The Optical Spectra of a-Si:H and a-SiC:H Thin Films Measured by the Absolute Photothermal Deflection Spectroscopy (PDS)

2014 ◽  
Vol 213 ◽  
pp. 19-28 ◽  
Author(s):  
Zdenek Remes ◽  
Ravi Vasudevan ◽  
Karol Jarolimek ◽  
Arno H.M. Smets ◽  
Miro Zeman
Keyword(s):  
Thin Films ◽  
Spectral Range ◽  
Near Infrared ◽  
Energy Gap ◽  
Chemical Vapor ◽  
Visible Spectral Range ◽  
Localized States ◽  
Rf Plasma ◽  
Detection Range ◽  
The Absolute

The new absolute PDS setup allows to measure simultaneously the absolute values of the optical transmittance T, reflectance R and absorptance A spectra in the spectral range 280 2000 nm with the typical spectral resolution 10 nm in ultraviolet and visible spectral range and 20 nm in the near infrared region. The PDS setup provides the dynamic detection range in the optical absorptance up to 4 orders of magnitude using non-toxic liquid perfluorohexane Fluorinert FC72. Here we demonstrate the usability of this setup on a series of intrinsic as well as doped a-Si:H and a-SiC:H thin films deposited on glass substrates by radio frequency (RF) plasma enhanced chemical vapor deposition (CVD) from hydrogen, silane and methane under various conditions. The increase of the Tauc gap with increasing carbon concentration in intrinsic a-SiC:H was observed. The defect-induced localized states in the energy gap were observed in doped a-Si:H as well as undoped a-SiC:H below the Urbach absorption edge.

scholarly journals Optical Constant and Conformality Analysis of SiO2 Thin Films Deposited on Linear Array Microstructure Substrate by PECVD

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 510
Author(s):  
Yongqiang Pan ◽  
Huan Liu ◽  
Zhuoman Wang ◽  
Jinmei Jia ◽  
Jijie Zhao
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Deposition Rate ◽  
Optical Constant ◽  
Photoelectron Spectroscopy ◽  
Linear Array ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
X Ray ◽  
Sio2 Thin Film

SiO2 thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH4 and N2O as precursor gases. The stoichiometry of SiO2 thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO2 thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO2 thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO2 thin films are studied. The conformality of SiO2 thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO2 thin film from 20.84 to 41.92 nm/min. The conformality of SiO2 thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO2 thin films.

Near-infrared broadband cavity-enhanced sensor system for methane detection using a wavelet-denoising assisted Fourier-transform spectrometer

The Analyst ◽  
2018 ◽  
Vol 143 (19) ◽  
pp. 4699-4706 ◽  
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Zidi Liu ◽  
Qixin He ◽  
Qiaoling Du ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Spectral Range ◽  
Near Infrared ◽  
Wavelet Denoising ◽  
Visible Spectral Range ◽  
Sensor System ◽  
Trace Gas ◽  
Fourier Transform Spectrometer ◽  
Methane Detection

The majority of broadband cavity-enhanced systems are used to detect trace gas species in the visible spectral range.

scholarly journals Crystallization and visible–near-infrared luminescence of Bi-doped gehlenite glass

2018 ◽  
Vol 5 (12) ◽  
pp. 181667 ◽  
Author(s):  
M. Majerová ◽  
R. Klement ◽  
A. Prnová ◽  
J. Kraxner ◽  
E. Bruneel ◽  
...  
Keyword(s):  
Spectral Range ◽  
Near Infrared ◽  
Broad Band ◽  
Visible Spectral Range ◽  
Peak Temperature ◽  
Minor Amount ◽  
Glass Microspheres ◽  
Scanning Calorimetry ◽  
Crystallization Peak ◽  
High Temperature Xrd

