemical Heterogeneity of Low Rank Coal Characterized by Micro-FTIR and Its Correlation with Hydrophobicity

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 239
Author(s):  
Wei Wang ◽  
Long Liang ◽  
Yaoli Peng ◽  
Maria Holuszko
Keyword(s):  
Surface Chemistry ◽  
Functional Group ◽  
Group Composition ◽  
Contact Angles ◽  
Low Rank ◽  
Surface Chemical ◽  
Carbonyl Groups ◽  
Low Rank Coal ◽  
Different Types ◽  
Aliphatic Carbon

Micro-Fourier transform infrared (micro-FTIR) spectroscopy was used to correlate the surface chemistry of low rank coal with hydrophobicity. Six square areas without mineral impurities on low rank coal surfaces were selected as testing areas. A specially-designed methodology was applied to conduct micro-FTIR measurements and contact angle tests on the same testing area. A series of semi-quantitative functional group ratios derived from micro-FTIR spectra were correlated with contact angles, and the determination coefficients of linear regression were calculated and compared in order to identify the structure of the functional group ratios. Finally, two semi-quantitative ratios composed of aliphatic carbon hydrogen, aromatic carbon hydrogen and two different types of carbonyl groups were proposed as indicators of low rank coal hydrophobicity. This work provided a rapid way to predict low rank coal hydrophobicity through its functional group composition and helped us understand the hydrophobicity heterogeneity of low rank coal from the perspective of its surface chemistry.

Metal wire cutting by repeated application of low‐power laser pulses

1992 ◽  
Vol 63 (6) ◽  
pp. 3516-3518
Author(s):  
Joseph B. Bernstein ◽  
Simon S. Cohen ◽  
Peter W. Wyatt
Keyword(s):  
Low Power ◽  
Laser Pulses ◽  
Metal Wire ◽  
Repeated Application ◽  
Power Laser ◽  
Wire Cutting

scholarly journals Laser Activated and Electroless Metalized Polyurethane Coatings Containing Copper(II) L-Tyrosine and Glass Microspheres

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5571
Author(s):  
Piotr Rytlewski ◽  
Bartłomiej Jagodziński ◽  
Rafał Malinowski ◽  
Bogusław Budner ◽  
Krzysztof Moraczewski ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Laser Pulses ◽  
Surface Activation ◽  
Glass Microspheres ◽  
Polyurethane Coatings ◽  
Electroless Metallization ◽  
Metallized Layer ◽  
193 Nm ◽  
Coating Matrix ◽  
Lower Size

Polyurethane coatings containing copper(II) L-tyrosine and glass microspheres were laser irradiated and underwent electroless metallization. Various sizes of glass microspheres were incorporated into the polyurethane coating matrix in order to examine their effects on surface activation and electroless metallization. The surface of the coatings was activated by using ArF excimer laser emitting ultraviolet radiation (λ = 193 nm) using different number of laser pulses and their fluence. The effects of surface activation and metallization were evaluated mainly based on optical and scanning electron microcopies (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoelectron spectroscopy (XPS). It was found that the presence of glass microspheres enabled the reduction in copper complex content, intensified the ablation process (higher cone-like structures created) and resulted in higher content of copper metallic seeds. On the other hand, the glass microspheres concentration, which was higher for lower size microspheres, was advantageous for obtaining a fully metallized layer.

scholarly journals The Effect of Two-Stage Acid Treatment on Surface Behavior and Improvement of Bioactivity of Nitinol Alloy

2020 ◽  
Vol 11 (3) ◽  
pp. 10690-10702
Keyword(s):  
Surface Roughness ◽  
Chemical Modification ◽  
Surface Chemistry ◽  
Healing Process ◽  
In Vitro Study ◽  
Surface Chemical ◽  
Two Stage ◽  
Nitinol Alloy ◽  
Surface Chemical Modification

