Magnesium Oxide Substrates Research Articles

(100) Three-Axis-Oriented BaTiO3, (Ba0.7Sr0.3)TiO3Thin Film Prepared by Chemical Solution Deposition Method

Epitaxially grown (100) three-axis-oriented (Ba0.7Sr0.3)TiO3 thin film on (100) platinum (Pt) coated (100) magnesium oxide (MgO) substrate and (100) three-axis-oriented BaTiO3 thin film with BaZrO3 buffer layer were prepared on an MgO(100) substrate using the chemical solution deposition method. The growth of the film was found to depend on the annealing condition. Transmission electron microscope revealed cube-on-cube epitaxial growth. The thin films exhibited a (100) three-axis-orientation that followed the (100) orientation of the MgO substrate and the (100) orientation of the Pt or BaZrO3 bottom layer, as observed from an X-ray pole figure measurement and the selected area electron diffraction patterns.

The Effect of Substrate Clamping on Laminated Magnetoelectric Composite

Abstract laminated composites on silicon or magnesium oxide substrates. The magnetoelectric voltage coefficient is calculated as function of interface coupling factor k, volume ratio of piezoelectrics to piezomagnetic, and volume ratio of substrates to composite. It was found that the magnetoelectric voltage coefficient decreases as the interface coupling factor k weakens, while the volume ratio of piezoelectrics to piezomagnetic vmax shifts to lead-rich compositions. The magnetoelectric voltage coefficient of laminated composites decreases sharply with increasing substrates thickness ratio, which shows strong substrate clamping effect to the magnetoelectric composite.

(100)-Oriented SrTiO3/BaTiO3 Artificial Superlattices Fabricated by Chemical Solution Deposition

Epitaxially grown SrTiO3(100)/BaTiO3(100) artificial superlattices with 7-nm-thick layers were synthesized on (100) platinum-coated (100) magnesium oxide substrates by a chemical solution depositio...

Microstructural and electrical properties of Ce0.9Gd0.1O1.95 thin film electrolyte in solid oxide fuel cells – CORRIGENDUM

Microstructural and electrical properties of Gd-doped CeO2 (GDC; Ce0.9Gd0.1O1.95) thin films prepared by pulsed laser deposition as an electrolyte in solid-oxide fuel cells (SOFCs) were investigated. The GDC thin films were prepared on various substrates including single-crystal yttria-stabilized zirconia (YSZ) and magnesium oxide (MgO) substrates. The GDC thin-film electrolytes with different grain sizes and grain morphologies were prepared by varying the deposition parameters, such as substrate temperature, oxygen partial pressure, target repetition rate, and laser ablation energy. The microstructural properties of these films were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Alternating-current (AC) and direct-current (DC) electrical measurements through in-plane method show that the electrical property of the GDC thin film strongly depends on grain size, e.g., the total conductivity of the films deposited at 700 °C (7.3 × 10−3 S/cm) is about 20 times higher than the ones deposited at room temperature (3.6 × 10−4 S/cm) at the measurement temperature of 600 °C.

Surface acoustic waves in thin films of barium strontium titanate on magnesium oxide substrates

It is established that, using a thin barium strontium titanate (BST) film as the active element in a surface acoustic wave (SAW) device, it possible to double the working frequency of the converter due to the formation of a periodic domain structure in the BST film. A thin ferroelectric film device with a standard electrode structure is capable of effectively exciting the SAW second harmonic. Variation of the external polarizing voltage applied to the electrodes ensures field-controlled electromechanical feedback in the converter.

Structure and lattice dynamics of heterostructures based on bismuth ferrite and barium strontium titanate on magnesium oxide substrates

Bismuth ferrite films doped with neodymium on MgO single-crystal substrates with an epitaxial barium strontium titanate thin (1–2 nm) sublayer have been prepared by rf sputtering of ceramic targets at an elevated oxygen partial pressure and at temperatures below the ferroelectric and magnetic transition temperatures. It has been revealed using X-ray diffraction and Raman scattering spectroscopy that, in these bismuth ferrite films, a new phase (not observed in bulk samples) is formed. The symmetry of this phase is monoclinic, the unit cell contains two formula units, and the spontaneous polarization vector deviates from the [111]cub direction and can have different components along the x, y, and z axes.

