bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Friction and Wear on PECVD Diamond Films.
Authors: Languell M. L. , Davidson J. L. , Wert J. J. , George M. A. , Collins W. E. , Burger A.
Published: April 2011

The effects of friction and wear were examined on plasma enhanced chemical vapor deposition (PECVD) diamond films deposited on tungsten substrates. The tribology of diamond on diamond was studied and the changes in surface roughness and the bearing ratio were determined before and after wear. The (111) textured heteroepitaxial films were studied morphologically by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The changes in morphology involved a transition from the large as grown diamond crystallites with a mean diameter of 10 μm to a surface with grains as small as 100 nm. The nature of the wear-modified films will be discussed regarding the possible mechanisms for the surface changes.

Work partially supported by NASA Lewis Research Center grant NAG3–1430.
On the Nature of the Native Defect ESR in Thin Diamond Films
Authors: Shinar J. , Jia H. , Lang D. P. , Pruski M.
Published: April 2011

The X-band ESR of thin diamond films deposited from 99.5% H2/0.5% CH4 is compared to that of films similarly prepared from D2CD4 and H2/13CH4. The main line and the satellites at ±7.2 G are unaffected by annealing at T <. 1100°C, but their intensity is reduced upon annealing at T ∼ 1200°C. As the satellites are absent from the deuterated films, they are attributed to newly identified dangling bond-H centers, either on internal microvoid surfaces or embedded in the tetrahedral network. This is consistent with the 13C spin-lattice relaxation rate, which indicates that the distribution of paramagnetic centers is homogeneous to within ∼0.04 μm. However, they may be nonuniformly distributed on a finer scale, consistent with the concentrations in m ulti vacancies or stacking faults recently suggested by Fanciulli and Moustakas.
On the Structure of Thin diamond Films: A 1H and 13C Nuclear Magnetic Resonance Study
Authors: Shinar J. , Pruski M. , Lang D. P. , Hwang S.-J. , Jia H.
Published: April 2011

The 1H and 13C nuclear magnetic resonance (NMR) of thin diamond films deposited from naturally abundant (1.1 at.%) as well as 50% and 100% 13C-enriched CH4 heavily diluted in H2is described and discussed. Less than 0.6 at.% of hydrogen is found in the films which contain crystallites up to ∼15 μm across. The 1H NMR consists of a broad 50–65 kHz wide Gaussian line attributed to H atoms bonded to carbon and covering the crystallite surfaces. A narrow Lorentzian line was only occasionally observed and found not to be intrinsic to the diamonds. The 13C NMR demonstrates that >99.5% of the C atoms reside in a quaternary diamond-like configuration. The 13C spin-lattice relaxation times T1 are four orders of magnitude shorter than in natural diamond and believed to be due to 13C spin diffusion to paramagnetic centers, presumably carbon dangling bonds. Analysis of T1 indicates that within the 13C spin diffusion length of ∼0.05 μm these centers are uniformly distributed in the diamond crystallites, possibly concentrated on the internal surfaces of a relatively dense system of nanovoids.
Radiation Defects in SiC - Electron Irradiation With Different Energies
Authors: Volm D. , Meyer B. K. , Mokhov E. N. , Baranov P. G.
Published: April 2011

Radiation defects in 6H SiC introduced by electron irradiation at energies of 400 keV and 1 MeV are studied by low-temperature photoluminescence and Zeeman spectroscopy. We observe a new two line spectrum at 2.547 and 2.528 eV which dominates in the spectrum of the sample irradiated at 400 keV. For 1 MeV irradiation numerous recombination lines are observable and also the well known D1 center lines appear. Annealing the sample at 1100 °C leads to the disappearance of almost all lines but the D1 lines are still present.
Properties Of crystalline 3C-SIC Grown From Methyl Trichlorosilane
Authors: Moore W. J. , Kaplan R. , Freitas J. A. , Altaiskii Y. M. , Zuev V. L. , Ivanova L. M.
Published: April 2011

Cubic silicon carbide grown by thermal decomposition of methyl trichlorosilane in hydrogen has been studied in infrared (IR) transmission, cyclotron resonance (CR), and photoluminescence (PL). Sample characteristics include: The nitrogen concentration, determined from CR and IR can be of the order of 1015 cm-3 or less. Ionized impurity concentrations determined from the linewidths of CR and IR spectra can be less than 7 × 1014 cm-3. Low temperature electron mobilities from CR are near 105 cm2 v-1 s-1. Carrier freeze-out is consistent with either uncompen-sated donors with activation energy near 50 meV or heavily compensated donors with 20 meV activation energy. The latter choice, however, is excluded by the low ionized impurity concentration. These high quality samples show little or no evidence of the apparently shallow (< ∼20 meV) donor which usually dominates the low temperature conductivity of 3C-SiC grown on Si. Nitrogen donor excitation spectra are in excellent agreement with effective mass theory. Only nitrogen donors at 54.2 meV and an unidentified effective-mass donor at 47.8 meV are observed. If material with the characteristics described above can be reliably reproduced then there is substantial expectation that high quality electronic devices based on 3C-SiC can be fabricated.
Growth of Beta Silicon Carbide Film on Si by Hot-Filament CVD
Authors: Rong Zhang , Hongtao Shi , Shidong Yu , Youdou Zheng , Yuliang He , Xiangna Liu
Published: April 2011

