bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth of Single Crystal Copper Films on Diamond Using Fcc-Iron Seed Layers
Authors: Pappas D. P. , Harris V. G. , Hoff H. A. , Watena G. L. , Glesener J. W. 
Published: April 2011

ABSTRACTCopper films were grown on a single crystal diamond substrate using an iron seed layer. The effect of the crystalline structure of the iron seed on the Cu films was studied with extended x-ray absorption fine structure (EXAFS) and scanning electron microscopy (SEM). The EXAFS study shows that the 10 Å Fe seed layer is in an fee structure, and has collapsed into a bec structure by the time 20 Å of Fe has been deposited. In the SEM pictures it is observed that subsequent layers of Cu grow as continuous films for thin fcc-Fe seeds, and grow in an island mode for the thick, bcc-Fe seeds.
Effect of Oxygen on the Textured Diamond Growth over Nickel Substrates
Authors: Ramesham R. , Rose M. F. , Askew R. F. , Bozack M. 
Published: April 2011

ABSTRACTMicrowave plasma has been used to grow diamond films using CH4 and H2 over nickel substrates. Nucleation of the diamond has been achieved by manual scratching and ultrasonic agitation of the substrates. The substrate was left in the H 2 microwave plasma to remove any oxide film present prior to the diamond growth. According to SEM the morphology of the grown films was (100) textured over the entire surface. Our interest is to study the effect of O2 on the growth rate and the morphology of as-deposited diamond films. Infact, O2 has a tendency to preferentially etch the diamond (etch rate: 111 > 110 >100). Injection of O2 into the reaction mixture could enhance the 100 texture further. Raman analysis confirms the deposited films as diamond. Effect of O2 on the nature of the films and the characterization of as-deposited films is described.
Initial Stages of Growth of Thin Films of III-V Nitrides and Silicon Carbide Polytypes by Molecular Beam Epitaxy
Authors: Davis Robert F. , Ailey K. S. , Kern R. S. , Kester D. J. , Sitar Z. , Smith L. , Tanaka S. , Wang C. 
Published: April 2011

ABSTRACTThe morphology and interface chemistry occurring during the initial deposition of BN, AlN and GaN films via metal evaporation and N2 decomposition under UHV conditions have been determined. FTIR spectroscopy and TEM revealed the consecutive deposition of an initial 20Å layer of a-BN, 20–60Å of oriented h-BN, and a final layer of polycrystalline c-BN. This sequence is attributed primarily to increasing intrinsic compressive stress in the films. XPS analysis revealed the growth of GaN on sapphire to occur via the Stranski-Krastanov mode; growth on SiC showed characteristics of three-dimensional growth. AlN grew layer-by-layer on both substrates. Vicinal 6H-SiC(0001) substrate surfaces contain closely spaced, single bilayer steps. During deposition of Si and C at 1050°C, 6H layers initially form and step bunching occurs. The latter phenomenon results in more widely spaced steps, the nucleation of 3C-SiC both on the new terraces and at the larger steps and formation of double position boundaries. The C/Si ratio in the gaseous reactants also affects the occurrence of these three phenomena.
Acceptor Binding Energy And Band Lineup Of III-V Nitride Alloys And Mocvd Growth Of GaN On GaAs - Or GaP-Coated Si
Authors: Ueta Yoshihiro , Sakai Shiro , Kamiya Yasushi , Sato Hisao 
Published: April 2011

