The development of infrared sensing platform requires adapted materials. In this work, we used sputtered gold nanoparticles on a chalcogenide glass to demonstrate that these infrared materials can be ...used as substrate for surface enhanced infrared absorption (SEIRA) spectroscopy. The sputtering parameters were optimized to get the highest possible enhancement. To assess it, a self-assembled monolayer of 4-nitrothiophenol was used. These preliminary results are promising and pave the way for various configurations of waveguide for integrated optical components.
The primary objective of this study is the development of transparent thin film materials in the IR enabling strong infrared absorption of organic compounds in the vicinity of metal nanoparticles by ...the surface plasmon effect. For developing these optical micro-sensors, hetero-structures combining gold nanoparticles and chalcogenide planar waveguides are fabricated and adequately characterized. Single As sub(2)S sub(3) and Ge sub(25)Sb sub(10)Se sub( 65) amorphous chalcogenide thin films are prepared by radio-frequency magnetron sputtering. For the fabrication of gold nanoparticles on a chalcogenide planar waveguide, direct current sputtering is employed. Fabricated single layers or hetero-structures are characterized using various techniques to investigate the influence of deposition parameters. The nanoparticles of gold are functionalized by a self-assembled monolayer of 4-nitrothiophenol. Finally, the surface enhanced infrared absorption spectra of 4-nitrothiophenol self-assembled on fabricated Au/Ge-Sb-Se thin films hetero-structures are measured and analyzed. This optical component presents a ~24 enhancement factor for the detection of NO sub(2) symmetric stretching vibration band of 4-nitrothiophenol at 1336 cm super(-1).
The study is concerned with light-emitting Ge nanocrystals formed during the annealing of Ge
x
SiO
2
1 –
x
films produced by the high-vacuum cosputtering of germanium and quartz targets onto ...substrates at a temperature of 100°C. In accordance with the conditions of growth, the Ge molar fraction was varied from 10 to 40%. By means of electron microscopy and Raman spectroscopy, amorphous Ge nanoclusters ~4–5 nm in dimensions are detected in as-deposited films with a Ge content higher than 20 mol %. To crystallize amorphous nanoclusters, annealing at temperatures of up to 650°C is used. The kinetics of the crystallization of Ge nanoclusters is studied, and it is established that up to ~1/3 of the amorphous phase is retained in the system, supposedly at the interfaces between nanocrystals and the surrounding amorphous SiO
2
matrix. It is found that, upon annealing in normal atmosphere, germanium nanoclusters are partially or completely oxidized (at a Ge molar fraction of 30% and smaller). An intense infrared photoluminescence signal from quantum-confined Ge nanocrystals and a visible photoluminescence signal defined by defect complexes (oxygen vacancy + excess Ge atoms) are observed.
We have combined numerous characterization techniques to investigate the growth of tensile-strained and n-doped Ge films on Si(001) substrates by means of solid-source molecular-beam epitaxy. The Ge ...growth was carried out using a two-step growth method: a low-temperature growth to produce strain relaxed and smooth buffer layers, followed by a high-temperature growth to get high crystalline quality Ge layers. It is shown that the Ge/Si Stranski–Krastanov growth mode can be completely suppressed when the growth is performed at substrate temperatures ranging between 260°C and 300°C. X-ray diffraction measurements indicate that the Ge films grown at temperatures of 700–770°C are tensile-strained with typical values lying in the range of 0.22–0.24%. Cyclic annealing allows further increase in the tensile strain up to 0.30%, which represents the highest value ever reported in the Ge/Si system. n-Doping of Ge was carried out using a GaP decomposition source. It is shown that heavy n-doping levels are obtained at low substrate temperatures (210–250°C). For a GaP source temperature of 725°C and a substrate temperature of 210°C, a phosphorus concentration of about 1019cm−3 can be obtained. Photoluminescence measurements reveal an intensity enhancement of about 16 times of the direct band gap emission and display a redshift of 25meV that can be attributed to band gap narrowing due to a high n-doping level. Finally, we discuss about growth strategies allowing optimizing the Ge growth/doping process for optoelectronic applications.
