bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxy of SimGen Atomic Layer Superlattices
Authors: Baribeau J.-M. , Lockwood DJ. , Rowell N.L. , Dharma-Wardana M.W.C. , Houghton D.C. , Kechang Song
Published: March 2011

We report the MBE growth of various (SimGen)p atomic layer superlattices (ALS) and their characterization by Raman scattering spectroscopy, x-ray diffraction and photoluminescence. The structural properties of ALS prepared on (100) Si, (100) Ge and on various Si1-xGex (0.5<×<1) buffers were compared. Phonon peaks due to folding of acoustic modes were seen by Raman scattering spectroscopy in the frequency range 15-250 cm-1. The observed Raman spectra from the ALS were interpreted on the basis of a theoretical analysis of these systems. The study provided an estimation of the interfacial sharpness of the ALS. The photoluminescence investigation on annealed specimens revealed features between 800 and 900 meV that were ascribed to known dislocation lines in Si. No strong luminescent signal that could be unambiguously related to a direct bandgap behavior was detected.
Effects of Different CH4-H2 Gas Compositions on the Morphology and Growth of Diamond Grown by Hot Filament CVD
Authors: Farabaugh Edward N. , Feldman Albert
Published: March 2011

Diamond films have been grown on single crystal Si and polycrystalline mullite substrates by hot filament chemical vapor deposition. Both substrates offer a good thermal expansion match with diamond. Gas mixture ratios of CH4 :H2 ranged from 0.1–1.0%. The remaining deposition parameters were: substrate temperature, 750°C; filament temperature, 1800°C; gas pressure, 5×103 Pa; gas flow rate, 52 seem except for the 0.1% CH4 :H2 ratio deposition in which the flow rate was 120 seem. Film thicknesses were determined from cross sectional SEM micrographs. The average growth rates on the mullite increased nearly linearly with increasing CH4 gas fraction, ranging from 0.05 μm/hr to 0.21 μm/hr. Growth rates on the Si substrates were slightly lower for identical growth conditions. Surface SEM micrographs revealed that the roughness of the films decreased with increasing CH4 gas fraction during deposition. X-ray diffraction patterns showed that crystalline grain size in the films decreased with increasing CH4 gas fraction. No preferred crystallographic orientation was seen in the diffraction patterns. Isolated particles were also grown on Si substrates under the same deposition conditions as the film growth. As the CH4 gas fraction increased, the particle growth displayed increasing rates of secondary particle nucleation resulting in a less well faceted morphology.
Application of a Thermobalance for studying Deposition kinetics of Diamond Films
Authors: Czarnecki Jerry , Thumim David
Published: March 2011

Weight recording using a thermobalance type Cahn TG-171 has been applied to study Hot, Filament Enhanced Chemical Vapor Deposition (HFCVD) of carbon films from methane. Changes in the deposition rates during each individual process may indicate four stages of the deposition kinetics: 1- generation of nuclei (slow, linear); 2- growth on nuclei (exponential increase); 3- aggregation of crystals (slowing); 4- growth on the surface of diamond film, completely covering the substrate (linear). An attempt to determine the concentration of graphite in the deposited layer, based on differences in oxidation rates of diamond and graphite has been proposed, as supplementary to X-ray diffraction and Raman spectroscopy.
Investigations of Excimer Laser Effects on CVD Diamond Growth
Authors: Pehrsson Pehr E. , Nelson H. H. , Celii F. G.
Published: March 2011

We investigated UV laser irradiation as a method to modify the surface and gas phase chemistry in a diamond growth apparatus. In particular, attempts were made to reproduce reported laser-enhanced deposition. The variables included the laser wavelength and intensity, the precursor gas (and hence the gas-phase absorption), the flow rate, and the gas inlet orientation with respect to the filament. The samples were analyzed using optical microscopy, Scanning Electron Microscopy, the Scanning Auger Microprobe, and micro-Raman scattering. In all cases, the laser radiation suppressed or had no effect on diamond deposition in comparison to the adjacent unirradiated regions. The crystals that did grow in the irradiated regions were similar in size and morphology to those from the unirradiated areas, suggesting ablation or nucleation site blockage as possible deposition suppression mechanisms. The results suggest a novel method for diamond film patterning.
Regrowth of Damaged Layers in Diamond Produced by Ion Implantation
Authors: Sandhu G. S. , Liu B. , Parikh N. R. , Hunn J. D. , Swanson M. L. , Wichert Th. , Deicher M. , Skudlik H. , Lennard W. N. , Mitchell I. V.
Published: March 2011

We have used RBS/Channeling, perturbed angular correlation (PAC) and optical absorption to study the regrowth of disordered layers in diamond produced by implantation with carbon, or with carbon plus boron or indium ions. For C or C plus B implantation doses of 2 ×1015 cm−2 or less, complete recovery of channeling damage occurred after RTA at 1100°C or furnace annealing at 900°C. Optical measurements on samples implanted with high energy carbon ions show better recovery compared to the shallower implantations. PAC results showed that co-implantation with C and In caused a considerable fraction (∼15%) of the In-atoms to occupy well-defined lattice sites characterized by an electric field gradient having its major component along <111>, and a frequency of 116 MHz.
Selective Nucleation of Single Crystal CVD Diamond and its Applicability to Semiconductor Devices
Authors: Kawarada H. , MA J. S. , Yonehara T. , Hiraki A.
Published: March 2011