In this paper, we will report fabrication and structure study of single crystal β-SiC film on Si substrate by hot-filament chemical vapor deposition (HFC VD). The reaction sources are hydrogen-diluted methane(CH4) and Silane(SiH4). The wafer surface temperature is about 650°C. The typical growth rate is 200nm/h. Raman scattering spectrum shows a peak centering at 960cm-1 with a full width at half magnitude (FWHM) of 75cm-1. At room temperature, the photoluminescence spectrum gives a wide band at 580nm (2.2eV) with a FWHM of 55nm. Fourier transmission infrared (FT-IR) spectrum exhibits an absorption peak at 12.6 μm XRD and XPS analysis indicate that the epilayer is a stoichiometrical single crystal cubic silicon carbide film.
Electron Emission Properties of the Negative Electron Affinity (111)2×1 Diamond-Tio Interface
Authors: Bandis C. , Haggerty D. , Pate B.B
Published: April 2011

We report photoemission measurements from the (111)2×1 diamond-titanium monoxide (TiO) interface. Submonolayer deposition of TiO on the (111)2×1 diamond surface modifies the electron affinity of the surface from positive to negative. No change in the band bending was observed as a result of the TiO deposition. Total electron yield measurements from the diamond-TiO interface were also performed. The yield spectra, as expected for a negative electron affinity (NEA) surface, have emission thresholds that are in good agreement with the absorption coefficient of diamond. To further understand the emission properties of NEA (111) diamond surfaces we also compare the electron yield photo-excitation spectra of the diamond-TiO interface with the yield spectra of hydrogenated (111)1×1:H diamond surfaces.
Infrared Study of Trimethylgallium Adsorption on GaAs(100)
Authors: Gee Paul E. , Qi Haihua , Hicks Robert F.
Published: April 2011

Trimethylgallium (TMGa) adsorption on GaAs(100) has been studied by infrared spectroscopy. The adsorbed TMGa exhibits up to five C-H stretching vibrations between 2700 and 3000 cm−1 and five C-H deformations between 1100 and 1500 cm−1. The adsorbate uptake is a maximum at arsenic coverages of –65%. These and other results indicate that TMGa dissociatively adsorbs onto As dimers with methyl transfer to second-layer Ga atoms and to As atoms. Above 333 K, molecular desorption competes with adsorption, causing the saturation coverage to fall with increasing temperature. The desorption kinetics depend on the composition of the GaAs(100) surface. These kinetics suggest that above 773 K, TMGa is more likely to decompose on the c(2×8) than on a more Ga-rich surface.
Effect of Substrate Misonrentation on Ordering in Ga0.5In0.5P
Authors: Su L.C. , Ho I.H. , Stringfellow G.B. , Leng Y. , Williams C.C.
Published: April 2011

Ordering produced in Ga0.5ln0.5P epitaxial layers grown by OMVPE can be controlled by variations in the substrate misorientation as well as the growth temperature and the growth rate. The ordering produced at a growth temperature of 620°C and a relatively low growth rate of 0.5 μm/hr is found to depend strongly on both the direction and angle of substrate misorientation. Transmission electron microscope images and transmission electron diffraction (TED) patterns as well as electrostatic force microscopy (EFM) and photoluminescence (PL) has been studied for misorientation angles of 0, 3, 6, and 9° from (001) toward the (111)B, (111)A, and [010] directions in the lattice. Misorientation in the (111)B direction (to produce [110] steps) increases ordering for angles of up to approximately 4°. Increasing the misorientation angle in the (111)A direction actually leads to a decrease in the degree of order observed. Misorientation in the [010] direction also decreases the degree of order, although the effect is much less than observed for misorientation in the (111)A direction. The most highly ordered material produced under these growth conditions is for a misorientation angle of 3° in the (111)A direction. Increasing the growth temperature to 720°C produces completely disordered material. This wide variation in ordering behavior has allowed the growth of an order/disorder heterostructure for a substrate misorientation of 3° in the (111)A direction. The heterostructure consists of a Ga0.52In0.48P layer grown at 740°C followed by an ordered layer grown at 620°C. The x-ray diffraction results show that both layers are precisely lattice-matched to the GaAs substrate. TED patterns show that the first layer is completely disordered and the top layer is highly ordered, with only a single variant. EFM images of the order/disorder heterostructure show a pronounced contrast at the interface, attributed to the large difference in the nature of the surface states in the ordered and disordered materials. The 10 K PL spectrum consists of two sharp and distinct peaks at 1.995 and 1.830 eV from the disordered and ordered materials, respectively. The peak separation represents the largest energy difference between ordered and disordered materials reported to date. Such heterostructures may be useful for photonic devices.
Application of Selective Area MOVPE for DFB Gratings with Modulated Coupling Coefficient
Authors: Tidemand-Petersson Peer , Albrektsen Ole , Møller-Larsen Anders , Salzman Joseph
Published: April 2011

A new application of selective area metalorganic vapour phase epitaxy is demonstrated: fabrication of distributed feedback (DFB) gratings with sub-micron period and modulated coupling coefficient Kc. A SiO2 mask layer defines the InGaAs(P) grating pattern as well as the lateral variation in growth rate and, hence, thickness of the grating. In this way K can be varied along the laser cavity in a controlled and reproducible manner.
The Optimization of Interfaces in InAsSb/InGaAs Strained-Layer Superlattices grown by Metal-Organic Chemical Vapor Deposition
Authors: Biefeld R. M. , Baucom K. C. , Kurtz S. R.
Published: April 2011

We have prepared InAsSb/InGaAs strained-layer superlattice (SLS) semiconductors by metal-organic chemical vapor deposition (MOCVD) using a variety of growth conditions. The presence of an InGaAsSb interface layer is indicated by the x-ray diffraction patterns. The optimized growth conditions involved the use of low pressure, short purge times between the growth of the layers, and no reactant flow during the purges. We used MOCVD to prepare an optically pumped, single heterostructure InAsSb/InGaAs SLS / InPSb laser which emitted at 3.9 μm with a maximum operating temperature of approximately 100 K.
Enhancement of Gold on n-InGaAs Schottky Barrier Height by Using a thin p-InP Layer
Authors: Yang Bing , Chen J. C. , Choa F. S.
Published: April 2011