ABSTRACTThe acceptor binding energy is calculated to find out the best acceptor impurity in InN, GaN and AlN. Be is predicted to be the shallowest acceptor and the next are Mg and Zn. Group IV elements such as C or Si are very deep. Band lineup is calculated to be ΔEc : ΔEv = 2.1 eV : 0.76 eV = 0.73 : 0.27 = 2.8 : 1 for GaN/AlN and ΔEc : ΔEv = 0.88 eV : 0.66 eV = 0.57 : 0.43 = 1.3 : 1 for GaN/InN. GaN is grown on GaAs and GaP-coated Si substrate by MOCVD. GaAs intermediate layer gives better GaN compared to GaP intermediate layer. It is suggested that the lower bulk modulus of GaAs than that of GaP gives this difference.
Surface Preparation of Single Crystal C(001) Substrates for Homoepitaxial Diamond Growth
Authors: Humphreys T. P. , Posthill J. B. , Malta D. P. , Thomas R. E. , Rudder R. A. , Hudson G. C. , Markunas R. J. 
Published: April 2011

ABSRACTA novel substrate preparation procedure which can be employed to remove the original surface from as-received C(001) natural diamond substrates has been developed. A description of the various substrate processing steps which includes, low-energy ion implantation of C and O, high-temperature annealing, electrochemical etching and surface plasmas treatments is presented. Also demonstrated is the growth of topographically excellent homoepitaxial films by rf-plasma-enhanced chemical vapor deposition using water/ethanol mixtures on C(001) substrates.
Raman and Photoluminescence Studies of Undoped and Magnesium-Doped Gan Films on Sapphire
Authors: Freitas Jaime A. , Asif Khan M. 
Published: April 2011

ABSTRACTRoom temperature Raman scattering measurements performed on undoped GaN films indicate that high crystalline quality wurtzite material has been deposited on the basal plane of sapphire. Photoluminescence study of these films show that thicker films (t > 4μm) are homogeneous along the growth direction. The PL spectra of Mg-doped films are dominated by an intense emission band around 3.1 eV associated with recombination processes involving donor-acceptor pairs.
Redistribution of Hydrogen in Gan, Ain, and Inn
Authors: Zavada J. M. , Wilson R. G. , Pearton S. J. , Abernathy C. R. 
Published: April 2011

ABSTRACTHydrogen incorporation during gas-phase growth of III-V nitrides is thought to play an important role in determining the apparent doping efficiency, due to unintentional passivation of dopants. Hydrogen implantation can also be used for electrical and optical isolation of neighboring devices, as in other lll-V materials such as GaAs. We have implanted2H at 40 keV to doses of 5 × 1015cm-2at room temperature into epitaxial layers of GaN, AIN and InN grown by MOMBE on GaAs substrates, and measured the ion ranges and hydrogen redistribution upon subsequent furnace annealing. The hydrogen profiles remain unchanged for annealing temperatures up to 800–900°C for GaN and AIN, and 600° for InN. Samples were also deuterated from an ECR plasma at 250 or 400°C for 30 min, producing2H incorporation depths of ≤ 1 μ in GaN. With annealing, there is no significant hydrogen redistribution observed at temperatures up 800°C. Hydrogen concentrations remain in the range ∼ 1019cm-3under these conditions. At 900°C considerable hydrogen outdiffusion to the surface occurs. The thermal stability of hydrogen in these III-V nitride films indicates the need for post-growth annealing at high temperatures to achieve appreciable doping efficiencies.
Free Carrier Absorption in N-Type 6H-SiC
Authors: Engelbrecht F. , Helbig R. 
Published: April 2011

ABSTRACTFree carrier absorption (FCA) in n-type 6H-SiC doped with nitrogen has been studied in the energy range 50–250 cm-1 using samples of different free carrier concentrations ranging from 2.0–1016cm-3 to 7.0–1017cm-3. The index of wave number dependence of FCA p varies between -1.4 and -0.55 depending on free carrier concentration and electron mobility. The experimental results are in good agreement with the classical expression for the FCA coefficient. Quantum mechanical expressions for the FCA coefficient do not reproduce the measured p values. It is supposed that this is due to fact that the requirement for the application of perturbation theory ΩT ≫ 1 is not fulfilled. We investigated the anisotropy of FCA with respect to the c-axis and find a strong difference between ∝ ┴ and ∝∥.
Comparison of Surface Cleaning Processes for Diamond C(001)
Authors: Baumann Peter K. , Humphreys T. P. , Nemanich R. J. 
Published: April 2011

