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The authors have fabricated combinatorial Ni–Ti–Pt ternary metal gate thin film libraries on HfO2 using magnetron co-sputtering to investigate flatband voltage shift (ΔVfb), work function ([uppercase_phi_synonym]m), and leakage current density (JL) variations. A more negative ΔVfb is observed close to the Ti-rich corner than at the Ni- and Pt-rich corners, implying smaller [uppercase_phi_synonym]m near the Ti-rich corners and higher [uppercase_phi_synonym]m near the Ni- and Pt-rich corners. In addition, measured JL values can be explained consistently with the observed [uppercase_phi_synonym]m variations. Combinatorial methodologies prove to be useful in surveying the large compositional space of ternary alloy metal gate electrode systems. [ABSTRACT FROM AUTHOR]

Electronic structures of (LaAlO3)1-x(Al2O3)x composite films (x=0, 0.2, 0.33, 0.5, and 1) for large scale integration (LSI) gate dielectrics deposited on p-type Si (100) substrates by a combinatorial pulsed laser deposition method have been analyzed using photoelectron spectroscopy and x-ray absorption spectroscopy. The systematic peak shifts due to chemical shifts were observed for core-level spectra. The conduction-band offset became smaller with increasing ratio of Al2O3, while the valence-band offset became larger. This precise determination of the band diagram revealed that LaAlO3 (x=0) had the optimum band offset for LSI gate dielectrics. [ABSTRACT FROM AUTHOR]

The effects of nitridation on open volumes in thin HfSiOx films fabricated by metal-organic chemical vapor deposition were studied using monoenergetic positron beams. It was found that positrons were annihilated from the trapped state by open volumes that exist intrinsically in amorphous HfSiOx structures. In an as-deposited film, the positrons were annihilated from two different types of open volume. After plasma nitridation, the probability of positrons trapped by larger open volumes decreased, which is attributed to nitride trapped by such regions. The mean size of the open volumes increased after annealing, suggesting expansion of the open volumes due to the incorporation of nitride into the HfSiOx matrix. [ABSTRACT FROM AUTHOR]

Self-assembled nanoskyscrapers of ferroelectric Bi4Ti3O12 were fabricated by a bottom-up process: flux-mediated epitaxy using an admixture flux. By combinatorial technique, we have discovered a novel flux, VOx, to assist the unique crystal growth for the in-plane alignment of the long c axis of Bi4Ti3O12 on a SrTiO3(001) substrate. We report on the self-assembly of an isolated epitaxial (110)-oriented Bi4Ti3O12 nanoplate and the direct measurement of the piezoelectric properties by a scanning probe microscope technique. Piezoelectric lattice displacement showed a typical butterfly curve, indicating good ferroelectric property. [ABSTRACT FROM AUTHOR]

Sulfide was employed as a buffer layer for the growth of SrTiO[SUB3] (STO) thin films on Si. In order to utilize a relationship of a 45° rotational lattice match between Si and STO, ZnS, with almost the same lattice constant as Si, was used as the buffer. The buffer layer showed a partially disordered region at the ZnS/Si interface, owing to steady interdiffusion between ZnS and Si. STO film on ZnS buffered Si showed the rotational epitaxy with respect to Si and sharp STO/ZnS interface. Propagation of stacking faults from the ZnS/Si interface was observed, but those plane defects were terminated at the rotational STO/ZnS interface, resulting in high-quality STO films. The dielectric constant of the STO/ZnS film was 34. [ABSTRACT FROM AUTHOR]

Oxide thin films are usually grown on substrates which offer the smallest mismatch with the desired structure of the film. The choice of high-quality substrates with suitable lattice constants is unfortunately very limited. Coherently grown films are therefore always under tensile or compressive in-plane strain. We report on the growth of a Ba[sub 1-x]Sr[sub x]TiO[sub 3]/BaTiO[sub 3] bilayer buffer on a SrTiO[sub 3] substrate. Changing the Sr/Ba ratio in the Ba[sub 1-x]Sr[sub x]TiO[sub 3] layer can be used to select a desired in-plane lattice constant in the 3.9 to 4.0 Å range. The thinner BaTiO[sub 3] film serves as a compliant layer while the thicker Ba[sub 1-x]Sr[sub x]TiO[sub 3] film determines the final surface lattice constant. This is achieved by a combination of low-temperature deposition and annealing at 1350 °C. X-ray diffraction and high-resolution transmission electron microscopy were used to show that the final buffer layer surface is fully relaxed, cubic, and essentially defect free, while all lattice mismatch between the substrate and the buffer is relieved by misfit dislocations at the compliant BaTiO[sub 3]/SrTiO[sub 3] interface. [ABSTRACT FROM AUTHOR]