Using selective nucleation at edges or corners of μ m-size dots of Si, periodically arrayed diamond particles have been reproducibly fabricated. The particles are grown from single nuclei and have nearly-single crystal features. The properties of the diamond arrays compared with polycrystalline films have been investigated using cathodoluminescence and Schottky diodes.
Domain Size Determination in Diamond Thin Films
Authors: LeGrice Y. M. , Nemanich R. J. , Glass J. T. , Lee Y. H. , Rudder R. A , Markunas R. J.
Published: March 2011

In this study we develop a method which utilizes the linewidth of the diamond peak at 1332 cm−1 to determine the diamond domain sizes. We have carried out calculations based on the phonon dispersion curves of diamond and the breakdown of wavevector selection rules in Raman scattering. The linewidths of a series of diamond samples were calculated, and from this theory the dimensions of the diamond regions were obtained. The calculated domain sizes ranged from 57 to 100Å and were compared to values obtained from SEM micrographs which were between 5000 and 25000Å. This is consistent with other results which have found that domain sizes calculated from this theory are in general consistent with sizes determined from electrical conductivity measurements, not from microscopy techniques. In addition, this theory allows for the calculation of the amount of frequency shift due to microcrystallinity, so that the residual stress in the film can be found.
Characterisation of Thin Film and Single-Crystal CVD Diamond by Absorption and Luminescence Spectroscopy
Authors: Collins A. T. , Kamo M. , Sato Y.
Published: March 2011

Polycrystalline films and single crystals of diamond produced by microwaveassisted chemical vapour deposition (CVD) have been examined using absorption and cathodoluminescence spectroscopy. Measurements have been carried out on material as-grown, and after radiation damage by 2 MeV electrons.
CW Four-Wave Mixing in Synthetic Diamond
Authors: Redman D. A. , Rand S. C.
Published: March 2011

We report efficient CW optical phase conjugation and resonantly enhanced four-wave mixing spectroscopy of the N-V color center in synthetic diamond. An ultra-narrow resonance is observed in the room temperature nearly degenerate four-wave mixing spectrum upon excitation within the vibronic band at 579 nm, furnishing the triplet manifold decay rate.
Characterization of Heavy Metal Contamination in Diamond Films Using Sims, Txrf, and RBS
Authors: Hockett R. S. , Knowles James
Published: March 2011

Intentionally contaminated DC and microwave plasma deposited diamond films were used to evaluate the characterization capability of SIMS, TXRF and RBS for heavy metal measurements. The results showed SIMS is the preferred analytical technique for heavy metal impurities in the diamond films, and TXRF for the top surface analysis of the substrate and pre-processed substrate. In addition TXRF may provide a quick, non-destructive qualitative characterization of the diamond film surface and bulk. The RBS can provide qualitative and quantitative information if the impurity levels are high enough (above 1013 atoms/cm2).
Far-Infrared Spectroscopic Study of Diamond Films
Authors: Gatesman A. J. , Giles R. H. , Phillips G. C. , Waldman J. , Bourget L. P. , Post R.
Published: March 2011

High quality polycrystalline diamond films grown on Si substrates by microwave plasma enhanced chemical vapor deposition were characterized in a far-infrared spectroscopic study. The spectroscopic transmissivity data were used to derive a model for the complex refractive index (n – ik) as a function of wavelength in the 10 to 200 cm−1 frequency regime. Similar transmissivity and reflectivity data from samples of varying thickness were used to validate this model. The continuum of measured transmissivity and reflectivity data from 10 to 200 cm−1 were shown to be in excellent agreement with the values calculated from the refractive index model. The films were shown to have low loss in this frequency regime.
Deep Level Transient Spectroscopy Study of Thin Film Diamond
Authors: Srikanth K. , Ashok S. , Zhu W. , Badzian A. , Messier R.
Published: March 2011

We have demonstrated the applicability of DLTS to semiconducting diamond thin films. This paper includes details on the capacitance-voltage measurements, the DLTS spectrum and the DLTS spectra as a function of bias. Our study was done with an aluminum Schottky contact on polycrystalline diamond film. We found a strong temperature dependence of the Schottky diode capacitance with a reduction of effective dopant concentration from 4 × 1014 cm−3 at 300K to 2 × 1014 cm−3 at 200K. The DLTS signal had a good signal to noise ratio, characteristic line-shape and clear peaks. The trap concentration was 8 × 1013 cm−3 (at 400/s rate window) with an activation energy of 0.31 eV and a capture cross section of 1.15 × 10−18 cm−2. The spectra showed a bias dependence of peak height and position.
N-Type Doping and Diffusion of Impurities in Diamond
Authors: Kajihara S. A. , Antonelli A. , Bernholc J.
Published: March 2011

First-principles calculations were used to study Li, Na, and P as prospective shallow donors in diamond. As expected, P prefers the substitutional site while Li and Na are interstitial donors. All three impurities were found to be shallow. However, their solubilities are very low, which makes them unsuitable for incorporation into diamond via in-diffusion. Instead, kinetic trapping during growth or ion implantation must be used. Interstitial impurities are particularly appropriate for ion implantation, since there is no need to replace host atoms. Considering the stability of the impurity at the dopant site, substitutional P is expected to diffuse by the vacancy mechanism and to have a high activation energy by analogy to self-diffusion. For Li and Na, the activation energies for interstitial channel diffusion are 0.85 and 1.6 eV, respectively. Li is thus a fast diffuser even at room temperature, while Na would remain stable up to moderate temperatures.
Electrical Behavior of Diffused Impurities in Diamond Single Crystals
Authors: Narducci Dario , Cuomo Jerome J.
Published: March 2011

