N. Rowell - Academia.edu (original) (raw)
Papers by N. Rowell
ECS Meeting Abstracts
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Infrared Physics
ABSTRACT
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Journal of the Optical Society of America
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MRS Proceedings
ABSTRACTThe concentration dependence of optical phonons in strained In1-xGaxAs epilayers grown on... more ABSTRACTThe concentration dependence of optical phonons in strained In1-xGaxAs epilayers grown on InP (100) by chemical beam epitaxy has been characterized with oblique angle polarized far-infrared reflectivity measurements. In this powerful method, the reflectance spectra contain sharp Berreman peaks exactly at the optical phonon frequencies. For radiation polarized in the plane of incidence (p-polarized), peaks for both the TO and LO phonons were observed. For s-polarization only the TO modes were observed. For heavily doped substrates the TO film phonons were observed as reflectance minima, whereas for lightly doped substrates they were seen as maxima. The measured spectra were curve resolved to separate the effects of the various modes which included GaAs-like longitudinal and transverse optic (LO and TO), a disorder induced, and InAs-like LO and TO phonons. The dielectric response function and phonon frequency dependences for all modes were obtained versus Ga fraction for x fro...
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IEEE Transactions on Sonics and Ultrasonics
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Infrared Physics
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. RADECS 91 First European Conference on Radiation and its Effects on Devices and Systems, 2000
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Conference Digest Conference on Precision Electromagnetic Measurements, 2000
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Conference Proceedings. 2000 International Conference on Indium Phosphide and Related Materials (Cat. No.00CH37107), 2000
We have used transmission electron microscopy and low temperature photoluminescence to study the ... more We have used transmission electron microscopy and low temperature photoluminescence to study the growth by chemical beam epitaxy of self-assembled InAs/InP quantum dots. Square dots 30-40 nm in width were grown with a density of 1010 cm-2. By partially covering the dots with InP and exposing them to a phosphorus overpressure the mean height of the dots, and hence their
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ECS Transactions, 2009
ABSTRACT
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Beilstein journal of nanotechnology, 2014
We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE)... more We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE) in ordered arrays on SiO2/Si(111) substrates. The production method employs Au catalysts with self-limited sizes deposited in SiO2-free sites opened-up in the substrate by focused ion beam patterning for the preferential nucleation and growth of these well-organized NWs. The NWs thus produced have a diameter of 200 nm, a length of 200 nm, and a Ge concentration x = 0.15. Their photoluminescence (PL) spectra were measured at low temperatures (from 6 to 25 K) with excitation at 405 and 458 nm. There are four major features in the energy range of interest (980-1120 meV) at energies of 1040.7, 1082.8, 1092.5, and 1098.5 meV, which are assigned to the NW-transverse optic (TO) Si-Si mode, NW-transverse acoustic (TA), Si-substrate-TO and NW-no-phonon (NP) lines, respectively. From these results the NW TA and TO phonon energies are found to be 15.7 and 57.8 meV, respectively, which agree very w...
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MRS Proceedings, 1992
ABSTRACTRoom temperature Raman spectra are reported of Si1−xGex layers on Si substrates (for 0.08... more ABSTRACTRoom temperature Raman spectra are reported of Si1−xGex layers on Si substrates (for 0.08≤x≤0.2). The samples were grown using atmospheric pressure chemical vapor deposition techniques. Layer thicknesses varied from 0.1 — 10μm. The relative frequency shift of the Si-Si phonon mode for the SiGe strained epilayers from an incommensurate pseudo-alloy of the same composition is used as a quantitative measure of the lattice strain. For thicknesses below a critical value the Raman data indicate that the films are highly strained and the growth is commensurate with the substrate whereas thicker films are partially or fully relaxed. Phonon lines are sensitive to the interfaces and alloy layers. The results are consistent with other characterization studies, such as TEM and X-ray rocking curve measurements, of the same samples.
