Differential Reflectance Spectra Research Articles

Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

Femtosecond pump-probe (PP) differential reflectivity spectroscopy (DRS) and four-wave mixing (FWM) experiments were performed simultaneously to study the initial temporal dynamics of the exciton line-shapes in GaN epilayers. Beats between the A-B excitons were found \textit{only for positive time delay} in both PP and FWM experiments. The rise time at negative time delay for the differential reflection spectra was much slower than the FWM signal or PP differential transmission spectroscopy (DTS) at the exciton resonance. A numerical solution of a six band semiconductor Bloch equation model including nonlinearities at the Hartree-Fock level shows that this slow rise in the DRS results from excitation induced dephasing (EID), that is, the strong density dependence of the dephasing time which changes with the laser excitation energy.

Antimony segregation in GaAs-based multiple quantum well structures

Sb segregation effects have been studied in structures grown by organometallic vapor phase epitaxy. The structures are formed by periodic exposure of the GaAs (0 0 1) surface to trimethylantimony (TMSb), followed by GaAs growth. Reflectance-difference spectra obtained during growth show a strong influence of Sb on the surface reconstruction, reducing the concentration of As dimers. Transmission electron microscope images and X-ray diffraction (XRD) measurements show that a periodic multiple quantum well (MQW) structure is formed by the TMSb/GaAs growth sequence. A fraction of the deposited Sb is incorporated as a one monolayer thick Sb-rich quantum well in each period. The incorporation of impurity Sb, as the GaAs layers are grown, results in the formation of a graded GaAs 1− x Sb x barrier layer above each QW layer. The impurity profile inferred from XRD measurements is in good agreement with a one-dimensional segregation model based on the partitioning of Sb between the growing barrier layer and a surface floating layer. The Sb floating layer is shown to desorb under exposure to tertiarybutylarsine.

Electronic anisotropy of the GaAs(001) surface studied by energy loss spectroscopy

High-Resolution Electron-Energy-Loss Spectroscopy (HREELS) has been applied to investigate the anisotropy of the GaAs(001)-c(4×4) and β2(2×4) reconstructions. Measurements have been performed on high-quality samples grown in situ by Molecular Beam Epitaxy. The loss intensity is different in the directions parallel and perpendicular to dimers, particularly close to the fundamental gap. We construct relative difference intensity spectra which can be directly compared with the differential reflectivity spectra of the RAS spectroscopy. A one-to-one correspondence is found between experimental and calculated electronic transitions up to about 3eV. The surface anisotropy given by EELS is about two orders of magnitude higher than that measured optically. The contributions to the anisotropy originate entirely from a few atomic layers beneath the surface. In the β2 phase we find direct evidence of transitions involving the dimers of the top atomic layer which are well separated by those involving bulk states modified by the surface.

Optical reflectance study of the wetting layers in (In, Ga)As self-assembled quantum dot growth on GaAs(001)

We have studied in situ Stranski-Krastanov growth surface of (In,Ga)As grown by molecular-beam epitaxy on GaAs (001) using reflectance-difference (RD) spectroscopy and reflection high-energy electron diffraction. The surface of the two-dimensional wetting layer shows various structures depending on the InAs coverage and the growth temperature. At relatively low substrate temperature, the growth transition from two-dimensional to three-dimensional occurs on the $(2\ifmmode\times\else\texttimes\fi{}3)$ surface of (In,Ga)As, whereas at high-temperature the transition occurs on the $(2\ifmmode\times\else\texttimes\fi{}4)$ surface of InAs. Comparing the measured RD spectra with the calculations based on the tight-binding surface-linear-response method, we found that both [110]-In and $[1\ifmmode\bar\else\textasciimacron\fi{}10]$-As dimers are necessary for the $(2\ifmmode\times\else\texttimes\fi{}3)$ and $(2\ifmmode\times\else\texttimes\fi{}4)$ surfaces to explain the observed RD spectra. Time-resolved measurements demonstrate that disappearance of excess As surface triggers the islanding process. Furthermore, the In-dimer-related signal shows a redshift near the growth transition due to the strain relaxation.