Gehlenite glass microspheres, doped with a different concentration of Bi 3+ ions (0.5, 1, 3 mol%), were prepared by a combination of solid-state reaction followed by flame synthesis. The prepared glass microspheres were characterized from the point of view of surface morphology, phase composition, thermal and photoluminescence (PL) properties by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and PL spectroscopy. The closer inspection of glass microsphere surface by SEM confirmed a smooth surface. This was further verified by XRD. The basic thermal characteristics of prepared glasses, i.e. T g (glass transition temperature), T x (onset of crystallization peak temperature), T f (temperature of the inflection point of the crystallization peak) and T p (maximum of crystallization peak temperature), were estimated from the DSC records. High-temperature XRD experiments in the temperature interval range 600–1100°C were also performed. The PL emission properties of prepared glasses and their polycrystalline analogues (glass crystallized at 1000°C for 10 h) were studied in the visible and near-infrared (NIR) spectral range. When excited at 300 nm, the glasses, as well as their polycrystalline analogues, exhibit broad emission in the visible spectral range from 350 to 650 nm centred at about 410–450 nm, corresponding to Bi 3+ luminescence centres. The emission intensity of polycrystalline samples was found to be at least 30 times higher than the emission of their glass analogues. In addition, a weak emission band was observed around 775 nm under 300 nm excitation. This band was attributed to the presence of a minor amount of Bi 2+ species in prepared samples. In the NIR spectral range, the broad band emission was observed in the spectral range of 1200–1600 nm with the maxima at 1350 nm. The chemistry of Bi and its oxidation state equilibrium in glasses and polycrystalline matrices is discussed in detail.

Fabrication and Characterization of RF Plasma Polymerized Thin Films from 3,7-Dimethyl-1,6-octadien-3-ol for Electronic and Biomaterial Applications

2010 ◽  
Vol 123-125 ◽  
pp. 323-326 ◽  
Author(s):  
Kateryna Bazaka ◽  
Mohan V. Jacob ◽  
Robert A. Shanks
Keyword(s):  
Thin Films ◽  
Optical Band Gap ◽  
Energy Gap ◽  
Polymer Chains ◽  
Rf Plasma ◽  
Circuit Boards ◽  
Average Roughness ◽  
Free Surfaces ◽  
Complete Dissociation

Poly(linalool) thin films were fabricated using RF plasma polymerisation. All films were found to be smooth, defect-free surfaces with average roughness of 0.44 nm. The FTIR analysis of the polymer showed a notable reduction in –OH moiety and complete dissociation of C=C unsaturation compared to the monomer, and presence of a ketone band absent from the spectrum of the monomer. Poly(linalool) were characterised by chain branching and a large quantity of short polymer chains. Films were optically transparent, with refractive index and extinction coefficient of 1.55 and 0.001 (at 500 nm) respectively, indicating a potential application as an encapsulating (protective) coating for circuit boards. The optical band gap was calculated to be 2.82 eV, which is in the semiconducting energy gap region.

scholarly journals Natural slab photonic crystals in centric diatoms

2019 ◽  
Author(s):  
Johannes W. Goessling ◽  
William P. Wardley ◽  
Martin Lopez Garcia
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Spectral Range ◽  
Near Infrared ◽  
Light Regulation ◽  
Visible Spectral Range ◽  
Mating Strategies ◽  
Unit Cell ◽  
Critical Parameters ◽  
Centric Diatom

AbstractNatural photonic crystals can serve in mating strategies or as aposematism for animals, but they also exist in some photosynthetic organisms, with potential implications for their light regulation. Some of the most abundant microalgae, named diatoms, evolved a silicate exoskeleton, the frustule, perforated with ordered pores resembling photonic crystals. Here we present the first combined experimental and theoretical characterization of the photonic properties of the diatom girdle, i.e. one of two structures assembling the frustule. We show that the girdle of the centric diatom Coscinodiscus granii is a well-defined slab photonic crystal, causing, under more natural conditions when immersed in water, a pseudogap for modes in the near infrared. The pseudogap disperses towards the visible spectral range when light incides at larger angles. The girdle crystal structure facilitates in-plane propagation for modes in the green spectral range. We demonstrate that the period of the unit cell is one of the most critical factors for causing these properties. The period is shown to be similar within individuals of a long-term cultivated inbred line and between 4 different C. granii cell culture strains. In contrast, the pore diameter had negligible effects upon the photonic properties. We hence propose that critical parameters defining the photonic response of the girdle are highly preserved. Other centric diatom species, i.e. Thalasiosira pseudonana, C. radiatus and C. wailesii, present similar unit cell morphologies with various periods in their girdles. We speculate that evolution has preserved the photonic crystal character of the centric girdle, indicating an important biological functionality for this clade of diatoms.

scholarly journals Photocatalysis Goes Thinner Than a Hair: Carbon Nitride Thin Films as All-in-one Technology for Photocatalysis

2021 ◽  
Author(s):  
Stefano Mazzanti ◽  
Giovanni Manfredi ◽  
Alex J. Barker ◽  
Markus Antonietti ◽  
Aleksandr Savateev ◽  
...  
Keyword(s):  
Thin Films ◽  
Carbon Nitride ◽  
Energy Gap ◽  
Morphological Changes ◽  
Photophysical Properties ◽  
Chemical Vapor ◽  
Triplet Energy ◽  
Photocatalytic Reactions ◽  
Area Unit ◽  
Triplet Excited States

