bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Properties of Hydrogen Ated Amorphous Germanium Nitride a-GeNx:H
Authors: Hioki M. , Nitta S. , Takeda Y. , Yamamoto K. , Sasaki M. , Itoh T. , Nonomura S.
Published: April 2011

The properties of a-GeNx:H films have been studied including the effects of oxygen and carbon impurities. The contamination of a-GeNx:H with oxygen and carbon is expressed as a-GeNx(OyCz):H, where x=N/Ge, y=O/Ge and z=C/Ge. The characteristics of a-GeNx(OyCz):H are summarized as follows: the sample is transparent at the center of a film, and the color of a film varies to light yellow and to brown at the outer edge depending on the magnetic field of the magnetron sputtering. The compositional ratios of the film vary from x=0.34 to 0.28, y=0.15 to 0.25 and z=0.05 to 0.02 at the center and at outer edge of a film, respectively. Optical gap energy EO5, obtained by the photon energy at optical absorption coefficient of 5×103 cm−1, are 2.9 eV at the center and 1.7 eV at the outer edge of a film. Eo5 increases with the nitrogen content x in a-GeNx(OyCz):H but is independent of the content of oxygen and carbon.
Structural Relaxation of Vacancies in Amorphous Silicon
Authors: Kim Eunja , Lee Young Hee , Chen Changfeng , Pang Tao
Published: April 2011

We have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp2 + p bonding near the band edges. We have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.
An AFM Study of The Effect of Growth Method and Conditions on The Microstructure of A-Si:H
Authors: Kwon Daewon , David Cohen J. , Garcia Ricardo
Published: April 2011

We utilized atomic force microscopy (AFM) to investigate the microstructure at the surface of thick (>4000 Å) hydrogenated amorphous silicon films. The films were prepared by standard glow discharge (GD) as well as hot wire chemical vapor deposition (HWCVD) techniques. We studied a series of films with substrate temperatures ranging between 200 °C and 400 °C. We also studied the effects of various gas mixtures at fixed growth temperature on the observed microstructure. We found that the average feature grain size in the micro structure varied between 40 nm and 90 nm as the substrate temperature was changed and also as the different gas mixtures were employed during growth. The grain size decreased with increasing substrate temperatures for the films grown from 100 % silane independent of whether the growth method were GD or HWCVD. Gas dilution with argon or hydrogen also resulted in a size reduction, as did PH3 doping at dilute levels. These results rule out the possibilities that the observed features arise from particle production in the reactor chamber itself. The relation of the observed micro structure to the electronic properties of a-Si:H is discussed.
In-Situ Monitoring of Surface Hydrogen on the a-SiGe:H Films
Authors: Toyoshima Y. , Ganguly G. , Ikeda T. , Saitoh K. , Kondo M. , Matsuda A.
Published: April 2011

The bonded hydrogen on the growing surface of hydrogenated amorphous silicon germanium (a-SiGe:H) alloy films has been investigated by use of infrared reflection absorption spectroscopy (IR-RAS). When the alloy films are Si-rich, the surface hydrogen bonded to Si atoms is found to behave in a similar way to those on the hydrogenated amorphous silicon (a-Si:H) films. This means that the thermal desorption stability of surface Si hydride species is not significantly affected by the coexistence of a small amount (typically 20 at.%) of Ge. On the contrary, the desorption behavior of surface hydrogen depends on the alloy composition when the a-SiGe:H films are Ge-rich. A surface reaction scheme is provided in an attempt to explain this series of behavior in surface hydrogen on the a-SiGe:H films.
Light-Induced Metastable Defects or Light-Induced Metastable H Atoms in a-Si:H Films?
Authors: Godet C.
Published: April 2011

In hydrogenated amorphous silicon (a-Si:H) films, the increase of the metastable defect density under high-intensity illumination is usually described by an empirical two-parameter stretched-exponential time dependence (characteristic time τSE and dispersion parameter β). In this study, a clearly different (one-parameter) analytic function is obtained from a microscopic model based on the formation of metastable H (MSH) atoms in a-Si:H films. Assuming that MSH atoms are the only mobile species, only three chemical reactions are significant : MSH are produced from doubly hydrogenated (SiH HSi) configurations and trapped either at broken bonds or Si-H bonds, corresponding respectively to light-induced annealing (LIA) and light-induced creation (LIC) of defects. Competition between trapping sites results in a saturation of N(t) at a steady-state value Nss. A one-parameter fit of this analytical function to experimental data is generally good, indicating that the use of a statistical distribution of trap energies is not necessary.
Evidence of Hysteresis in a New p-i-n-i-p-i-n Amorphous Silicon Device
Authors: Caputo D. , De Cesare G. , Palma F.
Published: April 2011

A novel device based on a-Si:H p+-i-n−-i-p−-i-n+ structure, showing a hysteresis in its current-voltage curve is reported. A numerical device model allows to investigate in detail the fundamental role of the two lightly doped n− and p− layers, where charge trapping determines the bistable behavior of the device. The ON condition is mantained until the ambipolar charge injection overcomes the fixed charge. The transition OFF-ON starts when, increasing the applied voltage, one of the two lightly doped layers becomes completely depleted. The transition ON-OFF is, instead, mainly dependent on the recombination processes occurring in the central doped layers. Devices with hysteresis around 2 V and tum-on voltage around 12 are presented.
High Sensitivity Photochemical Sensors Based on Amorphous Silicon
Authors: Fortunato E. , Malik A. , Séco A. , Maçarico A. , Martins R.
Published: April 2011