Reflectance difference spectroscopy of an ultrathin indium arsenide layer on indium phosphide (001)

A model system has been created which allows the surface and bulk contributions to the reflectance difference spectrum to be distinguished. In particular, an indium arsenide film, less than 10 Å thick, has been grown on indium phosphide (001). Reflectance difference spectra of the InAs/InP surfaces were collected and compared to those of InP and InAs. It was found that the InAs/InP heterostructures exhibited electronic transitions between surface states characteristic of InAs (001), while retaining the surface-perturbed bulk transitions characteristic of InP (001). Furthermore, the optical anisotropy arising from the arsenic dimer bonds was shifted 0.2 eV higher for InAs/InP compared to that for InAs. This shift is proportional to 1/a2, where a is the bulk lattice constant.

Determination of carrier concentration in n-ZnSe by reflectance difference spectroscopy: Experimental results and model calculation

We have performed in situ and ex situ measurements of reflectance difference (RD) spectra for Cl-doped n-type ZnSe grown by molecular beam epitaxy. The linear electro-optic (LEO) effect (or Pockels effect) in the depletion layer induces characteristic RD features near the E1 and E1+Δ1 transition energy. The intensity of these features is correlated with the carrier concentration determined from capacitance–voltage measurements. A quantitative model is presented to explain the observed dependence of the LEO signal on the carrier concentration. This model quantitatively considers the effect of the finite surface state density. A good fit with the experimental results was obtained by assuming the surface state densities of 3.8×1013 and 2.6×1013 cm−2 eV−1, respectively, for in situ measurement of a Se-terminated surface at 300 °C and for ex situ measurement of an oxide-covered surface at room temperature.

Structure-sensitive oxidation of the indium phosphide (001) surface

The oxidation of anion- and cation-rich indium phosphide (001) has been investigated by exposure to unexcited molecular oxygen. Indium phosphide oxidation is an activated process and strongly structure sensitive. The In-rich δ(2×4) surface reacts with oxygen at 300 K and above. Core level x-ray photoemission spectra have revealed that the O2 dissociatively chemisorbs onto the δ(2×4), inserting into the In–In dimer and In–P back bonds. By contrast, the P-rich (2×1) reconstruction does not absorb oxygen up to 5×105 Langmuir at 300 K, as judged by the unperturbed reflectance difference spectrum and low energy electron diffraction pattern. Above 455 K, oxygen reacts with the (2×1) inserting preferentially into the In–P back bonds and to a lesser extent into the phosphorus dimer bonds.

Observation of oscillating behavior in the reflectance difference spectra of oxidized Si(001) surfaces

Layer-by-layer oxidation of Si(001)-(2×1) surfaces was observed using the reflectance difference (RD) spectroscopy. Distinctive features in the RD spectra appeared near the E1 (3.3 eV) and E2 (4.2 eV) transition energies of Si. The polarity of these features was repeatedly reversed as the oxide thickness was increased to 4 monolayers (MLs). Oscillation of the RD amplitude near the E1 transition energy was observed in real time during the oxidation process. A half period of the oscillation corresponds to the oxidation of 1 ML. These results demonstrate the possibility of in situ counting and control of the number of oxidized layers.

Rapid synthesis of nanocrystalline SnO 2 powders by microwave heating method

Nanocrystalline SnO 2 powders of about 3 nm in size have been prepared by a microwave irradiation heating technique from an aqueous solution in the presence of SnCl 4 and urea. The nanocrystalline SnO 2 particles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetric (DSC), thermogravimetric analysis (TG), and reflection spectrum. A bandgap is estimated to be 4.5 eV from the optical measurement of the nanoparticles.

Oxidation Mechanism of Silicon Surface. In situ Counting of the Number of Oxidized Si Layers by the Reflectance-Difference Oscillation Technique.

