bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Treatment of the Glass Fibers in Low Pressure Microvave Plasma
Authors: Parosa Ryszard 
Published: March 2011

ABSTRACTIn the method described here, oxygen and air plasmas were generated at pressure of 1 – 10 Torr in quartz tube placed inside various kinds of microwave cavieties. Cavieties were supplied by 10 to 500 W of microwave power / f=2.45 GHz /. Processed fiber was fastly moved across the plasma region by special driving system. Experimentally the optimal process conditions, i.e. treatment time and gas pressure, were found. Moreover, a special construction of a “long” plasma reactor for industrial application of the process was worked out.
Novel Rf-Plasma System for the Synthesis of Ultrafine, Ultrapure Sic and Si3N4
Authors: Vogt Gerald J. , Hollabaugh Charles M. , Hull Donald E. , Newkirk Lawrence R. , Petrovic John J. 
Published: March 2011

ABSTRACTA novel high-temperature plasma tube has been developed that overcomes the meltdown problem of the conventional water- and gas-cooled quartz plasma tubes commonly used. The key feature of this system is the placement of heavywalled, water-cooled copper fingers inside a quartz mantle to shield the mantle from the intense radiation of the plasma. The copper fingers act as transformers to couple the plasma to the applied rf field.This system has been used to produce ultrafine, ultrapure silicon carbide powder by reaction of silane and methane. Powder of β-SiC has been obtained with a BET surface area of >160 m2 /g and a particle size range of 10 to 20 nm as measured by TEM. Likewise, powder of silicon nitride has been synthesized by reaction of silane and ammonia in the plasma. The resulting powder is approximately 50% Si3N4 with a mixture of α- and β-polymorphic forms. Boron carbide has also been successfully synthesized from diborane and methane.
Use of Optical Emission Spectroscopy as a Diagnostic Technique for Plasma Deposition of Hydrogenated Amorphous Silicon and Carbon
Authors: Kampas F. J. 
Published: March 2011

ABSTRACTOptical emission intensities have been measured as a function of composition for silane-argon and silane-hydrogen mixtures used in the deposition of hydrogenated amorphous silicon. It was found that changes in silane fraction have a large effect on the electron concentration and energy distribution in the discharge.
Rapid Solidification by Plasma Deposition
Authors: Apelian D. 
Published: March 2011

ABSTRACTRapid solidification processes (RSP) have been reviewed. The structural refinement one may obtain via RSP and the consolidation methods which need to be utilized have also been reviewed. The merits of low pressure plasma deposition (LPPD) or rapid solidification by plasma deposition (RSPD) as a means of combining both the atomization and consolidation steps of RSP is highlighted. The applications and challenges of RSPD are discussed.
High Concentrations of Erbium In Crystal Silicon by Thermal Or Ion-Beam-Induced Epitaxy of Erbium-Implanted Amorphous Silicon
Authors: Custer J. S. , Polman A. , Snoeks E. , van den Hoven G. N. 
Published: March 2011

ABSTRACTSolid phase epitaxy and ion-beam-induced epitaxial crystallization of Er-doped amorphous Si are used to incorporate high concentrations of Er in crystal Si. During solid phase epitaxy, substantial segregation and trapping of Er is observed, with maximum Er concentrations trapped in single crystal Si of up to 2 × 1020 /cm3. Ion-beam-induced regrowth results in very little segregation, with Er concentrations of more than 5 × 1020 /cm3 achievable. Photoluminescence from the incorporated Er is observed.
Optical Direct and Indirect Excitation of Er3+ Ions In Silicon
Authors: Majima A. , Uekusa S. , Ootake K. , Abe K. , Kumagai M. 
Published: March 2011

