bluuebunny/crossref_metadata_2025 huggingface dataset:
First Principles Based Solution to the Boltzmann Transport Equation for Co/Cu/Co Spin Valves
Authors: Maclaren J.M. , Malkinski L. , Wang J.Q.
Published: April 2011

We present the results of a first principles based semi-classical study of electronic transport in Co/C/u/Co spin valves. The model is parameterized using Bloch states obtained from local spin-density electronic structure calculations and lifetimes appropriate to sputtered films. The approach is used to study the variation in giant magnetoresistance (GMR) with the individual layer thicknesses. Using values for the lifetimes for electrons in the Co and Cu layers that reproduce the resistivities of sputtered films, we are able to rationalize the variation in the current in the plane (CIP) GMR in a set of Co/Cu/Co spin valves produced under similar conditions. Important contributions to the GMR come from two sources, a channeling effect in the Cu which is a direct result of the different sized Fermi spheres for majority Cu and Co electrons, and from within a region in the Co layers within about one to two mean free paths of the interface. Unlike the CIP GMR, values for the current perpendicular to the plane (CPP) GMR are much larger and much less sensitive the variations in the individual layer thicknesses.
Large Anisotropy Via Oblique Sputtering of Ta Underlayers
Authors: Bonevich J.E. , McMichael R.D. , Lee C.G. , Chen P.J. , Miller W. , Egelhoff W.F.
Published: April 2011

Anisotropy fields in excesss of 120kA/m(1500Oe)have been produced in 3 nm to 5 nm thick polycrystalline films of Co with Ta underlayers. The unusualy high anisotropy is magnetostatic in origin, and is induced by corrugations on the surface of an obliquely sputtered Ta underlayer. Cross-sectional TEM reveas 8 nm columnar grains of Ta tilted toward the Ta source and elongated perpendicuar to the Ta flux in the film plane. The anisotropy field of the Co film increases with both the underlayer thickness and the angle between theTa source and the film normal. In spin valve samples, the anisotropy is attenuated by more than an order of magnitude across a 4nm thick Cu spacer. Magnetoresistance measurements on a spin valve indicate less than 2° dispersion in hard axis directions, and despite the nanometer-scale roughness of the underlayer, there is weak broadening of the ferromagnetic resonance line.
In situ electrical resistance measurements of Al-Ge films in the TEM using a modified heating holder
Authors: Verheijen M.A. , Donkers J.J.T.M. , Thomassen J.F.P. , van den Broek J.J. , van der Rijt R.A.F. , Dona M.J.J. , Smit C.M.
Published: April 2011

A TEM specimen holder has been developed for the measurement of the electrical resistance of a TEM sample as a function of temperature. A Philips TEM heating holder was modified for this purpose. This creates the opportunity to directly correlate changes in the resistance to microstructural changes as a function of temperature.

The microstructure of Al-Ge films of several thicknesses has been studied in an in-situ annealing experiment and has been recorded on videotape, while simultaneously acquiring resistance data. These in-situ TEM studies confirm that the irreversible decrease in resistance of these films is caused by crystallisation. During this transition segregation occurs, resulting in crystalline Al and Ge phases.
Characterization of Cu-Al alloy/SiO2 interface microstructure
Authors: Wang Pei-I , Murarka S. P. , Yang G.-R. , Barnat E. , Lu T.-M. , Chen Y.-C. , Li Xiang , Rajan K.
Published: April 2011

Cu-Al alloys have been recommended for application as the diffusion barriers/adhesion promoters for advanced copper based metallization schemes. This approach to barrier formation is to generate an ultra-thin interfacial layer through Cu alloying without significantly affecting the resistivity of Cu. In this paper the microstructure of the bilayers of Cu/Cu-5 at%Al and Cu-5 at%Al/Cu sputter deposited on SiO2 before and after thermal annealing is investigated by transmission electron microscopy (TEM). Interfacial layer is observed in both cases. The variation of the resistance of the Cu-Al alloy film is consistent with its microstructure. The x-ray diffraction (XRD) spectra of Cu-5 at%Al on SiO2 shows that the addition of Al into Cu intends to favor the Cu (111) texture. These results will be presented and discussed showing that films of Cu doped with Al appear to act as a suitable barrier and adhesion promoter between SiO2 and Cu.
In Situ Curvature and Diffraction Studies of Pd Films on Si(001) During Solid-State Reaction
Authors: Gergaud P. , Thomas O. , Chenevier B. , Ghetta V. , Mouroux A. , Zhang S.L.
Published: April 2011

The stress evolution during silicide formation from thin metal films on Si substrates is not well understood. It requires a detailed knowledge of the mechanical properties of each substance, i.e. metal, silicide(s) and Si, in the reacting system. In situ curvature measurement generally gives access to the overall force in the layered stack, whereas in situ X-ray diffraction (XRD) provides information about the mechanical strain in each crystalline sublayer. In this study, we performed both in situ XRD and curvature measurements on the Pd/Si(001) system. From both measurements, we found out that the in-plane strain in the metal and in the silicide is compressive. Whereas it decreases all along the solid-state reaction for the silicide, it slightly increases for the metal. We then compared our results with the qualitative model proposed by Zhang and d'Heurle. This model suggests a high compressive stress in the silicide at the very first stage of the reaction. This is in good agreement with our experimental results. Finally, the measured strains were then translated into force per unit width and compared to in-situ curvature measurement results. A good qualitative agreement between these two different measurements was also found.
Ab Initio Studies of AlSb (001) Adatom Behavior and Reconstruction
Authors: Modine N. A. , Kim Hanchul , Kaxiras E.
Published: April 2011