This article describes an application of reflectance-difference (RD) spectroscopy, that is a surface-sensitive optical technique, to monitoring of the oxidation process on Si. The RD spectrum of a single-domain Si(001) surface shows repeated inversion of its polarity as oxidation proceeds in the layer-by-layer mode. Taking advantage of this oscillation, we have demonstrated in situ measurements of the oxide thickness with atomic-layer precision, which allows the determination of oxidation rate for each monolayer of Si. Such layer-resolved kinetic data will expectedly advance our understanding of the atomistic mechanisms of the oxidation processes.

Polarizability of truncated spheroidal particles supported by a substrate: model and applications

The light scattering by three-dimensional clusters supported by a substrate is modelled by representing clusters by truncated spheroids whose polarizability is calculated via a multipolar development of the potential in the quasi-static limit. The determination of the mean island radius, density and aspect ratio from the optical response is examined. The strong influence of both the particle-substrate interaction and the particle shape on the optical behaviour is demonstrated, showing the limits of effective medium and dipolar theories. The Surface Differential Reflectance spectra of silver on MgO(100) and titanium or aluminium on α-Al2O3(0001) surfaces have then been modelled by using the above model, illustrating the capability of optical means to deal with various metals, including those belonging to transition series. In all cases, it is highlighted that the aspect ratio is central in modelling the optical response of supported particles.

Hydrogen atoms as a probe of the optical anisotropy of indium phosphide ( [formula omitted

The reflectance difference spectra of the InP(0 0 1) (2×1) and δ(2×4) reconstructions have been characterized using hydrogen as a probe of the surface bonds. Bands observed at 1.9, 3.1, 4.1, and 4.6 eV on the (2×1) and at 2.8, 3.7, and 4.6 eV on the δ(2×4) decrease in direct proportion to the hydrogen coverage. By comparing the changes in the reflectance difference spectra to the changes in the atomic structure of the surfaces, it is possible to relate the peaks to transitions involving specific valence bond states.

Reflectance-difference spectroscopy of semi-insulating GaAs(110) around the fundamental gap

We report on a theoretical model to describe reflectance-difference (RD) spectra for the (110) surface of zinc-blende semiconductors due to anisotropic strains induced by 60\ifmmode^\circ\else\textdegree\fi{} dislocations. We obtain expressions for the RD spectrum at critical points of \ensuremath{\Gamma} symmetry that predict second-energy-derivative RD line shapes as far as the strain-induced energy shifts are small compared to spectra broadening energies. The second-derivative line shape contrasts with the first-derivative line shape observed previously for the GaAs(001) surface. We further report on experimental RD spectra of semi-insulating GaAs(110) in the 1.2--1.6 eV energy range and show that such spectra comprise a component that is well described by our theoretical model. Results obtained in the present work prove the existence of dislocation-induced components in RD GaAs spectra. We expect that they will contribute to further development of RD spectroscopy as a surface and near-surface optical probe for zinc-blende semiconductors.

Reflectance difference spectroscopy of mixed phases of indium phosphide (001)

Reflectance difference spectra of mixed (2×1) and (2×4) phases of indium phosphide (001) have been recorded and benchmarked against scanning tunneling micrographs of the surface. The line shapes are found to be linear combinations of the spectra of the pure (2×1) and (2×4) structures, Δr/rmixed=xΔr/r(2×4)+(1−x)Δr/r(2×1), where x is the weighting factor. Thus, in the absence of adsorbates, the reflectance difference spectra can be used to estimate the surface composition, i.e., the fractional coverage of phosphorous is ΘP=1−0.81x±0.06x.