Hydrogenated amoiphous silicon photochemical sensors based on Pd-MIS structures were produced by Plasma Enhanced Chemical Vapor Deposition with two different oxidized surfaces (thermal and chemical oxidation). The behaviour of dark and illuminated current-voltage characteristics in air and in the presence of a hydrogen atmosphere is explained by the changes induced by the gases in the work function of the metal, modifying the electrical properties of the interface. The photochemical sensors produced present more than 2 orders of magnitude variation on the reverse dark current when in presence of 400 ppm hydrogen to which it corresponds a decrease of 45% on the open circuit voltage.
Gallium Nitride Doped with Zinc and Oxygen - The Crystal for the Blue Polarized Light-Emitting Diodes
Authors: Sidorov V. G. , Drezhuk A. G. , Zaitsev M. V. , Sidorov D. V.
Published: April 2011

Epitaxial layers and light-emitting i-n-structures with the active region of GaN doped simultaneously with zinc and oxygen have been grown. Effective up to 60% blue polarized luminescence has been observed. Investigated properties of grown layers and structures are presented. A discussion of issues related to GaN utilization based on its found properties is also included.
Raman Scattering and Photoluminescence of Mg Doped GaN Films Grown by Molecular Beam Epitaxy
Authors: Popovici G. , Xu G. Y. , Botchkarev A. , Kim W. , Tang H. , Salvador A. , Strange R. , White J. O. , Morkoζ H.
Published: April 2011

Raman, photoluminescence, and Hall measurements are reported for Mg doped GaN films grown by molecular beam epitaxy. The compressive and tensile stress determined by the Raman shift of the phonon lines is due to the growth conditions rather than the presence of Mg in the film. The photoluminescence peak of near band-to-band transitions is also shifted to larger (smaller) energies by the compressive (tensile) stress. The study of the longitudinal optical phonon of the Ai branch shows that its Raman line shape is affected not only by phonon-plasmon interactions but by the crystalline quality of the film, as well.
Optical Anisotropy of the Optical Response for Strained GaN Epilayers Grown Along the <10–10> Direction
Authors: Andenet A. , Gil B. , Le Vaillant Y.-M. , Clur S. , Briot O. , Aulombard R. L.
Published: April 2011

Group theory states that the spectroscopy of excitons in GaN epilayers grown with biaxial stress on M Plane (10–10)-oriented substrates is strongly anisotropie in the growth plane, in contrast to the situation if growth occurs on conventional C plane substrates. In addition, we predict existence of nine radiative transitions instead of five, three for each family of A, B, and C excitons. We calculate the in-plane anisotropy and show that, due to the crossed configuration of the wurtzite crystal field and the built-in strain one, the A exciton is significantly coupled to the electromagnetic field in π polarization (E//c).
A Chemical and Structural Study of the AlN-Si Interface
Authors: Beye R. , George T.
Published: April 2011

Samples of AlN grown on silicon [111] substrates were examined using electron energy loss spectroscopy (EELS) and selected area diffraction (SAD) with high-resolution transmission electron microscopy (TEM) to determine the source of out-of-plane tilts and in-plane rotations of the AlN crystallites at the Si interface. SAD results indicate that the interfacial crystallites are sheared along vertical planes, with random, intercrystalline rotation. The interfacial phenomena are believed to be the result of Si-Al-N interaction. Analytical experiments show no evidence of silicon nitride formation, witnessed by nitrogen-K peak shape, up to the Si interface. No evidence of substrate-epilayer interdiffusion was observed. Chemical interaction within one monolayer of the interface is therefore suspected as the cause of the epilayer tilts and rotations.
Growth of Ternary Silicon Carbon Nitride as a New Wide Band Gap Material
Authors: Cheni L. C. , Chen C. K. , Bhusari D. M. , Chen K. H. , Wei S. L. , Chen Y. F. , Jong Y. C. , Lin D. Y. , Li C. F. , Huang Y. S.
Published: April 2011

Growth of pure crystalline carbon nitride (c-CN) with crystal sizes large enough to enable measurement of its properties has not been achieved so far. We report here that incorporation of silicon in the growth of CN can promote formation of large, well faceted crystallites. Crystalline thin films of SiCN have been grown by microwave plasma-enhanced chemical vapor deposition using CH4, N2, and SiH4 gases. Auger electron spectroscopy, scanning electron microscopies, and X-ray diffraction spectroscopy have been employed to characterize the composition, the morphology and the structure of the films. The new crystalline ternary compound (C; Si)xNy exhibits hexagonal structure and consists of a network wherein the Si and C are believed to be substitutional elements. While the N content of the compound is about 35%, the extent of Si substitution varies from crystal to crystal. In some crystals, the Si content can be as low as 10%. Optical properties of the SiCN compounds have been studied by photoluminescence (PL) and piezoreflectance (PzR) spectroscopies. From the PzR measurement, we determine the band gap of the new crystals to be around 3.8 eV at room temperature. From the PL measurement, it is found that the compounds have a strong subband-gap emission centered around 2.8 eV at room temperature, which can be attributed to the effect of defects containing in the crystals.
Current Transport in W and WSIX Ohmic Contacts to Ingan and Inn
Authors: Vartuli C. B. , Pearton S. J. , Abernathy C. R. , MacKenzie J. D. , Lovejoy M. L. , Shul R. J. , Zolper J. C. , Baca A. G. , Hagerott-Crawford M. , Jones K. A. , Ren F.
Published: April 2011