In this study, we demonstrate the enhancement of n-In0.53Ga0.47A s Schottky barrier height by using a thin (300-1800 Å) p-InP surface layer. An increase in the barrier height of 0.46 eV, making the total barrier height 0.66 eV, was obtained in a Au/p-InP/n-InGaAs structure, resulting in a great reduction of leakage currents. Results of the electrical measurements are summarized in table 1. The barrier height of n- In0.53Ga0.47As was increased from 0.2 eV to 0.66 eV when a 1200-Å-thick p-InP surface layer was employed.
Fermi Level Pinning in Au Schottky Barriers on InGaP and InGaAlP
Authors: Gorbyley V.A. , Chelniy A.A. , Chekalin A.A. , Polyakov A.Y. , Pearon S.J. , Smirnov N.B. , Gnorkov A.V. , Leiferov B.M. , Popova E.V. , Kusikov V.A. , Balmashnov A.A.
Published: April 2011

It is shown that in Au/InGaP and Au/InGaAlP Schottky diodes the Fermi level is pinned by metal-deposition-induced midgap states. Hydrogen plasma treatment of such diodes greatly improves the reverse currents. The measured Schottky barrier heights seem to correlate with the valence band offsets measured by DLTS on quantum well structures.
The Use of Tetraethyltin as an N Type Dopant Source in GAAs, ALGAAs, and ALAS for Lasers and Bragg Reflectors Grown by MOCVD
Authors: Pinzone C. J. , Neff I. G. , Chelakara R. V. , Fertitta K. , Dupuis R. D.
Published: April 2011

The use of Tetraethyltin (TESn) as a source of donors in GaAs and its A1xGal-xAs alloys with x varied from 0 to 1 has been investigated for the growth of heterostructures by low pressure metalorganic chemical vapor deposition. (LP-MOCVD). The donor activity increases in the binary and ternary alloys as a function of tetraethyltin molar flow fraction and with increasing temperature. High quality one quarter wave Distributed Bragg reflectors (DBRs) were grown with TESn as an n type dopant source with no degradation in reflectivity observed. No surface accumulation of tin was observed and the morphology of all epitaxial samples was excellent. Sn incorporation in AlAs produced n type material as determined by Van der Pauw Hall measurements. The use of TESn as a convenient and controllable dopant source in structures such as vertical cavity surface emitting lasers which incorporate DBRs as well as other heterostructure devices is therefore practical..
Growth Temperature Uniformity of MBE-Grown GaAs Determined by Scanning Room Temperature Photoluminescence
Authors: Stair K. , Bird T. , Moretti A. , Chambers F. , Choi-Feng C.
Published: April 2011

We have used scanning room temperature photoluminescence to map GaAs quantum well widthsand AIGaAs barrier compositions over 2-inch and 3-inch diameter epitaxial layers grown by MBE at temperatures ranging from 600 to 700ºC. Analysis of these maps allows a nondestructive quantitative analysis of the GaAs growth rate uniformity from which we can calculate the temperature distribution during growth. We have used this technique to compare the thermal uniformity of various substrate holders designed for use in the Intevac ModGenII MBE system.
Dopant and As4/Ga Flux Ratio Influence on the Electrical and Structural Properties of LT GaAs
Authors: O'Hagan S. P. , Missous M.
Published: April 2011

Double crystal x-ray diffraction and Hall effect measurements have been performed on GaAs layers grown by molecular beam epitaxy at low substrate temperature (200-250°C). The concentration of excess As incorporated in undoped material is found to be a strong function of growth temperature but not of As4/Ga beam equivalent pressure ratio at a given temperature. Doping with Si or Be at concentrations of 1019cm−3 or greater has resulted in significant reduction of excess As concentration in layers grown at 250'C. This effect is seen to diminish with reducing substrate temperature. The effect is not seen when Se is used as the doping source. Reducing As overpressure in the presence of such a high doping concentrations has led to highly electrically active n- and p-type layers grown at 250'C.
A Molecular Dynamics Study of InGaAs Layers on GaAs Substrates
Authors: Moran G J , Morrison I , Matthai C C
Published: April 2011

We have performed molecular dynamics simulations of thin layers of InGaAs on GaAs substrates for different In concentrations to determine the critical thickness before strain relaxation occurs. We have considered both dislocation formation and islanding as possible mechanisms for strain relief. The results for the critical thickness for strain relief by misfit dislocations is slightly lower than that found using elasticity theory. For high In concentrations, facetted islands are found to be stable and are energetically favoured.
Optical Properties of Light-Hole Excitons in MOVPE Grown (Ga,In)As-GaAs Quantum Wells
Authors: Bigenwald P. , Laire O. , Zhang X. , Briot O. , Gil B. , Cloitre T. , Aulombard R.L.
Published: April 2011

We study the optical properties of metalorganic vapour phase epitaxy (MOVPE) grown (Ga,In)As-GaAs single quantum wells as a function of the growth parameters. Our objective is to study the properties of the type II light-hole excitons with light-hole wave function delocalized in the thick GaAs layers and electrons confined in the ternary alloy. However, marked structures (like for type I excitons) are observed in the reflectivity spectra. This we interpret in the context of a novel approach of the exciton problem via a self-consistent calculation of the electron-hole interaction.
Optical Studies of The Uniformity of Thermally Induced In-Plane Strain in Thin Gallium Arsenide Films
Authors: Taysing-Lara M. , Shen H. , Wraback M. , Pamulapati J. , Dutta M.
Published: April 2011