Reflectance-difference spectroscopy of mixed arsenic-rich phases of gallium arsenide (001)

The relationship between the reflectance difference spectra and the atomic structure of arsenic-rich reconstructions of GaAs(001) has been investigated. Scanning tunneling micrographs reveal that a roughening process occurs as the surface structure changes with decreasing arsenic coverage from 1.75 to 0.75 monolayers (ML). At 1.65 ML As, small pits, one bilayer in depth and having the same $c(4\ifmmode\times\else\texttimes\fi{}4)$ reconstruction as the top layer, form in the terraces. At the same time, gallium atoms are liberated to the surface, disrupting the $c(4\ifmmode\times\else\texttimes\fi{}4)$ ordering. At about 1.4 ML As, $(2\ifmmode\times\else\texttimes\fi{}4)$ domains nucleate and grow on top of the $c(4\ifmmode\times\else\texttimes\fi{}4).$ Further desorption of arsenic causes the underlying layer to gradually decompose into a metastable $(2\ifmmode\times\else\texttimes\fi{}n)$ phase $(n=2,$ 3, or 4), and finally into the $(2\ifmmode\times\else\texttimes\fi{}4).$ In the reflectance difference spectra, negative peaks at 2.25 and 2.8 eV correlate with the $c(4\ifmmode\times\else\texttimes\fi{}4)$-type arsenic dimers. However, the intensity of the latter feature strongly depends on the presence of adsorbates, such as alkyl groups and gallium adatoms. By contrast, the intensity of the positive peak at 2.9 eV is directly proportional to the density of $(2\ifmmode\times\else\texttimes\fi{}4)$-type dimers.

