scholarly journals Optical Properties of Thin Germanium Films

1972 ◽  
Vol 25 (6) ◽  
pp. 743 ◽  
Author(s):  
RE Denton ◽  
SG Tomlin
Keyword(s):  
Optical Constants ◽  
Wavelength Region ◽  
Normal Incidence ◽  
Random Structure ◽  
Amorphous Films ◽  
Amorphous Germanium ◽  
Long Wavelength ◽  
Wide Range ◽  
Germanium Films ◽  
Absorption Law

The refractive and absorption indices of thin amorphous germanium films have been obtained from measurements, at normal incidence, of reflectances and transmittances over a wide range of wavelengths. The optical constants derived were in general agreement with the results of Tauc et al. (1964) except in the long wavelength region beyond the absorption edge. The absorption followed the law for indirect transitions from 0�72 to 1�1 eV, and the same law, but with a change in the slope of the curves, from 1�1 eV to the limit of our measurements at about 1�5 eV. The results are consistent with the view that the energy band structure of amorphous germanium is not essentially different from that of the crystalline material, except that the random structure eliminates the restriction that allows only direct transitions with the result that the absorption law for amorphous films is of the same form as for indirect transitions in crystals.

scholarly journals DEVELOPMENT OF A METHOD FOR THE SYNTHESIS OF PLASMONIC GOLD NANOPARTICLES FOR A WIDE SPECTRAL REGION 520-720 nm

2017 ◽  
Vol 12 (5) ◽  
pp. 56-64
Author(s):  
I. I. Faskhutdinova ◽  
A. S. Mikhailov ◽  
B. I. Shapiro
Keyword(s):  
Gold Nanoparticles ◽  
Colloidal Stability ◽  
Wavelength Region ◽  
Reducing Agent ◽  
Plasmon Band ◽  
Long Wavelength ◽  
Aggregation Processes ◽  
Wide Range ◽  
Minimal Quantity ◽  
The Stability

A method of the synthesis of plasmon gold nanoparticles by the reduction of HAuCl4 with organic reductants, such as formalin, sodium citrate and hydroquinone has been studied. It is shown that, depending on the concentration of the reagents, the temperature of synthesis and the type of the reducing agent, the position of the maximum of the plasmon band varies in a wide range from 520 nm to 720 nm. A one-stage method using hydroquinone as a reducing agent for the synthesis of long-wave plasmonic gold nanoparticles that form agglomerates of smaller particles with a plasmon absorption band in the red region of the spectrum is proposed. Since the resulting sol is rapidly precipitated due to the aggregation processes, it has been found necessary to use stabilizers for its subsequent application. The influence of some stabilizers (gelatin, as well as surface-active substances polydimethyldiallylammonium chloride and cetyltrimethylammonium bromid) on the stability of the gold sol synthesized by the hydroquinone method has been studied. It is shown that all the types of investigated stabilizers even in a minimal quantity provide the colloidal stability of the sol for several hours. However, only a natural polymer, gelatin, stabilizes the sol so that the maximum absorption of the plasmon band remains in the long-wavelength region of the spectrum.

Low Temperature Fabrication of Microcrystalline Silicon Germanium Films by RF Reactive Magnetron Sputtering

2006 ◽  
Vol 910 ◽  
Author(s):  
Isao Nakamura ◽  
Toru Ajiki ◽  
Masao Isomura
Keyword(s):  
Magnetron Sputtering ◽  
Silicon Germanium ◽  
Energy Gap ◽  
Wavelength Region ◽  
Reactive Magnetron Sputtering ◽  
Reactive Magnetron ◽  
Microcrystalline Silicon ◽  
Long Wavelength ◽  
Glass Substrates ◽  
Germanium Films

AbstractMicrocrystalline silicon germanium films (μc-SiGe) were fabricated on Corning #7059 glass substrates by the RF reactive magnetron sputtering method. The μc-SiGe films with Ge fraction of 0.7-0.8 could be crystallized at of 200 °C by H2 introduction into the sputtering gases. The absorption coefficients of the films decrease in long wavelength region corresponding to the photon energies below the energy gap by the decrease in the substrate temperature and become close to those of single crystal Si0.25Ge0.75. The dark conductivities show lower values of 10-7 S/cm at 200 °C and 300 °C with H2 introduction. Besides, the photosensitivities are observed in these samples. These results indicate that the H2 introduction into the sputtering gas has two important effects to decrease the crystallization temperature of the μc-SiGe and to improve the film properties by reducing the dangling bond defects.

scholarly journals Fe II Fluorescence in Symbiotic Stars

2004 ◽  
Vol 191 ◽  
pp. 132-136
Author(s):  
M. Eriksson ◽  
H. Veenhuizen ◽  
G.M. Wahlgren ◽  
S. Johansson
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Extreme Temperature ◽  
Wavelength Region ◽  
Symbiotic Stars ◽  
Optimal Conditions ◽  
Short Wavelength Region ◽  
Long Wavelength ◽  
Wide Range ◽  
Emission Strength

AbstractFe II fluorescence by PAR has been investigated in eight symbiotic stars having a wide range in temperature of the hot component and orbital period. The data used are spectra obtained from the IUE archive. All pumping lines investigated in this work are in the short wavelength region of IUE (1200-2000 Å), except for He ɪɪ λ1084.942 and O VI λ1032.041. The resulting Fe ɪɪ fluorescence lines are mainly in the long wavelength region (2000-3300 Å), but a few fall in the same region as the pumping lines. The aim is to understand the optimal conditions for formation of Fe ɪɪ fluorescence lines caused by PAR. Three of the selected systems, RR Tel, AG Peg and V1016 Cyg, have 10-30 active Fe ɪɪ channels. Two conditions connect those systems to each other: The hot component is a white dwarf of extreme temperature (80·103-150·103 K) and all three systems are so called symbiotic novae and have had outbursts during the last 150 years. Three systems, AG Dra, RW Hya and R Aqr, have only 2-3 active Fe ɪɪ channels. In the two remaining systems, CI Cyg and T CrB, Fe ɪɪ fluorescence lines were totally absent. These two systems have two features in common: The emission strength of highly ionized elements is less than in most symbiotic systems, and the hot component is suspected to be an accreting main sequence star rather than a white dwarf.