Microstructural investigation of strontium titanate films grown by interval pulsed laser deposition

Strontium titanate (SrTiO3) films were deposited on (001) magnesium oxide (MgO) substrates by pulsed laser interval deposition (PLID). The growth modes of the films were monitored by in-situ reflection high-energy electron diffraction (RHEED). The microstructures were investigated by transmission electron microscopy (TEM). It has been shown that PLID can enhance the two dimensional (2D) growth of this system, which has the large lattice misfit of 7.9%. The addition of a mono TiO2 buffer layer to the MgO substrate surface further improved the 2D growth mode. TEM results revealed that the films grown in 2D mode with large lattice mismatch were dominated by antiphase boundaries (APBs) and holes. All the holes were connected by antiphase boundaries. The holes were rectangular in shape, with facets along the [100] and [010] directions, and they ran though the whole film thickness. Threading and misfit dislocations have also been identified as growth defects in the films grown with and without a TiO2 buffer layer. However, the density of defects varies with growth mode.

Growth of epitaxial iron nitride ultrathin film on zinc-blende gallium nitride

The authors report the growth of iron nitride on zinc-blende gallium nitride using molecular beam epitaxy. First, zinc-blende GaN is grown on a magnesium oxide substrate having (001) orientation; second, an ultrathin layer of FeN is grown on top of the GaN layer. In situ reflection high-energy electron diffraction is used to monitor the surface during growth, and a well-defined epitaxial relationship is observed. Cross-sectional transmission electron microscopy is used to reveal the epitaxial continuity at the gallium nitride-iron nitride interface. Surface morphology of the iron nitride, similar to yet different from that of the GaN substrate, can be described as plateau valley. The FeN chemical stoichiometry is probed using both bulk and surface sensitive methods, and the magnetic properties of the sample are revealed.

Generation and removal of pits during chemical mechanical polishing process for MgO single crystal substrate

Magnesium oxide (MgO) single crystal is an important substrate for high temperature superconductor, ferroelectric and photoelectric applications. The function and reliability of these devices are directly affected by the quality of polished MgO surface because any defect on the substrate, such as pit or scratch, may be propagated onto device level. In this paper, chemical mechanical polishing (CMP) experiments were conducted on MgO (1 0 0) substrate using slurry mainly comprised of 1-hydroxy ethylidene-11-diphosphonic acid (HEDP) and silica or ceria particles. Through monitoring the variations of the pits topography on substrate surface, generation and removal mechanism of the pits were investigated. The experimental results indicate that the pits were first generated by an indentation or scratch caused by particles in the slurry. If the rate of chemical etching in the defect area is higher than the material removal rate, the pits will grow. If chemical reaction in the defect area is slower than the material removal rate, the pits will become smaller and eventually disappear. Consequently, these findings may provide insight into strategies for minimizing pits during CMP process.

Thermal and irradiation induced interdiffusion in magnetite thin films grown on magnesium oxide (0 0 1) substrates

Epitaxial Fe 3O 4(0 0 1) thin films (with a thickness in the range of 10–20 nm) grown on MgO substrates were characterized using low-energy electron diffraction (LEED), conversion electron Mössbauer spectroscopy (CEMS) and investigated using Rutherford backscattering spectrometry (RBS), channeling (RBS-C) experiments and X-ray reflectometry (XRR). The Mg out-diffusion from the MgO substrate into the film was observed for the directly-deposited Fe 3O 4/MgO(0 0 1) films. For the Fe 3O 4/Fe/MgO(0 0 1) films, the Mg diffusion was prevented by the Fe layer and the surface layer is always a pure Fe 3O 4 layer. Annealing and ion beam mixing induced a very large interface zone having a spinel and/or wustite formula in the Fe 3O 4-on-Fe film system.