LINEAR OPTICAL SPECTROSCOPIES FOR SURFACE STUDIES

Surface Review and LettersVol. 07, No. 04, pp. 399-410 (2000) No AccessLINEAR OPTICAL SPECTROSCOPIES FOR SURFACE STUDIESYVES BORENSZTEINYVES BORENSZTEINLaboratoire d'Optique des Solides, UMR CNRS 7601, Universitée Pierre et Marie Curie, Case 80, 4 Place Jussieu, 75252 Paris Cedex 05, Francehttps://doi.org/10.1142/S0218625X00000403Cited by:22 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited By 22Noncontact AFM and differential reflectance spectroscopy joint analyses of bis-pyrenyl thin films on bulk insulators: Relationship between structural and optical propertiesFranck Bocquet, Laurent Nony, Franck Para, Philipda Luangprasert and Jean-Valère Naubron et al.22 June 2018 | Physical Review B, Vol. 97, No. 23Silicene multilayers on Ag(111) display a cubic diamondlike structure and a √3×√3 reconstruction induced by surfactant Ag atomsYves Borensztein, Alberto Curcella, Sébastien Royer and Geoffroy Prévot6 October 2015 | Physical Review B, Vol. 92, No. 15Optical referencing in differential reflectance spectroscopyH Zaglmayr, C G Hu, L D Sun and P Zeppenfeld22 September 2014 | Measurement Science and Technology, Vol. 25, No. 11Large differences in the optical properties of a single layer of Si on Ag(110) compared to siliceneYves Borensztein, Geoffroy Prévot and Laurence Masson9 June 2014 | Physical Review B, Vol. 89, No. 24Unusual Two-Stage Kinetics of Ethylene Adsorption on Si(100) Unraveled by Surface Optical Spectroscopy and Monte Carlo SimulationRomain Coustel, Yves Borensztein, Olivier Pluchery and Nadine Witkowski27 August 2013 | Physical Review Letters, Vol. 111, No. 9In-situ, Real-Time Investigation of Organic Thin Film Growth Using Reflectance Difference SpectroscopyLidong Sun and Peter Zeppenfeld1 Jan 2013Optical differential reflectance spectroscopy on thin molecular filmsRoman Forker, Marco Gruenewald and Torsten Fritz1 Jan 2012 | Annual Reports Section "C" (Physical Chemistry), Vol. 108Characterization of Chemical Bonding in Ion-Implanted Polymers by Means of Mid-Infrared ReflectivityVictor G. Ivanov, Georgi Hadjichristov and Eric Faulques1 September 2009 | Applied Spectroscopy, Vol. 63, No. 9Adhesion of growing nanoparticles at a glance: Surface differential reflectivity spectroscopy and grazing incidence small angle x-ray scatteringR. Lazzari, G. Renaud, C. Revenant, J. Jupille and Y. Borensztein24 March 2009 | Physical Review B, Vol. 79, No. 12Optical differential reflectance spectroscopy of ultrathin epitaxial organic filmsRoman Forker and Torsten Fritz1 Jan 2009 | Physical Chemistry Chemical Physics, Vol. 11, No. 13Reflectance-anisotropy spectroscopy and surface differential reflectance spectra at the Si(100) surface: Combined experimental and theoretical studyMaurizia Palummo, Nadine Witkowski, Olivier Pluchery, Rodolfo Del Sole and Yves Borensztein30 January 2009 | Physical Review B, Vol. 79, No. 3Adsorption of Phenylacetylene on Si(100)-2 × 1: Kinetics and Structure of the AdlayerOlivier Pluchery, Romain Coustel, Nadine Witkowski and Yves Borensztein26 October 2006 | The Journal of Physical Chemistry B, Vol. 110, No. 45Investigation of molecule chemisorption on Si(001)2 × 1 surfaces by surface reflectance spectroscopiesO. Pluchery, N. Witkowski and Y. Borensztein1 Nov 2005 | physica status solidi (b), Vol. 242, No. 13Probing the Si-Si Dimer Breaking of Si(100)2×1 Surfaces upon Molecule Adsorption by Optical SpectroscopyY. Borensztein, O. Pluchery and N. Witkowski7 September 2005 | Physical Review Letters, Vol. 95, No. 11In situ differential reflectance spectroscopy of thin crystalline films of PTCDA on different substratesHolger Proehl, Robert Nitsche, Thomas Dienel, Karl Leo and Torsten Fritz22 April 2005 | Physical Review B, Vol. 71, No. 16Optical response of clean and hydrogen-covered vicinal Si(001) 2 × 1 surfacesY Borensztein and N Witkowski21 September 2004 | Journal of Physics: Condensed Matter, Vol. 16, No. 39Apparatus for real time in situ quantitative studies of growing nanoparticles by grazing incidence small angle X-ray scattering and surface differential reflectance spectroscopyG Renaud, M Ducruet, O Ulrich and R Lazzari1 Aug 2004 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Vol. 222, No. 3-4Formation of Solid-State Excitons in Ultrathin Crystalline Films of PTCDA: From Single Molecules to Molecular StacksHolger Proehl, Thomas Dienel, Robert Nitsche and Torsten Fritz25 August 2004 | Physical Review Letters, Vol. 93, No. 9Isotropic and anisotropic optical reflectances of clean and hydrogen‐covered Si(001)2x1 surfacesY. Borensztein, N. Witkowski and S. Royer5 December 2003 | physica status solidi (c), No. 8Direct Kinetic Study of the Reaction of Cl 2•- Radical Anions with Ethanol at the Air−Water InterfaceR. S. Strekowski, R. Remorov and Ch. George20 March 2003 | The Journal of Physical Chemistry A, Vol. 107, No. 14GranFilm: a software for calculating thin-layer dielectric properties and Fresnel coefficientsRémi Lazzari and Ingve Simonsen1 Nov 2002 | Thin Solid Films, Vol. 419, No. 1-2NESSPIOM?Network for enhanced semiconductor surface processing throughin situ optical monitoringMartyn E. Pemble1 January 2001 | Surface and Interface Analysis, Vol. 31, No. 10 Recommended Vol. 07, No. 04 Metrics History Received 5 June 2000 PDF download