The dependence of the electrical properties on the evolving doping profile during diffusion processes was studied, as well as the role of the vacancies in determining the electrical properties of diamonds. To this aim, B was deposited on diamond single-crystal by physical vapor deposition. The element was then thermally diffused into diamond at 800°C under helium atmosphere. The deposited layer was finally removed and subsequent annealing cycles were carried out. The diffusion profiles were tracked by Nuclear Analysis Techniques. For comparison, the same element was implanted in diamonds at 70 K and at room temperature. Electrical contacts of different metals were deposited on diamond and the current-voltage and the capacity-voltage characteristics were measured. A comparative analysis of the electrical behavior of implanted and diffused samples was carried out, which elucidated the electronic activity of point defects in diamond.
Low Temperature Metal Organic Chemical Vapor Deposition (LTMOCVD) of Electronic Materials
Authors: Kaloyeros Alain E. , Toscano Paul J. , Rizk Richard B. , Tulchinsky Victor , Greene Alex
Published: March 2011

High quality amorphous and crystalline silicon carbide thin films were produced by low temperature metal-organic chemical vapor deposition (LTMOCVD) using the organometallic precursor tetraethynylsilane, Si(C2 H)4. LTMOCVD, which was developed by the present investigators, uses single source precursors containing all the elemental constituents desired in the target material already directly bonded. This approach eliminates the inherent limitations of conventional MOCVD where separate precursors are used for each of the individual components of the desired compound. LTMOCVD thus combines the ability to deposit films at low temperatures, which is characteristic of physical deposition techniques, with the ability to provide complete coverage at steps or irregularities on the semiconductor surface, which is characteristic of chemical deposition techniques. In addition, the precursors employed are non-toxic, non-hazardous and easy to handle. Consequently, LTMOCVD can produce compound semiconductors on thermally fragile or chemically sensitive substrates. The SiC films were grown in a hot-wall CVD reactor at a reactor pressure of 10−6-10−3 torr and substrate temperature in the range 300–700°C. Characterization studies were performed using electron diffraction (ED), Auger electron spectroscopy (AES), Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The results of these studies showed that the films were uniform, continuous, adherent and highly pure– contaminant levels were below the detection limits of the techniques employed.
Doped Amorphous SiC, Mixed Carbide and Oxycarbide Thin Films by a Liquid Route
Authors: Chu C-J , Liimatta E. , Mackenzie J. D.
Published: March 2011

A new family of disordered materials called amorphous covalent ceramics (ACC) has been obtained by pyrolysis of metal-organic polymers. The transformation from polycarbosilane to amorphous and microcrystalline SiC has been studied. New a-SiC:H thin films have also been prepared by the polymer solution. Electrical and optical properties of this new a-SiC have studied. Amorphous binary carbide and oxycarbide have also been prepared by crosslinking polycarbosilane and metal alkoxides. The p-n control of this new a-SiC:H has been achieved, which also lead to the possible device applications.
Growth of Epitaxical SiC Layers onto on and off Axis 6H SiC Substrates by Ion Beam Deposition
Authors: More K. L. , Withrow S. P. , Haynes T. E. , Zuhr R. A.
Published: March 2011

Thin films of β SiC have been grown epitaxically onto on axis (0001) 6H α SiC substrates using ion beam deposition. The ion beam deposition technique involves the direct deposition of alternating layers of 13C+ and 30Si+. The carbon and silicon ions were obtained from an ion implanter by decelerating mass analyzed ion beams to 40 eV. The SiC substrate was held at ∼973 K. Thin films of α-SiC (a mixture of α- polytypes) were obtained following deposition onto off axis (∼2°) 6H α-SiC. High resolution electron microscopy and Rutherford backscattering techniques were used to determine the structure and crystalline perfection of the resulting layers.
Sem Observation of Growth and Defect Formation of Heteroepitaxially grown sic on (100) Silicon
Authors: Molnar B. , Shirey L. M.
Published: March 2011

Single crystal, cubic SiC films used in this study were grown by a two step CVD process on (100) oriented silicon substrates. The two surfaces of such grown SiC films are different. The SiC surface at the Si/SiC interface is more conductive than the SiC/air surface. This Si/SiC surface appears smooth under optical microscopy, but Scanning Electron Microscopy (SEM) reveals characteristic “growth features” on it. Each growth feature protrudes from the smooth SiC surface, and most often it either fills or borders the rectangular shallow pyramids present on the (100) Si surfaces. Plasma etching of the SiC at the Si/SiC interface creates cavities with vertical boundaries. Some of the cavities have been traced to the original location of some growth features.
Cubic Boron Nitride Crystals Grown at High Pressure: PN Junction, Crystallographic Polarity and Some Properties
Authors: Mishima Osamu
Published: March 2011

Studies on the cubic boron nitride (cBN) crystals grown by the temperature difference method at high pressure are reviewed. The electron beam induced current measurement, the electrical measurement, and the optical measurement demonstrated that the cBN is a good potential candidate as a wide-gap semiconductor material. The Raman spectrum and the reflectance and transmittance spectra of the cBN were obtained. The crys-tallographic polarity of cBN crystals was directly determined from the Rutherford backscattering spectroscopy (RBS).