ABSTRACTOptical direct and indirect excitation of erbium (Er) ions in silicon substrates was performed in order to investigate the high efficiency of Er3+− related 1.54µm emission (4I13/2→4I15/2) for direct excitation that is not concerned with the indirect band gap and low quantum efficiency of a Si host. The samples were prepared by ion-implantation or thermal diffusion methods. In each sample, photoluminescence (PL) showed the peaks originating from 4I13/2→4I15/2 of Er3+ ions.In Er thermally diffused samples, optical excitation for energy level 4I11/2 of Er3+ ions was successfully effected by photoluminescence excitation spectroscopy (PLE). The PLE spectra consisted six peaks (963. lnm, 965.Onm, 976.lnm, 978.9nm and 980.9nm) which were caused by direct excitation (4I15/2→4I11/2) of Er3+ ions. The emission directly excited is about 2 times more intense than the indirectly excited emission. The six peaks originating from the splitting of the 4I11/2 levels meant that Er3+ ions were in the sites of noncubic symmetry. The samples prepared by Er ion-implantation did not show the effect.
Effect of The Er3+ Concentration On The Luminescence of Ca1−xErxF2+x Thin Films Epitaxially Grown On Si(100)
Authors: Barriere A.S. , Raoux S. , Favennec P.N. , L'haridon H. , Moutonnet D. 
Published: March 2011

ABSTRACTCa1−xErxF2+x thin films, with a substitution rate, x, varying from 1 to 20%, were deposited on Si(100) substrates by sublimation of high purity solid solution powders under ultra-high-vacuum. Rutherford backscattering studies have shown that the films have the composition of the initial solid solution powders, are quite homogeneous and are epitaxially grown on the substrates.The optical properties of these films were studied by means of cathodoluminescence and photoluminescence. At room temperature, the emissions due to the de-excitations from the 4S3/2, 4F9/2, 4I11/2 and 4I13/2 excited levels to the 4I15/2 ground state of Er 3+ (4f11) ions are easily detected (λ = 0.548, 0.66, 0.98 and 1.53 µm)The strong 1.53 µm infrared luminescence, which presents evident potential applications for optical communications, is maximum for an erbium substitution rate included between 15 and 17%. These Er concentrations are three or four orders of magnitude greater than the optimum ones in the case of Er-doped semiconductors, which are close to 1018 cm−3.In the visible range, the luminescences are also important.They allow us to detect high energy ion or electron beams. However their maximum efficiencies were observed for a relatively low erbium concentration, close to 1%. These different behaviours are explained by the cross relaxation phenomena, which depopulate the higher levels to the benefit of the 4I13/2→ 4I15/2 transition. The energy distribution of the Stark sublevels of the 4I15/2 state, which results from crystal field splitting, was deduced from a photoluminescence study at 2K. The obtained results show that the environment of the luminescent centres does not change with the erbium concentration.At last, it must be noted that the refractive index of the layers increases with the erbium concentration, leading to the realization of optical guides. Consequently opto-electronic components could be developed from such erbium doped heterostructures.
Luminescence Study of The INTRA-4f Emissions from GaAs:(Er+O) and AlxGal1−xAs:(Er+O)
Authors: Colon Jose E. , Elsaesser David W. , Yeo Yung Kee , Hengehold Robert L. , Pomrenke Gernot S. 
Published: March 2011

ABSTRACTA systematic photoluminescence study of erbium and oxygen co-implantation into GaAs and AlxGal1−xAs with × = 0.1, 0.2, 0.3, and 0.4 was carried out. The addition of oxygen greatly enhanced the Er emission intensity from AlxGal1−xAs:Er while the O and Er co-doping into GaAs rather made the Er emission intensity decrease from that of the GaAs:Er. The Er emission intensity from AlxGal1−xAs:(Er+O) generally increases with increasing Al mole fraction and O dose up to 1 × 10 15/cm2, but it does not depend much on the substrate conductivity.
Lattice Location and Photoluminescence of Er in GaAs and Al0.5Ga0.5As
Authors: Alves E. , Da Silva M.F. , Melo A. A. , Soares J.C. , Van Den Hoven G.N. , Polman A. , Evans K.R. , Jones C.R. 
Published: March 2011