We discuss a recent investigation of adatom behavior on the AlSb(001) surface using first-principles electronic structure methods based on the density functional theory. For Al and Sb adatoms, we find a number of novel adatom structures that differ dramatically from previous results for the superficially similar group-III arsenides. In particular, we conclude that it is energetically favorable for an Al adatom to incorporate substitutionally into the outermost layer of the AlSb surface. This observation helps motivate a proposed new reconstruction for the AlSb(001) surface. Finally, we argue that the unusual adatom behavior identified for this surface probably results from the presence of a dimer row composed of a double layer of group-V atoms in the reconstruction, and therefore, it should be generic to all of the antimonides, as well as, the c(4 × 4) reconstruction of the arsenides and phosphides.
Formation and Evolution of InAs Nanowires on an InP(001) Surface
Authors: Yang Haeyeon , Smathers J. B. , Ballet P. , Workman C. L. , Salamo G. J.
Published: April 2011

We have used in-situ scanning tunneling microscopy (STM) to study the formation and evolution of InAs islands on an InP (001) surface. The InAs islands are produced by (i) exchange of P-atoms with As-atoms or by (ii) direct deposition of In and As. In both cases InAs nanowires arem elongated along the [ī 10] direction with a length over 1 µm. We observe these nanowires to be stable under an arsenic environment while unstable with no arsenic flux, and eventually transform into a rectangular-based pyramid with a truncated top. These observations indicate that surface reconstruction can play a role in the selection of quantum wire or dot growth.
Effects of the Dislocation Density and Surface Energy on Phase Diagrams of the S-K Growth Mode for the GaInN/GaN and GaPSb/GaP Systems
Authors: Nakajima K. , Ujihara T. , Miyashita S. , Sazaki G.
Published: April 2011

The growth of thin films has been categorized into three types namely the Frank-van der Merwe (FM) mode, the Stranski-Krastanov (SK) mode, and the Volmer-Weber (VW) mode. The strain, surface, and interfacial energies were calculated for the three types of growth mode of the GaInN/GaN and GaPSb/GaP systems by considering the effects of the dislocation density and reconstruction of dangling bonds. The phase diagrams of the growth modes were determined for the GaInN/GaN and GaPSb/GaP systems. In the GaInN/GaN system, the VW mode appears in the most region of the phase diagram. The region of the VW mode becomes smaller as the dislocation density increases. In the GaPSb/GaP system, the SK and VW modes appear and the region of these modes becomes larger as the reconstruction ratio increases
Movpe Strip-Like Self-Organization of InAs Grown on InP Vicinal Surfaces
Authors: Auvray Laurent , Soulière Véronique , Dumont Hervé , Dazord Jacques , Monteil Yves , Bouix Jean
Published: April 2011

We have investigated the influence of MOVPE growth parameters on the surface morphology of InAs nanostructures grown on 0.2° misoriented (001)InP substrates. Thin layers of nominal thickness of about 3 and 6 ML were deposited at 500°C with V/Ill flux ratios ranging from 50 to 240. The samples were cool down from 500 to 350°C during 6 minutes under either arsine or phophine atmosphere. The influence of this step has been found to greatly determine the surface morphology of the nanostructures observed by atomic force microscopy. Dots self-aligned along the steps and forming a non continuous strip, regularly spaced every 3-4 terraces have been obtained. The morphology of the strips can be varied with the growth conditions (V/III flux ratio). In this work, we will propose a mechanism for the formation of the strips observed during the cooling under phosphine atmosphere taking into account an As » P exchange.
Step Bunching, Chemical Ordering, and Diffusivity in Si1−yCy Heteroepitaxy
Authors: Grosse Frank , Croke Edward T. , Gyureb Mark F. , Floydc Margaret , Smith David J.
Published: April 2011

The growth of Si1−yCy on Si(001) and Si(118) surfaces is investigated experimentally and theoretically. A step instability is found on (118) surfaces leading to step bunching, under low C-concentrations. This behavior is explained by increased diffusivity of Si dimers in the vicinity of carbon. Self adjusting step bunches are found in kinetic Monte Carlo simulations with ordering of the carbon along nearly (001) planes. Experimental parameters (i.e., temperature, flux rate, and tilt angle of the substrate), which are controllable experimentally, can be used to adjust the length scale of the step bunching.
The Growth of High Quality GaAs Epilayers on Stripe Patterned InP Substrates With a Transferred GaAs Fused Layer
Authors: Hwang Sung Min , Park Young Ju , Kim Eun Kyu , Choi In-Hoon
Published: April 2011

Both the wafer fusion and the heteroepitaxy technology were used successfully to obtain high quality GaAs layer on the InP substrate where the lattice mismatch was 3.7 %. The enhancement of the lateral growth rate was a crucial factor for the formation of high quality QWR in the patterned fusion layer. This technique can provide a way of overcoming the limitation of heteroepitaxy caused by misfit problems and its subsequent quality degradation. It is expected that the overgrowth technique on the patterned fusion layer can be applicable to the photonic device fabrication on the other substrate such as Si.
2-D Precursors and Interdiffusion in CdSe/ZnSe Self-Assembled Quantum Dots
Authors: Dobrowolska M.
Published: April 2011