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Physical Review B, 1975
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Physical review. B, Condensed matter, Jan 15, 1993
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Physical Review B, 1979
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Quantum Well and Superlattice Physics II, 1988
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Photonic Applications in Biosensing and Imaging, 2005
Photoluminescent porous Si (pSi) is a potentially attractive material for biosensor devices. Its ... more Photoluminescent porous Si (pSi) is a potentially attractive material for biosensor devices. Its ease of fabrication, large active surface area and unique optical properties are just some important attributes. Among other transduction techniques, it is possible to monitor the onset of molecular binding events through the effective quenching of the bright pSi photoluminescence. Here we present the study of effective
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MRS Proceedings, 2005
Infrared vibrational spectroscopy in an attenuated total reflection geometry has been employed to... more Infrared vibrational spectroscopy in an attenuated total reflection geometry has been employed to investigate the presence of organic and inorganic thin layers on Si-wafer surfaces. Three different processes were compared for surface contaminant removal; microwave plasma, UV-ozone, and a piranha solution cleaning. The CH vibrations at 2928 and 2856 cm-1 characteristic of organic contaminants were monitored before and after each cleaning procedure to determine how well it removed surface contaminants. We found that native oxide removal from the Si surface should only be carried out after a cleaning essay. We observed that surface oxide removal exposed a hydrophobic bare Si surface, attracting organic molecules present in solution or the ambient. A large increase of the CH vibrational signature was observed for a Si wafer after an HF dip. A combination of plasma cleaning followed by UV-Ozone treatment was found the most effective one for Si wafer cleaning. We were able to evaluate the...
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MRS Proceedings, 2005
The photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) w... more The photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) was investigated in the presence of colloidal Ag nanoparticles. The acid passivated Si surface has a weak PL at 1125 nm. Upon exposure to a Ag nanoparticle sol, the PL quenched exponentially with a characteristic decay time of ∼ 18 minutes. It is known that the metal mediated charge-transfer process provides a pathway for energy decay and leads to a quenching of luminescence in light emitting material. An in-situ study of the surface passivated Si revealed that the Ag nanoparticle was likely to have come into contact or was sited close enough to the semiconductor surface through adsorption to cause effective PL quenching.
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ECS Meeting Abstracts
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Infrared Physics
ABSTRACT
Bookmarks Related papers MentionsView impact
Journal of the Optical Society of America
Bookmarks Related papers MentionsView impact
MRS Proceedings
ABSTRACTThe concentration dependence of optical phonons in strained In1-xGaxAs epilayers grown on... more ABSTRACTThe concentration dependence of optical phonons in strained In1-xGaxAs epilayers grown on InP (100) by chemical beam epitaxy has been characterized with oblique angle polarized far-infrared reflectivity measurements. In this powerful method, the reflectance spectra contain sharp Berreman peaks exactly at the optical phonon frequencies. For radiation polarized in the plane of incidence (p-polarized), peaks for both the TO and LO phonons were observed. For s-polarization only the TO modes were observed. For heavily doped substrates the TO film phonons were observed as reflectance minima, whereas for lightly doped substrates they were seen as maxima. The measured spectra were curve resolved to separate the effects of the various modes which included GaAs-like longitudinal and transverse optic (LO and TO), a disorder induced, and InAs-like LO and TO phonons. The dielectric response function and phonon frequency dependences for all modes were obtained versus Ga fraction for x fro...
Bookmarks Related papers MentionsView impact
IEEE Transactions on Sonics and Ultrasonics
Bookmarks Related papers MentionsView impact
Infrared Physics
Bookmarks Related papers MentionsView impact
. RADECS 91 First European Conference on Radiation and its Effects on Devices and Systems, 2000
Bookmarks Related papers MentionsView impact
Conference Digest Conference on Precision Electromagnetic Measurements, 2000
Bookmarks Related papers MentionsView impact
Conference Proceedings. 2000 International Conference on Indium Phosphide and Related Materials (Cat. No.00CH37107), 2000
We have used transmission electron microscopy and low temperature photoluminescence to study the ... more We have used transmission electron microscopy and low temperature photoluminescence to study the growth by chemical beam epitaxy of self-assembled InAs/InP quantum dots. Square dots 30-40 nm in width were grown with a density of 1010 cm-2. By partially covering the dots with InP and exposing them to a phosphorus overpressure the mean height of the dots, and hence their
Bookmarks Related papers MentionsView impact
ECS Transactions, 2009
ABSTRACT
Bookmarks Related papers MentionsView impact
Beilstein journal of nanotechnology, 2014
We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE)... more We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE) in ordered arrays on SiO2/Si(111) substrates. The production method employs Au catalysts with self-limited sizes deposited in SiO2-free sites opened-up in the substrate by focused ion beam patterning for the preferential nucleation and growth of these well-organized NWs. The NWs thus produced have a diameter of 200 nm, a length of 200 nm, and a Ge concentration x = 0.15. Their photoluminescence (PL) spectra were measured at low temperatures (from 6 to 25 K) with excitation at 405 and 458 nm. There are four major features in the energy range of interest (980-1120 meV) at energies of 1040.7, 1082.8, 1092.5, and 1098.5 meV, which are assigned to the NW-transverse optic (TO) Si-Si mode, NW-transverse acoustic (TA), Si-substrate-TO and NW-no-phonon (NP) lines, respectively. From these results the NW TA and TO phonon energies are found to be 15.7 and 57.8 meV, respectively, which agree very w...
