Application of Waveguide Raman Spectroscopy to High-Index Dielectric Films

1988 ◽  
Vol 42 (2) ◽  
pp. 326-330 ◽  
Author(s):  
David R. Tallant ◽  
Karen L. Higgins ◽  
Alan F. Stewart
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Structural Information ◽  
Single Layer ◽  
Amorphous Film ◽  
Fused Silica ◽  
Oxide Thin Film ◽  
Dielectric Films ◽  
Refractory Oxide ◽  
Silica Substrate

Waveguide Raman spectroscopy has been applied to the analysis of single-layer, refractory-oxide, thin-film coatings on fused silica. With the use of the film as a waveguide, the interaction of the laser probe beam with the film is maximized, and interference from the silica substrate is minimized. An amorphous film of Ta2O5 was found to be an excellent waveguide, yielding an intense Raman spectrum. Even though polycrystalline films of Y2O3, ZrO2, HfO2, and ThO2 were found to be poor waveguides, they still yielded Raman spectra containing useful structural information. Such Raman spectra showed that the ThO2 film was initially in an unusual structural form, which spontaneously transformed into cubic ThO2. Even for films yielding relatively weak Raman bands, substrate Raman scattering was not a serious interference. Representative spectra are presented, along with a brief discussion of the requirements for coupling optical beams into films with large refractive indices.

Annealing Temperature and Substrate Effects on the Raman Spectra of Transferred CVD Graphene

2012 ◽  
Vol 1407 ◽  
Author(s):  
Barbara M. Nichols ◽  
Yasmine R. Doleyres ◽  
Gregory P. Meissner
Keyword(s):  
Raman Spectra ◽  
Intensity Ratio ◽  
Substrate Surface ◽  
Single Layer ◽  
Fused Silica ◽  
Single Layer Graphene ◽  
Hole Doping ◽  
Pmma Layer ◽  
Layer Graphene ◽  
Before And After

ABSTRACTThis work explores the influence of the post-transfer anneal temperature and the substrate on transferred graphene and its Raman properties. Graphene grown by low pressure chemical vapor deposition on copper foils was transferred to SiO2/Si, fused silica, and silicon substrates via a process that involves coating the graphene with PMMA as a protective handling layer during the wet chemical etching of the copper and then placing the PMMA/graphene onto the substrate. The PMMA layer was then removed by heating in a hydrogen/argon atmosphere at temperatures ranging from 350 to 550 °C or by exposing the PMMA to heated acetone vapor/liquid. Raman spectroscopy measurements, taken before and after PMMA removal, reveal differences in the prominent Raman features, the G and G’ peaks, upon annealing. These changes include (1) a shift in the average G and G’ peak positions when comparing Raman spectra before and after PMMA removal and (2) a decrease in the G’:G peak intensity ratio (IG’/IG), which is typically used as a measure of the number of graphene layers. For both the as-transferred graphene and graphene removed by the heated acetone, the IG’/IG peak ratio was approximately 2, indicating single layer graphene. However, when the graphene was annealed at temperatures above 350 °C, the IG’/IG intensity ratio varied from 0.5 to 1.5. These changes in the Raman spectra are similar to those observed in exfoliated single layer graphene supported on SiO2/Si substrates and are indicative of graphene-substrate interaction effects that lead to hole doping of the graphene [1,2]. These trends were observed for graphene transferred to all three substrates, regardless of the substrate surface roughness and/or composition.

Raman Spectral Characterization of Pure and Doped Fused Silica Optical Fibers

1975 ◽  
Vol 29 (4) ◽  
pp. 337-344 ◽  
Author(s):  
G. E. Walrafen ◽  
J. Stone
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Optical Fibers ◽  
Fused Silica ◽  
Laser Raman ◽  
Laser Raman Spectra ◽  
Raman Spectral ◽  
Oh Content ◽  
Absorption Measurements

The utility of Raman spectroscopy as a means of characterizing the properties of pure and doped fused silica has been investigated. Laser-Raman spectra were obtained by forward scattering from solid optical fibers ∼35 to 85 m in length using 514.5 nm excitation with an “image slicer” and a Cary model 81 instrument. Clad and unclad fibers of fused silica and doped fibers having SiO2-GeO2 and SiO2-GeO2-B2O3 cores were examined. Raman spectra were also obtained from bulk samples of glasses, including pure GeO2, pure B2O3, and various compositions of SiO2-GeO2, SiO2-B2O3, and SiO2-GeO2-B2O3. The addition of dopants to fused silica was found to alter the Raman spectrum both by the appearance of new bands, roughly proportional to dopant concentration and not common either to the fused silica or to the dopant alone, and by the marked alteration of other Raman bands, which is indicative of changes in the local intermolecular order. Thus, addition of GeO2 produces new Raman bands at ∼675 and ∼1000 cm−1; and of B2O3, new bands at ∼940 and ∼1350 cm−1. Addition of GeO2 and/or B2O3 weakens the relatively sharp Raman lines near 485 and 600 cm−1 (and a similar but small effect was also noted with increasing OH content). GeO2 and B2O3 together also produce observable narrowing of the broad intense 440 cm−1 Raman contour. These spectral effects are interpreted, respectively, in terms of a decrease in the concentrations of [Formula: see text] and [Formula: see text] defects produced by dopant addition and of a concomitant reordering of the silica structure. Raman spectroscopy thus appears to be a useful optical technique for elucidating the properties of dopants that have been especially chosen for good optical transmission and hence are not easily detectable by absorption measurements.