This paper discusses structural and optical data taken on a series of MBE grown samples where n monolayers of CdSe (0.5< n < 2.6) was deposited on (and subsequently capped by) ZnSe. The cross-sectional scanning transmission electron microscopy (STEM) images observed on samples with lowest CdSe coverages reveal the co-existence of 2D ZnCdSe platelets and 3D islands, showing clearly that the platelets act as precursors for the formation of the 3D islands. The STEM data also present direct graphic evidence that interdiffusion plays an important role in the dynamics of CdSe quantum dot formation. The macro- and micro-photoluminescence results fully confirm the STEM data. For coverages below 1.5 monolayers, photoluminescence data show only the emission characteristic of 2D platelets, while for coverages between 1.5 and 1.9 monolayers simultaneous emissions from 2D and 3D islands are observed. The sample obtained by depositing the highest (2.6 monolayer) CdSe coverage shows only the emission characteristic of 3D islands.
In Situ Real-Time Studies of Oxygen Incorporation in Complex Oxide Thin Films Using Spectroscopic Ellipsometry and Ion Scattering and Recoil Spectrometry
Authors: Mueller A.H. , Gao Y. , Irene E.A. , Auciello O. , Krauss A.R. , Schultz J.A.
Published: April 2011

The surface termination of c-axis oriented YBa2Cu3O7-δ (YBCO) and the oxygen incorporation mechanism has been investigated using a unique combination of spectroscopic ellipsometry (SE) and time of flight ion scattering and recoil spectrometry (ToF-ISARS). The high surface sensitivity of the ToF-ISARS technique combined with the bulk oxygen sensitivity of SE are shown to yield complimentary information. The SE provided the film orientation and quality, while ToF-ISARS supplied surface compositional and structural information and enabled isotopic 18O tracer studies. It was determined that the 0 content of the film had little effect on the surface termination of the film, indicating a lack of labile Cu(l) sites at the c-axis oriented YBCO surface. Also, strong evidence for a Ba or BaO terminated structure is shown. The data related to the 18O tracer studies indicate that O from the reaction ambient incorporates only into the labile Cu(1) sites during both deposition and annealing, while stable O sites were populated with O from the sputtered target, indicating either the need for sputtered atomic O or sputtered YCuO complexes to occupy the stable Cu(2) sites.
Reactive Cluster Epitaxy: CoSi2 Nanoparticles on (111) Si
Authors: Zimmermann C.G. , Yeadon M. , Kleinschmit M. , Averback R.S. , Gibson J.M.
Published: April 2011

The formation of epitaxial CoSi2 islands of nanoscopic dimensions is reported using the technique of reactive cluster deposition. Co clusters in the size range 5-50nm were synthesized by sputtering a high purity Co target inside a UHV sputtering chamber. The clusters were then deposited on the reconstructed Si (111) surface. Upon annealing the particles reacted with the Si substrate to form epitaxial CoSi2.

Our observations were made using a JEOL 200CX transmission electron microscope modified for in-situ sputtering and ultrahigh vacuum conditions.
Pd/AlN/Si or SiC Structure for Hydrogen Sensing Device
Authors: Serina Flaminia , Huang C. , Auner G. W. , Naik R. , Ng S. , Rimai L.
Published: April 2011

An AlN (insulator) MIS Hydrogen Sensor was created using plasma source molecular beam epitaxy (PSMBE) deposition on Si (111) and 6H-SiC. A Pd layer was deposited on top of the AlN film via magnetron sputtering technique utilizing a hard mask. Pd was chosen since H2 readily diffuses within its bulk, thus Pd acts not only as a metal electrode of the MIS structure, but also as a catalyst for hydrogen dissociation. To optimize the design structure several sensors with different AlN and Pd thickness have been developed. RHEED and XRD measurements show that AlN film is epitaxial on both Si (111) and 6H-SiC substrates. The sensors were characterized using capacitance versus voltage C(V) and I(V) measurements, at different frequencies ranging from 1kHz to 1 MHz. Shifts in the C-V and I-V curves occurred with the introduction of hydrogen in the chamber. The temperature, hydrogen partial pressure, effects of oxygen and hydrocarbon gases, insulator and metal thicknesses on sensor response were analyzed.
Comprehensive Study of the Electrothermal Operation of SiC Power Devices Using a Fully Coupled Physical Transport Model
Authors: Lades M. , Kaindl W. , Wachutka G.
Published: April 2011

Based on an extended electrothermal drift-diffusion model formulated within the framework of phenomenological transport theory, a consistent set of material parameters for 4H- and 6H-SiC is presented. Furthermore we report on detailed numerical studies of the coupled effect between transient impurity kinetics and impact ionization, which alters the reverse blocking characteristics of power devices under short switching conditions.
Implanted Bipolar Technology in 4H-SiC
Authors: Wright N. G. , Johnson C. M. , O'Neill A. G. , Horsfall A. , Ortolland S. , Adachi K. , Knights A. P. , Coleman P.G.
Published: April 2011

A simple ion-implanted bipolar transistor technology in 4H-SiC is presented. Suitable for both high-voltage vertical devices and lateral high-temperature transistors (for circuit applications), the technology is based on an implanted boron p-well with nitrogen and boron (or aluminium) implanted n+ and p+ regions respectively. The effects of base doping and carrier lifetime on device performance have been studied using TCAD techniques. It is shown that understanding the strong variation of carrier concentration with temperature (due to deep activation levels) and applied field (so-called field ionization) is critical in device design optimisation. The effects of post-implant anneal conditions on the physical and electrical characteristics of the junctions are investigated. It is shown that annealing can remove much of the damage induced by high dose nitrogen implantation but that residual damage is still present. The electrical characteristics of simple BJT transistors with breakdown voltages in excess of 1000V and common-emitter gains of ∼2 is related to the level of such residual damage.
Low Temperature Lateral Epitaxial Growth of Silicon Carbide on Silicon
Authors: Jacob Chacko , Chung Juyong , Hong Moon-Hi , Pirouz Pirouz , Nishino Shigehiro
Published: April 2011

