An Alternate Mechanism for Porous Si Photoluminescence: Recombination in SiHx Complexes

1991 ◽  
Vol 256 ◽  
Author(s):  
S. M. Prokes ◽  
O. J. Glembocki ◽  
V. M. Bermudez ◽  
R. Kaplan ◽  
L. E. Friedersdorf ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Porous Silicon ◽  
Hydrogen Content ◽  
Hydrogen Desorption ◽  
Porous Si ◽  
Temperature Range ◽  
Silicon Hydrides ◽  
Alternate Mechanism ◽  
Pl Intensity

ABSTRACTPorous silicon layers have been formed which exhibit photoluminescence (PL) peaks that do not blueshift with increasing porosity. Hydrogen desorption experiments have been performed in vacuum under anneals between 230°C–390°C. Simultaneous, in-situ PL measurements show that the PL intensity decreases and disappears with decreasing hydrogen content. Infrared spectroscopy (IR) measurements also show loss of hydride species in the same temperature range. These results indicate that hydrogen is important in the PL process. We suggest that silicon hydrides are the source of PL in porous SI.

scholarly journals Evolution Mechanism of Macromolecular Structure in Coal during Heat Treatment: Based on FTIR and XRD In Situ Analysis Techniques

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Dun Wu ◽  
Wenyong Zhang
Keyword(s):  
Heat Treatment ◽  
Infrared Spectroscopy ◽  
Infrared Spectrum ◽  
Functional Groups ◽  
Coal Sample ◽  
Diffraction Peak ◽  
Coal Rank ◽  
Coal Structure ◽  
Temperature Range

Owing to the complexity and heterogeneity of coal during pyrolysis, the ex situ analytical techniques cannot accurately reflect the real coal pyrolysis process. In this study, according to the joint investigation of Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), the structural evolution characteristics of lignite-subbituminous coal-bituminous coal-anthracite series under heat treatment were discussed in depth. The results of the infrared spectrum of coal show that the different functional groups of coal show different changes with the increase of coal rank before pyrolysis experiment. Based on in situ infrared spectroscopy experiments, it was found that the infrared spectrum curves of the same coal sample have obvious changes at different pyrolysis temperatures. As a whole, when the pyrolysis temperature is between 400 and 500°C, the coal structure can be greatly changed. By fitting the infrared spectrum curve, the infrared spectrum parameters of coal were obtained. With the change of temperature, these parameters show regular changes in coal with different ranks. In the XRD study of coal, the absorption intensity of the diffraction peak (002) of coal increases with increasing coal rank. The XRD patterns of coal have different characteristics at different pyrolysis temperatures. Overall, the area of (002) diffraction peak of the same coal sample increases obviously with the increase of temperature. The XRD structural parameter of coal was obtained by using the curve fitting method. The changing process of two parameters (interlayer spacing (d002) and stacking height (Lc)) can be divided into two main stages, but the average lateral size (La) does not change significantly and remains at the 2.98 ± 0.09 nm. In summary, the above two technologies complement each other in the study of coal structure. The temperature range of both experiments is different, but the XRD parameters of coal with different ranks are reduced within the temperature range of less than 500°C, which reflects that the size of coal-heated aromatic ring lamellae is reduced and the distance between lamellae is also reduced, indicating that the degree of condensation of coal aromatic nuclei may be increased. Correspondingly, the FTIR parameters of coal also reflect that, with increasing temperature, the side chains of coal are constantly cracked, the oxygen-containing functional groups are reduced, and the degree of aromatization of coal may be increased.

scholarly journals In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces

2014 ◽  
Vol 5 ◽  
pp. 2222-2229 ◽  
Author(s):  
Fabio Lupo ◽  
Cristina Tudisco ◽  
Federico Bertani ◽  
Enrico Dalcanale ◽  
Guglielmo G Condorelli
Keyword(s):  
Porous Silicon ◽  
Photoelectron Spectroscopy ◽  
Relevant Information ◽  
Silicon Surfaces ◽  
Porous Si ◽  
Wet Chemistry ◽  
X Ray ◽  
Covalently Bonded ◽  
Phthalocyanine Ring

Free 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100) and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring–surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm−1 due to –NH stretches. Finally, XPS results revealed that the different surface–phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process.

In-Situ Photoluminescence Investigation of the Initial Porous Silicon Formation in 0.2M NH4F (pH 3.2)

1996 ◽  
Vol 452 ◽  
Author(s):  
T. Dittrich ◽  
V. Y. Timoshenko ◽  
J. Rappich
Keyword(s):  
Porous Silicon ◽  
Surface Recombination ◽  
Current Switch ◽  
Current Voltage ◽  
Galvanostatic Regime ◽  
Pl Intensity ◽  
Rapid Current ◽  
Si Nanostructures ◽  
P Type

AbstractThe porous silicon (por-Si) formation in 0.2M NH4F (pH 3.2) is investigated in-situ by photoluminescence (PL). The p-type Si(100) samples are treated electrochemically in the galvanostatic regime starting from Ihe hydrogenated surface. Single pulses of a N2 laser are used to probe stroboscopically the radiative band-band recombination of the bulk c-Si and the PL of por-Si. The PL intensity of c-Si is correlated with the current density during the current-voltage scan and indicates changes of surface recombination by the onset of chemical reactions. The PL intensity of c-Si increases rapidly after switching off the anodic current while the PL intensity of por-Si is not influenced by the rapid current switch. This shows that the passivation of the surfaces of the Si nanostructures is not affected by the por-Si formation at the surface of the bulk c-Si.