The temperature dependence of the specific contact resistance of W and WSi0.44 contacts on n+ In0.55Ga0.35N and InN was measured in the range -50 °C to 125 °C. The results were compared to theoretical values for different conduction mechanisms, to further elucidate the conduction mechanism in these contact structures. The data indicates the conduction mechanism is field emission for these contact schemes for all but as-deposited metal to InN where thermionic emission appears to be the dominant mechanism. The contacts were found to produce low specific resistance ohmic contacts to InGaN at room temperature, ϱc ∼ 10-7 Ω ·cm2 for W and ϱc of 4× 10-7 Ω ·cm for WSix. InN metallized with W produced ohmic contacts with ϱc ∼ 10-6 Ω ·cm and ϱc ∼ 10-6 Ω ·cm. for WSix at room temperature.
Low Resistance Contacts to P-Type GaN
Authors: Kim Taek , Khim Jinseok , Chae Suhee , Kim Taeil
Published: April 2011

We report the low resistance ohmic contacts to p-GaN using a Pd/Au bimetal scheme. A specific contact resistivity of 9.1 × 10-3 Ω-cm2 was obtained after annealing. The metallization was e-beam evaporated on 2 μm-thick p-GaN (∼ 9 × 1016/cm3) layers grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The comparison with other contacts showed that the contact resistivity of the Pd/Au contacts was at least one order smaller than those of Pt/Au and Ni/Au contacts.
Pulsed Laser Deposition of Gallium Nitride on Sapphire
Authors: Talyansky V. , Vispute R. D. , Sharma R. P. , Choopun S. , Downes M. J. , Venkatesan T. , Li Y. X. , Salamanca-Riba L. G. , Wood M. C. , Lareau R. T. , Jones K. A.
Published: April 2011

We have fabricated high quality single crystalline GaN films on sapphire (0001) substrates using pulsed laser deposition. Our best GaN films on sapphire (0001) featured the FWHM of the GaN (002) peak rocking curve of 7 arcmin, the RBS minimum yield of only 3%, and the energy gap width of 3.4 eV. The effect of the deposition temperature on the crystalline quality of the films is discussed.
Optimization of the Ast Hot Liner™ for Sub-Micron Production
Authors: Riley Terrence J. , Bremensdorfer Rolf , Marcus Steve
Published: April 2011

In an effort to develop an emissivity independent temperature measurement technique for the AST Rapid Thermal Processor (RTP), AST has conceived of the Hot Liner™. The Hot Liner is a silicon nitride coated silicon wafer which is permanently installed in the process chamber, immediately below the wafer. The pyrometer, which is calibrated to a production wafer, views the constant emissivity Hot Liner to produce repeatable temperatures on product wafers regardless of their backside emissivity.

Given the repeatability of the Hot Liner, the wafer temperature uniformity must then be optimized in order to achieve 0.25μm capable processing. AST has developed a methodology which incorporates process monitors (ion implanted test wafers) to establish process uniformity in addition to multiple thermocouple wafers to verify across wafer temperature uniformity. The process monitors are used to separately optimize the ramp and steady state steps in the production recipe.

Utilizing the AST methodology to optimize processing with the Hot Liner has allowed AMD to significantly improve its RTA processing. The Hot Liner greatly decreases backside and pyrometer effects which yields limited wafer to wafer variation (< 5C, 3σ). In combination with the optimization process this results in excellent within wafer uniformity (< 3C, 3σ).
Ultra Low Thermal Budget Rapid Thermal Processing for Thin Gate Oxide Dielectrics: Reduction of Suboxide Transition Regions in Low Temperature Processed Si/SiO2Structures by A 900°C 30 Second Rapid Thermal Anneal
Authors: Lucovsky G. , Hinds B.
Published: April 2011

Device quality gate dielectric heterostructures have been prepared using a three step plasma/rapid thermal sequence [1] in which kinetic effects determine the time-temperature aspects of the processing. The steps for forming the interface and for depositing dielectric layers have been performed at low temperature, ∼300°C, by plasma-assisted processing. Following this a low rapid thermal anneal (RTA) provides interface and bulk dielectric chemical and structural relaxations, thereby yielding device performance and reliability essentially the same as obtained using higher thermal budget conventional or rapid thermal processing.
Uniform Ultra-Thin Oxides Grown by Rapid Thermal Oxidation of Silicon in N2O Ambient
Authors: Xing G. C. , Lopes D. , Miner G. E.
Published: April 2011

In this paper, we report the study of rapid thermal oxidation of silicon in N2O ambient using the Applied Materials RTP Centura rapid thermal processor, and N2O oxide thickness and compositional uniformities with respect to gas flow rate and wafer rotation speed as well as other process parameters. It was found that N2O oxide uniformity is strongly dependent on gas flow rate and wafer rotation speed in addition to process pressure. With optimized setting of the process parameters, excellent oxidation uniformities (one sigma < 1%) were obtained at atmospheric pressure N2O ambient. Nitrogen concentrations of such uniform oxides grown at 1050°C atmospheric pressure N2O oxidation processes were 1.7% for a 40Å oxide and 2.5% for a 60Å oxide, respectively, as characterized by SIMS analysis.
Aluminum Gate Metallization for AMLCDs
Authors: Kim Joo-Han , Kanicki Jerzy , den Boer Willem
Published: April 2011