To reduce the defect density inherent in conventional heteroepitaxial growth of SiC on Si, selective epitaxy followed by lateral epitaxial growth was performed in a conventional atmospheric pressure chemical vapor deposition (APCVD) system. The source gas was primarily hexamethyldisilane (HMDS). Hydrogen was used as the carrier gas and small amounts of hydrogen chloride (HCl) were added to improve the selectivity. Si(001) wafers, with an oxide layer (∼ 700 nm thick) as a mask, were used as substrates. The grown films were analyzed using optical microscopy and scanning electron microscopy (SEM). In earlier work, we had demonstrated the problems associated with the application of this technique – viz., oxide degradation and high growth temperature. Using HMDS, the growth temperature has been considerably reduced allowing the continued use of an oxide mask. Selective growth was demonstrated in films grown at 1250° and below.
GaN based quantum dot heterostructures
Authors: Reshchikov M. A. , Cui J. , Yun F. , Baski A. , Nathan M. I. , Morkoç Hadis
Published: April 2011

GaN dots have been grown on c-plane sapphire and (111) Si substrates by reactive molecular beam epitaxy. A new method involving two-dimensional growth followed by a controlled annealing during which dots are formed was employed. Due the dot nature and large dot density, relatively high luminescence efficiencies were obtained on both substrates. Single layer dots were used for AFM analysis whereas 30 layer dots were used for photoluminescence experiments. AlN barrier layers, some too thick for mechanical interaction, some thin enough for vertical coupling were used. Strong polarization effects lead to a sizeable red shift, which depends on the size of the dots.
Characterization of Thin GaN Layers Deposited by Hydride Vapour Phase Epitaxy (HVPE) on 6H- SiC Substrates
Authors: Wolan J.T. , Koshka Y. , Saddow S.E. , Melnik Yu. V. , Dmitriev V.
Published: April 2011

In this study, the near-surface regions of air-exposed thin GaN layers deposited by hydride vapour phase (HVPE) epitaxy on 6H-SiC substrates have been examined. Chemical-state identification and in-depth elemental distribution profiles are evaluated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and secondary ion mass spectroscopy (SIMS). The epilayers show a high degree of chemical purity as determined by XPS and SIMS. Low temperature photoluminescence (PL) were performed and is dominated by donor-acceptor pairs (DAP) emission. Layer thickness was measured to be ∼ 600-700 nm and an abrupt, well-defined heterointerface is observed using scanning electron microscopy (SEM) and SIMS.
TEM Study of High Quality GaN Grown by OMVPE Using an Intermediate Layer
Authors: Benamara M. , Liliental-Weber Z. , Kellermann S. , Swider W. , Washburn J. , Mazur J.H. , Bourret-Courchesne E. D.
Published: April 2011

We report on high quality GaN layers grown with the use of one intermediate layer. The defect analysis shows that the density of dislocation is only 8×107/cm2 in these layers, compared to over 1010/cm2 for layers grown without the intermediate layer (IL). Electron microscopy on cross-section samples shows that deposition under certain specific conditions of a low- temperature IL directly benefits the quality of the subsequently deposited GaN layer. The growth of the GaN top layer appears to be similar to growth observed for lateral epitaxial overgrowth layers. This first time observation opens the possibility for using standard growth methods of GaN compounds to achieve a dislocation density comparable to that achieved with lateral overgrowth epitaxy.
Channeling defects in group-III nitrides during dry etching processes
Authors: Breitschädel O. , Hsieh J.T. , Kuhn B. , Scholz F. , Schweizer H.
Published: April 2011

The effects of Ar+ ion beam etching (IBE) of AlGaN/GaN heterostructures and GaN/InGaN/GaN quantum well structures were investigated dependent on different ion incidence angles. The AlGaN/GaN heterostructure was measured before and after etching with respect to mobility and sheet resistance. The InGaN quantum well structure was measured with PL to determine the PL intensity and the energy shift, respectively. This experiments show that ion channeling is a significant defect generation phenomena in group- III nitrides at vertical ion incidence angle and can be minimized by tilting the sample against the ion beam.
The Formation and Characterization of Epitaxial Titanium Carbide Contacts to 4H-SiC
Authors: Lee S.-K. , Danielsson E. , Zetterling C.-M. , Östling M. , Palmquist J.-P. , Högberg H. , Jansson U.
Published: April 2011

Epitaxial TiC Ohmic and Schottky contacts to 4H-SiC were formed by a new deposition method, UHV co-evaporation with Ti and C60, at low temperature (< 500°C). We achieved a contact resistivity of 2 × 10−5Δcm2 at 25°C for as deposited Ohmic contacts on Al ion implanted 4H-Silicon carbide. The rectifying behavior of TiC Schottky contacts was also investigated using I-V and C-V. The measured Schottky barrier height (SBH) was 1.26 eV for n-type and 1.65 eV for p-type 4H-SiC using C-V measurements for frequencies ranging from 1kHz to 1MHz. LEED, RBS, XPS, and XRD measurements were performed to analyze composition ratio, interface reaction, and structural properties of the TiC epitaxial layer.
The Materials Properties of a Nickel Based Composite Contact to n-Sic for Pulsed Power Switching
Authors: Cole M. W. , Joshi P. C. , Ren F. , Hubbard C. W. , Wood M. C. , Ervin M. H.
Published: April 2011