In-plane anisotropic strain can be employed in the design of a new class of optoelectronic devices, such as high contrast, polarization sensitive spatial light modulators. One of the key issues involved in realizing these devices is obtaining a controllable and uniform in-plane strain. We have studied the uniformity of thermally induced in-plane strain in MOCVD grown GaAs lift-off thin films mounted on LiTaO3 or CaCO3 substrates. The experiment exploits the straininduced splitting of the excitonic interband transition at low temperature through absorption measurements using a Ti-Sapphire laser focused to a spot size less than 100 μm. The polarization vector of the incident light was oriented along an axis which enhances both features. From the energy positions of these transitions, the magnitude as well as the type of the in-plane strain was determined. Topographic scans performed over a 1.4mm X 1.4mm area for the sample bonded to CaCO3, and along a 2 mm line for that bonded to LiTaO3 revealed variations in strain of less than 5%.
Van Der Waals Epitaxy Versus Homoepitaxy of Low Temperature GaAs (111) Layers
Authors: Gray Jennifer L. , Rumaner L.E. , Yoo H.M. , Ohuchi F.S.
Published: April 2011

In the design of GaAs devices, material selection for heteroepitaxy is limited due to the large amount of strain produced by lattice mismatch. To overcome this problem, a new growth method has been proposed called van der Waals Epitaxy (VDWE). This process attempts to decouple the interface through the growth of a van der Waals bonded crystal layer in-between the two materials with dissimilar lattice constants, thereby accommodating the lattice mismatch. Typical van der Waals materials such as GaSe, have hexagonal crystal structures and are grown with the c-axis perpendicular to the surface due to the nature of the bonding. These materials have a low surface energy and are not very reactive. In addition, they are only stable at relatively low temperatures. This poses two constraints to the growth of GaAs on GaSe. Initial experiments were done to investigate the possibility of growing GaAs (111) layers homoepitaxially at temperatures compatible with van der Waals crystals, with high crystallinity and a smooth surface. Twinned growth layers 1.7μm thick, were obtained at 350° C on a GaAs (111)B substrate using MBE. Further experiments looked at homoepitaxial growth on (111)A substrates and at slightly higher temperatures. These results were then compared to GaAs layers grown on GaSe layers in which nucleation occurs on a van der Waals surface as opposed to the covalently bonded GaAs substrate. The relative quality of the layers was analyzed using RHEED and TEM.
Liquid Phase Epitaxial Growth and Characterization of GaAs on InP Substrates
Authors: Kim Dong-Keun , Lee Hyung-Jong , Lee Byung-Teak
Published: April 2011

Optimum growth conditions were investigated to obtain high quality heteroepitaxial GaAs layers on InP substrates by liquid phase epitaxy (LPE). Addition of about 0.005wt% of Se to the Ga growth melt effectively suppressed dissolution of the InP substrates into the melt during the initial stage of the growth, resulting in a significantly improved surface morphology. The crystallinity and the surface morphology could be further improved by growing undoped GaAs layers on thin Se-doped buffer GaAs as well as using InP substrates patterned with grating structure. The transmission electron microscopy observation indicated that the misfit dislocations interact with each other at the grating region, resulting in a lower dislocation density in the upper GaAs layer. The (400) double crystal X-ray diffraction peaks of the undoped GaAs showed fullwidth- at-half-maximum of about 380 arcsec, which is comparable with the previously reported values using more sophisticated growth techniques.
MOVPE Growth and Doping of ZnTe Using Tertiarybutylphosphine as the Metalorganic Doping Precursor
Authors: Perkins N. R. , Dawson-Elli David F. , Kuech T.F.
Published: April 2011

ZnTe has gained attention as a promising material for short wavelength optoelectronic applications. Unlike ZnSe, ZnTe can be doped p-type but not n-type. There are few reports detailing the growth and doping of ZnTe films through the MOVPE technique. We present growth and doping studies for ZnTe formed through low pressure MOVPE. Dimethylzinctriethylamine and diisopropyltelluride were chosen as the metalorganic precursors. Growth studies were carried out on both GaAs (100) and GaSb (100) substrates. Growth morphology was very sensitive to both the lattice mismatch and the initial surface preparation. This is particularly evident on the GaSb substrates. ZnTe growth temperatures ranged from 340 to 420°C, and growth rates of up to 1 μm/hour were achieved. ZnTe was found to be readily doped using tertiarybutylphosphine, with p-type concentrations ranging from 4×1016 cm−3 to 2x1019 cm−3, and corresponding room temperature hole mobilities between 55 and 12 cm2/V-sec. Tertiarybutylphosphine was also observed to significantly improve the surface morphology for growths on GaSb substrates.
Structure and Electronic Properties of Misfit Dislocations in ZnSe/GaAs(001) Heterojunctions
Authors: Chen Y. , Liu X. , Weber E. , Bourret E. D. , Olego D. J. , Dorman D. R. , Gaines J. M. , Tasker N. R. , Liliental-Weber Z. , Haller E. , Washburn J.
Published: April 2011

Studies of the structure and electrical properties of regular and irregular misfit dislocations in undoped and N-doped ZnSe epilayers grown on GaAs(001) substrates by transmission electron microscopy (TEM), cathodoluminescence (CL) are reported. In undoped ZnSe epilayers, two sets of misfit dislocation arrays were observed: a straight orthogonal array along [110] and, and an irregular array roughly along [100] and [010] directions. The CL observations suggest that the irregular dislocations trap carriers more efficiently than the dislocations along <110>, possibly due to the high density of kinks existing along the zig-zag irregular dislocations. These irregular dislocations can be eliminated by doping nitrogen in the ZnSe epilayer with [N]≥l×1018 cm−3.
A Study of the Photoluminescence and Reflectivity Spectra of MOCVD Grown MnSe
Authors: Blasio M. Di , Aigouy L. , Averous M. , Calas J. , Tomasini P. , Haidoux A. , Tedenac J.C.
Published: April 2011