Aluminum metallization incorporating the anodic aluminum oxide has been optimized for high-performance amorphous silicon thin film transistors (a-Si:H TFTs). For such a device, the off-current is less than the picoampere and the ON-OFF current ratio is ∼2×107, the field effective mobility is about 1.25 cm /Vsec in the linear region and the subthreshold swing is about 0.38 V/decade. These electrical performances are acceptable for high-definition AMLCDs.
Very-Low Surface Roughness in Laser Crystallized Polycrystalline Silicon
Authors: Mourgues K. , Pichon L. , Raoult F. , Mohammed-Brahim T. , Briand D. , Bonnaud O. , Lemoine D. , Boher P. , Sthelé M. , Sthelé J. L.
Published: April 2011

Excimer laser (ECL) crystallization of silicon films on low temperature substrates is one of the most promising technique for large-area polycrystalline silicon films. Crystallization techniques using pulsed-ECL were extensively studied. They are characterized by films with high structural and electrical properties but low uniformity. In this way, the technology using single shot ECL with very large excimer laser (VEL) may be very promising. It was used for the crystallization of amorphous undoped films deposited by PECVD or by LPCVD The LPCVD technique is the most commonly used deposition technique of silicon. It presents numerous advantages and the hydrogen content in the films, known to constitute a drawback in the crystallization process leading to an increased surface roughness, is negligible (∼1 at.%). However, even with these low hydrogen content LPCVD films, high surface roughness is observed after the laser crystallization. Hence surface roughness appears as one of the major problems to be solved in the high performance TFT's realization from laser crystallized films.

In this work, the reduction of the surface roughness, determined from Atomic Force Microscopy observations, is presented. This reduction originated from the use of a surface oxidation and an etch treatment to remove the oxide. The mean height of the roughness is then reduced by about 50%.

Using these low surface roughness polycrystalline films, TFT's are then realized.
Fabrication Technologies of Field Emitter Arrays
Authors: Choi J. H. , Ryu Y. S. , Kang J. H. , Jang J. E. , Kim J. M. , Hong J. P. , Lim D. Y. , Michine V.
Published: April 2011

Total internal reflection (TIR) holographic lithography is studied as a new method for field emitter array (FEA) fabrication. Four basic parameters of the process - scan speed, laser power, focus distance and step distance, are analyzed to optimize the hole patterns. In addition, the characteristics of the Aluminum (Al) parting layer are studied to minimize the stress produced by Molybdenum (Mo) layer during Spindt-type tip formation process.
Mocvd SrS:Ce for Applications in Electroluminescent Devices
Authors: Endisch D. , Barth K. , Lau J. , Peterson G. , Kaloyeros A. E. , Tuenge D. , King C. N.
Published: April 2011

SrS:Ce is an important material for full color electroluminescent (EL) flat panel displays. Using a combination of SrS:Ce/ZnS:Mn and appropriate color filters high quality full color displays have been demonstrated [1]. Major issues for commercially viable process integration of SrS:Ce are the combination of high luminance, high growth rate, and process temperatures below 600°C for compatibility with low cost glass substrates. This work describes the process development and optimization of metal-organic chemical vapor deposition (MOCVD) of SrS:Ce. MOCVD is a promising candidate for deposition of SrS:Ce because it can provide the required growth rates and allows control of crystal structure and stoichiometry. Growth of SrS:Ce was performed in the temperature range from 400°C to 530°C using Sr(tmhd)2, Ce(tmhd)4, and H2S as precursors. The structure of the SrS:Ce was found to be strongly dependent on the H2S flow. A brightness of 15 fL and an efficiency of 0.22 lm/W has been achieved (40 V above threshold voltage, 60 Hz AC). Film analysis included Rutherford backscattering (RBS), X-ray diffraction (XRD), atomic force microscopy (AFM), and EL measurements. Results on the correlation between process parameters, film structure, grain size and EL performance will be presented.
Development of Large area Excimer VUV and UV Sources from a Dielectric Barrier Discharge
Authors: Zhang Jun-Ying , Boyd Ian W.
Published: April 2011

A large-area, high power density, high efficiency, and low cost excimer VUV and UV source, which is capable of producing narrow-band radiation tunable between the near UV (λ=354 nm) and the deep UV (λ=126 nm), is described.

This UV source is based on the principle that the radiative decomposition of excimer states created by a dielectric barrier discharge (silent discharge) in a rare gas, such as Ar2* (λ=126 nm), Kr2* (λ=146 nm), Xe2* (λ=172 nm) or molecular rare gas-halide complexes, such as ArCl* (λ=175 nm), KrCl* (λ=222 nm), XeCl* (λ=308 nm). Conversion efficiencies (from input electrical to output optical energy) as high as 22% can be achieved under optimum conditions. This powerful and economical lamp provides a useful UV source for low temperature photon-initiated processes and is an interesting alternative to conventional UV lamps for industrial large-scale low temperature processes. For industrial large-area processing and for the deposition of highly complex structures, these narrow band VUV and UV sources with high photon fluxes have definite advantages. Several applications of these excimer sources are reviewed, including photo-deposition of dielectric and metallic thin films, photo-oxidation of silicon, surface modification, etching of polymer, and photo degradation of pollutants.
Study of Electrical Transport Across Interfaces between Wide Gap Semiconductor and Metal Oxides
Authors: Talyansky V. , Vispute R. D. , Sharma R. P. , Choopun S. , Downes M. J. , Venkatesan T. , Iliadis A. A. , Wood M. C. , Lareau R. T. , Jones K. A.
Published: April 2011