Organic π-conjugated polymers are promising heterogeneous photocatalysts that involve photoredox or energy transfer processes. In such settings, the materials are usually applied in the form of a dispersion in liquid medium, which is bound to certain technological limits of applicability. Herein, we present an innovative approach using carbon nitride thin films prepared via chemical vapor deposition (CVD) at different vessel walls and using them as batch and microfluidic photoreactors. This approach allows not only to fabricate technologically relevant and reusable devices, also photophysical properties of carbon nitride, such as singlet-triplet energy gap and lifetime of triplet excited states, are improved, when the material is assembled in thin films. These morphological changes are employed to maximize performance of the materials in photocatalytic reactions, in which the carbon nitride thin films show at least one orders of magnitude higher activity per area unit compared to photocatalysis using suspended particles.<br>

scholarly journals Efficient near-infrared quantum cutting by cooperative energy transfer in Bi3TeBO9:Nd3+ phosphors

2022 ◽  
Author(s):  
T. Zhezhera ◽  
P. Gluchowski ◽  
M. Nowicki ◽  
M. Chrunik ◽  
A. Majchrowski ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Spectral Range ◽  
Near Infrared ◽  
Emission Spectra ◽  
Luminescent Properties ◽  
Infrared Emission ◽  
Fluorescence Decay ◽  
Visible Spectral Range ◽  
Visible Radiation ◽  
Quantum Cutting

Abstract An efficient near-infrared quantum cutting process by cooperative down-conversion of active Bi3+ and Nd3+ ions was demonstrated in Bi3TeBO9:Nd3+ phosphors. In particular, the near-infrared emission of Nd3+ ions enhanced by Bi3+ ions of a series of novel Bi3TeBO9:Nd3+ microcrystalline powders doped with Nd3+ ions in various concentrations was investigated. In order to investigate the luminescent properties of BTBO:Nd3+ powders, the excitation and emission spectra and the fluorescence decay time were measured and analyzed. In particular, the emission of Bi3TeBO9:Nd3+ at 890 and 1064 nm was excited at 327 nm (via energy transfer from Bi3+ ions) and at 586.4 nm (directly by Nd3+ ions). The highest intensity emission bands in near-infrared were detected in the spectra of Bi3TeBO9:Nd3+ doped with 5.0 and 0.5 at.% of Nd3+ ions upon excitation in ultraviolet and visible spectral range, respectively. The fluorescence decay lifetime monitored at 1064 nm for Bi3TeBO9:Nd3+ powders shows the single- or double-exponential character depending on the concentrations of Nd3+ ions. The possible mechanisms of energy relaxation after excitation Bi3TeBO9:Nd3+ powders in ultraviolet or visible spectral range were discussed. The investigated Bi3TeBO9:Nd3+ phosphors efficiently concentrate the ultraviolet/visible radiation in the near-infrared spectral range and can be potentially used as effective spectral converters. Graphical abstract

Fabrication NiO: Cu / Si Heterojunction by the Aerosol-Assisted Chemical Vapor Deposition (AACVD)

2021 ◽  
Vol 19 (4) ◽  
pp. 57-64
Author(s):  
Zaid Mohammed Jassim ◽  
Saba Abdulzahra Obaid AL Shiaa
Keyword(s):  
Thin Films ◽  
Vapor Deposition ◽  
Energy Gap ◽  
Low Cost ◽  
Chemical Vapor ◽  
Rare Metals ◽  
Cu Doping ◽  
Cu Film ◽  
High Absorption Coefficient ◽  
High Absorption

In this research, as the thin films were formed by an AACVD process, copper doped nickel oxide was used to prepare the Cu doped Ni thin films by ratio doping (Cu/Ni = 0, 7.5, 10 and 12.8 at w.t %). Thin films of Cu doped NiO were heated at a crystallization temperature of 400 °C for 2 hours. The thin films obtained by the AACVD method have a film thickness of the order (45-62 nm). Promising solar cells that could be created by NiO film as the absorber using Cu doping. The NiO:Cu film has promising optical characteristics; about (3.5-2.8 eV) energy gap band and a high absorption coefficient, which means that the most suitable absorber can be commercially developed using the NiO:Cu film. Furthermore, there are no rare metals in the NiO: Cu film The best conversion efficiency with the heterojunction of NiO: Cu/Si and NiO:Cu was 2.8571429% which showed the possibility of a very low cost solar cell.

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