ABSTRACTEpitaxial Er-doped GaAs and Al0.5Ga0.5As films, 1.6 μm thick, grown by MBE on (100) GaAs substrates at 560°C, with Er concentrations in the range 9 × 1017 to 2 × 1020 cm−3 were studied with RBS/channeling and photoluminescence techniques. Angular scans in the <110> and <111> axial and (111) planar directions indicate that the Er atoms in GaAs are located on interstitial sites. In Al0.5Ga0.5As doped with 5 × 1019 Er cm−3, 70% of the Er atoms are on positions slightly displaced from the interstitial site, the rest presumably substitutional. In Al0.5Ga0.5As doped with 9 × 19 Er cm−3, more than 88% of the Er atoms are on substitutional sites.Photoluminescence around 1.54 μm is observed at room-temperature in Er-doped Al0.5Ga0.5As. Both the low and highly Er-doped samples show similar luminescence intensities; the luminescence lifetimes are on the order of 1 ms. The Er-doped GaAs does not show any measurable signal at room-temperature. Correlation of the luminescence data to the Er lattice location suggests that only substitutional Er in AlGaAs is in the luminescent trivalent state.
Optical Activation of Ion Implanted Rare-Earths
Authors: Favennec P.N. , L'haridon H. , Moutonnet D. , Salvi M. , Gauneau M. 
Published: March 2011

ABSTRACTA review of the main results concerning the ion implantation of the rare-earth elements is given.To obtain the best optical activation of rare-earths, we attempt to optimize the implantation (energy, dose) and annealing (temperature, duration) conditions. The studied materials are Si, II-VI binaries (ZnTe, CdS), III-V binaries (GaAs, InP), III-V ternaries (GaAlAs, GaInAs) and III-V quaternaries (GaInAsP).
Preparation and Properties of Gallium Phosphide Doped by Rare-Earth Elements
Authors: Pyshkin Sergei L. , Anedda Alberto 
Published: March 2011

ABSTRACTGaP single crystals have been grown from 5at.% solution of P in Ga with (0.01-0.1)at.% of La, Sm or Gd as dopants. Electric properties, photoconductivity and luminescence of the crystals have been investigated by standard methods.Energy levels of impurities, mobility and concentration of current carriers have been determined in wide temperature region. It was shown that nitrogen (N) and other uncontrolled impurities present in the crystals due to some peculiarities of crystal growth. The intrinsic RE impurity luminescent spectra can be seen only together with spectra of excitons bounded on N traps. The evaluation of quantum eficiency for RE impurity made on the base of luminescence decay measurements gives the value close to 1. The interpretation of GaP:RE luminescence spectra is presented as intrashell transitions activated by bound exciton recombination as well as D-A and D-valency band transitions between some contaminating impurity (donor) and RE element (acceptor).
Mocvd Erbium Sources
Authors: Greenwald Anton C. , Rees William S. , Lay Uwe W. 
Published: March 2011

ABSTRACTThe overall objective of this research is to develop source materials for doping AIGaAs. We compared Er(C5H5)3 to Er{N[Si(CH3)3]2)3 for purity, decomposition kinetics and doping of germanium films deposited from Ge(CH3)4 in a hydrogen atmosphere. Cyclopentadienyl erbium left large amounts of carbon both in pure metal films, and in the germanium film, at low pressure and temperatures to 850°C. Bis-(tri-methylsilyl) erbium amide decomposed cleanly without carbon, nitrogen or silicon in the deposited film.
Esr of Rare Earth Impurities (Dy3+, Er3+, Yb3+) in The Narrow Gap Semiconductor PbTE.
Authors: Gennaro A.M. , Martins G.B. , Rettori C. , Barberis G.E. , An C.Y. 
Published: March 2011