ABSTRACTTwo wet chemical cleaning processes (a conventional chromic acid clean and an electrochemical etch) and a H-plasma exposure have been employed to clean natural type lib semiconducting diamond C(001) wafers. The effects of these processes on the diamond surface have been assessed and compared. As evidenced by Auger electron spectroscopy (AES), an oxygen free surface could be obtained following annealing to 900°C for the electrochemical process compared to 1050°C for the chromic acid etch. In addition, the technique of Atomic Force Microscopy (AFM) demonstrated the presence of oriented pits on the surface of samples electrochemically etched for long times at high currents. Furthermore, heteroepitaxial Cu films have been grown on the diamond substrates cleaned by a process as described above. By means of Ultraviolet Photoemission Spectroscopy (UPS) a Schottky barrier height of ΦB≊ 1.0 eV was measured. Furthermore, the presence a negative electron affinity (NEA) has been determined.
Characterization of Defects in N-Type 6H-SiC Single Crystals by Optical Admittance Spectroscopy
Authors: Evwaraye A. O. , Smith S. R. , Mitchel W. C. 
Published: April 2011

ABSTRACTOptical admittance spectroscopy is a technique for measuring the conductance and capacitance of a junction under illumination as a function of the wavelength of the light and the frequency of the measuring AC signal. This technique has been applied to characterize deep defect levels in 6H-SiC:N. Nitrogen is a donor atom in 6H-SiC which substitutes for carbon in three inequivalent sites (h, k1, k2). giving rise to n-type conduction. Deep defect levels attributable to transition metal impurities have also been identified in 6H-SiC:N. We have examined persistent photoconductance in this material by optical admittance spectroscopy.
The Effect of Phosphine Pressure on the Band Gap of Ga0.5In0.5P
Authors: Kurtz Sarah R. , Arent D. J. , Bertness K. A. , Olson J. M. 
Published: April 2011

ABSTRACTThe band gap of Ga0.51n0.5P is studied as a function of phosphine pressure, B-type substrate misorientation, growth rate, and growth temperature, with emphasis placed on the effect of the phosphine pressure. Over most of the parameter space explored (high temperatures, large substrate misorientations, and low growth rates), the band gap increases with decreasing phosphine. This increase is proposed to be caused by lower phosphorus coverage of the surface, resulting in a different surface structure that doesn't promote ordering. The implications of this effect on the observed variations of band gap with growth temperature, substrate misorientation, and growth rate are discussed. For regions of parameter space in which the ordering appears to be kinetically limited by surface diffusion, the band gap increases slightly with phosphine pressure, consistent with observations that increased group-V pressure decreases the group-III surface diffusion length.
Study of GaInP/GaAs/GaInP Double Heterostructures Grown by MOCVD with Photoreflectance and Photoluminescence
Authors: Kuan H. , Shei S.C. , Tzou W.J. , Su Y. K. 
Published: April 2011

ABSTRACTThe GaInP-GaAs single quantum well structures grown by metal-organic chemical vapor deposition (MOCVD) were investigated by photoreflectance (PR) and photoluminescence (PL) spectroscopies. The built-in electric field in the GaAs close to the top surface was evaluated using the observed Franz-Keldysh oscillations. The fundamental energy gaps and broadening parameters were also determined. The full width at half maximum (FWHM) of the GaInP PL peak is 11 meV
New Technology and Developments in Compound Semiconductor Vertical RDR-MOCVD Growth Systems
Authors: McKee M. , Tompa G.S. , Zawadzki P.A. , Thompson A. , Gurary A. , Beckham C. , Schumaker N.E. , Moy K. 
Published: April 2011