We report on the fabrication of single-crystalline thin films of RBa[sub 2]Cu[sub 3]O[sub 7-y] (R: rare-earth element, R123) using an approach of vapor-liquid-solid tri-phase epitaxy. This method is based on application of pulsed-laser deposition under appropriate compositions and conditions predetermined from the relevant thermodynamic phase diagram. The laser-ablated gases of R, Ba, and Cu, and their oxides dissolve into a liquid Ba[sub 3]Cu[sub 5]O[sub x](3BaCuO[sub 2]+2CuO) layer placed on the film/substrate surface, penetrate to reach the liquid-solid interface with a seed R123, and are condensed into the solid R123 phase under a quasiequilibrium state. The uniform single-crystalline nature of the film was verified by x-ray diffraction, atomic-force microscopy, and transmission electron microscopy by the observation of giant grain size and atomic-scale surface smoothness. [ABSTRACT FROM AUTHOR]

We have fabricated Si/β-FeSi[sub 2] particles/Si structures by reactive deposition epitaxy for β-FeSi[sub 2] and molecular-beam epitaxy (MBE) for Si. It was found that the photoluminescence (PL) intensity of β-FeSi[sub 2] strongly depended on MBE-Si growth temperature for embedding β-FeSi[sub 2] in Si. Room temperature 1.6 μm electroluminescence was realized from a Si-based light-emitting diode by embedding the β-FeSi[sub 2] active region with Si grown at 500 °C. Observation with transmission electron microscopy revealed that the a axis of β-FeSi[sub 2] from which PL was observed was about 9% longer than that of β-FeSi[sub 2] without PL or of bulk β-FeSi[sub 2]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Epitaxial anatase thin films were fabricated on lattice-matched (-0.2%) LaAlO[sub 3] (001) substrates in the layer-by-layer fashion by laser molecular-beam epitaxy. X-ray diffraction and transmission electron microscope show the films to exhibit high crystallinity and atomically defined interfaces. By virtue of the adoption of LaAlO[sub 3] substrate, which is transparent to photoexcitation of TiO[sub 2], optical band gaps could be determined to be 3.3 eV at room temperature. A photoluminescence band due to recombination of self-trapped excitons was observed at 5 K to give the peak maximum at 2.2 eV. As a result of the high degree of orientation of the epitaxial films, anisotropic optical absorption was clearly observed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The room-temperature epitaxial growth of CeO[sub 2] films on Si(111) substrates was examined in situ by combined use of a coaxial impact-collision ion scattering spectroscopy (CAICISS) and the laser molecular beam epitaxy (laser MBE). It was found that the crystal quality of CeO[sub 2] ultrathin films (∼3 nm thick) as-grown in UHV (∼10[sup -9] Torr) could be improved remarkably by a few minutes of O[sub 2] gas exposure (∼10[sup -5] Torr) at room temperature. A three-fold symmetry in the Ce signal intensity of azimuth rotational CAICISS spectra, which exhibited the type-B epitaxial growth ([1¯10][sub CeO[sub 2]]|[11¯0][sub Si]), was observed for the films thicker than about 1 nm. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the interface structure of CeO[sub 2]/Si(111). Result of the reaction between CeO[sub 2] and Si at the interface; Effect of post annealing in oxygen atmosphere on crystalline CeO[sub 2] and SiO[sub 2] thickness; Usefulness of the modified structure of CeO[sub 2]/SiO[sub 2]/Si as a silicon-on-insulator structure.