Novel Ni/WSi/Ti/Pt composite Ohmic contacts to n-SiC were investigated as a function of annealing temperatures up to 1000°C. The onset of Ohmic behavior occurred at annealing temperatures of 900°C. Annealing at temperatures between 950°and 1000°C yielded excellent Ohmic behavior. At these temperatures the contact-SiC interface was smooth, defect free and characterized by a narrow Ni2Si reaction region. The annealed contacts possessed atomically smooth surface morphologies and exhibited minimal contact expansion. The residual carbon, resultant from SiC decomposition, was constrained by reaction with the WSi and Ti metallization layers forming carbide phases of W and Ti. The locations of the carbide phases were spatially distant from the metal semiconductor interface. Our results demonstrate that the Ni/WSi/Ti/Pt composite Ohmic contact maintains the desirable electrical properties associated with Ni contacts and possess excellent interfacial, compositional and surface properties which are required for reliable high power and high temperature device operation.
High-Dose Titanium Ion Implantation into Epitaxial Si/3C-SiC/Si Layer Systems for Electrical Contact Formation
Authors: Lindner Jörg K.N. , Wenzel Stephanie , Stritzker Bernd
Published: April 2011

High-dose titanium implantations have been performed into ion beam synthesized heteroepitaxial layer systems of Si/3C-SiC/Si(100) in order to study the formation of titanium silicide layers in the silicon top layer. The structure and composition of layers was analysed using RBS, XRD, XTEM and EFTEM. The sputtering rates of 180 keV Ti ions were determined using the lower SiC/Si interface as a marker. A homogeneous surface layer with the stoichiometry of TiSi2 was formed by a nearly stoichiometric implantation and subsequent annealing. The formation of more metal-rich silicides was observed at doses where the peak Ti concentration largely exceeds the TiSi2 stoichiometry and where the total amount of Ti atoms in the top layer is greater than the amount needed to convert the entire Si top layer into TiSi2. Under these conditions, strong solid state reactions of the implanted Ti atoms with the buried SiC layer and the silicon substrate are observed.
UV Radiation Effects on the Sol-Gel Processing of Ferroelectric PZT Thin Films
Authors: Brinkman K. S. , Schwartz R. W. , Ballato J.
Published: April 2011

Sol gel solutions have been modified with hydrogen peroxide to improve the durability of photo-irradiated films to water and acidic solvents for photo-patterning. The solutions used for film fabricati.on are aqueous based and contain acetylacetonate (acac). UV-Vis absorption studies indicate that peroxide modifies the acetylacetonate ligand (in this case the zirconium precursor) creating a new absorbing species at longer wavelength which also affects the response of the acac ligand to UV radiation. Precursor modification and UV treatments have also been shown to impact the texture and improve the microstructure of resulting films. Depth profiling by radio-frequency glow discharge atomic emission spectroscopy indicates reduction in the carbon to hydrogen ratios of films crystallized after exposure to UV radiation.
Ferroelectric Na0.5K0.5NbO3/SiO2/Si Thin Film Structures for Nonvolatile Memory
Authors: Cho C.-R. , Grishin A. M.
Published: April 2011

Highly c-axis oriented Na0.5K0.5NbO3 (NKN) films have been prepared on thermally grown thin SiO2 template layer onto Si(001) wafer by pulsed laser deposition technique. X-ray diffraction ø-2ø-scan data show multiple-cell structuring along the polar axis in NKN films grown onto SiO2 with thickness up to 45 nm. On the other hand, the film deposited onto amorphous ceramic (Coming) glass is a mixture of slightly c-axis oriented NKN and pyrochlore phases, while the film onto Pt(lll)/Ti/SiO2/Si(001) shows perfect [111] orientation. This implies small amount of SiO2 crystallites distributed in amorphous silica matrix inherits Si(001) orientation and serves as a key factor in highly oriented growth of NKN films. Au upper electrodes have been defined on the top of NKN(270nm)/SiO2/Si structures to investigate Metal-Ferroelectric-Insulator-Silicon (MFIS) diode characteristics for Field Effect Transistor (MFIS-FET) nonvolatile memory applications. C-V measurements yield memory window of 4.14 V at 10 V of gate voltage.
Fundamental Advances in Transparent Conducting Oxides
Authors: Coutts Timothy J. , Young David L. , Li Xiaonan
Published: April 2011

Increasingly large-volume markets for large-area, flat-panel displays and photovoltaic panels are likely to be established in the early years of the next century and transparent conducting oxides (TCOs) of improved opto-electronic properties will be required to enable some of these applications to be realized. Our work is focusing on improving both the fabrication-limited properties of the materials (extrinsic), and materials-limited properties (intrinsic). The emphasis on achieving improved electrical and optical properties hinges on achieving higher electron mobility via intrinsic and/or extrinsic properties. To this end, we have investigated the properties of several TCOs including cadmium oxide, tin oxide, zinc oxide, cadmium stannate and zinc stannate. These may be deposited by chemical vapor deposition (CVD) or sputtering and we hope to establish the capability to fabricate compounds and alloys in the cadmium oxide, tin oxide, zinc oxide ternary phase diagram.