ABSTRACTCompound semiconductors are at the heart of todays advanced digital and optoelectronic devices. As device production levels increase, so too does the need for high throughput deposition systems. The vertical rotating disk reactor (RDR) has been scaled to dimensions allowing metal organic chemical vapor deposition (MOCVD) on multiple substrates located on a 300 mm diameter platter. This symetric large area reactor affords easy access over a wide range of angles for optical monitoring and control of the growth process. The RDR can be numerically modeled in a straightforward manner, and we have derived scaling rules allowing the prediction of optimum process conditions for larger reactor sizes. The material results give excellent agreement with the modeling, demonstrating GaAs/AlAs structures with <±0.9% thickness uniformities on up to 17-50mm or 4-100mm GaAs substrates. Process issues related to reactor scaling are reviewed. With high reactant efficiencies and short cycle times between growths, through the use of a vacuum loadlock, the costs per wafer are found to be dramatically less than in alternative process reactors. The high reactant utilization, in combination with a dedicated and highly efficient exhaust scrubbing system, minimizes the systems environmental impact.
Chemical Beam Epitaxy (CBE) and Laser-Enhanced CBE of GaAs Using Tris-Dimethylaminoarsenic
Authors: Dong H. K. , Li N. Y. , Tu C. W. , Geva M. , Mitchel W. C. 
Published: April 2011

ABSTRACTIn this paper, we report chemical beam epitaxy (CBE) of GaAs, and for the first time, Arion laser-assisted CBE using triethylgallium (TEGa) and tris-dimethylaminoarsenic (TDMAAs), a safer alternative to arsine. Samples grown at substrate temperatures above 490° C show n-type conduction, while those grown at lower temperatures show p-type conduction. An unintentional doping concentration of n∼lx1016 cm-3 with an electron mobility of 5200 cm2/V.s at 300 K and 16000 cm2/V.s at 77 K have been achieved. These are the best results reported for GaAs grown with TDMAAs. Laser-assisted CBE of GaAs is studied in the substrate temperature range of 240-550°C. There are two different substrate-temperature regions for laser-enhanced growth, 265 to 340°C and 340 to 440°C, which are believed to be caused by different TEGa decomposition mechanisms. The laser-assisted growth with TDMAAs, compared to AS4 or AsH3, shows a wider range of growth enhancement at low substrate temperatures.
A Second-Harmonic Generation Study of GaAs-Oxide Removal Using a Hydrogen Plasma
Authors: Kimura Takahiro , Yamada Chikashi 
Published: April 2011

ABSTRACTWe observed a second-harmonic generation (SHG) in reflection from a GaAs (100) surface during an oxide removal process using a pulsed hydrogen plasma. We found that the P-polarized SH intensity under P-polarized excitation decreased in the [011] azimuth of incidence and increased in the [011] azimuth of incidence during hydrogen plasma irradiation. The input polarization angle dependence of the P-polarized SH intensity before and after oxide removal was fitted to a model which includes both the surface and bulk SHG contributions. We estimated the thickness of the removed oxide based on the bulk SHG contribution change.
AlGaAs Surface Reconstruction after Cl2 Chemical Etch and Ultra High Vacuum Anneal
Authors: Hong M. , Mannaerts J. P. , Grober L. H. , Thiel F. A. , Freund R. S. 
Published: April 2011

ABSTRACTWe report attaining (3x2) surface reconstruction with streaky reflection high energy electron diffraction (RHEED) patterns on Al0.4Ga0.6As after in-situ Cl2 chemical etch and ultra high vacuum (UHV) anneal. Secondary ion-mass spectrometry (SIMS) analysis at the regrown/etched Al0.4Ga0.6 As interface reveals impurities of O and C in the level of (5±1) × 1012 cm-2 and (3±1) × 1012 cm-2, respectively. These impurity levels are 10 times less than those of Al0.4Ga0.6 As after in-situ electron cyclotron resonance (ECR) plasma etch and UHV anneal without Cl2 chemical etch.
Doping Efficiency and Deep Traps in MOCVD-Grown InGaAlP as Influenced by Stoichiometry and Hydrogen Passivation
Authors: Gorbylev V.A. , Chelniy A.A. , Chekalin A.A. , Polyakov A.Y. , Peaon S.J. , Smirnov N.B. , Govorkov A.V. , Leiferov B.M. , Popova E.V. , Kusikov V.A. , Balmashnov A.A. 
Published: April 2011