Abstract: The compositional optimization of infrared-transparent conducting oxides was performed using high throughput screening of combinatorial libraries. Complete ternary composition spreads of NiO–Mn2O3–Co3O4 alloys were deposited onto conducting Nb-doped SrTiO3 substrates using the pulsed laser deposition technique. Resistance–temperature relations of each composition in the spread were determined using a custom-designed scanning probe. The binary NiCo2O4 oxide showed the lowest electrical resistivity of about 0.1Ωcm but unacceptably large resistance–temperature dependence (3.5%/°C). Electrically conducting ternary alloys along the line Mn0.45Ni0.63Co1.92O4–Mn0.60Ni0.72Co1.68O4–Mn0.69Ni0.81Co1.50O4 exhibited much lower temperature sensitivity (of about 1.5%/°C) as well as electrical resistance comparable to that of NiCo2O4. From this screening we propose new compounds for the thin-film ITCO sensors. [Copyright &y& Elsevier]

Pt/Fe and Pt/Ag/Fe layered films were deposited by DC magnetron sputtering on MgO(001), SrTiO3(001), and Al2O3(0001) single crystalline substrates at room temperature. The films were post-annealed between 623K and 1173K for 30 s in flowing N2 atmosphere. The onset of the L10-FePt phase formation in films deposited on MgO(001) and SrTiO3(001) substrates was observed after annealing between 773 and 873 K, while chemical L10 ordering sets in for Pt/Fe bilayers on Al2O3(0001) at lower temperatures accompanied by strong (001)-texture. It is concluded that elastic stress, arising from the difference in thermal expansion coefficients between film and substrate, promotes ordering and texture formation. [ABSTRACT FROM AUTHOR]

We investigated the Schottky barrier height (SBH) behavior of binary alloy Schottky contacts on n-type zinc oxide (n-ZnO) single crystals. Pt–Ru alloy electrodes were deposited on the Zn-polar and O-polar faces of ZnO substrates by combinatorial ion-beam deposition under identical conditions. The crystal structures of the Pt–Ru alloy film changed from the Pt phase (cubic structure) to the Ru phase (hexagonal structure) in the Pt–Ru alloy phase diagram with decreasing Pt content. The SBH, determined from current–voltage measurements, decreased with decreasing Pt content, indicating that the SBH behavior also followed the Pt–Ru alloy phase diagram. The alloy electrodes on the Zn-polar face showed better Schottky properties than those on the O-polar face. Hard x-ray photoelectron spectroscopy revealed a difference in the interface oxidization of the Pt–Ru alloy: the interface of the O-polar face and Pt–Ru mixed phase with poor crystallinity had a more oxidized layer than that of the Zn-polar face. As a result of this oxidization, the O-polar face, Pt–Ru mixed, and Ru phases showed poor Schottky properties. [ABSTRACT FROM AUTHOR]

We have applied a combinatorial technique to fabricate work function (WF) tuned Pt-W alloy films and used the films as metal electrodes for HfO2/SiO2/Si capacitors. As the ratio, RPt, of Pt to W changes from 0 to 1, the WF value varies continuously from 4.7 to 5.5 eV. This tunability enables us to systematically investigate the effect of WF variation on electrical properties. After a forming gas annealing process, the values of flatband voltage (Vfb) from capacitance-voltage properties are almost constant, regardless of the WF variation, because of oxygen vacancy formation that results in Fermi level pinning. On additional oxidizing gas annealing (OGA), the effect of WF value on Vfb becomes dominant. However, the difference in Vfb between W and Pt is 0.34 V, which is much smaller than the observed WF difference of 0.8 eV. We attribute this phenomenon to the lowering of the effective WF due to an electric dipole, induced by oxygen vacancy formation at the metal/HfO2 interface. Moreover, a decrease in Vfb in W-rich regions was observed following the OGA, suggesting the formation of a W-O bond at the interface. These results clearly indicate that the control of bonding states at the metal/HfO2 interfaces on an atomic scale is essential for the realization of a combination of metal and high-k dielectric films in future complementary metal-oxide-semiconductor devices. [ABSTRACT FROM AUTHOR]

The impact of TiN deposition on thin HfO2 films formed on Si substrates was studied using x-ray photoelectron spectroscopy and a monoenergetic positron beam. For the predeposition sample, the positrons implanted into Si were found to diffuse toward the HfO2/Si interface under the influence of the electric field, suggesting the presence of negative charges in HfO2. After TiN was deposited by chemical vapor deposition, no large change in the defect species was observed. After TiN was deposited by physical vapor deposition, however, positive charges were introduced at the TiN/HfO2 interface, which were associated with the incorporation of nitride into HfO2 and/or the plasma damage at the surface of HfO2, and the resultant formation of positively charged oxygen vacancies. [ABSTRACT FROM AUTHOR]