We have grown YBa2Cu3O7 (YBCO) and Pr1.85Ce0.15CuO4 (PCCO) polycrystalline films on n-type GaN using pulsed laser deposition. The diodes fabricated out of these heterostructures exhibited a strong rectifying behavior with transport characteristics that were found to fit well to the thermionic emission model. The effective barrier heights for YBCO and PCCO based diodes were found to be 788 meV and 236 meV, respectively. Rutherford Backscattering structural analysis of the heterostructures is also discussed.
Effect of Lattice Strain on Growth Mechanisms and Electrical Transport Behavior of Epitaxial CaRuO3 Thin Films
Authors: Eom C. B. , Rao R. A. , Gan Q. , Cava R. J. , Krajewski J. J. , Suzuki Y. , Gausepohl S. C. , Lee M.
Published: April 2011

We have observed both metallic and semiconducting behavior in epitaxial thin films of the metallic oxide CaRuO3 deposited under identical conditions on (100) SrTiO3 substrates of varying crystalline quality. X-ray diffraction studies showed that while semiconducting films with enlarged unit cells were obtained on single crystal SrTiO3 substrates, metallic films with lattice parameters close to the bulk material grew on poor crystalline quality SrTiO3 substrates. The films deposited on (100) LaAlO3 substrates consistently showed metallic behavior. Atomic force microscope images suggest that the semiconducting films had a coherent two dimensional nucleation. In contrast, three dimensional island-like incoherent growth was seen in the metallic films. It is believed that in the coherent films a strain induced substitution of the small Ru4+ cations by the larger Ca2+ cations occurs, breaking the conduction pathway within the three dimensional network of the RUO6 octahedra and leading to a metal-insulator transition. This unique phenomenon - which is not observed in bulk material - can be significant in technologically important epitaxial perovskite oxide heterostructures.
Surface Structure and Morphology of Mg-Segregated, Epitaxial Fe3O4 Thin Films on Mgo(001)
Authors: Anderson J. F. , Kuhn Markus , Diebold Ulrike , Shaw K. , Stroyanov P. , Lind D.
Published: April 2011

We have investigated the structural and compositional changes that are induced by the segregation of substrate Mg to the surface of 1μm-thick Fe3O4 films on MgO(001). The thin films have been grown with plasma-assisted MBE, and characterization with RHEED (reflection high-energy electron diffraction), x-ray diffraction (XRD), and Superconducting Quantum Interference Device (SQUID) magnetometry show slightly strained, single-crystalline Fe3O4 films. For the surface studies, we have combined Low-Energy Electron Diffraction (LEED) and Scanning Tunneling Microscopy (STM). Initial and final surface characterization employed X-ray Photoelectron Spectroscopy (XPS) and Ion Scattering Spec-troscopy (ISS) respectively. The surfaces of the MBE-grown samples are flat and show a (√2 × √2)R45° reconstruction with respect to the Fe3O4 surface unit cell. We observe the onset of Mg segregation to the surface at around 700 K, with long, narrow extensions of terraces being observed growing along the [110] and [110] directions. Upon prolonged heating at 800 K, massive Mg segregation to the surface is observed. Heating in an oxygen atmosphere induces a 1×4 surface reconstruction, and results in extremely long (≈ 1000 Å), wide terraces.
Reactive Growth and Properties of Epitaxial Fe-Mg-O Spinel Films on (100) MgO
Authors: Senz S. , Graff A. , Teichert C. , Zimnol M. , Sieber H. , De S. K. , Oepen H. P. , Hesse D. , Kirschner J. , Gösele U. M.
Published: April 2011

Epitaxial Mg-Fe-O spinel thin films were prepared by solid state reactions between MgO(lOO) substrates and thin films or vapors of iron oxide. Iron or iron oxide was deposited by electron beam evaporation in an oxygen background pressure onto a heated MgO crystal. The formation of MgFe2O4 at high temperatures proceeds via cation counter-diffusion in the fixed oxygen sublattice. Depending on substrate temperature, oxygen partial pressure and target material, epitaxial spinel films of different composition and magnetic properties were obtained. Crystal structure, composition and sub-micron morphology were investigated by RBS, XRD, TEM/SAED and EDX. Magnetic hysteresis loops were recorded at room temperature using the magneto-optic Kerr effect. Thickness interference fringes observed by XRD confirm the growth of smooth films. The main feature found in TEM plane view samples is a network of cation antiphase boundaries. The film composition measured by RBS varied from Fe2+ɛO3 films deposited at 340 °C substrate temperature to a solid solution of Fe2+E03 and MgFe2O4 at 500 °C to MgFe2O4 above 800 °C. EDX line-scans show a single phase MgFe2O4 spinel for a substrate temperature of 850 °C, without variation of composition with position or depth. At substrate temperatures higher than 800 °C Fe2+ was additionally dissolved in the MgO substrate, forming a FexMg1-xO solid solution.
Oxide Epitaxial Lift-Off (OELO)
Authors: Eddy M. M. , Hanson R. , Rao M. R. , Zuck B. , Speck J. S. , Tarsa E. J.
Published: April 2011

Epitaxially grown oxides of both SrTiO3 (STO) and YBa2Cu3O7-δ (YBCO) have been removed from their growth substrate and transferred for integration into other circuits (microwave devices) and onto other substrate material (glass). The enabling element in the separation process is the high selectivity of etching between YBCO and other oxide materials. Thus, a thin layer of YBCO is used as the sacrificial layer in the structure, allowing rapid etchant ingress under the device structures and separation from the growth substrate. Initial demonstrations of microwave device tuning using a lifted-off STO layer is detailed.
Processing Of PbTi03 And Pb(ZrxTi1−x)03 Thin Films By Novel Single-Solid-Source Metalorganic Chemical Vapor Deposition
Authors: Lu Ping , Li Hang , Sun Shan , Tuttle Brace
Published: April 2011