ABSTRACTIt is shown that the low electrical activity of Zn in MOCVDgrown InGaAlP is related to hydrogen passivation during growth and that the effect is sensitive to growth conditions. We also discuss the results of hydrogen plasma treatment of p- and n-InGaAlP layers.
Ge Optical Interconnects on a GaAs Surface
Authors: Dubey M. , McLane G.F. , Jones K.A. , Lareau R.T. , Eckart D.W. , Han W.Y. , Roberts C. , Dunkel J. , West L.C. 
Published: April 2011

ABSTRACTGermanium films were deposited on GaAs (100) substrates at temperatures between room temperature (RT) and 500°C using ultra high vacuum (UHV) E-beam and sputtering deposition methods. The Ge film deposited in UHV at 100°C was amorphous and had a flat absorbance curve over the range investigated, 4000 - 500 cm-1, with a value of 0.03 at 1000 cm1 (10μm). Films deposited by E-beam at RT and 50°C had comparably low absorbances, but they contained a peak at 830 cm-1, which was possibly due to absorption by a Ge-O bond. The amorphous film deposited at 150°C and the single crystal films deposited at 400 and 500°C by E-beam had larger absorbances caused by free carrier absorption. The amorphous Ge sputtered film deposited at RT had a relatively low absorbance, but it contained the absorption peak attributed to Ge-O. The absorbance increased dramatically when it was annealed at 400 or 500°C due to the rapid out diffusion of Ga and As through the relatively open structure.
Plasma assisted nitrogen doping of ZnSe grown by MOVPE
Authors: Cloitre T. , Briot O. , Briot N. , Gil B. , Aulombard R.L. 
Published: April 2011

ABSTRACTWe designed a plasma cell for nitrogen doping of ZnSe, using a metal organic vapour phase epitaxy (MOVPE) horizontal reactor. With the following growth conditions: Tg=300°C, P=1 Torr and a molar VI/II ratio of 5, successful p-type doping was obtained, as assessed by photoluminescence experiments, but with a free carrier concentration still too low to be detected by transport measurements. The passivation of nitrogen active species by hydrogen is discussed. The possible interaction with the carrier gas has been studied through the use of H2, N2 and He as carrier gases. We demonstrate that the use of helium as carrier gas leads to sensible improvement of the photoluminescence features related to nitrogen acceptor. On the other hand, the use of N2 as carrier gas leads to poor homogeneity of the layers with few effects on the doping level.
Effects of Post-Deposition Processing on the Ultimate Grain Size in Metastable Semiconductor Thin Films to be Used in IR Detectors
Authors: Lee Susanne M 
Published: April 2011

ABSTRACTThrough post-deposition annealing in a differential scanning calorimeter (DSC), we have manufactured both thin (200 nm) and bulk (8000 nm) single phase films of crystalline Ge1–xSnx, using rf sputtering. The Sn concentrations produced ranged up to 31 at.%, well beyond the solid solubility limit of this system. There was a marked difference, in the asdeposited structure, between thick and thin films produced under the same deposition conditions. Quantitative models for both systems are given in this paper and were deduced frorn DSC measurements in conjunction with electron microscopy. The metastable crystalline state in the thin films formed by nucleation and growth from an amorphous phase; whereas in the thick films, the desired phase was already present in the as-deposited films and only growth of preexisting grains was observed upon post-deposition annealing. When annealed to high temperature, the Sn phase separates from the alloys and we postulate here that it does so by nucleation and growth of β-Sn. With this hypothesis, the Sn separation in the 8000 nm thick films was accurately modeled by a two-mechanism process, however, in the 200 nm thick films, only one phase separation mechanism was necessary to accurately fit the data. Both models were corroborated by the subsequent melting behavior of the phase separated Sn which, though it varied depending on the sample being measured, always exhibited a melting endotherm starting 25–35°C lower than the bulk melting temperature of Sn. Speculation on the reasons for this are presented.
Phase Formation and Microstructural Development During Solid-State Reactions in Ti-Al Multilayer Films
Authors: Michaelsen Carsten , Wöhlert Stefan , Bormann RÜdiger 
Published: April 2011