ABSTRACTElectron Spin Resonance experiments of several diluted rare-earths (Dy3+, Er3+, Yb3+) in the narrow gap semiconductor PbTe show ground states appropriated with a cubic crystal field splitting of the lowest multiplet (J). The data permits the determination of the sign and ratio of the cubic crystal field parameters A4 <r4>and A6< r6 >. These results suggest that the rare-earths substitute the Pb2+ ions and that the crystal field is mainly associated to an octahedron of Te2− ions. The observed ESR spectra also show lower symmetry sites probably associated with nearest neighbor Pb2+ vacancies.
Tie Effect of Rare-Earth Elements on the Entroy of Radiation Defects Ionization in N-Type Go
Authors: Petrov V.V. , Kharohenko T.D. , Yavid V.Yu. 
Published: March 2011

ABSTRACTTe analyses of the processes of radiation defect formation in germanium doped with phosphorus in the presence of rare-earth element neodimium and without it has been carried out.It has been shown that the presence of neodimium in n-Ge results in the change of enthalpy and entropy of the major radiation defect ionization (complex with the level being near EB-0.20 eV). The change of enthalpy by 0.03-0.04 eV as well as more than six fold increase of entropy of the complex ionization in Ge:Nd has been stated to be connected with the local deformation of the lattice around defect formed in the process of irradiation.
Annealing Studies of Er-Implanted GaAs and the Excitation Mechanism of Er in GaAs
Authors: Elsaesser D. W. , Colon J. E. , Yeo Y. K. , Hengehold R. L. , Pomrenke G. S. 
Published: March 2011

ABSTRACTElectrical and optical measurements were performed on p-type GaAs implanted with 1013 Er ions/cm2 at an energy of 1 MeV. The samples were annealed at 650, 750, 850, or 900 °C for 15 seconds using the rapid thermal annealing technique. Although annealing at 650 °C was insufficient to recover measureable electrical conductivity in the implanted region, Er3+ 4f-4f emissions were still observed. Annealing at 750 TC produced a large concentration of hole traps at EV + 360 meV, and the most intense Er-related emissions at 1.54 μm. The two higher annealing temperatures returned the implanted region to the conductivity of the substrate but resulted in weak Er-related emissions. Two distinct Er-related centers were found, and they are believed to be the cause of the intense and weak emissions, an Er-interstitial and Er substituting for Ga, respectively.
Photoluminescence Study of Energy Transfer Processes in Erbium Doped AlxGal−xAs Grown by MBE
Authors: Zhang Tong , Sun J. , Edwards N.V. , Moxey D.E. , Kolbas R.M. , Caldwell P.J. 
Published: March 2011

ABSTRACTSharp photoluminescence from the intra-4f shell of Er3+ is observed from erbium doped AlxGal-xAs (0 ≤x ≤ 1) grown by molecular beam epitaxy. The intensity of the luminescence from the erbium is strongly dependent on the aluminum composition with a maximum at x ≈ 0.6. We will present a model that explains the variation in intensity based on the energy transfer coupling efficiency between the host semiconductor and the optically active erbium ions. The coupling efficiency is dominated by the alignment or misalignment of the erbium energy levels with the energy bands of the host semiconductor and by the excess carrier lifetime in the host. The data and model, which are presented here for the first time, are consistent with our previous work on the effects of co-doping with Be or Si and with other workers' measurements of thermal quenching in rare earth doped semiconductors.
Luminescence Properties of Yb- and Nd- Implanted CdS
Authors: Alshawa A. K. , Lozykowski H. J. , Li T. , Brown I. 
Published: March 2011

ABSTRACTThe photoluminescence (PL) and time resolved spectra of Nd- and Yb-implanted CdS samples are studied under pulsed and CW excitations using Ar+ ion laser for different excitation intensities and temperature (9 - 300 K). The samples were annealed under different conditions using the thermal-pulse method. For CdS:Nd, the PL spectra was recorded in the range 890-930 nm (transitions 4F3/2→4I9/2) and for CdS:Yb it was recorded in the range 985 - 1010 nm (transitions 2F5/2 →2F7/2). The Rise time and decay time were studied for both CdS:Nd and CdS:Yb at different emission lines as a function of temperature and excitation power.
Electrically Pumped Rare Earth Doped Semiconductor Lasers
Authors: Pankove Jacques I. , Feuerstein Robert J. 
Published: March 2011