The properties of the materials have been investigated using a wide variety of techniques including high-resolution electron microscopy, atomic force microscopy and X-ray diffraction, as well as Mössbauer, Raman and UV/visible/NIR spectroscopies. We have measured the transport properties (conductivity, Hall, Seebeck and Nernst coefficients) and have obtained the effective mZLss, relaxation time, Fermi energy, and scattering parameter. This information has been obtained as a function of carrier concentration, which depends on the deposition and annealing procedures. We have found that the mobilities of free-electrons in the cadmiumbearing compounds are greatly superior to those in the other materials, because they have much longer electron relaxation times. In the case of cadmium oxide, there is also great benefit from a much lower effective mass. We are gaining a clearer understanding of the fundamental microscopic attributes needed for TCOs, which will be required in more-demanding, and rapidly emerging, applications.
In2O3 Based Multicomponent Oxide Transparent Conducting Films Prepared by R.F. Magnetron Sputtering
Authors: Minami Tadatsugu , Miyata Toshihiro , Toda Hidenobu , Suzuki Shingo
Published: April 2011

Transparent and conductive thin films using new multicomponent oxides consisting of a combination of different In2O3 based ternary compounds have been prepared on room temperature substrates by r.f. magnetron sputtering. Transparent and conductive (Ga,In)2O3-MgIn2O4, (Ga,In)2O3-Zn2In2O2, (Ga,In)2O3-In4Sn3O12, Zn2In2O5,-In4Sn3O12 and Zn21n2O5-MgIn2O4 films were prepared over the whole range of compositions in these multicomponent oxides. The electrical and chemical properties of the resulting films could be controlled by varying the composition in the target. The resistivity, band-gap energy, work function and etching rate of the resulting multicomponent oxide films ranged between the properties of the two ternary compound films. This paper also presents a discussion of a significant spatial distribution of resistivity found on the substrate of the multicomponent oxide films as a function of composition. The resistivity distribution is attributable to the oxygen concentration on the substrate surface rather than the bombardment effect of high energy particles.
IR-Transparent Electrically Conductive CuAlxOy Deposited by Reactive Magnetron Co-Sputtering
Authors: Johnson L. F. , Moran M. B. , Savrun E. , Sarikaya M. , Kolega R. R.
Published: April 2011

This paper reports on progress in the fabrication of IR-transparent electrically conductive copper aluminum oxide (CuAlxOy) by reactive magnetron co-sputtering from high-purity-Cu and -Al targets in an argon-oxygen-gas mixture. Recent equipment modifications have resulted in much better control of deposition parameters like forward and reflected power and, consequently, much better control of film composition. Applying the correct amount of power to each target and adjusting the oxygen-partial pressure have significantly reduced the growth of surface-oxide layers on the metal targets. Equipment and process improvements have eliminated the sputterrate inconsistencies and arcing that led to lack of composition control in our earliest films. We now have much better control of film composition and are beginning to understand the relationship between the electro-optical properties and the molecular structure of the films using Fourier transform infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), inductively coupled plasma (ICP) emission spectroscopy, high resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS). A pair of weakly intense FTIR absorption bands at 1470 and 1395cm−1 is present in films that have enhanced electrical conductivity and IR transparency. Understanding the origin of these bands could speed development of CuAlO2 as a wide-bandgap-conductive oxide since these bands are clearly associated with enhanced conductivity and carrier mobility. The best film to date transmits about 80% in the mid-wave IR and has a sheet resistance of 160Δ;/sq.
Exploration of New Properties of Oxides by the Growth Control Using Pulsed Laser Epitaxy
Authors: Koinuma Hideomi , Koidal Takashi , Komiyama Daisuke , Lippmaa Mikk , Ohtomo Akira , Kawasaki Masashi
Published: April 2011

Metal oxides exhibit a wide variety of properties originating mainly from strong electron correlation. Electronic properties of oxides had been utilized mostly in the bulk form till recently and people frequently observed significant changes in such properties when these materials were converted into thin films. For the electronic application in recent years, hybridization and integration of materials in thin film forms are becoming more and more important. In view of our recent studies on high-Tc superconducting junctions and ZnO light emitting devices, this paper is devoted to stimulate the exploration of oxides as new innovative electronic materials by discussing the control of epitaxial thin film growth.
Growth of ZnO/MgZnO Superlattice on Sapphire
Authors: Muth J.F. , Teng C.W. , Sharma A.K. , Kvit A. , Kolbas R.M. , Narayan J.
Published: April 2011

The optical and structural properties of ZnO/MgZnO superlattices were investigated by transmission electron microscope, transmission measurement and photoluminescence. The uncoupled wells ranged in thickness from ∼ 30 Å to 75 Å Modulation of the Mg content was observed in Z-contrast TEM indicating the alloy composition was periodic. The density of stacking faults in the superlattice was extremely high, however the photoluminescence in the narrowest well case was blue shifted, and substantially brighter than comparable bulk layers of ZnO and MgZnO indicating that the emission was enhanced. Excitonic features were observed in the optical absorption spectra and also revealed that diffusion of Mg from the barrier layers into the well was occurring.
Surface Investigations on Single Crystal Anatase TiO2
Authors: Hengerer R. , Kavan L. , Bolliger B. , Erbudak M. , Tzel M. Gr
Published: April 2011