scholarly journals Формирование аморфных нанокластеров и нанокристаллов германия в пленках GeSi-=SUB=-x-=/SUB=-O-=SUB=-y-=/SUB=- на кварцевой подложке с использованием печных и импульсных лазерных отжигов

2020 ◽  
Vol 54 (3) ◽  
pp. 251
Author(s):  
Zhang Fan ◽  
С.А. Кочубей ◽  
M. Stoffel ◽  
H. Rinnert ◽  
M. Vergnat ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Absorption Edge ◽  
Near Infrared ◽  
Laser Annealing ◽  
High Vacuum ◽  
Infrared Region ◽  
Fused Silica ◽  
Silica Substrate ◽  
Germanium Nanocrystals ◽  
Germanium Clusters

Abstract Nonstoichiometric GeO_0.5[SiO_2]_0.5 and GeO_0.5[SiO]_0.5 germanosilicate glassy films are produced by the high-vacuum coevaporation of GeO_2 and either SiO or SiO_2 powders with deposition onto a cold fused silica substrate. Then the films are subjected to furnace or laser annealing (a XeCl laser, λ = 308 nm, pulse duration of 15 ns). The properties of the samples are studied by transmittance and reflectance spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy. As shown by analysis of the Raman spectra, the GeO[SiO] film deposited at a substrate temperature of 100°C contains amorphous Ge clusters, whereas no signal from Ge–Ge bond vibrations is observed in the Raman spectra of the GeO[SiO_2] film deposited at the same temperature. The optical absorption edge of the as-deposited GeO[SiO_2] film corresponds to ~400 nm; at the same time, in the GeO[SiO] film, absorption is observed right up to the near-infrared region, which is apparently due to absorption in Ge clusters. Annealing induces a shift of the absorption edge to longer wavelengths. After annealing of the GeO[SiO_2] film at 450°C, amorphous germanium clusters are detected in the film, and after annealing at 550°C as well as after pulsed laser annealing, germanium nanocrystals are detected. The crystallization of amorphous Ge nanoclusters in the GeO[SiO] film requires annealing at a temperature of 680°C. In this case, the size of Ge nanoclusters in this film are smaller than that in the GeO[SiO_2] film. It is not possible to crystallize Ge clusters in the GeO[SiO] film. It seems obvious that the smaller the semiconductor nanoclusters in an insulating matrix, the more difficult it is to crystallize them. In the low-temperature photoluminescence spectra of the annealed films, signals caused by either defects or Ge clusters are detected.

The Growth and Characterization of Zinc Oxide Thin Film on Fused Silica and SiO2/Si(100) Substrates

2002 ◽  
Vol 744 ◽  
Author(s):  
C. Jin ◽  
A. Tiwari ◽  
H. Porter ◽  
M. Park ◽  
J. Narayan
Keyword(s):  
Free Exciton ◽  
Optical Microscope ◽  
Fused Silica ◽  
Oxide Thin Film ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Silica Substrate ◽  
Diffraction Patterns ◽  
Effect Of Oxygen ◽  
Surface Morphologies

ABSTRATCTIn this work, ZnO thin films were grown on amorphous fused silica and pre-oxidized silicon substrates by using pulsed laser deposition technique. X-ray diffraction patterns showed that the films were highly crystalline and c-axis oriented. The surface morphologies of the films were observed by using scanning electron microscope and optical microscope. Free exciton absorption was observed at room temperature for the film grown on fused silica substrate. The strong near-UV luminescence peaked at 380 nm were observed for all the films and was attributed to the phonon-related exciton emission. The effect of oxygen partial pressure on the luminescence intensity is also reported.

Characterization of Crystalline Phases in Fly Ash by Microfocus Raman Spectroscopy

1984 ◽  
Vol 43 ◽  
Author(s):  
Barry E. Scheetz ◽  
William B. White
Keyword(s):  
Raman Spectroscopy ◽  
Fly Ash ◽  
Raman Spectra ◽  
Structural Information ◽  
Crystalline Phases ◽  
Individual Basis ◽  
Laser Raman ◽  
Raman Microprobe

AbstractThe laser Raman microprobe was used to interrogate individual fly ash particles as small as 1 μm diameter and record “fingerprint” Raman spectra from both crystalline and non-crystalline components.of the fly ash. When compared to reference patterns of known crystalline phases, the Raman spectra can be used to identify crystalline phases and can give some structural information on other phases. Furthermore, because this method characterizes fly ash particles on an individual basis, correlations to both color and morphology of the particles can be made.