The RBS experiment showed that the (111) surface which adjoins to the (100) surface at an obtuse angle so that the edge between the (111) and the (100) is parallel to the <110> direction of striations on the (100) face is a triply bonded nitrogen-terminating face. The result seems to disagree with that derived from other semiconductor compounds.
Boron Phosphide as a Refractory Semiconductor
Authors: Kumashiro Y. , Hirabayashi M. , Takagi S.
Published: March 2011

The crystal growth, characterization and various characteristics such as electrical, thermal and semiconducting properties of boron phosphide (BP) single crystalline wafers made by chemical vapor deposition technique are summrized. It is demonstrated that Schottky diode using single crystal and thermoelectric device employing sintered polycrystal are promising application for electronic materials.
In-Situ Synthesis and Magnetically Stabilized Kyropoulos Growth of Undoped Indium Phosphide
Authors: Bachowski Stephen , Ahern Brian S. , Hilton Robert M. , Adamski Joseph A.
Published: March 2011

The Kyropoulos growth technique has been combined with in-situ synthesis to yield high purity undoped crystals of 300 to 700 gm charges of InP. Etched wafers show a uniform dislocation density across 70mm diameter in contrast with the "W" pattern created by LEC. Use of an axial magnetic field in Kyropoulos growth reduces the dislocation density by an order of magnitude, to 1 × 104cm-2. By combining Kyropoulos growth with in-situ synthesis of the indium phosphide, high mobility (4.6×104 at 77 C) undoped single crystals have been obtained.
Electrical Properties of Heavily Be-doped GaAs grown by Molecular Beam Epitaxy
Authors: Shibata H. , Makita Y. , Yamada A. , Ohnishi N. , Mori M. , Nakayama Y. , Beye A. C. , Mayer K. M. , Takahashi T. , Sugiyama Y. , Tacano M. , Ishituka K. , Matsumori T.
Published: March 2011

Electrical properties of heavily Be-doped GaAs grown by molecular beam epitaxy were investigated systematically in a wide range of Be-concentration from 1× 1014 up to 2× 1020 cm-3 by using yan der Pauw technique. Probable carrier scattering mechanisms observed in this work are discussed by taking into account the radiative mechanisms of several new photoluminescence emissions previously observed in the band-edge-emission region of the samples. All samples were checked their electrical properties first at room-temperature. Five selected samples out of them were measured from 10° K up to room-temperature. Samples having the carrier concentration from 1014 to 1018 cm3 presented typical semiconductor-like conduction with finite carrier excitation energy. For samples having carrier concentration 7× 1016 cm -3, the conduction mechanism at high temperature region above 30β K was dominated by holes thermally excited into valence band. At low temperature region below 30° K . it was dominated by holes hopping from neutral to ionized acceptors with the assistance of phonons. Hole mobilities of samples having the carrier concentration from 1017 to 1018 cm-3 showed an anomalous behavior in the low temperature region, which suggests the presence of a new type of carrier scattering mechanism. A radiative center denoted by lg-gl observed in this concentration region will be a candidate scattering center to explain these electrical behaviors. Samples having the carrier concentration larger than 1019 cm-3 demonstrated typically metallic electric conduction not owing to thermally excited carriers, which means that an impurity band is formed but merged with valence band. The density of state of this combined valence band mixed with impurity band can be supposed to reflect carrier concentration dependence of the PL emission bands observed in this region, i.e. [g-g]α , [g-g]β and [g-g]γ .
Laser-Thermal Impurity Pumping of Shallow Donors in Ultrapure Germanium
Authors: Theiler T. , Keilmann F. , Haller E. E.
Published: March 2011

Extremely narrow far-infrared lines [1] of OH-donors in ultrapure germanium are used to probe the fundamental dynamic processes of impurities. We examine the 1s-2p transition as a function of laser intensity, using photothermal ionization spectroscopy (PTIS) modified by Zeeman tuning with frequency-fixed lasers. We observe a change of the resonance line shape in the intensity region near 10-4 W/cm2. This effect can be quantitatively understood in a rate equation model which shows that at the critical intensity the ground state becomes depleted and the dependence of the recombination on the degree of ionization becomes important. Therefore the critical intensity depends also on compensation.
Identification of Surface-Related Electron Traps in Undoped GaAs by Deep Level Transient Spectroscopy
Authors: Shin Ki-Chul , Park In-Shik
Published: March 2011

Using undoped GaAs containing grain boundary, we performed annealing test to identify the processes occurring during heat treatment. We propose EL2 as a complex of double vacancy, AsGa and Asi. From the concentration change at grain boundary region we temporarily conclude that EL3 is a simple intrinsic defect.
Pressure Dependence of a Deep Excitonic Level in Silicon
Authors: Northrop G.A. , Wolford D.J.
Published: March 2011

Certain optically active defects in silicon provide a unique opportunity to observe, in detail, the effect of hydrostatic pressure on a deep level. We present a photoluminescence (5 – 100K) study of one such defect, the I, radiation-damage center, under high hydrostatic pressures (1–50 kbar). While the energy variation of this level indicates the expected mutli-band nature typical of a deep level, a severe and continuous reduction in the observed luminescence intensity was also observed. Temperature dependence, time resolved photoluminescence, and photoluminescence excitation spectroscopy are employed to attempt to discern the mechanism involved.
Multiconfigurational Carbon-Group V Pair Defects in Silicon
Authors: Gürer E. , Benson B. W.
Published: March 2011

In addition to a new configuration of the previously reported multistable carbon-phosphorus pair, we report on two new multiconfìgurational defects in electron irradiated silicon doped, with arsenic and antimony. These defects are also identified as interstitial carbon-substitutional group V pairs, (). We identified two different types of metastability for . Type I is similar to the bistable carbon-carbon pair defect for which a bond switching mechanism has been reported [1]. Type II is similar to donor-acceptor pairs in silicon which show electrostatically driven metastability [2,3]. The three pairs have many similar features, but also show surprising donor related differences. In this paper we will discuss the general features of these defects.
Deep Levels in Superlattices
Authors: Dow John D. , Yuan Ren Shang , Shen Jun , Tsai Min-Hsiung
Published: March 2011