HIGHLY EPITAXIAL FERROELECTRIC LEAD STRONTIUM TITANATE ((Pb,Sr)TiO3) THIN FILMS WITH EXTRA LARGE DIELECTRIC TUNABILITY: A GOOD CANDIDATE FOR ROOM TEMPERATURE TUNABLE MICROWAVE ELEMENTS

ABSTRACT Lead Strontium Titanate ((Pb, Sr)TiO3, PST) thin films were epitaxially grown on (001) magnesium oxide (MgO), (001) lanthanum aluminate (LaAlO3, LAO), and (110) neodymium gallate (NdGaO3, NGO) substrates by pulsed laser deposition. Microstructural studies revealed that the as-grown PST films are with excellent epitaxial quality. PST films on MgO and LAO substrates exhibit a tetragonal distortion whereas the films on NGO substrates show an orthorhombic distortion. Dielectric property measurements at 1.0 MHz revealed that the room temperature dielectric constant is about 1500 with an extra large dielectric tunability value of 65% at 50 kV/cm for the PST film on the MgO substrate, and dielectric constant of 3100 with a dielectric tunability value of 48% at 50 kV/cm for the PST film on the LAO substrate. PST films on NGO substrates show anisotropic in-plane dielectric properties due to the anisotropic in-plane strain. A high zero-field dielectric constant of 4220 with a dielectric tunability value of 59% at 50 KV/cm was achieved along the a-axis of the PST film on the NGO substrate. All the films show dielectric losses smaller than 0.01. These excellent results suggest the highly epitaxial PST thin films can be a good candidate for developing room temperature tunable microwave device applications.

-NMR of a thin Pt film

We report beta-detected NMR (β-NMR) measurements on a 50 nm thick platinum (Pt) film grown on a magnesium oxide (MgO) substrate. The frequency of the β-NMR resonance in Pt was compared to the MgO reference frequency to estimate the Knight shift at various temperatures (100-300 K). The Knight shift was found to be negative and strongly temperature dependent. The implications are discussed and compared to other transition metals that have been studied via β-NMR previously.

On the hardness and the inherent ductility of chromium carbide nanostructured coatings prepared by RF sputtering

Homogenous and nanostructured chromium carbide thin coatings are prepared by RF sputtering. The nanoindentation tests are used to investigate the evolution of plastic deformation and hardness as a function of the grain size. The Cr 3C 2 films have been deposited on magnesium oxide substrates from a Cr 3C 2 target in pure argon atmosphere. Based on the effect of the deposition temperature, we have generated nanostructured Cr 3C 2 coatings with different mechanical properties. We have found that both crystalline texture and grain size increased with increasing the deposition temperature. The nanostructured chromiumcarbide film with grain size in the order of 5 nm, prepared at a deposition temperature of 600 °C, showed a higher hardness as well as a good ductility compared to the samples prepared at 850 °C or at room temperature. The cyclic nanoindentation measurements at constant loading rate allowed qualitative characterization of the change in the irreversible plastic work for the samples considered in this report.

Growth and Microstructural Studies of Strontium Titanate Films Grown by Standard and Interval Pulsed Laser Deposition

Strontium titanate films were grown by standard and interval pulsed laser interval deposition on (001) strontium titanate and magnesium oxide substrates. Reflection high-energy electron diffraction (RHEED) was used to monitor the growth mode of the films. The microstructures were investigated using transmission electron microscopy. The temporal evolution of the RHEED intensity confirmed a layer-by-layer growth mode in the homoepitaxial case. In heteroepitaxy, three dimensional growth occurred. Misfit dislocations and threading dislocations were the dominant defects. The film grown using the standard deposition was relaxed; the film grown using interval deposition was under in-plane tension and showed fewer threading dislocations.