Raman Spectroscopy of Barium Titanate Thin Films

1994 ◽  
Vol 341 ◽  
Author(s):  
Lawrence H. Robins ◽  
Debra L. Kaiser ◽  
Lawrence D. Rotter ◽  
Gregory T. Stauf
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Structural Information ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Cubic Phase ◽  
Bulk Single Crystal ◽  
X Ray ◽  
Film Substrate

AbstractRaman spectroscopy was used to examine the structure of polycrystalline and epitaxial barium titanium oxide thin films grown by metal-organic chemical vapor deposition. The Raman spectra confirmed the presence of the tetragonal ferroelectric phase of BaTiO3 and also revealed several other Ba-Ti-O phases. These films were also characterized by X-ray diffraction and TEM imaging. The structural information provided by the Raman spectra was qualitatively consistent with the X-ray and TEM results. The temperature dependencies of the Raman spectra of two films were examined in the range 25°C-175°C. Raman peaks due to tetragonal BaTiO3 were observed at temperatures well above 132°C, which is the tetragonal-cubic phase transition temperature for bulk single-crystal BaTiO3. This may indicate stabilization of the tetragonal phase by an anisotropic film-substrate interaction or by inter-grain stresses.

scholarly journals Towards Higher Alcohol Formation using a single-layer MoS2 activated Au on Silica: Methanol Carbonylation to Acetaldehyde

2019 ◽  
Author(s):  
Kortney Almeida ◽  
Katerina L. Chagoya ◽  
Alan Felix ◽  
Tao Jiang ◽  
Duy Le ◽  
...  
Keyword(s):  
Density Functional ◽  
Flow Reactor ◽  
Single Layer ◽  
Fused Silica ◽  
Process Conditions ◽  
Active Centers ◽  
Higher Alcohol ◽  
Silica Substrate ◽  
Biomass Characterization ◽  
Imaging And Spectroscopy

We demonstrate that a fused silica substrate can be rendered active for acetaldehyde (CH3CHO) synthesis from a gas mixture of carbon monoxide (CO) and methanol (CH3OH) under mild process conditions (308 kPa and 393 K) by deposition first of a homogenous single-layer MoS2 film and subsequently of a sub-mnonolayer (1 Angstrom) loading of gold. In operando monitoring of the catalyst performance in a flow reactor reveals uncompromised activity even after 2 hours on stream. The carbonylation of methanol to a C2 species represents a crucial step toward the formation of higher alcohols from syngas derived from methane or biomass. Characterization of the film by imaging and spectroscopy reveals that the single-layer MoS2 film disperses the gold loading into nanoscale islands; density functional theory (DFT) calculations identify low-coordinated edge sites on these islands as active centers for the carbon-carbon coupling at barriers significantly below 1 eV.

SEM analysis of DC magnetron sputtered beryllium films

1988 ◽  
Vol 46 ◽  
pp. 960-961
Author(s):  
E. F. Lindsey ◽  
C. W. Price ◽  
E. L. Pierce ◽  
E. J. Hsieh
Keyword(s):  
Fine Structure ◽  
Electron Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Ion Beam ◽  
Secondary Electron Emission ◽  
Sem Analysis ◽  
Fused Silica ◽  
Grain Structure ◽  
Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

Submicron Simultaneous IR and Raman Spectroscopy (IR+Raman): Breakthrough Developments in Optical Photothermal IR (O-PTIR) Combined for Enhanced Failure Analysis

2019 ◽  
Author(s):  
Jay Anderson ◽  
Mustafa Kansiz ◽  
Michael Lo ◽  
Curtis Marcott
Keyword(s):  
Raman Spectroscopy ◽  
Failure Analysis ◽  
Data Quality ◽  
Raman Spectra ◽  
Spatial Resolution ◽  
Far Field ◽  
Field Mode ◽  
Microscopic Scale ◽  
Analytical Tools ◽  
Ir And Raman

Abstract Failure analysis of organics at the microscopic scale is an increasingly important requirement, with traditional analytical tools such as FTIR and Raman microscopy, having significant limitations in either spatial resolution or data quality. We introduce here a new method of obtaining Infrared microspectroscopic information, at the submicron level in reflection (far-field) mode, called Optical-Photothermal Infrared (O-PTIR) spectroscopy, that can also generate simultaneous Raman spectra, from the same spot, at the same time and with the same spatial resolution. This novel combination of these two correlative techniques can be considered to be complimentary and confirmatory, in which the IR confirms the Raman result and vice-versa, to yield more accurate and therefore more confident organic unknowns analysis.

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