Surface properties, including morphology, submicron morphology, and surface chemistry, are essential factors that affect the quality and manner of biological responses at the site of tissue contact with the implant, affecting the bone healing process. In this in vitro study, morphology and biocompatibility of nitinol (NiTi) memory alloy surfaces mechanically polished and modified with a chemical solution consisting of three types of acid (HCl-HF-H3PO4) and then chemical operations in solution (HNO3 and HCl) with a Volumetric scale of 1:1 and examined at ambient temperature. 75 samples were used for surface chemical modification, biological evaluations, and surface roughness, and also 9 samples as control. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and nitinol alloy (NiTi) surface roughness measurements were performed to analyze the surfaces. Besides, MG-63 cells were cultured on different nitinol alloy levels to evaluate adhesion and cell growth and proliferation. Data were analyzed using t-test and one-way analysis of variance. The results show that the chemical surface modification operation with two-stage acid solution had a higher roughness compared to the unmodified surfaces and the surface chemical modification operation with the acidic solution with an only solution consisting of (HCl-HF-H3PO4). Cell culture evaluations also showed that the two-stage modified nitinol levels showed significant cell adhesion and significant growth and proliferation compared to the tertiary acid-modified and unmodified levels. The surface chemical modification method for nitinol alloy can change the surface chemistry and change the surface morphology and create sub-micron scale roughness. This can increase the connectivity of the implant tissue and reduce the toxic effect of nickel.

In‐Situ Fabrication of YBa2Cu3O7‐x Superconducting Thin Films Directly on Silicon Substrates with Tc0 > 77K

1989 ◽  
Vol 169 ◽  
Author(s):  
C. B. Lee ◽  
R. K. Singh ◽  
S. Sharan ◽  
A. K. Singh ◽  
P. Tiwari ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Pulses ◽  
Superconducting Film ◽  
Laser Evaporation ◽  
Silicon Substrates ◽  
Superconducting Thin Films ◽  
Si Substrates ◽  
In Situ Fabrication ◽  
Substrate Temperatures

AbstractWe report in‐situ fabrication of c‐axis textured YBa2Cu3O7‐x superconducting thin films with Tco > 77K on unbuffered silicon substrates by the biased pulsed laser evaporation (PLE) technique in the temperature range of 550‐650°C. At substrate temperatures below 550°C, no c‐axis texturing of the superconducting film was observed. The YBa2Cu3O7‐x superconducting films were fabricated by ablating a bulk YBa2Cu3O7 target by a XeCl excimer laser (λ = 308 nm, τ = 45 × 10‐9 sec) in a chamber maintained at an oxygen pressure of 0.2 torr . The thickness of the films was varied from 0.3 to 0.5 nm depending on the number of laser pulses. Extensive diffusion was observed in thin films deposited at substrate temperatures above 550°C. However, microstructurally, with increase in the substrate temperature the films exhibited larger grain size and greater degree of c‐axis texturing (measured by the ratio of the (005) and (110) X‐ray diffraction peaks). This was found to give rise to better superconducting properties with Tco exceeding 77 K for YBa2Cu3O7‐x films deposited on Si substrates at 650°C.

scholarly journals Excimer Laser Induced Spatially Resolved Formation and Implantation of Plasmonic Particles in Glass

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1035
Author(s):  
Maximilian Heinz ◽  
Jörg Meinertz ◽  
Manfred Dubiel ◽  
Jürgen Ihlemann
Keyword(s):  
Excimer Laser ◽  
Metallic Nanoparticles ◽  
Glass Matrix ◽  
Laser Pulses ◽  
Building Blocks ◽  
Phase Mask ◽  
Spatially Resolved ◽  
Stable Glass ◽  
193 Nm ◽  
Doped Glass

Metallic nanoparticles are important building blocks for plasmonic applications. The spatially defined arrangement of these nanoparticles in a stable glass matrix is obtained here by nanosecond excimer laser irradiation at 193 nm. Two approaches are addressed: (1) Laser induced formation of particles from a dopant material pre-incorporated in the glass, (2) Particle formation and implantation by irradiation of material pre-coated on top of the glass. Silver nanoparticles are formed inside Ag+ doped glass (method 1). Gold nanoparticles are implanted by irradiation of gold coated glass (method 2). In the latter case, with a few laser pulses the original gold film disintegrates into particles which are then embedded in the softened glass matrix. A micron sized spatial resolution (periodic arrangements with 2 µm period) is obtained in both cases by irradiating the samples with an interference beam pattern generated by a phase mask. The plasmonic absorption of the nanoparticles leads to a contrast of the optical density between irradiated and non-irradiated lines of up to 0.6.

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