The physics of deep levels in semiconductors is reviewed, with emphasis on the fact that all substitutional impurities produce deep levels - some of which may not lie within the fundamental band gap. The character of a dopant changes when one of the deep levels moves into or out of the fundamental gap in response to a perturbation such as pressure or change of host composition. For example, Si on a Ga site in GaAs is a shallow donor, but becomes a deep trap for x>0.3 in AℓxGa1-xAs. Such shallow-deep transitions can be induced in superlattices by changing the period-widths and quantum confinement. A good rule of thumb for deep levels in superlattices is that the energy levels with respect to vacuum are relatively insensitive (on a >0.1 eV scale) to superlattice period-widths, but that the band edges of the superlattices are sensitive to changes of period. Hence the deep level positions relative to the band edges are sensitive to the period-widths, and shallow-deep transitions can be induced by band-gap engineering the superlattice periods.
Hydrogen Passivation Studies in Dislocated CZ and FZ Silicon
Authors: Dubé C. , Kalejs J. P. , Rajendran S.
Published: March 2011

Hydrogen passivation using a Kaufmann ion source at 400°C has been carried out on FZ and CZ silicon dislocated by four-point bending at high temperatures. The results differ from those reported for dislocations passivated in silicon sheet grown by the EFG technique. A model for hydrogen diffusion and trapping is presented to argue that the differences observed are not produced by hydrogen transport effects in the bulk.
The Formation of Silicon-Rich Silicides
Authors: Ronay Maria , Schad R.G.
Published: March 2011

Diffusion studies of mono and bilaycrs of transition-metal films on silicon showed that the formation of η′ —Cu3Si lowers the formation temperature of subsequently forming ReSi2 by 400°C. This is due to the creation of a large amount of silicon self-interstitials accompanying the formation of the copper suicide, which lowers the activation energy for silicon diffusion. The generalization of this result - stating that the formation of all suicides, in which the volume density of silicon is much larger than in elementary silicon injects silicon self-intcrstitials into the silicon lattice - gives new insight into suicide formation, silicide-cnhanccd dopant diffusion and the self-diffusion of silicon itself6.
Diffusion and Interdiffusion in Multilayered Semiconductor Systems
Authors: Ourmazd A. , Kim Y. , Bode M.
Published: March 2011

We apply quantitative chemical mapping techniques to study thermal interdiffusion and ion-implantation induced intermixing at single heterointerfaces at the atomic level. Our results show thermal interdiffusion to be strongly depth dependent. This is related to the need for the presence of native point defects (interstitials and vacancies) to bring about interdiffusion. Since their initial concentration in the bulk is negligible, the point defects must be injected at the surface and transported to the interface for interdiffusion to occur. In the case of ion-implanted samples, we find the passage of a single energetic ion through a sample at 77 K causes significant intermixing, even when the sample receives no subsequent thermal treatment.
Diffusion of Ion Implanted Mg and Be in GaAs
Authors: Robinson H. G. , Deal M. D. , Stevenson D. A.
Published: March 2011

Annealed Mg implants into GaAs show three diffusion regions: 1) rapid uphill diffusion in the peak of the implant; 2) rapid concentration-independent diffusion in the tail; and 3) slow concentration-dependent diffusion in between. Implanted Be, in contrast, exhibits only concentration-dependent diffusion. Constant Fermi level experiments show that this diffusion is actually hole-dependent. Uphill diffusion can be induced in Be implants by co-implanting with a heavier element such as Ar. Paradoxically, this retards the concentration-dependent diffusion. This behavior can be explained with the Substitutional-Interstitial-Diffusion (SID) mechanism and an understanding of the defect chemistry after implantation. In the region of uphill diffusion, the dopants are seen to getter from areas of excess Ga interstitials toward areas of excess Ga vacancies. The magnitude of the Ga interstitial gradient with respect to the dopant concentration is shown to be critical for the uphill diffusion. The reduction in concentration-dependent diffusion with co-implants is thought to be caused by implant damage allowing dopant atoms to shift from interstitial to substitutional sites.
Defect Formation During Zn Diffusion into GaAs
Authors: Luysberg Martina , Jäger W. , Urban K. , Perret M. , Stolwijk N.A. , Mehrer H.
Published: March 2011

The microstructure induced by the Zn diffusion at 1170 K into doped and undoped semi-insulating GaAs single crystals was characterized for various diffusion times t < 1740 min by analytical electron microscopy. The results were compared with Zn concentration profiles obtained by spreading resistance measurements (SRM) on the same samples. At the diffusion front the formation of prismatic interstitial dislocation loops, dislocation networks, and of cavities partly filled with Ga was observed. Closer to the surface facetted voids and, for the undoped samples, vacancy-type dislocation loops formed. The near surface region of highest Zn-concentration showed a high density of Zn-rich precipitates. A model is presented which accounts .for these observations. It is based on fast interstitial Zn diffusion and the kick-out mechanism for interstitial-substituional exchange.
The Metastability of the EL2 and DX Defects in GaAs and 3-5 Alloys
Authors: von Bardeleben H.J. , Bourgoin J.C.
Published: March 2011