Linear Optical Spectroscopies for Surface Studies

Surface Review and LettersVol. 07, No. 04, pp. 399-410 (2000) No AccessLINEAR OPTICAL SPECTROSCOPIES FOR SURFACE STUDIESYVES BORENSZTEINYVES BORENSZTEINLaboratoire d'Optique des Solides, UMR CNRS 7601, Universitée Pierre et Marie Curie, Case 80, 4 Place Jussieu, 75252 Paris Cedex 05, Francehttps://doi.org/10.1142/S0218625X00000403Cited by:22 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited By 22Noncontact AFM and differential reflectance spectroscopy joint analyses of bis-pyrenyl thin films on bulk insulators: Relationship between structural and optical propertiesFranck Bocquet, Laurent Nony, Franck Para, Philipda Luangprasert and Jean-Valère Naubron et al.22 June 2018 | Physical Review B, Vol. 97, No. 23Silicene multilayers on Ag(111) display a cubic diamondlike structure and a √3×√3 reconstruction induced by surfactant Ag atomsYves Borensztein, Alberto Curcella, Sébastien Royer and Geoffroy Prévot6 October 2015 | Physical Review B, Vol. 92, No. 15Optical referencing in differential reflectance spectroscopyH Zaglmayr, C G Hu, L D Sun and P Zeppenfeld22 September 2014 | Measurement Science and Technology, Vol. 25, No. 11Large differences in the optical properties of a single layer of Si on Ag(110) compared to siliceneYves Borensztein, Geoffroy Prévot and Laurence Masson9 June 2014 | Physical Review B, Vol. 89, No. 24Unusual Two-Stage Kinetics of Ethylene Adsorption on Si(100) Unraveled by Surface Optical Spectroscopy and Monte Carlo SimulationRomain Coustel, Yves Borensztein, Olivier Pluchery and Nadine Witkowski27 August 2013 | Physical Review Letters, Vol. 111, No. 9In-situ, Real-Time Investigation of Organic Thin Film Growth Using Reflectance Difference SpectroscopyLidong Sun and Peter Zeppenfeld1 Jan 2013Optical differential reflectance spectroscopy on thin molecular filmsRoman Forker, Marco Gruenewald and Torsten Fritz1 Jan 2012 | Annual Reports Section "C" (Physical Chemistry), Vol. 108Characterization of Chemical Bonding in Ion-Implanted Polymers by Means of Mid-Infrared ReflectivityVictor G. Ivanov, Georgi Hadjichristov and Eric Faulques1 September 2009 | Applied Spectroscopy, Vol. 63, No. 9Adhesion of growing nanoparticles at a glance: Surface differential reflectivity spectroscopy and grazing incidence small angle x-ray scatteringR. Lazzari, G. Renaud, C. Revenant, J. Jupille and Y. Borensztein24 March 2009 | Physical Review B, Vol. 79, No. 12Optical differential reflectance spectroscopy of ultrathin epitaxial organic filmsRoman Forker and Torsten Fritz1 Jan 2009 | Physical Chemistry Chemical Physics, Vol. 11, No. 13Reflectance-anisotropy spectroscopy and surface differential reflectance spectra at the Si(100) surface: Combined experimental and theoretical studyMaurizia Palummo, Nadine Witkowski, Olivier Pluchery, Rodolfo Del Sole and Yves Borensztein30 January 2009 | Physical Review B, Vol. 79, No. 3Adsorption of Phenylacetylene on Si(100)-2 × 1: Kinetics and Structure of the AdlayerOlivier Pluchery, Romain Coustel, Nadine Witkowski and Yves Borensztein26 October 2006 | The Journal of Physical Chemistry B, Vol. 110, No. 45Investigation of molecule chemisorption on Si(001)2 × 1 surfaces by surface reflectance spectroscopiesO. Pluchery, N. Witkowski and Y. Borensztein1 Nov 2005 | physica status solidi (b), Vol. 242, No. 13Probing the Si-Si Dimer Breaking of Si(100)2×1 Surfaces upon Molecule Adsorption by Optical SpectroscopyY. Borensztein, O. Pluchery and N. Witkowski7 September 2005 | Physical Review Letters, Vol. 95, No. 11In situ differential reflectance spectroscopy of thin crystalline films of PTCDA on different substratesHolger Proehl, Robert Nitsche, Thomas Dienel, Karl Leo and Torsten Fritz22 April 2005 | Physical Review B, Vol. 71, No. 16Optical response of clean and hydrogen-covered vicinal Si(001) 2 × 1 surfacesY Borensztein and N Witkowski21 September 2004 | Journal of Physics: Condensed Matter, Vol. 16, No. 39Apparatus for real time in situ quantitative studies of growing nanoparticles by grazing incidence small angle X-ray scattering and surface differential reflectance spectroscopyG Renaud, M Ducruet, O Ulrich and R Lazzari1 Aug 2004 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Vol. 222, No. 3-4Formation of Solid-State Excitons in Ultrathin Crystalline Films of PTCDA: From Single Molecules to Molecular StacksHolger Proehl, Thomas Dienel, Robert Nitsche and Torsten Fritz25 August 2004 | Physical Review Letters, Vol. 93, No. 9Isotropic and anisotropic optical reflectances of clean and hydrogen‐covered Si(001)2x1 surfacesY. Borensztein, N. Witkowski and S. Royer5 December 2003 | physica status solidi (c), No. 8Direct Kinetic Study of the Reaction of Cl 2•- Radical Anions with Ethanol at the Air−Water InterfaceR. S. Strekowski, R. Remorov and Ch. George20 March 2003 | The Journal of Physical Chemistry A, Vol. 107, No. 14GranFilm: a software for calculating thin-layer dielectric properties and Fresnel coefficientsRémi Lazzari and Ingve Simonsen1 Nov 2002 | Thin Solid Films, Vol. 419, No. 1-2NESSPIOM?Network for enhanced semiconductor surface processing throughin situ optical monitoringMartyn E. Pemble1 January 2001 | Surface and Interface Analysis, Vol. 31, No. 10 Recommended Vol. 07, No. 04 Metrics History Received 5 June 2000 PDF download