The impact of nitridation on open volumes in thin HfSiOx films fabricated on Si substrates by atomic layer deposition was studied using monoenergetic positron beams. For HfSiOx, positrons were found to annihilate from the trapped state due to open volumes which exist intrinsically in an amorphous structure. After plasma nitridation, the size of open volumes decreased at a nitrogen concentration of about 20 at. %. An expansion of open volumes, however, was observed after postnitridation annealing (PNA) (1050 °C, 5 s). We found that the size of open volumes increased with increasing nitrogen concentration in HfSiOx. The change in the size of open volumes was attributed to the trapping of nitrogen by open volumes, and an incorporation of nitrogen into the amorphous matrix of HfSiOx during PNA. We also examined the role of nitrogen in HfSiOx using x-ray photoelectron spectroscopy and first principles calculations. [ABSTRACT FROM AUTHOR]

Thin Hf0.6Si0.4Ox and Hf0.3Al0.7Ox films fabricated by metal-organic chemical-vapor deposition and atomic-layer-deposition techniques were characterized using monoenergetic positron beams. Measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positions indicated that positrons annihilated from the trapped state by open volumes that exist intrinsically in amorphous structures of the films. For HfSiOx, the mean size of the open volumes and their size distribution decreased with increasing postdeposition annealing (PDA) temperature. For HfAlOx, although the overall behavior of the open volumes in response to annealing was similar to that for HfSiOx, PDA caused a separation of the mean size of the open volumes. When this separation occurred, the value of the line-shape parameter S increased, suggesting an oxygen deficiency in the amorphous matrix. This fragmentation of the amorphous matrix can be suppressed by decreasing the annealing time. [ABSTRACT FROM AUTHOR]

There has been considerable debate regarding the origin of ferromagnetism in the ferromagnetic semiconductor anatase phase TiO2 doped with Co, ranging from carrier induced ferromagnetism in a framework of diluted magnetic semiconductor to merely the precipitation of ferromagnetic and metallic Co precipitates in the TiO2 matrix. This paper reports on a systematic investigation of the structures, together with the electronic and magneto-optical properties, of thin films of anatase phase TiO2, doped with Co. Films of anatase Ti1-xCoxO2 (x=0–0.10) were grown epitaxially on LaSrAlO4 (001) substrates, using pulsed laser deposition method. In order to control n-type carrier concentration, the oxygen pressure during the growth was systematically varied, yielding films with insulative, semiconductive (carrier concentration n∼1×1017 cm-3), and metallic (n∼2×1019 cm-3) properties. Reflection high energy electron diffraction patterns, atomic force microscopy, and transmission electron microscopy show no evidence of Co segregation in these films. Magneto-optical response was examined by measuring magneto-optical circular dichroism (MCD) spectra at room temperature. A large MCD peak appears at a photon energy close to the band gap of TiO2. The magnetic field dependence of MCD signal indicates ferromagnetic behavior, which is similar to that of the magnetization. The MCD intensity increases systematically with the increase of n or x. Since MCD response originates from charge carriers at the band edge, one can conclude that interaction between the charge carriers and Co impurities is essential to realize ferromagnetism. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Co-doped ZnO(Zn[sub 1-x]Co[sub x]O) and Co, Al codoped ZnO(Zn[sub 1-x]Co[sub x]O:Al) films were grown on c-plane sapphire (0001) substrates by pulsed laser deposition using a KrF excimer laser. In order to enhance homogeneous substitution of Co[sup 2+] for Zn[sup 2+] in the ZnO film, an alternating deposition (AD) method was employed for doping. ZnO films doped with the same elements were grown without employing the AD method under the same fabrication conditions to compare with the corresponding AD films. Despite Co incorporation, the Zn[sub 1-x]Co[sub x]O film by AD methods showed better crystallinity than pure ZnO film. Also, the crystallinity of Zn[sub 1-x]Co[sub x]O:Al films by AD methods was better than those of Zn[sub 1-x]Co[sub x]O and ZnO:Al films by conventional doping methods. Root mean square roughnesses of the films by AD methods were less than 1.6 nm. Absorption peaks caused by d–d transitions were observed at 1.88, 2.01, and 2.19 eV in Zn[sub 1-x]Co[sub x]O films. The electric conductivity of Zn[sub 1-x]Co[sub x]O:Al film by AD methods was comparable to that of ZnO:Al film by conventional methods in spite of Co doping and lower Al concentration. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses a study which investigated the interface reaction between nickel thin film and bulk SiC during heat treatment by MeV ion backscattering spectrometry. Formation of polycrystalline nickel-silicide; Kinds of applications in which SiC has attracted much attention; Factor led by a lack of direct compound identification in the techniques used; Problem encountered in the use of the backscattering technique for light elements.