The metastability of the EL2 and DX defects in GaAs and Ga1-x AlxAs alloys is discussed in the context of recent hydrostatic pressure and photo-EPR results. A unified model is presented based on the metastable trapping of carriers in excited effective-mass (EM) states derived from secondary conduction band (CB) minima. The metastability is attributed to small lattice relaxation effects.
Characteristics of Doping and Diffusion of Heavily Doped N and P type InP and InGaAs Epitaxial Layers grown by Metal Organic Chemical Vapor Deposition
Authors: Pinzone C.J. , Ha N. T. , Gerrard N. D. , Dupuis R. D. , Luftman H. S.
Published: March 2011

Electronic and photonic device applications of the InGaAs/InP materials system often require the growth of epitaxial material doped to or near the solubility limit of the impurity in the host material. These requirements present an extreme challenge for the crystal grower. To produce devices with abrupt dopant profiles, preserve the junction during subsequent growth, and retain a high degree of crystalline perfection, it is necessary to understand the limits of dopant incorporation and the behavior of the impurity in the material.

In this study, N-type doping above 1019 cm-3 has been achieved in InP and InGaAs using Sn as a dopant P-type Zn doping at these levels has also been achieved in these materials but p type activation above ~3 × 1018 cm-3 in InP has not been seen. All materials were grown by the metalorganic chemical vapor deposition (MOCVD) crystal growth technique. Effective diffusion coefficients have been measured for Zn and Sn in both materials from analysis of secondary ion mass spectra (SIMS) of specially grown and annealed samples.
Defects in MBE-grown Silicon Epilayers Studied with Variable-Energy Positrons
Authors: Simpson P.J. , Schultz P.J. , Mitchell I.V. , Jackman T.E. , Aers G.C.
Published: March 2011

Few non-destructive techniques are available which provide information regarding defect type, concentration and depth distribution in semiconductors. The variable-energy positron beam technique has recently demonstrated a sensitivity to near surface defects and impurities at low defect concentrations. In the present study, intrinsic silicon (100) epilayers of ~3000 Å thickness grown by MBE at different temperatures were examined by this method for evidence of changing defect concentration and type.
Structural Transitions in Titanium/Amorphous-Silicon Multilayers
Authors: Ma E. , Clevenger L.A. , Thompson C.V. , DeAvillez R.R. , Tu K.N.
Published: March 2011

We report a quantitative investigation of silicidation in Ti/amorphous-Si thin-films using Differential Scanning Calorimetry (DSC), thin-film X-ray diffraction and Cross-sectional Transmission Electron Microscopy (XTEM). Multilayered thin films were used to facilitate calorimetric observation of the heat released or absorbed at many reacting interfaces. It is shown that calorimetric analysis, combined with structural analysis using X-ray diffraction and XTEM, is effective in providing both kinetic and thermodynamic information about interdiffusion reactions in thin films. The present paper describes experimental results for multilayers with an atomic concentration ratio of 1 Ti to 2 Si and modulation periods ranging from 10 to 60 nm. A thin amorphous titanium suicide layer was found to exist between the as-deposited Ti and a-Si layers. Heating the multilayer film caused the amorphous Ti-silicide to grow over a broad temperature range by an exothermic reaction. An endothermic relaxation occurs during the late stage of amorphous suicide growth. Heating to temperatures over 800K causes C49-TiSi2 to form at the a-si1icide/a-Si interface. Temperatures at which all the above structural transitions occur vary with modulation period. Analysis of the DSC data indicates an activation energy of 3.1 eV for the formation of C49-TiSio, which is attributed to both the nucleation and the early growth of the suicide. The heat of formation for C49-TiSi2 from a reaction of a-silicide and a-Si was found to be -30±5KJ/mol. Nucleation appears to be the controlling step in C49-TiSi2 formation.
Enhancement of Oxygen Precipitation in Quenched Czochralski Silicon Crystals
Authors: Hara A. , Fukuda T. , Hirai I. , Ohsawa A.
Published: March 2011

We studied oxygen precipitation in quenched Czochralski silicon crystals. The larger the cooling rate and the higher the quenching temperature, the more oxygen precipitated. The defects enhancing oxygen precipitation are eliminated by annealing above 900°C. The defects are formed and removed repeatedly by quenching and slow cooling. We think that the aggregation of vacancies is related to those defects.
Surface and Interface Damage Characterization of Reactive Ion Etched MBE Regrown GaAs
Authors: Cole M.W. , Dutta M. , Rossabi J. , Smith D.D. , Lehman J.L.
Published: March 2011

Damage resulting from reactive ion etching (RIE) and wet etching of MBE grown GaAs and the defects generated in subsequent GaAs regrowth was evaluated by Transmission Electron Microscopy (TEM), photoluminescence (PL) , and Raman spectroscopy. The samples were reactively etched with HCl and Cl2 at two power densities; 0.3 W/cm2 and 0.6 W/cm2. A wet chemical (H2O:H3PO4:H2O2) etched sample was used for comparison. The LO phonon intensities measured by room temperature Raman spectroscopy showed a strong correlation to the relative PL intensities, where the HCl sample was found to be inferior to the others. TEM microstructural evaluation showed both HCl RIE samples to have significant interface roughness, with the sample etched at 0.6 W/cm2 showing the most structural damage in the regrowth region. Defect densities for the Cl2. and wet etched samples were two orders of magnitude lower than that of the HCl etched samples. The extent of disorder in the regrowth region was largest for the HCl sample with respect to the Cl2 and wet etched samples. These microstructural and optical results suggest that the H+ ion plays an important role in the generation of crystal defects during the RIE process.
Preparation and Characterization of Molybdenum Disulfide Microcrystals in Colloidal Dispersion
Authors: Lu E. , Persans P. D. , Ruppert A. F. , Chianelli R. R.
Published: March 2011