Ferroelectric PbTiO3(FT) and Pb(ZrxTi1−x)03 (PZT) thin films have been deposited on (100) MgO and (111) Pt/SiO2/(100)Si substrates by using a novel single-solid-source metalorganic chemical vapor deposition (MOCVD) technique. The new technique uses a powder delivery system to deliver the mixed precursor powders directly into a hot vaporizer from room temperature, therefore, avoiding any problems associated with polymerization or decomposition of the precursors before evaporation. The technique simplifies MOCVD processing significantly and can improve process reliability and reproducibility. The deposited FT and PZT films have a perovskite structure and are highly oriented with respect to the substrate. With improvement of process control, systematic studies of film evolution under various growth conditions have been carried out. Effects of substrate, substrate temperature, system vacuum, and precursor ratios in the mixture on film microstructure and properties will be presented in this paper.
Equilibrium Domain Structures of Epitaxial Perovskite Ferroelectric Films
Authors: Pamir Alpay S. , Roytburd Alexander L.
Published: April 2011

Possible equilibrium domain structures due to elastic interactions between the film and the substrate as a result of a cubic-tetragonal transformation observed in epitaxial perovskite ferroelectric films are analyzed. The formation of both two- and three-domain states is taken into account. A stability map which shows domain stability regions as a function of temperature is developed in coordinates of misfit strain and tetragonality of the lattice of the ferroelectric phase. Misfit dislocation generation at the growth temperature is found to have a profound effect on domain selection. As an example a PbTiO3(001) film grown on a MgO(001) substrate is considered and theoretical findings are compared with experimental results in the literature.
Defect Generation And Evolution In The Hydrothermal Growth Of Epitaxial BaTiO3Thin Films
Authors: Zhao L. , Chien A. T. , Lange F. F. , Speck J. S.
Published: April 2011

The structure of epitaxial BaTiO3thin films prepared by hydrothermal synthesis on (001) SrTiO3substrates was studied by transmission electron microscopy (TEM). The growth evolution was followed from initial island formation, through island impingement and fusion. Plan view and cross-section imaging demonstrated that the films grew by an unusual islanding mechanism. Electron diffraction showed the islands and the fully formed film are single crystal with mosaic character and in all cases strain relaxed. Cross-section TEM of the early growth films showed a several monolayer thick interfacial layer and the film/substrate region had no misfit dislocations. In the fully formed films, this interfacial layer was not observed, however a clear misfit dislocation network was observed. Defects analysis shows that the misfit dislocations have pure edge character with <100> Une directions, and <010> Burgers vectors (parallel to the film/substrate interface).
Correlations Between YBa2Cu3O7-δ Thin Film Materials Properties and RF Device Performance
Authors: Kaplan T. S. , Salazar M. T. , Huang Q. , Barfknecht A. , Lu Z.
Published: April 2011

Better knowledge of the relationships between YBa2Cu307-δ (YBCO) materials properties and the RF performance of devices made from these materials should lead to improved device performance and yields. A variety of materials tests were performed on our production YBCO films which were patterned into standard microstrip resonators. The materials parameters were then compared with the unloaded Q of the resonators at 77 K. As expected, films with higher Q's tended to have higher Tc, higher Jc, greater film thickness, and better crystallinity. The last was based on narrower YBCO rocking curve peak, lower second phase density (judged by lower resistivity and greater θ-2θ (005) peak area), and a narrower θ-2θ (005) peak. The room temperature sheet resistance was found to be a useful predictor of microwave performance for films that are otherwise similar.
Submicron to Nanometer Size Single Particle Measurements
Authors: Barbara B. , Wernsdorfer W. , Orozco E. Bonet , Hasselbach K. , Benoit A. , Mailly D. , Demoncy N. , Pascard H. , Francois L. , Duxin N. , Pileni M.P.
Published: April 2011

Low temperature magnetization measurements of individual ferromagnetic particles and wires are presented (0.1 < T(K) < 6). The detector was a Nb micro-bridge-DC-SQUID, fabricated using electron-beam lithography. The angular dependence of the switching field could be explained approximatively by simple classical micromagnetic concepts (uniform rotation, curling…). However, dynamical measurements evidenced nucleation and propagation of domain walls, except for the smallest particles of about 20 nm. The variation of the mean switching field distribution (as a function of temperature and field sweeping rate) and of the probabilities of switching (as a function of temperature and the applied field) allowed to study in details the dynamics of magnetization reversal of individual particles. For sub-micron particles, we found that above a crossover temperature of 1K, the mean switching field and the switching probability follow a thermally activated model. For temperatures below IK, the dynamics of magnetization reversal becomes temperature independent which is interpreted in terms of deviations from the Néel-Brown model of magnetization reversal due to surface roughness and oxidazation. Although this crossovei temperature is much too large to be interpreted with current models of quantum tunneling, such an effect cannot be excluded. Measurements performed on ferromagnetic nanoparticles of good quality (single crystalline and with a diameter smaller than 25 nm), allowed us to show for the first time that the magnetization reversal can be described by thermal activation over the anisotropy energy barrier, as originally proposed by Néel. The observation of telegraph noise strengthens these results. Our measurements open the door to the observation of macroscopic quantum tunneling oí the magnetization in an individual particle containing 103-105 spins.
Transmission X-Ray Diffraction and Mössbauer Spectroscopy Study of Annealed Magnetoresistive Ag/Ni8iFei9 Multilayers
Authors: Bouat Sophie , Rodmacq Bernard , Auric Pierrette
Published: April 2011

We have studied the variation of the structural and magnetic properties of 5-μm thick self-supported Ag/Ni81Fe19 multilayers upon annealing by means of transmission X-ray diffraction and Mössbauer spectroscopy as well as magnetoresistance (MR) and magnetisation measurements.