The effect of hydrogen on near-atmospheric nitrogen plasma and low temperature growth of GaN thin film was investigated. To investigate nitrogen plasma diluted with hydrogen, optical emission spectroscopy (OES) was employed. OES indicates that hydrogen enhances the generation of the nitrogen first positive system and first negative systems by providing an additional kinetic pathway. The plasma also decomposed triethylgallium and generated Ga ions even at room temperature. Using this plasma, GaN film grew on sapphire substrate epitaxially at growth temperatures of above 170 °C and crystallized at 55 °C. [ABSTRACT FROM AUTHOR]

We have investigated the carrier induced magnetic properties of anatase Ti1-x-yNbxMyO2 (M=Co,Fe) epitaxial films grown by the pulsed laser deposition technique. For Ti0.95-xNbxCo0.05O2, the n-type carrier density could be controlled in a wide range (4.9×1017 cm-3 to 2.7×1021 cm-3) by Nb doping (x=0–0.2). The temperature dependence of the resistivity showed metallic behavior, suggesting that Ti0.95-xNbxCo0.05O2 undergoes a semiconductor to metal transition along with a slight carrier doping less than x<0.03. In both Co-doped and Fe-doped films, we have confirmed hysteresis in M-H curves, and the anomalous Hall effect at room temperature. This strongly suggests that the charge carriers are spin polarized and mediate ferromagnetic interaction between local spins on transition metal ions. In the case of Ti0.94-xNbxFe0.06O2, ferromagnetism is sensitive to carrier concentration. That is, the x=0.002 film is nonmagnetic even at 3 K, while room-temperature ferromagnetism appears at x=0.01. [ABSTRACT FROM AUTHOR]

High-quality interface between an insulator and ZnO as a wide-band-gap semiconductor should realize devices based on field-effect carrier modulation or superlattices having large band offset over 1 eV. We demonstrate that LiGaO[SUB2] could be a possible candidate for this purpose. Heteroepitaxy of LiGaO[SUB2] is demonstrated on ZnO films, giving atomically sharp interface and fairly good exciton-related optical properties in the ZnO under layer. Although slight distortion of a basal-plane hexagon with a lattice mismatch of about 3% in LiGaO[SUB2] gives multidomain epitaxial structure with relaxed lattices, a possible solution is proposed to realize coherent heterointerface. [ABSTRACT FROM AUTHOR]

We used hard x-ray photoelectron spectroscopy to investigate the interfacial electronic states of a poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) contact on a ZnO single crystal. An understanding of the interfacial band structure is useful for putting the organic contact to practical use. We observed upward band bending of the ZnO layer a few nanometers from the interface. The detected ZnO bulk region exhibited a flat band structure, meaning that the PEDOT:PSS does not greatly deplete the ZnO layer. The band bending caused the charge injection barrier formation with the result that the contact exhibited the Schottky property. [ABSTRACT FROM AUTHOR]

Abstract: Informatics tools are an important part of the high-throughput or combinatorial materials development process. Particularly for thin film studies, the rate of sample synthesis and characterization has increased to a point where the throughput of the whole materials development process is limited by the ability to process the characterization data and design new experiments. We describe in this work software tools that we have developed to solve the data management problems. In particular, we discuss the use of extensible markup language (XML) to address the problem of representing structurally varied experimental data in a data management system without having to make modifications to the core software parts whenever the materials processing or characterization tools or sample and data handling procedures change. [Copyright &y& Elsevier]