ABSTRACTThe interest in rare earth (RE) elements as luminescent centers is due to the narrowness and stability of the luminescent transitions. In this paper we review the mechanisms that can be used to electrically excite rare earth impurities in semiconductors: pair recombination energy exchange and impact excitation. The different means of providing energetic electrons for impact excitation are also discussed. We also propose a possible explanation for the temperature dependence of photoluminescence in silicon.
Novel Electronics Enabled by Rare Earth Arsenides Buried in III-V Semiconductors
Authors: Allen S. James , Brehmer Dan , PalmstrØm C.J. 
Published: March 2011

ABSTRACTHeterostructures consisting of III-V semiconductors and epitaxial layers of the rare earth monoarsenides can be grown by molecular beam epitaxy. By alloying ErAs with ScAs, lattice match can be achieved with (Al,Ga)As. Using magneto-transport measurements, we show that these layers are semi-metallic with equal electron and hole concentrations, 3.0 ×1020 cm−3. Shubnikov-de Haas oscillations are used to confirm the predicted Fermi surface geometry and measure the electron effective mass and the coupling to the 4f spin on the Er3+ ion. Remarkably, the material shows no transition from semimetal to semiconductor as the film thickness is reduced to three monolayers. Below three monolayers the films are not uniform and are believed to consist of islands three monolayers high.This system provides a unique opportunity to explore novel electronics based on controlled transport through semimetal/semiconductor heterostructures. Lateral transport through semimetal islands immersed in a δ-doped layer may provide a fast non-linear material for THz electronics. Vertical transport through thin epitaxial layers may enable resonant tunneling hot electron transistors with a semi-metal base. Preliminary experiments on transistor like test structures measure some transfer through a 10 monolayer thick semimetal base. They also identify overgrowth of the III-V semiconductor on the semimetal layer as the key materials issue.
Study of Srl−xErxF2+x Luminescent Thin Films Epitaxially Grown on InP (100).
Authors: Barriere A.S. , Mombelli B. , Kim B.Y. , Raoux S. , Garcia A. 
Published: March 2011

ABSTRACTErbium-substituted Srl-xErxF2+x strontium fluoride layers were grown on InP(100) substrates by sublimation under ultra-high vacuum of high purity solid solution powders.Their composition and the spatial distribution of the basic components were deduced from Rutherford backscattering (RBS), using a nuclear microprobe, and secondary ion mass spectrometry (SIMS). For x lower than 20% it is shown that the film composition is analogous with the initial sintered material and quite homogeneous. The ageing in air of the films was followed by infrared absorption studies. No significant water adsorption was revealed.The texture of the layers was studied by RBS in channelling condition. For x as high as 15% it is shown that the films are well crystallized and well epitaxially grown on InP (100) substrates.Infrared emission due to the 4I13/2-4I15/2 electronic transition on the 4f11 inner shells of Er3+ ions (1.53μm), which presents potential applications for optical communications, was studied at room temperature as a function of x. It is demonstrated that the highest luminescence efficiency of these layers corresponds to x upper than 20%.
Optical and Structural Properties of CaF2:Nd Films on Si-Based Substrates
Authors: Cho C.-C. , Duncan W.M. , Liu H.-Y. 
Published: March 2011

