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.

scholarly journals The Effect Of Thickness on The Optical Properties Of ZnS

2007 ◽  
Vol 4 (4) ◽  
pp. 647-652
Author(s):  
Baghdad Science Journal
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Near Infrared ◽  
High Vacuum ◽  
Ultra Violet ◽  
Infrared Region ◽  
Complex Dielectric Constant ◽  
Film Properties ◽  
Corning Glass ◽  
Different Thickness

Zinc sulfide(ZnS) thin films of different thickness were deposited on corning glass with the substrate kept at room temperature and high vacuum using thermal evaporation technique.the film properties investigated include their absorbance/transmittance/reflectance spectra,band gap,refractive index,extinction coefficient,complex dielectric constant and thickness.The films were found to exhibt high transmittance(59-98%) ,low absorbance and low reflectance in the visible/near infrared region up to 900 nm..However, the absorbance of the films were found to be high in the ultra violet region with peak around 360 nm.The thickness(using optical interference fringes method) of various films thichness(100,200,300,and 400) nm.The band gap measured was found to be in the range (3.52 -3.78 )eV.

scholarly journals Defect Related Emission in Calcium Hydroxide: The Controversial Band at 780 cm−1

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 266 ◽  
Author(s):  
Francesca Assunta Pisu ◽  
Daniele Chiriu ◽  
Pier Carlo Ricci ◽  
Carlo Maria Carbonaro
Keyword(s):  
Cultural Heritage ◽  
Calcium Hydroxide ◽  
Raman Spectra ◽  
Near Infrared ◽  
Specific Treatment ◽  
Emission Spectra ◽  
Infrared Region ◽  
Carbonation Process ◽  
Composite Band ◽  
Post Synthesis

Calcium hydroxide, a crystal involved in the cycle of calcination and carbonation of calcium oxide, finds several applications from cultural heritage to the dentistry branch or to the construction industry. When excited at 1064 nm, Raman spectra of calcium hydroxide show a broad composite band peaked at about 780 cm−1, corresponding to 1170 nm. Since it is not observed with visible excitation, the origin of this band is debated, being assigned to some pre-existent luminescent impurities or some structural defect of the lime formed after the synthesis of the material. To shed light on the formation of this band, we synthetised the lime paste starting from pure calcite powders. The obtained fresh Ca(OH)2 samples did not show any band in the investigated range, irrespective of the laser excitation applied. A detailed analysis of the excitation and emission spectra in the near infrared region did not show the 1170 nm band, supporting the hypothesis of a post-synthesis origin. Thus, we carried out thermal treatments at different temperatures (90–500 °C) and under different environments (in air or under nitrogen flux) on synthesised fresh Ca(OH)2 powders. We also investigated the time evolution of the samples, monitoring the Raman spectra over 90 days after a specific treatment. The collected data support the hypothesis of a defect-related luminescence centre, whose formation depends on the temperature and environment of the treatment, which appears as a preferential site for the carbonation process of the calcium hydroxide. These results can be useful in the field of Cultural Heritage for dating purposes, and to determine the conservation state of Ca(OH)2 containing relics to prevent the possible activation of degradation processes.

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.

scholarly journals Проявление квантоворазмерных эффектов в нанокристаллах и аморфных нанокластерах германия в плeнках GeSixOy

2020 ◽  
Vol 62 (3) ◽  
pp. 434
Author(s):  
М.П. Гамбарян ◽  
Г.К. Кривякин ◽  
С.Г. Черкова ◽  
M. Stoffel ◽  
H. Rinnert ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Oxygen Vacancies ◽  
High Vacuum ◽  
Film Structure ◽  
Sio2 Film ◽  
Amorphous Germanium ◽  
Germanium Nanocrystals ◽  
Increasing Temperature ◽  
Germanium Clusters ◽  
Deposited Films

The non-stoichiometric germanosilicate films of two types GeOx[SiO](1-x) and GeOx [SiO2](1-x) were obtained by high-vacuum evaporation of GeO2 and either SiO or SiO2 powders and sputtering on a cold Si (001) substrate. The as-deposited and annealed (550 and 650 oC, 1 hour) samples were studied by IR spectrocopy, electron microscopy, Raman spectroscopy and photoluminescence (PL). From an analysis of Raman spectra, it was found that the as-deposited GeO[SiO2] film did not contain germanium clusters, and the as-deposited GeO[SiO] film contained amorphous germanium clusters; according to electron microscopy, it’s size was ~3 nm. According to IR spectroscopy, the films contained Si-O, Ge-O, and Si-O-Ge bonds. After annealing at 550 °C, amorphous germanium clusters were detected in both films, and after annealing at 650 °C, germanium nanocrystals were observed. A wide PL band with a maximum of 1050 nm was found in the as-deposited films at low temperatures. PL is probably due to defects, presumably oxygen vacancies and excess germanium atoms. Annealing causes a transformation of both film structure and PL spectra. In films containing germanium nanoclusters, PL is observed with a maximum of 1500–1600 nm. In this case, the PL signal from defects decreased. The temperature dependence of the intensity of the PL peaks was studied; it decreased with increasing temperature but remained at temperatures up to 200 K. The contribution to the PL from germanium nanocrystals formed during annealing is discussed.

scholarly journals Fluoropolymer Film Formation by Electron Activated Vacuum Deposition

Surfaces ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 66-80
Author(s):  
Kostyantyn Grytsenko ◽  
Viachaslau Ksianzou ◽  
Yurii Kolomzarov ◽  
Peter Lytvyn ◽  
Birgit Dietzel ◽  
...  
Keyword(s):  
Near Infrared ◽  
Film Growth ◽  
Film Formation ◽  
High Vacuum ◽  
Infrared Region ◽  
Decomposition Temperature ◽  
Electron Cloud ◽  
Rf Plasma ◽  
Force Microscopy ◽  
Atomic Force

Polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE) were heated to their decomposition temperature in a high vacuum. The emitted fragments passed an electron cloud, condensed on a substrate and formed fluoropolymer film. Growth rate of PTFE and PHFP films increased up to a factor five in the presence of the electron cloud. Mass spectrometry revealed changes in the mass spectra of fragments generated by thermal decomposition only and formed under electron activation. The observed changes were different for each fluoropolymer. Infrared spectroscopy (IRS) showed that the structure of the films was close to the structure of the bulk polymers. Atomic force microscopy (AFM) has revealed different morphologies of PTFE, PHFP and PCTFE films, suggesting a Volmer–Weber growth mechanism for PTFE and PHFP but a Frank-van der Merwe one for PCTFE. All films were smooth at nanoscale and transparent from ultraviolet to near-infrared region. Additional radio frequency (RF) plasma ignited in the emitted fragments at a low pressure increased mechanical characteristics of the films without losing their optical transparency and smoothness.

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.

Ligand Influence Versus Electronic Configuration of d-metal Ion in Determining the Fate of NIR Emission from LnIII Ions: A Case Study with CuII, NiII and ZnII Complexes.

2021 ◽  
Author(s):  
Abhineet Verma ◽  
Sk Saddam Hossain ◽  
Sailaja S Sunkari ◽  
Joseph Reibenspies ◽  
Satyen Saha
Keyword(s):  
Metal Ion ◽  
Selection Rule ◽  
Near Infrared ◽  
Electronic Configuration ◽  
Infrared Region ◽  
Direct Excitation ◽  
Characteristic Emission ◽  
Nir Emission ◽  
Near Infrared Region

Lanthanides (LnIII) are well known for their characteristic emission in the Near-Infrared Region (NIR). However, direct excitation of lanthanides is not feasible as described by Laporte’s parity selection rule. Here,...

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