Size-Induced Changes in Optical and X-ray Photoelectron Spectra of GaN Nanoparticles Deposited at Lower Substrate Temperature

2005 ◽  
Vol 5 (11) ◽  
pp. 1858-1863 ◽  
Author(s):  
A. K. Mann ◽  
D. Varandani ◽  
B. R. Mehta ◽  
L. K. Malhotra ◽  
S. M. Shivaprasad
Keyword(s):  
Substrate Temperature ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Induced Changes ◽  
Lower Substrate Temperature

PROPERTIES AND PREPARATION OF AlN THIN FILMS BY REACTIVE LASER ABLATION WITH NITROGEN DISCHARGE

2000 ◽  
Vol 14 (14) ◽  
pp. 523-530 ◽  
Author(s):  
HONG-HAI WANG
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Substrate Temperature ◽  
Preferred Orientation ◽  
Photoelectron Spectra ◽  
Breakdown Field ◽  
Orientation Relationships ◽  
X Ray ◽  
Deposition Parameters ◽  
Nitrogen Discharge

Highly oriented AlN thin films have been deposited on (100) and (111) Si wafers by reactive laser ablation with nitrogen discharge at low substrate temperature. The composition and microstructure of films strongly depend on deposition parameters. X-ray photoelectron spectra showed that nitrogen discharge is of great importance to the composition of the films. The effect of substrate temperature on the preferred orientation of films has been investigated carefully by means of X-ray diffraction. Under optimizing deposition parameters — 1.0 J/cm 2 laser fluence, 5 Hz pulse frequency, 100 mTorr nitrogen pressure, 650 V discharge voltage and 200°C substrate temperature — the AlN films deposited on silicon substrates were smooth, dense and stoichiometric with very good preferred orientation. The orientation relationships between films and substrates were AlN(100)//Si(100) and AlN(110)//Si(111). The average refractive index was found to be 2.05 with the usage of an ellipsometer. The films had a band gap of 6.2 eV as measured by UV–visible absorption. The IR spectrum had an absorption characteristic of AlN. Examination of electric properties of films that was carried out on the metal–insulator–semiconductor structure of Au/AlN/Si showed that the dielectric constant, resistivity and breakdown field were 8.3, 2 × 1013 Ω· cm and 3 × 106 V/cm , respectively.

Photodissociation of Trimethylindium and Trimethylgallium on GaAs(100) at 193nm Studied by Angle-Resolved XPS

1992 ◽  
Vol 280 ◽  
Author(s):  
Satoshi Shogen ◽  
Masafumi Ohashi ◽  
Satoshi Hashimoto ◽  
Masahiro Kawasaki ◽  
Yasuo Hosokawa
Keyword(s):  
Substrate Temperature ◽  
Laser Irradiation ◽  
Photoelectron Spectroscopy ◽  
Gaas Substrate ◽  
Bond Cleavage ◽  
Photoelectron Spectra ◽  
Methyl Radicals ◽  
Adsorbed Species ◽  
X Ray ◽  
193 Nm

ABSTRACTThe chemisorption and photodecomposition of trimethylindium (TMIn) and trimethylgallium (TMGa) on GaAs(100) surfaces have been studied by angle-resolved X-ray photoelectron spectroscopy. The In-C bond cleavage of the adsorbed TMIn was observed when the substrate temperature was raised from 150 K to 300 K. The dissociation generates methyl radicals that react with the substrate Ga species to form the Ga-C bond. The In-C bond is also dissociated by 193 nm laser irradiation of TMIn adsorbed on the GaAs at 150 K. Irradiation at 351 nm caused no change in the X-ray photoelectron spectra since photodissociation is not due to the photoabsorption of the GaAs substrate but the photodecomposition of the adsorbed species. Similar results are observed for TMGa on a GaAs(100) substrate.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

scholarly journals Modification of Wood with Monoethanolamino-borate by The Data of X-Ray Photoelectron Spectroscopy

2018 ◽  
Vol 196 ◽  
pp. 04005
Author(s):  
Irina Stepina ◽  
Irina Kotlyarova
Keyword(s):  
Particle Size ◽  
Photoelectron Spectroscopy ◽  
Model Compound ◽  
Hydrolytic Stability ◽  
Photoelectron Spectra ◽  
Wood Cellulose ◽  
Rapid Loss ◽  
X Ray ◽  
Wood Protection ◽  
Cellulose Materials

The difficulty of wood protection from biocorrosion and fire is due to the fact that modifiers in use are washed out from the surface of the substrate under the influence of environmental factors. This results in a rapid loss of the protective effect and other practically important wood characteristics caused by the modification. To solve this problem is the aim of our work. Here, monoethanolaminoborate is used as a modifier, where electron-donating nitrogen atom provides a coordination number equal to four to a boron atom, which determines the hydrolytic stability of the compounds formed. Alpha-cellulose ground mechanically to a particle size of 1 mm at most was used as a model compound for the modification. X-ray photoelectron spectra were recorded on the XSAM-800 spectrometer (Kratos, UK). Prolonged extraction of the modified samples preceded the registration of the photoelectron spectra to exclude the fixation of the modifier molecules unreacted with cellulose. As a result of the experiment, boron and nitrogen atoms were found in the modified substrate, which indicated the hydrolytic stability of the bonds formed between the modifier molecules and the substrate. Therefore monoethanolaminoborate can be considered as a non-extractable modifier for wood-cellulose materials.

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

X-RAY PHOTOELECTRON SPECTRA OF PHOSPHORUS YLIDES. PROBING THE PHOSPHORUS-CARBON YLIDE BOND

1974 ◽  
Vol 3 (5) ◽  
pp. 405-408 ◽  
Author(s):  
Manabu Seno ◽  
Shinji Tsuchiya ◽  
Teruzo Asahara
Keyword(s):  
Photoelectron Spectra ◽  
Phosphorus Ylides ◽  
X Ray
Sign in / Sign up

Export Citation Format

Share Document