ABSTRACTBy thermally evaporating CaF2 and NdF3, we have grown Nd-doped CaF2 films on Si(111), A1/Si(111) and quarter-wavelength Ta2O5/SiO2 multilayer Bragg reflectors. The optical and structural properties of the CaF2:Nd films are characterized by photoluminescence spectroscopy (PL) and x-ray diffraction. The effects of different Nd concentration, growth temperatures and post-annealing were studied. Regardless of the substrates, the as-grown films show emission lines at wavelengths similar to bulk CaF2:Nd. Annealing the films at 700°C in forming gas results in a new emission pattern. Little difference between the PL spectra of polycrystalline and single crystal CaF2:Nd films is observed, indicating that the luminescence efficiency is insensitive to the crystalline quality of the films.
Mbe Growth of Rare-Earth Doped Fluoride Insulators on Semiconductors for Laser Applications
Authors: Lui M. , Mcfarlane R.A. , Yap D. 
Published: March 2011

ABSTRACTWith the recent success of using rare-earth doped fluoride crystals as high power visible upconversion lasers, we have explored the use of MBE grown fluoride layers for a possible waveguide laser. By confining the pumped light in a waveguide with dimensions on the order of a few micron, the pump power density will increase promoting higher efficiencies at room temperatures. Initially, we have grown planar waveguides of erbium doped ZnF2 on MgF2 substrates using molecular beam epitaxy and have formed channel waveguides by ion milling. By exciting individual channels with an 800 nm pump, we have generated strong upconversion fluorescence at 410 nm, 550 nm and 670 nm and at numerous weaker peaks. The fabrication techniques can be adapted to semiconductor substrates for making compact diode-pumped visible and infrared lasers. A number of fluoride materials that are useful as laser host crystals are lattice matched to GaAs (100) and GaAs (111) offering the possibility of integrating the channel waveguide laser with the semiconductor diode laser pump source. For example SrF2 may be grown on GaAs (100) as a cladding layer followed by PbF2 doped with a rare-earth ion. Also LaF3 may be grown on GaAs (111) followed by CeF3 doped with a rare-earth ion. Both PbF2 and CeF3 have low phonon energies and a higher index of refraction than their respective lattice matched cladding layers and should be capable of provide an attractive upconversion laser waveguide system. Our initial upconversion luminescence results on erbium doped PbF2 on GaAs (100) using a intervening SrF2 cladding layer are also reported.
Er-Doped GaAs for High Speed Photoconductor Applications
Authors: Gupta S. , Sethi S. , Bhattacharya P. K. , Williamson S. 
Published: March 2011

ABSTRACTThe observation of 1.54 μm luminescence in erbium-doped-GaAs (GaAs:Er) and AlxGal-xAs, has stimulated research efforts because of their potential application to light sources in optical communications. In this paper, we study a different aspect of the photoresponse behavior of this material. The dependence of the carrier lifetime on the doping concentration of Erbium is investigated in GaAs:Er grown by MBE. A reduction in the carrier lifetime down to ∼1 ps is observed for the highest doping (∼5×1019 cm−3) investigated. Together with the high-resistivity observed for the higher doping values, this material serves as a novel photoconductor material for high-speed optoelectronics.
Effects of Microstructure on Photoluminescence of SrS:Eu2+,SM3+ thin Films
Authors: Hua Susan Z. , Salamanca-Riba L. , Wuttig M. , Soltani P. K. 
Published: March 2011

ABSTRACTThe microstructure and its effects on the photoluminescence properties of SrS:Eu2+,Sm3+ thin films grown with different conditions were studied by transmission electron microscopy, x-ray diffraction and photoluminescence techniques. The SrS:Eu2+,Sm3+ thin films were prepared by e-beam evaporation at different substrate temperatures and growth rates. Both of these growth conditions affect the crystallinity of the thin films. The Sm3+ emission is stronger in the films grown at higher growth rates and at an optimum substrate temperature. We believe that the stronger Sm3+ emission is due to the higher population of Sm trivalent charge states in the films. Further increase of the substrate temperature increases the grain size in the films, but has no significant effect on the PL emission properties. In contrast, the Eu2+ emission is less sensitive to growth conditions.