We report the preparation and general, optical and resonant Raman scattering characterization of MoS2 platelets suspended in an insulating organic liquid. Structural results indicate that the platelets are predominantly 2H in structure and are about 500Å in diameter and 50–90 Å thick. The optical constants of the composite are close to those expected from the simple Maxwell-Garnett effective medium theory. We have observed resonant enhancement of the Raman cross-section for the MoS2 phonon mode at 408 cm−1 as the laser excitation energy is scanned through the “B” exciton.
Transport Properties of B-, P-Doped and Undoped 50 kHz PECVD Microcrystalline Silicon
Authors: Hachicha M.A. , Bustarret Etienne
Published: March 2011

Undoped 500 nm-thick silicon layers with a crystalline fraction around 95% and an average grain size of 20 nm have been deposited at 350°C by 50 kHz triode PECVD in a H2/SiH4 mixture, in the presence of a magnetic field. Their room temperature (rt) dc conductivity μrt is 0.03 Δ−1cm−1 for a Hall mobility of 0.8 cm 2V−1s−1.

The study by SIMS, infrared absorption, grazing angle x-ray diffraction and Raman scattering spectroscopies of the doped samples shows how the crystalline fraction and the grain size drop as the B2H6/SiH4 and PH3/SiH4 volumic ratios increase from 10 ppm to 1%.

The rt dc conductivity reaches 2 Δ−1 cm−1 (Hall mobility: 15 cm2V−ls−1) for a solid phase density of 1019 cm−3 boron atoms, and 30 Δ−1cm−1 (Hall mobility: 55 cm2V−ls−1) at the maximum P incorporation of 8 × 1020cm−3.
Properties of Binary Si:H Materials Prepared by Hydrogen Plasma Sputtering
Authors: Furukawa Shoji , Miyasato Tatsuro
Published: March 2011

Binary Si:H materials are prepared by means of the rf sputtering technique in pure hydrogen atmosphere on low temperature (about 100 K) and room temperature substrates. The physical properties of the obtained materials are very much affected by the rf power and substrate temperature during the deposition. The material prepared at a low substrate temperature with a low rf power has a wide optical gap, and shows a visible photoluminescence at room temperature. On the other hand, the material prepared at room temperature with a high rf power contains many Si microcrystals, whose diameters are relatively large, and its optical gap becomes very small. The latter condition causes the dependence of the crystalline direction of the material film on the substrate crystal even at the room temperature. An rf power-modulated multi-layered structure (superlattice) is also proposed, and an apparent diffraction peak can be observed in the low-angle X-ray scattering measurement.
Preparation and Characterization of Highly Conductive (100 S/cm) Phosphorus Doped νc-Si:H Films Deposited Using the VHF-GD Technique
Authors: Prasad Kshem , Finger F. , Curtins H. , Shah A. , Bauman J.
Published: March 2011

We report on the preparation and characterization of phosphorus doped gc-Si:H films produced by the very high frequency glow discharge (VHF-GD) at a plasma excitation frequency of 70 MHz. We present a systematic study of the deposition parameters i.e. hydrogen dilution of silane, VHF power density, gas phase doping ratio and deposition temperature and their influences on the electrical and structural properties of the material. In contrast to 13.56 MHz GD the VHF plasma conditions favour microcrystalline formation at low power densities; the resulting conductivities are significantly higher than those obtained at 13.56 MHz.
Preparation of High-Quality poly-Si and μc-Si Films by the SPC Method
Authors: Matsuyama T. , Nishikuni M. , Kameda M. , Okamoto S. , Tanaka M. , Tsuda S. , Ohnishi M. , Nakano S. , Kuwano Y.
Published: March 2011

We have achieved the highest total area conversion efficiency for an integrated type 10cm × 10cm a-Si solar cell at 10.2%. This value is the world record for a 10cm × 10cm a-Si solar cell. For further improvement of conversion efficiency in a-Si solar cells, it is necessary to develop materials with high-photosensitivity in the long wavelength region and materials with high conductivity. We have developed a Solid Phase Crystallization (SPC) method of growing a Si crystal at temperatures as low as 600°C. Using this method, thin-film polycrystalline silicon (poly-Si) with higP-photosensitivity in the long wavelength region and Hall mobility of 70cm2/V sec was obtained and quantum efficiency in the range of 800,∼ lO00nm was achieved up to 80% in the n-type poly-Si with grain size of about 2μm. We also succeeded in preparing a device-quality p-type microcrystalline silicon (μc-Si) using the SPC method at 620°C for 3 hours from the conventional plasma-CVD p-type amorphous silicon (a-5i) withoul using any post-doping process. Obtained properties of μd=2 × 103 (.cm) and a high optical transmittance in the 2.0 ∼ 3.0 eV range are better as a window material than the conventional p-type μc-Si:H. Therefore, it was concluded that the SPC method is better as a new technique to prepare high-quality solar cell materials.
Time-Resolved Spectra of Edge Emission of Cdse Mesoscopic Clusters in GeO2 Glass Matrix
Authors: Inokuma Takao , Ishikawa Mitsuru , Tanaka Akinori , Arai Toshihiro
Published: March 2011