Photoluminescence (PL) experiments at 2K are performed on MOCVD grown MnSe. The precursors used in the growth stage are methylpentacarbonylmanganese and diethylselenide. Pyrolysis of the percursors is realized inside a gradient reactor under a constant H2 flux, between 280-55°TC. The compound is epitaxially grown on various substrates (Si, InP, GaSb, GaAs, ZnTe/GaAs, etc.). On some of these samples the compound presents a zinc blende structure, while in the other samples rock salt formation has been identified. The first substrate is used because of its interest in Si technology, while the others are used because MnSe can be grown in the zinc blende phase for very thin layers. For the first time x-ray diffraction data has allowed us to determine the lattice constant of zincblende MnSe (aMnse (oct)=5.818Å), confirming the close approximation (a ∼ 5.9Å) used from the Zn1-xMnxSe alloy. These compounds have visible Mn++ transitions at 2.12-5eV; other features are also visible at 2.3-4, 2.7, and 3.0eV. The energy gap transition of tetrahedral thin film layers of MnSe is seen for the first time in PL spectra. A temperature dependant PL study is performed on MnSe in the 2-200K range. Reflectivity experiments are used to attempt to identify the internal manganese transitions. A qualitative PL analysis of the samples grown at different temperatures and on different substrates is provided. A Stokes shift is encountered when the results are compared.
Ordered Structures of Zn1-xFexSe Epilayers Grown on GaAs Substrates with ZnSe Buffer Layers
Authors: Wei H.-Y. , Beesabathina D. Prasad , Salamanca-Riba L. , Jonker B. T.
Published: April 2011

We observed the coexistence of two types of ordered structures, Cu3Au and CuPt, in Zn0.4Fe0.6Se epilayers grown on ZnSe buffer layers on (001) GaAs substrates by transmission electron microscopy. In addition, the Cu3Au ordered structure exists with a multi-faceted domain shape. Energy dispersive x-ray spectra from these domains showed higher Fe concentration than in the disordered matrix. However, in Zn0.5Fe0.5Se epilayers, we only observed CuAu-I ordered multi-faceted domains. The samples with relatively high Fe concentration (x ≈0.6) also showed domains of FeSe with a hexagonal structure with triangular form coexisting with Cu3Au ordered domains. Strain-induced interdiffusion takes place between the buffer layer and the epilayer as evidenced by a rough interface between the alloy and the buffer layer.
Single Crystal Multilayer Coating on ZnSe and CdSe
Authors: Alov D.L. , Kolchin A.A. , Rybchenko S.I.
Published: April 2011

CVD is applied to grow the multilayer structure on CdSe proposed as a promising coating for IR-optics. The coating is composed of alternately grown CdS and CdSe single crystal layers. The proposed coating characteristics are expected to be much better than those of the coatings produced by the sputtering method.
Influence of Surface Step Density on the Growth of Mercury Cadmium Telluride by Molecular Beam Epitaxy
Authors: Colin T. , Minsås D. , Gjøen S. , Sizmann R. , Løvold S.
Published: April 2011

We report for the first time the results of structural and optical characterizations performed on Mercury Cadmium Telluride (MCT) grown simultaneously by Molecular Beam Epitaxy (MBE) on (11 1)B 4°misoriented and (211)B CdZnTe substrates. These two Te-terminated surfaces differ only by the density and the nature of their surface steps. In MBE conditions we do not observe any difference of incorporation between the two orientations at low growth temperatures and only a slight difference in Te and Hg incorporations above 200°C. This study confirms that the growth mode is essentially the same on both orientations and the growth proceeds by step-flow. The higher step density on (211) surfaces allows broader tolerances on the substrate temperature for the growth of twin-free material. It also leads to higher crystalline quality for the lowest temperatures. These observations have been confirmed by magneto-absorption experiments on superlattices grown simultaneously on both orientations.
Atomic Scale Properties of Normal and Inverted MBE-Grown Interfaces as Revealed by Zeeman Studies
Authors: Grieshaber W. , Bodin C. , Cibert J. , Wasiela A. , Merle-D'Aubigne Y. , Gaj J. , Feuillet G.
Published: April 2011

The enhanced Zeeman effect of excitons in asymmetric CdZnTe-CdTe-CdMnTe quantum wells is studied quantitatively to gain information separately on the profile of the normal and inverted interfaces. The normal interface appears as more “abrupt” than the inverted interface. This behaviour is well accounted for if we assume that during the growth a rapid Cd/Mn exchange takes place between the surface layer and the subsurface one.
Interface Reaction Kinetics for Permalloy-Tantalum Thin Film Couples
Authors: Kellock A.J. , Baglin J.E.E. , Coffey K.R. , Howard J.K. , Parker M.A. , Neiman D.L.
Published: April 2011

Thermal interdiffusion mechanisms and kinetics have been studied for Ta-Permalloy (Ni80Fe20), Ta-Ni and Ta-Fe thin film couples, in the temperature range 300°C - 600°C. Interaction modes identified for the Ta-NiFe system include: fast diffusion of Ta into grain boundaries of NiFe, and nucleation and growth of Ni3Ta, with consequent depletion of Ni in the remaining NiFe, and eventual segregation of Fe.
Grain Boundary Diffusion in NiFe/Ag Bilayer Thin Films
Authors: Gall M. , Pellerin J.G. , Ho P.S. , Coffey K.R. , Howard J.K.
Published: April 2011