Utilizing a chemical transport reaction, we succeeded in growing large and clean anatase TiO2 single crystals whose surfaces could be characterized by standard physical and electro-chemical techniques. The examination of the structure of the clean (101) and (001) faces by low energy electron diffraction (LEED) and secondary electron imaging (SEI) showed that these surfaces are bulk terminated and thermodynamically stable. Impedance spectroscopy in aqueous solution revealed a slight difference in the flatband potential between the (101) and the (001) faces. This shift is also manifested in a different photocurrent onset potential and can be rationalized by a different water adsorption on the two surface structures. Voltammetry in aprotic solutions showed a different lithium insertion behavior for the two surfaces. This is explained by a different structural transparency of the anatase lattice in the two directions. Both findings favor the (001) over the (101) surface. These orientational dependencies may have some important technological relevance for the mesoscopic TiO2 films used in solar cells and lithium batteries.
Interface Stability in Hybrid Transition Metal-Oxide Magnetic Junctions
Authors: Sun J. Z. , Roche K. P. , Parkin S. S. P.
Published: April 2011

Recent experiments revealed an apparently bias-dependent tunneling magnetoresistance between a transition metal (such as Fe, Co) and an oxide barrier such as SrTiO3. We examine the materials issues involved in this type of hybrid transition metal-oxide junctions. The junction interface is shown to be unstable against thermal treatment or high-bias current stress. We conclude that the junction magnetoresistance is largely determined by the formation of an interface oxide layer different from the barrier or the transition metal electrode themselves.
Magnetic and Magneto-Optic Properties of Pulsed Laser Deposited CexY3−xFe5O12 Films
Authors: Kim Hyonju , Grishin Alex , Sbiaa R. , Gall H. Le , Rao K. V.
Published: April 2011

We present experimental studies of crystalline, magnetic, and magneto-optic (MO) properties and their correlation with the processing parameters of Ce-substituted yttrium iron garnet (CexY3−xFe5O12) thin films grown epitaxially onto single crystal Gd3Ga5O12 (111) substrates by Nd:YAG pulsed laser deposition technique. Rutherford backscattering (RBS) analysis and microprobe energy dispersive spectrometry (EDS) prove the background oxygen pressure, used for films growth, control films stoichiometry. Oxygen ambient pressure appears to be an important parameter to grow CexY3−x, Fe5O12 films with good crystallinity, magnetic properties, as well as enhanced MO effect. It is found that the film fabricated at 50 mTorr oxygen pressure exhibits a maximum Faraday rotation (FR) øF = 1.78 deg/νtm at λ = 633 nm, a maximum saturation magnetization 4πMs = 1255 Gauss with a minimum in-plane coercivity Hc = 35 Oe, and the narrowest full width at half maximum FWHM = 0.06° of the (444) Bragg reflection rocking curve. The analog of the Verdet constant V = øF / 4πMs, also found to be dependent on the oxygen ambient pressure, reaches the value as high as 1.4 deg/νm-kG at 633 nm, suggesting that this material is useful for MO applications.
Laser Processing of Parmod™ Functional Electronic Materials
Authors: Kydd Paul H. , Richard David L. , Chrisey Douglas B. , Church Kenneth H.
Published: April 2011

Parmod™ is a family of materials that can be printed and thermally cured to create metallic conductors on printed wiring boards. This additive process provides a way to produce circuitry direct from CAD files without the necessity for intermediate tooling of any kind. The printed images are converted to pure metallic traces in seconds at a temperature low enough to be compatible with commonly used rigid and flexible polymer-based substrates. This simple, two-step process eliminates the hazardous wastes and employee health and safety issues associated with conventional plate-and-etch photolithographic technology

Recently the Parmod™ technology has been extended from metals to oxides to enable printing passive electronic components such as resistors, capacitors and inductors, as well as the metallic interconnects. While thermal curing of the oxides provides useable electronic properties, particularly of resistors and capacitors, the performance of all these novel materials could be improved by laser processing. This paper discusses preliminary results on laser processing of Parmod™ conductors and components in two different systems
Ion Beam Induced Chemical Vapor Deposition of Dielectric Materials
Authors: Wanzenboeck H.D. , Lugstein A. , Langfischer H. , Bertagnolli E. , Gritsch M. , Hutter H.
Published: April 2011

Direct writing by locally induced chemical vapor deposition has been applied to direct-write tailor-made microstructures of siliconoxide for modification and repair of microelectronic circuits. Focused ion beam (FIB) tools are used for locally confined deposition of dielectric material in the deep sub-µm range. State-of-the-art procedures typically provide insufficient dielectrics with high leakage currents and low breakdown voltage. The detailed investigation of the deposition mechanisms in this study proposes an approach to significantly improve dielectric material properties. Siloxane and oxygen as volatile precursors introduced in a vacuum chamber are used to deposit siliconoxide at ambient temperatures on various substrates such as Si, GaAs, or metals. The deposition process was initiated by a focused Ga+-beam. As elementary electronic test vehicles for a systematic electrical investigation ion beam induced depositions in of capacitor architectures are applied. The chemical composition of the layers is investigated by secondary ion mass spectroscopy (SIMS) and reveals effects of atomic mixing at the interfaces. The variation of process parameters such as ion energy and ion dose, scan time and delay time lead to a better understanding of the mechanisms. The composition of the precursor gas mixture is of significant influence on insulating properties. The results demonstrate that optimized FIB-induced deposition of dielectrics offers a new window for in-situ post-processing of integrated circuits
Electrical Characteristics of Thermal Spray Silicon Coatings
Authors: Tan S.Y. , Gambino R.J. , Goswami R. , Sampath S. , Herman H.
Published: April 2011