RHEED study of titanium dioxide with pulsed laser deposition

Reflection high-energy electron diffraction (RHEED) operated at high pressure has been used to monitor the growth of thin films of titanium dioxide (TiO 2) on (1 0 0) magnesium oxide (MgO) substrates by pulsed laser deposition (PLD). The deposition is performed with a synthetic rutile TiO 2 target at low fluence. The topography and structure of the deposited layers are characterized using in situ high pressure RHEED and atomic force microscope (AFM). Based on these observations the growth mode of the films is discussed. The results will be compared to earlier results obtained for the growth of TiN films on (1 0 0) MgO.

Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles

The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidation and reduction reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 kelvin. A Wulff analysis of high-resolution in situ x-ray diffraction, combined with transmission electron microscopy, shows that this phenomenon is driven by the formation of a oxygen-rhodium-oxygen surface oxide at the rhodium nanofacets. This experimental access into the behavior of such nanoparticles during a catalytic cycle is useful for the development of improved heterogeneous catalysts.

Pulsed‐laser deposition of ZnO thin‐films on MgO substrates

AbstractZinc oxide thin‐films were grown by laser deposition technique on (111)‐ and (100)‐oriented magnesium oxide substrates (MgO). The deposition temperature was varied between 600 and 860 °C. In this temperature range the formation of Mg(OH)2 is thermodynamically unfavorable which prevents a degradation of the MgO surface. The films were characterized by scanning electron microscopy, Raman spectroscopy, and X‐ray diffraction. The results show that high‐quality c‐axis oriented ZnO thin‐films were grown on (111)‐oriented MgO. On (100)‐oriented MgO a more complex ZnO thin‐film formation was observed. At lower growth temperatures grains of different orientation were identified. Grains with orientations that deviated from (001) contain more residual stress, which manifests itself in a shift of the E2high phonon mode position to 442 cm–1. With increasing growth temperature the film structure becomes more uniform and at 860 °C large areas of either (001) or (101) orientation were found. The results also indicate that no amorphous ZnO buffer layer is formed at the interface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Microstructure and twinning in epitaxial NiMnGa films

Although magnetic shape memory alloys have attracted large scientific interest, miniaturization as single-crystalline thin films is still a greatly unresolved issue. In the present work we investigate the microstructure of epitaxial NiMnGa thin films which are fabricated by sputter deposition on magnesium oxide substrates at elevated temperatures. Transmission and scanning electron microscopy as well as atomic force microscopy studies are employed to relate surface topography to twin formation in 7 M martensitic NiMnGa films. Additional findings include pore formation in substrate proximity as well as minor precipitation with reduced nickel and gallium contents.

Field emission from lanthanum monosulfide thin films grown on the (100) magnesium oxide substrates

Lanthanum monosulfide (LaS) films were grown by pulsed laser deposition on the (100) magnesium oxide (MgO) substrates at an elevated substrate temperature and in a background gas of H2S. The thin films have been characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), and high resolution transmission electron microscopy. The film surface is composed of grainlike features with an average size of approximately 34nm. The root-mean-square variation of the film surface roughness measured over a 2×2μm2 area by AFM was found to be approximately 1.5nm. XRD data indicate that the average size of the nanocrystalline grains in the film is about 26nm, which is about twice the size of the grains found in LaS thin films deposited at room temperature on Si. The field emission (FE) properties of the films have been characterized by scanning anode field emission microscopy and are interpreted in terms of a recently developed patchwork FE model. The FE data indicate that there is roughly a seven times increase in emission area due to the (100) patch areas outcropping the surface for LaS∕MgO compared to LaS∕Si thin films.

Selective area synthesis of magnesium oxide nanowires

Single crystalline magnesium oxide (MgO) nanowires exhibiting a square cross section have been grown on (001)-oriented MgO and Si substrates using the vapor-liquid-solid growth mechanism. While the nanowires grow vertically aligned on MgO, they display random orientations on the silicon substrate. For growth on MgO substrates, the selective placement and density of the nanowires can be controlled by using electron beam lithography for prepatterning the gold catalyst layer. The nanowire samples have been characterized using field-emission scanning electron microscopy and transmission electron microscopy. The described process for selective placement of the nanowires is attractive for their use as templates for coaxial coatings and also for their manipulation for potential device fabrication.