In the virgin state, X-ray experiments show that both Ag and NiFe are (111) textured; the (220) in plane distances are 1.3 % smaller for Ag and 2 % larger for NiFe than the bulk values. Mässbauer spectra consist of a pure magnetic sextuplet, meaning that no non-magnetic layer is present at interfaces. The hyperfine field at 4.2 K is found only 3 % smaller than the bulk value and the Curie temperature is estimated from both Mossbauer and magnetisation at about 550 K.

Upon annealing, the (220) Ag distance starts increasing above 250°C, whereas the decrease of the (220) NiFe distance starts at a much lower temperature. The densification of the NiFe layers is accompanied by an increase of the Curie temperature, without any effect on the magnetic moment; both this relaxation and the improved structural quality of the layering are responsible for the increase of the MR ratio from 12 % to 16 % after annealing at 240°C. Although the multilayer structure improves up to 320°C, the appearance of localised defects above 250°C leads to a rapid increase of the remanent magnetisation and to a decrease of the MR ratio.
Strong Non-Linear MCD-Effects Due to Partially Circular Polarized Light Sources
Authors: Höchst Hartmut , Zhao Dai , Huber David L.
Published: April 2011

Most soft x-ray magnetic dichroism studies are carried out with light of mixed polarization. The effect of incomplete circular polarization is usually taken care off by linearly extrapolating the data to Pcirc=l. Using a classical model which includes the polarization factor we show that the MCD-effect, which is the normalized quantity 2(I+-I-)/(I++I-), is highly non-linear with regard to cire. With a specially designed quadruple reflection phase shifter we measured the MCD effect with Pcire<l as well as with Pcirc∼1. MCD spectra of Fe around the M2,3 transition verify our model calculations of the polarization dependence. The data indicate that the observed non-linear response of the MCD-effect to Pcirc can generally introduce large errors in the quantitative analysis of MCD data where spin  and orbital  moments are extracted by means of sum rules.
Brillouin Light Scattering Study of Spin Waves of Ni and Co Films
Authors: Ngaboyisonga J.M.V. , Donzelli O. , Nizzoli F. , Canotti G. , Gubbiotti G. , Pareti L. , Tonili G.
Published: April 2011

Thin films of Ni and Co have been investigated by Brillouin Light Scattering (BLS). The samples, grown by evaporation (Ni) and RF sputtering (Co) on silicon substrates, have thicknesses in the range 16–98 nm. The Damon-Eshbach surface mode and several bulk standing waves have been detected. A macroscopic approach has been adopted in order to calculate the dispersion relations of the spin waves. The method takes into account the dipolar and exchange interactions, together with bulk and surface magnetic anisotropies. The spin waves frequencies and the scattering cross section have been calculated by using the bulk and surface anisotropies as relevant fitting parameters.
Interrelation Between Structure and Magnetism of Ultra-Thin Mn Films Epitaxially Grown on (001) BCC Fe
Authors: Andrieu S. , Bauer Ph. , Fischer H. , Piecuch M. , Finazzi M. , Hricovini K. , Krill G. , Lefevre P. , Magnan H. , Chandesris D.
Published: April 2011

In this paper, the interrelation between structural and magnetic properties of ultra-thin Mn films epitaxially grown on (001) bcc Fe is studied. The Mn growth and in-plane structure were controlled by electron diffraction (RHEED). The structures of the Mn films were determined by using X-Ray absorption spectroscopy (SEXAFS). Finally, the magnetic properties were studied by using X-Ray magnetic circular dichroïsm (XMCD). All the experiments were performed under ultra-high vacuum. As shown by XMCD experiments, a magnetic transition is observed at 2 Mn monolayers. The analysis of RHEED and SEXAFS experimental results clearly demonstrates that a structural transition comes with this magnetic transition.
Alteration of MCD Spectra Due to thin film Interference Effects
Authors: Rioux D. , Allen B. , Höchst H. , Zhao D. , Huber D.L.
Published: April 2011

MCD spectra at the M2,3 edge of thin Fe films exhibit thickness-dependent variations in line shape as well as in the absolute MCD-effect. Our data indicate that more information is contained in the MCD spectra than simply the evolution of a magnetic moment and ferromagnetic order. We developed a model to predict line shape modulations as a function of film thickness and angle of light incidence. Using the Fresnel-Maxwell formalism we calculate interference effects between left and right circularly polarized light reflected from the vacuum-film-substrate interfaces which are verified by our MCD measurements. Since the observed interference effects are a function of the excitation wavelength, our results can be directly scaled to show the significance of these effects in the more commonly used L2,3 region of 3d ferromagnets. Our data point out that one might be ill advised to rely onL2,3 MCD experiments to try to extract the formation of magnetic moments in films of several 10s of Å in thickness.
Properties of Magneto-Optical Co-Pt and Magnetoresistive Co-Cu Alloy Films
Authors: Lee Y. P. , Kim K. W. , Lee G. M. , Kudryavtsev Y. V. , Chang G. S. , Whang C. N.
Published: April 2011