X-ray photoelectron spectroscopy (XPS) has been used to investigate grain boundary diffusion of Ag through 250 Å thick Ni80Fe20 (permalloy) films in the temperature range of 375 to 475°C. Grain boundary diffusivities were determined by modeling the accumulation of Ag on Ni80Fe20 surfaces as a function of time at fixed annealing temperature. The grain boundary diffusivity of Ag through Ni80Fe20 is characterized by a diffusion coefficient prefactor, D0,gb, of 0.9 cm2/sec and an activation energy, Ea,gb, of 2.2 eV. The Ni80Fe20 film microstructure has been investigated before and after annealing by atomic force microscopy and x-ray diffraction. The microstructure of Ni80Fe20 deposited on Ag underlayers remained relatively unchanged upon annealing.
Microstructural Development at Ti-Based Alloy/Coated SiC
Authors: Strangwood M. , Ponton C.B. , Delplancke M.P. , Vassileris V. , Winand R.
Published: April 2011

The kinetics of formation of reaction layers at the interface between a Ti-based alloy (β-21s) and graphite blocks coated first, by CVD techniques, with a 100 μm layer of SiC and then either TiC or C were determined. The rate controlling step for reaction at 900°C and 10 MPa for up to 6 hours was found to be carbon diffusion through the reaction layer. The behaviour was found to be consistent with that of composite systems for prolonged heat treatment and the same growth behaviour was exhibited by both systems. Incubation times of 0.42 and 0.9 hours were determined for reaction layer growth in the TiC- and C-coated systems respectively. The reaction layer/Ti-alloy bond strength was good but all couples failed readily, especially if any C layers remained. The growth conditions of TiC coatings by reactive magnetron sputtering were determined for two different types of gas mixtures: CH4/Ar and C2H2/Ar. The composition and structure of the films were extensively studied.
Grain Growth Suppression and Enhancement by Interdiffusion in Thin Films
Authors: King Alexander H. , Harris Karen E.
Published: April 2011

Grain structure and grain growth in thin metallic films are important because of their effects on properties such as yield strength, electrical resistance and electromigration resistance. Since almost all thin films are used in contact with a substrate and many also have contacts with overlayers, it is important to consider how interactions with other materials affect the grain growth process. In this paper we consider the effects of diffusive interactions. We will show that interdiffusion often accompanies grain growth and that it can result in a number of novel grain boundary reactions, driven by a variety of effects. Using TEM techniques, we demonstrate cases of grain growth suppression and grain growth enhancement resulting from interdiffusion of solute atoms in gold thin films. The reasons for the observed effects will be considered with a view to providing a fundamental understanding of the types of systems that might be expected to exhibit the various phenomena.
Role of the Epitaxy Relations in the CoCrPt Thin Films with Bilayer V/Cr Underlayers
Authors: Glijer Pawel , Sivertsen John M , Judy Jack H
Published: April 2011

The effects of grain-to-grain epitaxy conditions on the magnetic properties of high coercivity CoCr13Pt13 films with bilayer Cr/Cr, V/Cr and V/V underlayers were studied. V/Cr films were used in order to obtain underlayers that would differ from Cr only by a size of the lattice constant. Introduction of V instead of Cr as an underlayer changed the relative misfits between CoCrPt and the underlayer lattice and increased the amount of {0002} texture in the magnetic film. This effect led to a decrease in the in-plane coercivity. CoCrPt/V/Cr and CoCrPt/Cr/Cr films exhibited similar texture of the underlayer, the same microstructure and similar level of internal stress. Correspondingly the decrease in coercivity did not exceed 10% (from 2.7 kOe to 2.5 kOe). On the other hand CoCrPt/V/V film had more than 4 times smaller coercivity (0.6 kOe). In this case, change in the magnetic properties was caused not only by altered misfits but also by the change in microstructure, texture and state of stress in the film. Results obtained indicate that small changes in misfits between a magnetic layer and an underlayer can be effectively used to control coercivity only if other structural parameters remain unchanged.
GMR, Structural, and Magnetic Studies in NiFeCo/Ag Multilayer thin Films
Authors: Jarratt J.D. , Barnard J.A.
Published: April 2011

Giant Magnetoresistance (GMR), crystal structure, and magnetic properties have been investigated in a series of sputtered Ni66Fe16Co18/Ag multilayer films with induced uniaxial anisotropy. The film thickness ranges studied were 20 and 25 Å for NiFeCo, and 25 to 50 Å for Ag. GMR was only evident in the films after post-deposition annealing. This onset of GMR is thought to be due to the breaking up of the NiFeCo layers into ferromagnetic platelets or islands by the immiscible Ag diffusing perpendicular to the film plane along the grain boundaries. The magnitude and field sensitivity of the GMR was dependent on the annealing time and temperature. High angle x-ray diffraction (HXRD) was used to reveal the overall film structure and growth texture and low angle XRD (LXRD) was used to investigate the quality of the multilayer structures. M-H hysteresis loops revealed in-plane uniaxial anisotropy in as-deposited films which is eventually eliminated with annealing. The easy axis squareness experiences a pronounced decrease with lower temperature annealing, but then increases slightly with annealing temperature.
Pulsed Laser Deposition of Bi4Ti3O12 Thin Films on Indium Tin Oxide Coated Glass
Authors: Cho H-J. , Jo William , Noh T. W.
Published: April 2011

Bi4Ti3O12 thin films have been grown on indium tin oxide coated glass by pulsed laser deposition. The films are rapidly thermal annealed at 650 °C in various kinds of ambients. X-ray diffraction and scanning electron microscopy are used to investigate crystallization and microstructures, respectively. Using Auger electron microscopy, chemical compositions and depth profiles are examined. Optical and current-voltage characteristics measurements of the films show that their transmittance and leakage current behaviors are strongly dependent upon the microstructures. O2 partial pressure in the rapid thermal annealing process is found to be an important parameter which determines crystallization, microstructures, and leakage current behaviors of the Bi4Ti3O12 thin films.
Improved Surface Roughness at Poly-Oxide/Poly-Si Interface by a Novel Oxidation Method
Authors: Jun M.C. , Kim J.W. , Kim K.B. , Ahn B.C. , Han M.K.
Published: April 2011