Transport properties of evaporated versus sputtered amorphous germanium films

1980 ◽  
Vol 41 (10) ◽  
pp. 1173-1181 ◽  
Author(s):  
M.-L. Theye ◽  
A. Gheorghiu ◽  
T. Rappeneau ◽  
A. Lewis
Keyword(s):  
Transport Properties ◽  
Amorphous Germanium ◽  
Germanium Films

scholarly journals Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

1997 ◽  
Vol 180 ◽  
pp. 475-476
Author(s):  
M. G. Richer ◽  
G. Stasińska ◽  
M. L. McCall
Keyword(s):  
Planetary Nebula ◽  
Luminosity Function ◽  
Large Population ◽  
Wavelength Region ◽  
Planetary Nebulae ◽  
Surprising Result ◽  
Population Synthesis ◽  
Abundance Distribution ◽  
Wide Range ◽  
The Mean

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex < 12 + log(O/H) < 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders & Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

scholarly journals A coma-free super-high resolution optical spectrometer using 44 high dispersion sub-gratings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hua-Tian Tu ◽  
An-Qing Jiang ◽  
Jian-Ke Chen ◽  
Wei-Jie Lu ◽  
Kai-Yan Zang ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
Wavelength Region ◽  
Ultra Violet ◽  
High Spectral Resolution ◽  
Visible Range ◽  
High Dispersion ◽  
Charge Coupled Device ◽  
Wide Range ◽  
High Resolution Spectrometer

AbstractUnlike the single grating Czerny–Turner configuration spectrometers, a super-high spectral resolution optical spectrometer with zero coma aberration is first experimentally demonstrated by using a compound integrated diffraction grating module consisting of 44 high dispersion sub-gratings and a two-dimensional backside-illuminated charge-coupled device array photodetector. The demonstrated super-high resolution spectrometer gives 0.005 nm (5 pm) spectral resolution in ultra-violet range and 0.01 nm spectral resolution in the visible range, as well as a uniform efficiency of diffraction in a broad 200 nm to 1000 nm wavelength region. Our new zero-off-axis spectrometer configuration has the unique merit that enables it to be used for a wide range of spectral sensing and measurement applications.

Effects of hydrogen on structure and crystallization behavior of sputter-deposited amorphous germanium films

2020 ◽  
Vol 59 (7) ◽  
pp. 075506
Author(s):  
Yuki Hanya ◽  
Ryusuke Nakamura ◽  
Masayuki Okugawa ◽  
Manabu Ishimaru ◽  
Goro Oohata ◽  
...  
Keyword(s):  
Crystallization Behavior ◽  
Amorphous Germanium ◽  
Germanium Films ◽  
Sputter Deposited

Broadband multilayer-coated normal incidence blazed grating with ~10% diffraction efficiency through the 13-16 nm wavelength region

2009 ◽  
Vol 34 (6) ◽  
pp. 818 ◽  
Author(s):  
Lichao Zhang ◽  
Hui Lin ◽  
Chunshui Jin ◽  
Hongjun Zhou ◽  
Tonglin Huo
Keyword(s):  
Diffraction Efficiency ◽  
Wavelength Region ◽  
Normal Incidence ◽  
Blazed Grating

Analysis of Cu(InGa)Se2 Alloy Film Optical Properties and the Effect of Cu Off-Stoichiometry

2005 ◽  
Vol 865 ◽  
Author(s):  
P. D. Paulson ◽  
S. H. Stephens ◽  
W. N. Shafarman
Keyword(s):  
Optical Constants ◽  
Soda Lime ◽  
Alloy Film ◽  
Relative Volume ◽  
Soda Lime Glass ◽  
Distinctive Features ◽  
Glass Substrates ◽  
Wide Range ◽  
Two Phases

AbstractVariable angle spectroscopic ellipsometry has been used to characterize Cu(InGa)Se2 thin films as a function of relative Ga content and to study the effects of Cu off-stoichiometry. Uniform Cu(InGa)Se2 films were deposited on Mo-coated soda lime glass substrates by elemental evaporation with a wide range of relative Cu and Ga concentrations. Optical constants of Cu(InGa)Se2 were determined over the energy range of 0.75–C4.6 eV for films with 0 ≤ Ga/(In+Ga) ≤ 1 and used to determine electronic transition energies. Further, the changes in the optical constants and electronic transitions as a function of Cu off-stoichiometry were determined in Cu-In-Ga-Se films with Cu atomic concentration varying from 10 to 25 % and Ga/(In+Ga) = 0.3. Films with Cu in the range 16–24 % are expected to contain 2 phases so an effective medium approximation is used to model the data. This enables the relative volume fractions of the two phases, and hence composition, to be determined. Two distinctive features are observed in the optical spectra as the Cu concentration decreases. First, the fundamental bandgaps are shifted to higher energies. Second, the critical point features at higher energies become broader suggesting degradation of the crystalline quality of the material.

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