Bookmarks Related papers MentionsView impact
MRS Proceedings, 1992
ABSTRACTRoom temperature Raman spectra are reported of Si1−xGex layers on Si substrates (for 0.08... more ABSTRACTRoom temperature Raman spectra are reported of Si1−xGex layers on Si substrates (for 0.08≤x≤0.2). The samples were grown using atmospheric pressure chemical vapor deposition techniques. Layer thicknesses varied from 0.1 — 10μm. The relative frequency shift of the Si-Si phonon mode for the SiGe strained epilayers from an incommensurate pseudo-alloy of the same composition is used as a quantitative measure of the lattice strain. For thicknesses below a critical value the Raman data indicate that the films are highly strained and the growth is commensurate with the substrate whereas thicker films are partially or fully relaxed. Phonon lines are sensitive to the interfaces and alloy layers. The results are consistent with other characterization studies, such as TEM and X-ray rocking curve measurements, of the same samples.
Bookmarks Related papers MentionsView impact
Physical Review B, 1975
Bookmarks Related papers MentionsView impact
Physical review. B, Condensed matter, Jan 15, 1993
Bookmarks Related papers MentionsView impact
Physical Review B, 1979
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Quantum Well and Superlattice Physics II, 1988
Bookmarks Related papers MentionsView impact
Photonic Applications in Biosensing and Imaging, 2005
Photoluminescent porous Si (pSi) is a potentially attractive material for biosensor devices. Its ... more Photoluminescent porous Si (pSi) is a potentially attractive material for biosensor devices. Its ease of fabrication, large active surface area and unique optical properties are just some important attributes. Among other transduction techniques, it is possible to monitor the onset of molecular binding events through the effective quenching of the bright pSi photoluminescence. Here we present the study of effective
Bookmarks Related papers MentionsView impact
MRS Proceedings, 2005
Infrared vibrational spectroscopy in an attenuated total reflection geometry has been employed to... more Infrared vibrational spectroscopy in an attenuated total reflection geometry has been employed to investigate the presence of organic and inorganic thin layers on Si-wafer surfaces. Three different processes were compared for surface contaminant removal; microwave plasma, UV-ozone, and a piranha solution cleaning. The CH vibrations at 2928 and 2856 cm-1 characteristic of organic contaminants were monitored before and after each cleaning procedure to determine how well it removed surface contaminants. We found that native oxide removal from the Si surface should only be carried out after a cleaning essay. We observed that surface oxide removal exposed a hydrophobic bare Si surface, attracting organic molecules present in solution or the ambient. A large increase of the CH vibrational signature was observed for a Si wafer after an HF dip. A combination of plasma cleaning followed by UV-Ozone treatment was found the most effective one for Si wafer cleaning. We were able to evaluate the...
Bookmarks Related papers MentionsView impact
MRS Proceedings, 2005
The photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) w... more The photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) was investigated in the presence of colloidal Ag nanoparticles. The acid passivated Si surface has a weak PL at 1125 nm. Upon exposure to a Ag nanoparticle sol, the PL quenched exponentially with a characteristic decay time of ∼ 18 minutes. It is known that the metal mediated charge-transfer process provides a pathway for energy decay and leads to a quenching of luminescence in light emitting material. An in-situ study of the surface passivated Si revealed that the Ag nanoparticle was likely to have come into contact or was sited close enough to the semiconductor surface through adsorption to cause effective PL quenching.
Bookmarks Related papers MentionsView impact