We present a novel oxidation method to improve the surface roughness at the poly-oxide/poly-Si interface. Instead of directly oxidizing the poly-Si to the desired thickness of the SiO2, a thin oxide layer is thermally grown on the poly-Si layer and then an a-Si layer is deposited on the top of the oxide layer. The a-Si layer is used as a silicon-source during next step of oxidation. The a-Si layer is fully oxidized until the poly-oxide/poly-Si interface advances below the initial interface. For comparison, the poly-oxide/poly-Si interface is also obtained by the conventional oxidation method. The surface roughness at the interface is investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM). For the novel oxidation method with the 50 Å thick intermediate oxide, the rms surface roughness at the poly-oxide/poly-Si interface is 30 Å, whereas that is 120 Å for the conventional method.
Growth of Rock-Salt and Spinel Structured Oxides on α-Al2O3, c-ZrO2and MgO
Authors: Ramamurthy Sundar , Kotula Paul G. , Carter C. Barry
Published: April 2011

Pulsed-laser deposition has been used to grow thin films of the rock-salt and spinel structured oxides NiO, CoO and C03O4on single-crystal substrates of α-Al2O3, MgO and C-Z1O2. The resultant microstructures were characterized in plan-view by transmission electron microscopy and by low-voltage scanning electron microscopy. In all the depositions, the parameters could be controlled to grow predominantly single-crystal films. In the NiO/(0001)α-Al2O3and CoO/(100)c-ZrO2systems, {111}-oriented films were observed which were found to be twinned close to 60° and 90° about <111> respectively. Growth of cobalt oxide films on (100) MgO at 800°C and 15 mTorr of oxygen produced {100}-oriented domains of C03O4meeting at antiphase boundaries. These observations and other recent studies re-emphasize the role of substrate crystallography in governing the orientation relationships in the overlayer.
The Effects of High Temperature Exposure on the Fracture of Thin Tantalum Nitride Films
Authors: Moody N. R. , Venkataraman S. K. , Nelson J. C , Worobey W , Gerberich Andw. W.
Published: April 2011

Continuous microscratch testing was used in this study to determine the effects of elevated temperature exposure on the adhesion and toughness of thin tantalum nitride films. These films were sputter-deposited at room temperature on sapphire substrates to a nominal thickness of 600 nm with some films heated to 600°C in vacuum while others were heated to 600°C in air. The films heated in vacuum exhibited no changes in composition or structure while the films heated in air completely transformed to tantalum pentoxide. Comparison of the results shows that the interfacial fracture toughness increases from 0.5 MPa-m1/2 for as-sputtered films to 0.8 MPa-m1/2 for films heated in air. However, the toughness increases to more than 3.0 MPa-m1/2 when the films are heated in vacuum. The increase in toughness values follows the reduction in deposition defect content where formation of an oxygen deficient tantalum oxide layer in air from the as-sputtered film increases interfacial toughness slightly while full densification of the tantalum nitride films in vacuum increases toughness to very high levels.
Mass Conservation in Grain Growth
Authors: Wu David T.
Published: April 2011

Several alternatives to Hillert’s work on grain growth have been proposed. Unfortunately some of these theories have been shown to violate mass conservation. This paper introduces a way to enforce conservation for any model via a term representing self-interaction of the grain distribution.
Local Texture and Electromigration in Fine Line Microelectronic Aluminum Metallization
Authors: Hurd J. L. , Rodbell K. P. , Knorr D. B. , Koligman N. L.
Published: April 2011

Aluminum films 1 μm thick were deposited on oxidized silicon by sputtering and partially ionized beam evaporation to vary the crystallographic texture. These films were patterned into lines and subsequently annealed at 400 °C for 1 h. A strong correlation between the electromigration behavior and the blanket film texture (X-ray diffraction (XRD) / pole figures) has been reported previously for these films. In this work, an Electron Backscatter Diffraction (EBSD) a.k.a. Backscatter Kikuchi Diffraction (BKD) technique was employed using a scanning electron microscope (SEM) to interrogate individual grain orientations. BKD pole figures were acquired for lines ≥0.3 μm wide and for blanket (pad) regions. Identical, inverse pole figures were found for blanket films measured using both XRD and BKD (pads). Furthermore, the BKD (111) fiber texture shows a line width dependency, with narrow lines having a slightly improved texture over blanket (pad) regions. Local grain orientations were investigated near and within electromigration testing sites with characteristic void and hillock morphologies. The relationship of neighboring grain orientations to electromigration damage is shown.
Fabrication of Polycrystalline Si1−xGex Films on Oxide for Thin-Film Transistors
Authors: Tsai Julie A. , Tang Andrew J. , Reif Rafael
Published: April 2011

Polycrystalline-Si1−xGex films have been formed by various methods on oxide-coated Si substrates at temperatures ≤600°C. Compared to thermal growth, plasma deposition of poly-Si1−xGex promotes smoother films with smaller grains having a {200}-dominated texture. Poly-Si1−xGex Alms formed by plasma deposition of amorphous-Si1-xGex followed by a crystallization anneal have an even smoother surface with grain sizes enhanced by an order of magnitude and a weak {111} grain texture. Hydrogen incorporated in amorphous-Si1−xGex evolves completely during crystallization without disrupting the smooth surface morphology. The largest grain sizes (∶1.3μm) are achieved in poly-Si1−xGex films formed by Si+ ion implantation for amorphization with a subsequent recrystallization anneal.
Microstructures of Chemical-Vapour-Deposited Tin Films
Authors: Yoshikawa Noboru , Kikuchi Atsushi
Published: April 2011

A gas mixture consisting of TiCl4, H2 and N2 was fed into an externally-heated steel tube, and TiN was deposited on the inner wall by CVD. Microstuctures of the films were observed and their relationships with the preferred crystal orientations were studied. Distributions of the film growth rate and gas concentrations along the axial direction were calculated.