In situ reflectance-difference spectroscopy of doped CdTe and ZnTe grown by molecular beam epitaxy

We have used reflectance-difference (RD) spectroscopy (UV-visible energy range) during the growth and doping process of CdTe(001) and ZnTe(001) layers by molecular beam epitaxy (MBE). The MBE chamber is equipped with an electron cyclotron resonance cell to generate N plasma and a ZnCl2 effusion cell for the p- and n-type doping, respectively. After the first stages of the growth and prior doping, different spectral features were found as we changed from Cd or Zn to Te stabilized conditions due to surface anisotropy. However, as the doping of the growing layer further increased, the RD spectra of both surfaces showed resonances around E1 and E1+Δ1 interband transitions due to the linear electro optic (LEO) effect. Although RD spectra exhibit similar line shapes dominated by surface transitions, differences due to the LEO can be isolated. Different Fermi level pinning mechanisms are proposed for both materials because the RD measurements of the LEO strongly depend on surface termination.

Optical Response Spectra Calculation of Wide-Gap ZnSe Surfaces

Reflectance difference spectra of (110) and (001) ZnSe surfaces are calculated using the sp3s* tight-binding method. It is shown that the buckling (1 ×1) and Se-dimer (2 ×1) reconstructions well explain the observation for the (110) and (001) surfaces.

Self-assembled growth of InAs-quantum dots and postgrowth behavior studied by reflectance-difference spectroscopy

Initial stages of self-assembled growth of InAs dots on GaAs(001) and a postgrowth evolution of the deposited surface have been investigated by reflectance-difference (RD) spectroscopy and reflection high-energy electron diffraction (RHEED). A significant change in the RD spectrum occurs even at 0.1-monolayer (ML) deposition of InAs. With increasing InAs deposition, the As-dimer-elated RD sign is inverted, which indicates that the original As dimer along the [110] direction of the c(4×4) As-rich GaAs(001) surface becomes dimerized along the [−110] direction. Postgrowth behavior has been studied at 480°C after 1.9-ML deposition of InAs. During postgrowth, the As-dimer-related RD signal returns to signals observed at lower InAs deposition. This behavior gives evidence that the InAs coverage is reduced by postgrowth. Furthermore, positive offsets that increase in amplitude with photon energy appear in the RD spectra of the postgrown samples.