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Isothermal (700 °C) ultraviolet annealing (UVA) processing of crystallized Ba0.60Sr0.40TiO3 (BST) thin films for exposure times up to 225 min films has been studied. The BST films, grown on PtSi wafers via the metalorganic solution deposition (MOSD) technique, were crystallized via conventional furnace annealing (CFA) prior to UVA treatment, and the effects of UV annealing time on the structural, dielectric, and insulation properties were evaluated. The experimental results demonstrated significantly improved structural, dielectric, and insulation properties for the UVA films. Specifically, lattice parameter contraction (toward that of bulk BST60/40) and a 20% reduction in loss were observed for the UVA treated films with respect to the CFA/control film. Leakage current characteristics were found to be the most sensitive characterization technique to access material property modification as a result of UVA exposure time. Specifically, the 225 min UVA exposure time resulted in a three-order of magnitude reduction in leakage current density compared to the CFA film, and the lowest value observed was 1.06 × 10-7 A/cm2 at E = 300 kV/cm. The useable tunability (tunability value at the maximum acceptable leakage current, 500 pA) was found to be elevated by a factor of two with respect to that of the CFA/control BST film (52.31%/UVA film vs. 18.5%/control film). It is suggested that the improved material properties are due to the mitigation of unwanted oxygen vacancies within the film after UV-annealing. A mechanistic model is presented and discussed. [ABSTRACT FROM AUTHOR]

Oxide semiconductors are attractive materials for thin-film electronics and optoelectronics due to compatibility with synthesis on large-area, inexpensive glass and flexible plastic substrate. However, development of thin-film electronics has been hampered by the limited number of semiconducting oxides that are p-type. Here, we report on the properties of zinc-cobalt-oxide (Zn–Co–O) films, deposited at room temperature using pulsed laser deposition, that exhibit p-type conduction. Films are deposited at room temperature in a background of oxygen using a polycrystalline ZnCo2O4 ablation target. The p-type conduction is confirmed by positive Seebeck coefficient and positive Hall coefficient. Both electrical resistivity and carrier density are dependent on oxygen background pressure used during deposition. Zn–Co–O films deposited in 50 mTorr oxygen pressure appear to be amorphous based on x-ray diffraction, and show an electrical conductivity as high as 21 S cm-1. Distinct rectifying current-voltage characteristics are observed for junctions between Zn–Co–O and n-type InGaZnO films, exhibiting a threshold voltage of ∼2.5 V. P-type Zn–Co–O appears promising for thin-film electronic device technology. [ABSTRACT FROM AUTHOR]

The magnetic and transport properties of Mn-doped ZnO thin films co-doped with P are examined. Superconducting quantum interference device magnetometry measurements indicate that the films are ferromagnetic with an inverse correlation between magnetization and electron density as controlled by P doping. In particular, under conditions where the acceptor dopants are activated leading to a decrease in free-electron density, magnetization is enhanced. The result is consistent with hole-mediated ferromagnetism in Mn-doped ZnO, in which bound acceptors mediate the ferromagnetic ordering. Increasing the electron density decreases the acceptor concentration, thus quenching the ferromagnetic exchange. This result is important in understanding ferromagnetism in transition metal doped semiconductors for spintronic devices. [ABSTRACT FROM AUTHOR]

The magnetic and transport properties of Mn-doped ZnO thin films codoped with Sn are examined. Superconducting quantum interference device magnetometry measurements indicate that the films are ferromagnetic with an inverse correlation between magnetization and electron density as controlled by Sn doping. Magnetism in low free-electron density material is consistent with the bound magnetic polaron model, in which bound acceptors mediate the ferromagnetic ordering. Increasing the electron density decreases the acceptor concentration, thus quenching the ferromagnetic exchange. This result is important in understanding ferromagnetism in transition-metal-doped semiconductors for spintronic devices. [ABSTRACT FROM AUTHOR]

The residual stress and morphology of Pt electrodes were investigated using Ti and titanium oxide (TiOx) adhesion layers. Conventional or rapid thermal annealing (RTA) was used to compare the morphologies. The morphology depended on the substrate, adhesion layer, and annealing conditions, with large hillocks formed for electrodes incorporating Ti on Si. Electrode stacks utilizing TiOx adhesion layers resulted in residual stresses that were ∼50% less than those with Ti. Ba0.60Sr0.40TiO3 (BST) thin films were deposited onto several electrodes to investigate the integrity of the electrode/film heterostructures. Delamination or roughening of the film was observed depending on the adhesion layer. [ABSTRACT FROM AUTHOR]