By comparing the film microstructures with the calculated local deposition conditions, it is shown that formation of the films with (110) preferred orientation correlated with the conditions at high temperature and low partial pressure of TiCl4 on the substrate.
Deposition of Hydrogenated Si Films by Hydrogenation of the SiO2 Surface and Hydrogen Dilution with PE-CVD and ECR-CVD
Authors: Wang Kun-Chih , Yew Tri-Rung , Hwang Huey-Liang
Published: April 2011

This paper presents the results of low temperature deposition of poly-Si films deposited on SiO2 layers. Hydrogen dilution, hydrogen atom treatment, and hydrogenation of the SiO2 surface steps were applied to deposit the Si films. The above treatment steps were usually used in the plasma enhanced chemical vapor deposition and they were extended to be used in the electron cyclotron resonance chemical vapor deposition to identify the grain growth effects. The nucleation and microstructure of the silicon films were observed by cross-section transmission electron microscopy (XTEM).
Deposition and Crystallisation Behaviour of Amorphous Silicon Thin Films Obtained by Pyrolysis of Disilane Gas at Very Low Pressure
Authors: Kretz T. , Pribat D. , Legagneux P. , Plais F. , Huet O. , Magis M.
Published: April 2011

High purity amorphous silicon layers were obtained by ultrahigh vacuum (millitorr range) chemical vapor deposition (UHVCVD) from disilane gas. The crystalline fraction of the films was monitored by in situ electrical conductance measurements performed during isothermal annealings. The experimental conductance curves were fitted with an analytical expression, from which the characteristic crystallisation time, tc, was extracted. Using the activation energy for the growth rate extracted from our previous work, we were able to determine the activation energy for the nucleation rate for the analysed-films. For the films including small crystallites we have obtained En ∼ 2.8 eV, compared to En ∼ 3.7 eV for the completely amorphous ones.
Challenges For Flat Panel Display Phosphors
Authors: Maruska H. P. , Parodos T. , Kalkhoran N. M. , Halverson W. D.
Published: April 2011

Phosphors are a class of materials which emit visible light when impacted by either electrons or photons. Phosphors are the critical material in all self-emissive displays. The major display technologies which depend on phosphors are cathode ray tubes, flat cathode ray tubes (especially, field emission displays), thin film electroluminescent displays, and gas discharge plasma displays. Each of these technologies started with phosphors prepared in powder form, sprayed or screen printed onto a faceplate suitable for viewing. Electroluminescent displays have largely converted to thin film phosphors. It can be expected that, for many applications, the other competing technologies will also come to rely on more robust, high definition, thin film phosphors. Presently, full color displays must utilize several deposition and etching procedures to prepare the red, green, and blue pixels. Ion implantation of color centers is now paving the way for producing full color displays in a single host phosphor. We shall discuss the present limitations that compromise full color self-emissive displays, and present state-of-the-art solutions based on thin films and ion implantation.
Effect of Ion Doping Temperature on Electrical Properties of APCVD A-Si
Authors: Lee Kyung Ha , Moon Byeong Yeon , Chung Yoo Chan , Lee Seung Min , Kim Sung Chul , Kim Donggil , Jang Jin
Published: April 2011

We have studied the effect of ion doping on the electrical properties for atmospheric pressute chemical vapor deposition (APCVD) amorphous silicon (a-Si) films. The room temperature conductivities after ion doping at optimurr doping tenperatures for n− and p-type a-Si films were found to be > 10−2 and >10−4 S/cm, respectively. The unintentional hydrogen incorporation into a-Si during ion doping enhances the quality of ion doped APCVD a-Si as compared to that of plasma enhanced CVD (PECVD) a-Si:H. We obtained the field effect mobility of > 1 cm2/Vs for APCVD a-Si TFT using ion doped n+-layer.
Progress in Large Area Selective Silicon Deposition for TFT/LCD Applications
Authors: Souk Jun H. , Parsons Gregory N.
Published: April 2011

We have previously demonstrated selective area deposition of n+ microcrystalline silicon at 250°C using time modulated silane flow into a hydrogen plasma, and applied the technique to form high performance top-gate amorphous silicon TFT's with two mask sets. In this paper, we discuss issues related to process scale-up, including the effect of deposition rate on selectivity loss and non-uniformity. Uniformity can be achieved with higher growth rates by expanding the window for selectivity, and using conditions well within the process limits. We show that lower pressure and higher rf power can enlarge the window by enhancing the hydrogen-mediated silicon etching.
A Low Temperature Plasma-Assisted Deposition Process for Microcrystalline Thin Film Transistors, TFTS
Authors: He S. S. , Lucovsky G.
Published: April 2011

The drive-current of low-temperature (∼300°C) deposited TFTs has been increased by replacing the a-Si:H channel, and source and drain materials with μc-Si. Lightly B2H6 doped, near-intrinsic μc-Si has been used as the channel layer of the TFTs, and n+ μc-Si was used for the source and drain contacts. The compensation of intrinsic defects in the undoped μc-Si by boron doping increases the dark conductivity activation energy from ∼0.35 eV to 0.8 eV. TFI's were fabricated in a bottom gate structure, and required an H2 plasma treatment to produce devices with effective channel mobilities of ∼6.8 cm2/V-s and threshold voltages of ∼3.7 V in the saturation region.