Time-resolved edge emission spectra of CdSe clusters were measured at 80K. Cluster size and excitation Intensity dependences of the decay behavior were discussed in terms of the quantum size effect for electronic states.
Characterization of the Plasma Chemistry and Film Composition of PECVD Silicon Nitride Deposited from Silane-Nitrogen and Silane-Ammonia Mixtures with Argon Additions
Authors: Quinn W. E. , Bagley B. G. , Wilkens B. J. , Gallois B. M.
Published: March 2011

Silicon nitride films deposited from silane-nitrogen and silane-ammonia mixtures by PECVD contain large amounts of hydrogen. We have determined that adding argon to the gas mixture reduces the amount of hydrogen in the resulting films. Differences in film composition are obviously due to changes in the chemistry of the discharge which was characterized by line-of-sight mass spectrometry, optical emission spectroscopy and plasma double probe measurements. Substrate temperature was fixed at 325°C, pressure was 500 mtorr, the RF power was 0.25 watts cm−2, the silane to nitrogen ratio was varied from 0.003 to 0.02, the silane to ammonia ratio was varied from 0.01 to 0.5, and the argon additions were 10% of the total gas flow. Argon additions to the discharge increased the plasma density in both nitrogen and ammonia plasmas. Optical emission from N2 and Si-H species increased upon the addition of 10% argon to the silane-nitrogen discharge, whereas the N-H emission decreased upon addition of argon to the silane-ammonia discharge. Infrared transmission spectra of films deposited with and without argon show no change in peak position or intensity of Si-H and N-H absorption bands in the spectral range studied, despite a large (over 20%) reduction in hydrogen content, as determined by nuclear profiling, upon the addition of argon. These results suggest that a substantial fraction of the hydrogen in the films is not infrared active. We propose that the reduction in hydrogen content is due to bombardment of the growing film by argon ions, which sputter the adsorbed hydrogen molecules.
Radiofrequency Discharge Modeling
Authors: Boeuf J. P , Belenguer Ph , Wang J.
Published: March 2011

Selfconsistent fluid models of radiofrequency discharges in helium and silane are presented. The role of the sheath and plasma electric field in the electron energy gain and deposition mechanisms in both cases are discussed.
The Plasma Deposition of Semiconductor Multilater Structures
Authors: Hirose Masataka , Miyazaki Seiichi
Published: March 2011

The early stages of thin film deposition from the rf glow discharge of SiH4 or SiH4 + NH3 have been studied by analysing the structure of silicon based multiiayers consisting of hydrogenated amorphous silicon (a-Si:H, 10 – 200 A thick) and stoichiometric silicon nitride (a-Si3N4:H, 25 – 250 A) alternating layers. The x-ray diffraction, its rocking curve and x-ray interference of the multilayers have shown that the amorphous silicon/silicon nitride interface is atomically abrupt and the surfaces of the respective layers are atomically flat regardless of substrate materials. This indicates that the precursors impinging onto a substrate from the gas phase homogeneously cover the growing surface and the layer by layer growth proceeds on atomic scale. In the plasma deposition of the covalently bonded semiconductors and insulators, the island formation on a substrate surface at the beginning of the thin film growth is very unlikely.
In-Situ Gas Conversion Using a Wide Area Disc Shaped He-H2 Plasma and Organometallic Feedstocks
Authors: Pihlstrom B. , Sheng T. , Yu Z. , Collins G.
Published: March 2011

A wide area disc shaped plasma source of 20cm in diameter generated by a ring shaped cathode electron beam is used to decompose Trimethylgallium (TMGa) and Trimethylarsenic (TMAs). Volume photo-absorption of VUV photons and sensitized atom-molecule collisions with excited species and radicals can all assist dissociation of the organometallic feedstock reactants. In addition, the excited radical flux and VUV impingement on the film may also assist heterogeneous surface reactions and increase surface mobility of absorbed species. Mass spectrometry studies using deuterium as a replacement for hydrogen as a trace gas allowed for the elicidation of decomposition pathways of TMGa and TMAs. Byproducts of hydrogen and helium plasmas were also studied.
The Effect of Reactor Pressure on the Growth of Glow Discharge a-SiN:H
Authors: Varhue W. J. , Pandelisev K. A.
Published: March 2011

The electrical resistivity and N content of a-SiN:H films can be controlled by varying the reactor pressure. This appears to be a result of the increased dissociation of the ammonia feed gas by the change in the electron energy spectrum. The effect of ion bombardment of the substrate surface does not result in observable changes in film quality.
A Neutron Reflectivity Study of the Interfacial Magnetism of an Y/Gd Film
Authors: Ankner J.F. , Zabel H. , Neumann D.A. , Majkrzak C.F. , Matheny A. , Dura J.A. , Flynn C.P.
Published: March 2011

Using the technique of polarized-neutron reflectometry, we have studied the magnetic moment distribution in the interfacial region of an epitaxial film consisting of 97 Å Y(0001) atop 1000 Å Gd(0001). At T = 151 K, with an 80 gauss field applied parallel to the surface (basal plane), we observe two distinct ferromagnetic regions: the Gd bulk and a layer with reduced magnetic moment at the Y/Gd interface. Above the bulk Curie temperature, at T = 295 K , we observe no net magnetization in either the bulk or the interface.
The Study of Surfaces and Interfaces on the Reflectometer Crisp at the Isis Pulsed Neutron Source
Authors: Penfold J
Published: March 2011

The study of surfaces and interfaces using the specular reflection of neutrons on the reflectometer CRISP at the ISIS pulsed neutron source is discussed. The instrumentation, is briefly described, and the performance of the spectrometer being illustrated by some standard examples. Recent experimental results on the adsorption of surfactants at the air-water interface will be presented.