•We investigate the effect of tensile strain and n-doping on Ge optical properties.•We show that cyclic annealing allows getting a tensile strain up to 0.30% in Ge.•n-Doping of Ge/Si films is performed using a GaP decomposition source.•We show that n-doping is more important to enhance the photoluminescence intensity.•We present new growth strategies to develop Ge-based optoelectronic devices.
A micro-sensor based on selenide glasses for evanescent wave detection in mid-infrared spectral range was designed and fabricated. Ge-Sb-Se thin films were successfully deposited by radio-frequency ...magnetron sputtering. In order to characterize them spectroscopic ellipsometry, atomic force microscopy and contact angle measurements were employed to study near and middle infrared refractive index, surface roughness and the wettability, respectively. Selenide sputtered films were micro-patterned by means of reactive ion etching with inductively coupled plasma process enabling single-mode propagation at a wavelength of 7.7 mum for a waveguide width between 8 and 12 mum. Finally, optical waveguide surface was functionalized by deposition of a hydrophobic polymer, which will permit detection of organic molecules in water. Thus, the optical transducer is a ridge waveguide composed by cladding and guiding Ge-Sb-Se sputtered layers exhibiting a tailored refractive index contrast and a polymer layer onto its surface ready for environmental detections in middle infrared.
The synthesis of multifunctional high-quality oxide thin films is a major current research challenge given their potential applications. Herein, we report on p and n type tin oxides thin films as ...functional TCOs with photon management properties through doping with Nd3+ rare earth ions. We show that the structure, composition, carrier transport and optical properties of the sputtered Nd:SnOx films can be easily tuned by simply varying the Ar/O2 gas flow ratio (R) during the deposition step. The increase of the oxygen content leads to drastic changes of the material properties from p-type SnO to n-type SnO2. Furthermore, all Nd:SnOx films are found to be highly conductive with resistivities as low as 1 10-3 Omega cm-1 and carrier mobilities up to 129 cm2 V-1 s-1. Thanks to deep XPS and NEXAFS spectroscopies, we gained insight into the coordination and oxidation degrees of the elements within the matrices. The insertion and optical activation of the incorporated Nd3+ ions have been successfully achieved in both matrices. As a consequence, strong NIR luminescence lines, typical of Nd3+ ions, were recorded under UV laser excitation. We experimentally show that the efficient Nd3+ photoluminescence in the near infrared region originates from efficient sensitization from the host matrix, through energy transfer. We found that the SnO2 host matrix provides more efficient sensitization of Nd3+ as compared to the SnO matrix. An energy transfer mechanism is proposed to explain the observed behaviour.
Resumo Este trabalho é um estudo taxonômico da família Melastomataceae nas ilhas da Baía Babitonga, nordeste de Santa Catarina, região Sul do Brasil. A Baía compreende cerca de 160 km2 em um conjunto ...de 24 ilhas que abarcam cerca de 75% da área total de manguezais do estado de Santa Catarina. Foram efetuadas coletas entre 2004 e 2016, e coleções de herbários foram estudadas. Foram registradas 15 espécies, pertencentes a seis gêneros: Clidemia (2 spp.), Leandra (3 spp.), Miconia (5 spp.), Ossaea (1 sp.), Pleroma (1 sp.) e Tibouchina (3 spp.). São apresentadas chave de identificação para as espécies, descrições morfológicas, dados de distribuição geográfica e fenologia, e imagens das espécies.
Abstract This work is a taxonomic study of Melastomataceae from the islands of Babitonga Bay, northeast of Santa Catarina state, southern Brazil. The Bay has about 160 km2 in a set of 24 islands that harbourr about 75% of the total mangrove area of the state of Santa Catarina. Field expeditions were made between 2004 and 2016, and herbarium collections were studied. Fifteen species wereregistered from six genera: Clidemia (2 spp.), Leandra (3 spp.), Miconia (5 spp.), Ossaea (1 sp.), Pleroma (1 sp.) and Tibouchina (3 spp.). We present an identification key, aside morphological descriptions, data on geographic distribution and phenology, as well as images of species.