Co-Cu films of 1000 – 1500 Å thick were produced by means of flash-evaporation technique at 150 K, 400 K, 520 K and 720 K. The Co022Cu078 films produced at 400 K or 520 K exhibit the maximum value of MR of 16.5% at 77 K and 1.5 T. Co-Pt films of 200 Å thick with Pt buffer layers of 200 Å thick were prepared at room temperature (RT) by ultrahigh-vacuum cosputtering. The saturation polar Kerr rotation angles (θk) at RT of CoPt3 film are all larger than those of the Co/Pt multilayered (ML) film of the corresponding composition. The surface morphology, mean grain and magnetic domain sizes, and size distributions of the grains and magnetic domains of the Co alloy films have been investigated by magnetic force microscopy (MFM) and atomic force microscopy (AFM). The results were correlated with those obtained by using MO and optical spectroscopy at both RT and low temperatures (LT) in a spectral ramge of 0.5 – 4.4 eV, and magnetic investigations at both RT and LT including field-dependence measurement of MR. The overall results reflect the changes in the electronic structures and magnetic states of the constituent elements, induced by the structural transformation or correlated with the structures of the films.
Metalized Polypropylene Film in Capacitors: Characterization and The Effect of Interfacial Pressure on the Dielectric Strength
Authors: Tandon Shalabh , Farris Richard J.
Published: April 2011

Metalized polypropylene film used in high energy density capacitors has been mechanically characterized to determine its elastic constants. The out of plane coefficient of thermal expansion (CTE) of the orthotropic film is 10 times as large as the smaller in plane CTE. The out of plane modulus is twice as large compared to one of the in plane moduli. The effect of interfacial pressure on the dielectric breakdown is also studied for the same film. It is observed that the dielectric strength of the film decreases at first and then increases above 4 MPa of compressive stress.
Effect of Deposition and Annealing on The Thermomechanical Properties of Parylene Films
Authors: Todd Ryan E. , Miller Mikel , Ho Paul S.
Published: April 2011

Parylene polymers are vapor deposited and form semicrystalline films. The properties of these films vary with chemical structure, molecular weight, and morphology. The properties of parylene films deposited by changing the standard deposition process are evaluated and compared to control films. The thermomechanical properties of films produced by three modified processes, A, P, and PC, indicate the modified processes reduce the molecular weight. The films were also annealed to determine the stability of the film's properties during thermal cycling. These results also suggest that the modified films are lower molecular weight materials.
Effect of Post Plasma Treatment on Reliability and Dielectric Properties of SiOF Films Deposited by ECRCVD With SiF4 and O2
Authors: Lee Seoghyeong , Yoo Jae-Yoon , Oh Kyunghui , Park Jong-Wan
Published: April 2011

The effect of post plasma treatment on dielectric properties and reliability of fluorine doped silicon oxide (SiOF) films were investigated by measuring their C-V and I-V characteristics, XPS, AFM, and AES. The post plasma treatment of SiOF films was carried out in-situ at 300 °C in the deposition chamber. In this research, when the post plasma treatment time increased, we obtained the following results: (1) The etch rate of SiOF films decreased from 80Å/sec to 10Å/sec. (2) Surface roughness of the plasma treated SiOF films was increased due to the ion bombardment effect of the plasma. (3) The refractive index and relative dielectric constant increased from 1.391 to 1.461 and 3.14 to 3.9, respectively, due to the changes of surface chemistry by the post plasma treatment. (4) The leakage current density of SiOF films prepared by ECRCVD using SiF4 and O2 was less than 1 × 10−9A/cm2. (5) The breakdown field strength increased from 3.5 MV/cm to 8 MV/cm. (6) The thermal stability of the Cu/TiN/SiOF/Si system remained stable up to 600 °C.
Polynorbornene for Low K Interconnection
Authors: Grove N. R. , Kohl P. A. , Bidstrup-Allen S. A. , Shick R. A. , Goodall B. L. , Jayaraman S.
Published: April 2011

Within the microelectronics industry, there is an ongoing trend toward miniaturization coupled with higher performance. The scaling of transitors toward smaller dimensions, higher speeds, and lower power has resulted in an urgent need for low dielectric constant interlevel insulators. Low dielectric constant interlevel dielectrics have already been identified as being critical to the realization of high performance integrated circuits in the SLA Roadmap. Thus, there exists a need in the microelectronics industry for a thermally stable, noncorrosive low dielectric constant polymer with good solvent resistance, high glass transition temperature, good mechanical performance and good adhesive properties, particularly to copper. In addition, the desired dielectric material should be capable of being processed in environmentally friendly solvents, and the final thermal and electrical performance should not be affected by manufacturing or post environmental conditions. High glass transition temperature polynorbornenes are being developed which provide many of these desired features. This polymer family is produced via a new transition metal catalyzed polymerization. Attributes which make polynorbornene particularly attractive in microelectronics include: (i) excellent thermal performance, (ii) adhesion to conductors without the use of adhesion promoters or barrier layers, (iii) very low moisture absorption (< 0.1 wt %), and (iv) low dielectric constant (2.2 – 2.6). Side groups which have been added to the polynorbornene backbone improve adhesion, dielectric properties and mechanical properties.
Combined Tripod Polishing and Fib Method for Preparing Semiconductor Plan View Specimens
Authors: Anderson Ron , Klepeis Stanley J.
Published: April 2011

Combining substantial pre-thinning of semiconductor device specimens via tripod polishing, followed by multiple, selective material removal steps with a focussed ion beam (FIB) tool, offers some unique possibilities with regard to preparing plan-view specimens at precise locations in the material below, and in the interconnect layers above, the semiconductor surface. Extension of these methods to other types of specimens in different configurations allows for the fabrication of multiple specimens on the same TEM grid that may not be possible by any other means.