The Role of Silicon Monohydride and Dihydride in the Photoluminescence of Porous Silicon and Photoluminescence of Porous Silicon Buried Underneath Epitaxial GaP

1991 ◽  
Vol 256 ◽  
Author(s):  
C. Tsai ◽  
K.-H. Li ◽  
J. Sarathy ◽  
K. Jung ◽  
S. Shih ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Porous Silicon ◽  
Fourier Transform Infrared ◽  
Wide Bandgap ◽  
Photoluminescence Intensity ◽  
Porous Si ◽  
Sufficient Energy ◽  
Pl Intensity ◽  
Viable Method

ABSTRACTThermal annealing studies of the photoluminescence (PL) intensity and Fourier-transform infrared (FTIR) spectroscopy have been performed concurrently on porous Si. A sharp reduction in the PL intensity is observed for annealing temperatures > 300 °C and this coincides with desorption of hydrogen from the SiH2 surface species. The role of silicon hydride species on the photoluminescence intensity has been studied. The surfaces of luminescent porous Si samples were converted to a predominate SiH termination using a remote H-plasma. The as-passivated samples were then immersed in various concentrations of hydrofluouric solutions to regulate the recovery of SiH2 termination on the surface. Photoluminescence measurements and transmission Fourier-transform infrared spectroscopy have shown that predominant silicon monohydride (SiH) termination results in weak photoluminescence. In contrast, it has been observed that the appearance of silicon dihydride (SiH2) coincides with an increase in the photoluminescence intensity. To achieve electroluminescence it will be beneficial to generate carriers with sufficient energy to populate the states of the quantum-confined Si structures. A viable method to accomplish this is to utilize a wide-bandgap heterojunction injector such as GaP. Toward that end we report the successful formation of porous Si buried underneath GaP islands and we demonstrate that the buried porous Si layer exhibits strong photoluminescence.

Mechanism of in-Situ Photoluminescence Decay in Porous Silicon and its Application to Maskless Patterning

1992 ◽  
Vol 283 ◽  
Author(s):  
Mikio Takai ◽  
Sanae Indou ◽  
Hisanori Murase
Keyword(s):  
Porous Silicon ◽  
Laser Beam ◽  
Time Scale ◽  
Excitation Intensity ◽  
Porous Si ◽  
Photoluminescence Decay ◽  
Enhanced Oxidation ◽  
Maskless Patterning

ABSTRACTPL decay in a time scale of ms for fresh porous Si surfaces was investigated for different atmospheres and excitation intensities to clarify the mechanism of the PL decay. The PL excitation intensity and atmosphere were found to affect the decay of PL, which was due to laser enhanced oxidation.Locally PL excited areas of porous Si were also found to be etched in a HF solution. Maskless patterning using this effect could be performed by a scan of a focused laser beam followed by HF etching.

The reaction of amorphous Ni-Nb films with Si in the presence of a native SiO2 layer

1990 ◽  
Vol 48 (4) ◽  
pp. 664-665
Author(s):  
N. Rozhanski ◽  
A. Barg
Keyword(s):  
High Temperature ◽  
Crystallization Temperature ◽  
Diffusion Barriers ◽  
Sio2 Layer ◽  
Si Substrate ◽  
Cross Sectional ◽  
Plan View ◽  
Temperature Range ◽  
Sputter Deposited

Amorphous Ni-Nb alloys are of potential interest as diffusion barriers for high temperature metallization for VLSI. In the present work amorphous Ni-Nb films were sputter deposited on Si(100) and their interaction with a substrate was studied in the temperature range (200-700)°C. The crystallization of films was observed on the plan-view specimens heated in-situ in Philips-400ST microscope. Cross-sectional objects were prepared to study the structure of interfaces.The crystallization temperature of Ni5 0 Ni5 0 and Ni8 0 Nb2 0 films was found to be equal to 675°C and 525°C correspondingly. The crystallization of Ni5 0 Ni5 0 films is followed by the formation of Ni6Nb7 and Ni3Nb nucleus. Ni8 0Nb2 0 films crystallise with the formation of Ni and Ni3Nb crystals. No interaction of both films with Si substrate was observed on plan-view specimens up to 700°C, that is due to the barrier action of the native SiO2 layer.

Dependence of the intrinsic phase structure of Bi2O3 catalysts on photocatalytic CO2 reduction

2021 ◽  
Vol 11 (6) ◽  
pp. 2021-2025
Author(s):  
Liujin Wei ◽  
Guan Huang ◽  
Yajun Zhang
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Fourier Transform Infrared Spectroscopy ◽  
Phase Structure ◽  
Co2 Reduction ◽  
Fourier Transform Infrared ◽  
Time Resolved ◽  
Dependent Activity

The combination of time-resolved transient photoluminescence with in-situ Fourier transform infrared spectroscopy has been conducted to investigate the intrinsic phase structure-dependent activity of Bi2O3 catalyst for CO2 reduction.

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