Films of nonstoichiometric germanium-silicon glasses of two types-GeO.sub.xSiO.sub.(1 - .sub.x) and GeO.sub.xSiO.sub.2.sub.(1 - .sub.x)-are deposited onto cold Si (001) substrates by evaporating ...GeO.sub.2 and SiO (or SiO.sub.2) powders simultaneously in high vacuum. Film samples in their initial (as-deposited) state and after being annealed at 550 and 650°C for 1 h are investigated using IR and Raman spectroscopies and electron microscopy, and their photoluminescence (PL) is studied as well. Raman spectroscopy shows that, in contrast to the initial GeOSiO.sub.2 film, the initial GeOSiO one contains clusters of amorphous germanium, their size being ~3 nm, as found by electron microscopy. The presence of Si-O, Ge-O, and Si-O-Ge bonds in the films is established by IR spectroscopy. Clusters of amorphous germanium are found in both films after annealing at 550°C, while germanium nanocrystals are formed in the films subjected to annealing at 650°C. For the initial films, a broad band with a maximum at 1050 nm is registered in their low-temperature PL spectra, which may originate from such defects as oxygen vacancies and overstoichiometric germanium atoms. Annealing causes structural changes in the films and affects their PL behavior. The films containing germanium nanoclusters give rise to PL with a maximum at 1400-1600 nm, with the defect-related signal being diminished. The temperature dependence of PL intensity exhibits a decreasing behavior, but PL is observed to temperatures as high as 200 K. The contribution of germanium nanocrystals formed at the annealing stage to PL is discussed.
The study is concerned with light-emitting Ge nanocrystals formed during the annealing of Ge{sub x}SiO{sub 2}{sub 1–x} films produced by the high-vacuum cosputtering of germanium and quartz targets ...onto substrates at a temperature of 100°C. In accordance with the conditions of growth, the Ge molar fraction was varied from 10 to 40%. By means of electron microscopy and Raman spectroscopy, amorphous Ge nanoclusters ~4–5 nm in dimensions are detected in as-deposited films with a Ge content higher than 20 mol %. To crystallize amorphous nanoclusters, annealing at temperatures of up to 650°C is used. The kinetics of the crystallization of Ge nanoclusters is studied, and it is established that up to ~1/3 of the amorphous phase is retained in the system, supposedly at the interfaces between nanocrystals and the surrounding amorphous SiO{sub 2} matrix. It is found that, upon annealing in normal atmosphere, germanium nanoclusters are partially or completely oxidized (at a Ge molar fraction of 30% and smaller). An intense infrared photoluminescence signal from quantum-confined Ge nanocrystals and a visible photoluminescence signal defined by defect complexes (oxygen vacancy + excess Ge atoms) are observed.
The synthesis of multifunctional high-quality oxide thin films is a major current research challenge given their potential applications. Herein, we report on p and n type tin oxides thin films as ...functional TCOs with photon management properties through doping with Nd 3+ rare earth ions. We show that the structure, composition, carrier transport and optical properties of the sputtered Nd:SnO x films can be easily tuned by simply varying the Ar/O 2 gas flow ratio ( R ) during the deposition step. The increase of the oxygen content leads to drastic changes of the material properties from p-type SnO to n-type SnO 2 . Furthermore, all Nd:SnO x films are found to be highly conductive with resistivities as low as 1 × 10 −3 Ω cm −1 and carrier mobilities up to 129 cm 2 V −1 s −1 . Thanks to deep XPS and NEXAFS spectroscopies, we gained insight into the coordination and oxidation degrees of the elements within the matrices. The insertion and optical activation of the incorporated Nd 3+ ions have been successfully achieved in both matrices. As a consequence, strong NIR luminescence lines, typical of Nd 3+ ions, were recorded under UV laser excitation. We experimentally show that the efficient Nd 3+ photoluminescence in the near infrared region originates from efficient sensitization from the host matrix, through energy transfer. We found that the SnO 2 host matrix provides more efficient sensitization of Nd 3+ as compared to the SnO matrix. An energy transfer mechanism is proposed to explain the observed behaviour.
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