Polycrystalline silicon deposits were formed on a monocrystalline silicon substrate by thermal spraying. The resulting structure exhibits a device characteristic. Pressure-induced transformations of silicon, namely, Si-III (BC-8) and Si-IX are identified by X-ray diffraction in a Si-I matrix on deposits formed by vacuum plasma spray. The presence of the Si-III and Si-IX indicates that the pressure-quenched silicon deposit is highly conductive, as determined by four-point van der Pauw resistivity measurement. Hall mobility measurements, combined with photoconductivity results, indicate that the highly conductive silicon deposit displays the same range of mobility as a polycrystalline deposit containing only Si-I. The silicon deposit, with or without metastable phases, displays the same photoconductivity properties. The silicon deposit on a monocrystalline silicon substrate exhibits rectifying I–Vcharacteristics, possibly caused by band bending of trapping states associated with impurities segregating at the polycrystalline deposit/monocrystalline substrate interface
Synthesis and Radical Polymerization of Pyrocarbonate Functionalized Monomers: Application to Positive-Tone Photoresists
Authors: Vansteenkiste S.O. , Marleé Y. , Schacht E.H. , Damme M. Van , van Aert H. , Vermeersch J.
Published: April 2011

The synthesis of two new tert-butyl carbonic anhydride monomers, 4-vinylbenzoic and methacrylic tert-butyl carbonic anhydride was achieved successfully. Radical polymerization at 45°C yielded tert-butyl pyrocarbonate protected materials. Thermographic analysis showed that both polymers decompose cleanly at 135°C. The lithographic performance of both materials was evaluated in presence of 2,4,6-tris-(trichloromethyl)-s-triazine as photoacid generating species. It was demonstrated that the large polarity change resulted in a chemically amplified positive photoresist system
Manufacture of Microelectronic Circuitry by Drop-on-Demand Dispensing of Nano-particle Liquid Suspensions
Authors: Szczech J.B. , Megaridis C.M. , Gamota D.R. , Zhang J.
Published: April 2011

An emerging selective metallization process utilizes Drop-On-Demand (DOD) inkjet printing, and recent developments in nano-particle fluid suspensions to fabricate fine-line circuit interconnects. The suspensions consist of silver or gold particulates of 1–10 nm in size that are homogeneously suspended in an organic carrier solvent. A piezo-electric droplet generator driven by a bipolar voltage signal is used to dispense 50–70 µm diameter droplets traveling at 1-3 m/s before impacting a compliant substrate. The deposit/substrate composite is subsequently processed at 300°Cfor 15 minutes to allow for evaporation of the solvent carrier and sintering of the nano-particles, thereby yielding a finished circuit product. Test vehicles created using this technique exhibited features as fine as 120–200 µm wide and 1–3 µm thick. The circuitry performed well during environmental conditioning studies. However, repeatability of the results showed sensitivity to the generation of steady, satellite-free droplets. In an effort to generate droplets consistently, it is essential to develop a strong fundamental understanding of the correlation between device excitation parameters and fluid properties, and resolve the microrheological behavior of the conductive ink as it flows through the droplet generator.
Using Convective Flow Splitting for the Direct Printing of Fine Copper Lines
Authors: Cuk T. , Troian S.M. , Hong C.M. , Wagner S.
Published: April 2011

We have developed a technique for the printing of copper lines using solutions of a metal organic precursor, copper hexanoate. A 500-µm written liquid line is observed to split into two 100-µm wide lines. We observe further splitting into four parallel lines in experiments with written lines of copper hexanoate solution in chloroform. Surface profiles indicate that the thickness, width and number of lines formed are strongly dependent on the solution viscosity and volume per unit length deposited. From particle tracking visualization and surface profiling, we have found that evaporative cooling produces Marangoni convection patterns that accrete the solute along two key boundaries of flow
Ink Jet Deposition of Ceramic Suspensions: Modeling and Experiments of Droplet Formation
Authors: Reis N. , Derby B.
Published: April 2011

We have successfully printed green ceramic objects from slurries of Al2O3 dispersed in paraffin wax using a commercial ink-jet printer developed for pattern making (Sanders Prototype MM6PRO). Concentrated suspensions are generally more viscous than the fluids normally passed through ink jet heads. This may alter the response of the printing system to its process parameters, e.g. driving voltage and frequency. We have explored the influence of fluid properties on the ink jet behaviour using Computational Fluid Dynamics (CFD) modelling and a parallel experimental study to determine the optimum printing conditions for particulate suspensions.
A UV Direct-Write Approach for Formation of Embedded Structures in Photostructurable Glass-Ceramics
Authors: Fuqua P.D. , Taylor D.P. , Helvajian H. , Hansen W.W. , Abraham M.H.
Published: April 2011

Photostructurable glass-ceramics are a promising class of materials for MEMS devices. Previous work micromachining these materials used conventional photolithography equipment and masking techniques; however, we use direct-write CAM tools and a pulsed UV laser micromachining station for rapid prototyping and enhanced depth control. We have already used this class of materials to build components for MEMS thrusters, including fuel tanks and nozzles: structures that would prove difficult to build by standard microfabrication techniques.

A series of experiments was performed to characterize process parameters and establish the processing trade-offs in the laser exposure step. The hypothesis that there exists a critical dose of UV light for the growth of an etchable crystalline phase was tested by exposing the material to a fluence gradient for a variety of pulse train lengths, and then processing as usual. By measuring the dimensions of the etched region, we were able to determine the dose. We found that the dose is proportional to the square of the per-pulse fluence. This has allowed us to create not only embedded structures, but also stacked embedded structures. This also implies that we can embed tubes and tunnels with a single exposure inside a monolithic glass sample. We feel that this technique has promise for a number of applications, including microfluidics.