ABSTRACTThe phase selection which is generally observed in the early stages of solid-state reactions was studied using Ti-Al multilayer films as a model system.Although all Ti-Al intermetallic phases have similar driving forces of about 30 kJ/g-atom, TiAl3 is the only phase which is formed as long as the reactants are not consumed. The critical thickness beyond which a second phase is formed is larger than 100 μm. We found that the formation of TiAl3 takes place by nucleation and growth, demonstrating that the driving force available for first-phase formation is considerably reduced by a preceding formation of solid solutions. Furthermore, we observed that nucleation continues at later stages, indicating that non-equilibrium conditions are maintained which are possibly influenced by grain-boundary diffusion. However, the phase selection is determined by the different growth velocities, being much higher for TiAl3 than for all other phases.
Artificially Synthesized Non-Coherent Interfaces in Fe-Ti Multilayers and their Influence on Solid State Reactions
Authors: Yan Z.H. , Trudeau M.L. , Van Neste A. , Schulz R. , Ryan D.H. , Tessier P. , Bormann R. , Ström-Olsen J.O. 
Published: April 2011

ABSTRACTThe influence of the interfacial structure on the solid state reaction products in Fe-Ti multilayers has been studied using various preparation conditions and characterization techniques. Sharp and diffused interfaces were produced by using either sequential or co-evaporation in the interfacial region. The reaction product, in the case of the sharp interface, is the bcc supersaturated solid solution of Ti(Fe) while, in the case of the diffused interface, an amorphous phase is formed. Therefore, nucleating the amorphous phase at the interface by local co-evaporation alters the reaction path observed in Fe-Ti multilayers. The solid state reactions were studied using low and high angle X-ray diffraction and Mossbauer measurements. The results are discussed in light of recent thermodynamic calculations on the Fe-Ti system.
Correlation of Structure and Properties in Thin-Film Magnetic Media
Authors: Nolan T. P. , Sinclair R. , Ranjan R. , Yamashita T. , Tarnopolsky G. , Bennett W. 
Published: April 2011

ABSTRACTCorrelation of detailed microstructural information obtained from a temperature series (25–275°C) of otherwise identical CoCrTa/Cr recording media with detailed recording performance measurements demonstrates two mechanisms for magnetic isolation.Media were prepared by sputter deposition of 75 nm Cr underlayers and 60 nm Co84Cr12Ta4 layers onto circumferentially textured NiP plated aluminum substrates using an Intevac MDP-250 machine.High-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) show columnar isolation by voiding, via the mechanism of shadowing during low temperature growth. Shadowing decreases with increasing temperature until voiding disappears at 150°C. At high temperature (275°C), large intergranular separation is observed, which has been attributed to elemental segregation. This separation decreases as temperature decreases, until it disappears at 150°C.Detailed magnetic recording measurements show that the maximum normalized media noise power is observed at 150°C. It decreases as more isolated structures are formed by increasing or decreasing temperature. Uniform magnetization noise, a measurement related to crosstrack correlation length within a magnetization transition also shows this trend.It is suggested that HRTEM shows two different microstructural features that control magnetic correlation lengths and resulting media noise.