We present the correlation between film fabrication conditions (crystallization temperatures), microstructure, and dielectric phase shift of Ba1-xSrxTiO3 (BST) thin films synthesized by metal organic solution deposition (MOSD) on sapphire substrates. The structure, microstructure, surface morphology, and composition of the films were assessed by glancing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM), and Rutherford backscattering spectroscopy (RBS). The dielectric phase shift measurements were carried out using coplanar waveguide (CPW) test circuits over a frequency range of 2-18 GHz. Our results indicate that BST processed at 950°C achieved large relative phase shift response with low attenuation of the microwave signal. [ABSTRACT FROM AUTHOR]

Wide band gap semiconductors such as GaN and ZnO have continued to be at the forefront of spintronics research due to the demonstration of room-temperature ferromagnetism in these materials. A goal of this research is the fabrication of a spintronic device that may provide easy incorporation into existing GaN and ZnO technologies, higher integration density, and less power consumption that its electronic counterparts while achieving similar speeds. The progression of the ferromagnetic metals incorporated into GaN has moved from transition metals to rare earth metals such as the lanthanides. The properties of transition metal-doped ZnO thin films for the two most studied transition metal dopants, namely Mn and Co, are also discussed in this review. [ABSTRACT FROM AUTHOR]

Abstract: The growth and properties of delafossites CuCr1− x Mg x O2 thin films are examined. These films are grown by pulsed laser deposition. As a class of materials delafossites have received recent interest since some members show p-type behavior. While not considered true wide-bandgap materials due to a narrow indirect bandgap that fails to adsorb light due to a forbidden same parity transition, optical transparencies greater than 40% in the visible can be observed. In order to be useful for transparent device applications, CuCr1− x Mg x O2 films are needed with low resistivity and high optical transparency. Epitaxial films of CuCr1− x Mg x O2 were grown on c-sapphire, examining the effects of oxygen pressure and growth temperature on film properties. Films were realized with resistivity of ~0.02 Ω-cm and optical transparency of 40% in the visible. The formation of a problematic secondary minority spinel phase of (Cu,Mg)Cr2O4 is discussed. While conductivity increases substantially with Mg doping, the incidence of the spinel phase increases as well. [Copyright &y& Elsevier]

Semiconducting oxides offer the potential for exploring and understanding spin-based functionality in a semiconducting host material. Theoretical predictions suggest that carrier-mediated ferromagnetism should be favored for p-type material. Cu2O is a p-type, direct wide bandgap oxide semiconductor that may hold interest in exploring spin behavior. In this paper, the properties of Mn-doped Cu2O are described. Activities focused on understanding Mn incorporation during thin-film synthesis, as well as magnetic characterization. The epitaxial films were grown by pulsed-laser deposition. X-ray diffraction was used to determine film crystallinity and to address the formation of secondary phases. SQUID magnetometry was employed to characterize the magnetic properties. Ferromagnetism is observed in selected Mn-doped Cu2O films, but appears to be associated with Mn3O4 secondary phases. In phase-pure Mn-doped Cu2O films, no evidence for ferromagnetism is observed. [Copyright &y& Elsevier]

The epitaxial growth of CeO[sub 2] thin films has been realized on (100) InP substrates using reactive r.f. magnetron sputtering. Oxide films were nucleated in the presence of molecular hydrogen (4% H[sub 2]/Ar sputtering gas) in order to reduce the native oxide formation on the InP surface, which interferes with CeO[sub 2] epitaxy. A metal cerium target was used as the cation source, with water vapor serving as the oxidizing species. Epitaxial films were sputter-deposited at a substrate temperature of 550 °C in a H[sub 2]O vapor pressure of approximately 10[sup -3] Torr. Crystallinity of the oxide films was examined using θ-2θ X-ray diffraction, ω-rocking curves, and in-plane φ-scans. The best results were obtained when the initial nucleation layer was deposited with P(H[sub 2]O) < 10[sup -5] Torr, followed by deposition at P(H[sub 2]O) = 10[sup -3] Torr. The epitaxial growth of CeO[sub 2] on InP could prove enabling in efforts to integrate functional oxides with InP-based optoelectronic and microwave technologies. [ABSTRACT FROM AUTHOR]

The article presents the authors' comments on the symposium on Ferroelectricity and Piezoelectricity: Materials, Devices, and Applications, which was held at the International Materials Research Congress (IMRC) held in Cancun, Mexico, during August 16-21, 2009. According to the authors, the symposium focused on topics including nanotechnology, material design, and surface engineering of thin films. The authors say that the symposium has helped in the establishment of new collaborations.