MgO Film Thickness Research Articles

Ultra-thin bi-axially textured IBAD MgO template layers resolved by grazing incidence X-ray diffraction

We describe a method using grazing incidence diffractometry (GID) with a rotating anode X-ray source to measure the in-plane alignment of ∼10-nm thick MgO films deposited by ion beam assisted deposition (IBAD). In conjunction with these measurements, we have calibrated the IBAD film growth process by monitoring the film in situ with reflected high-energy electron diffraction and comparing the intensity versus time curve with results obtained from the ex situ GID measurements. GID has also been used to identify differences in the observed in-plane texture for samples with and without the addition of a homoepitaxial layer. Improvements in texture after the addition of the homoepitaxial layer are attributed to the healing of ion induced damage during growth of the IBAD layer. Further analysis has revealed that standard X-ray diffraction measurements of these overcoated films do not sufficiently quantify the in-plane alignment of the initial IBAD layers.

Thickness effect on secondary electron emission of MgO layers

Two series of MgO thin layers having various thicknesses were prepared on the Si substrate by electron-beam evaporation and by spin coating of MgO precursor solutions. We found that the magnitude of the secondary electron emission (SEE) yield of the MgO films strongly depends on the film thickness and the sample bias voltage. We ascribed it to the electric field through the insulating MgO layer, which allowed fast supply of electrons from the Si substrate to the surface. The mechanism of electron supply can be explained either as an acceleration through the MgO layer that becomes partially conductive upon primary electrons bombardment (radiation induced conductivity), or as a tunneling through the non-irradiated region of the insulating layer where the primary electrons cannot reach deeply into the sample with a certain penetration depth. The maximum SEE yield of the each MgO film on the Si substrate was observed when the penetration depth of primary electrons was close to the thickness of the MgO film, if the applied electric potential to the sample was low. Under a strong electric potential, the relationship between the penetration depth of primary electrons and the thickness of MgO films is not observed. It suggests the existence of the non-irradiated region, where electron supply is allowed by electron tunneling. Therefore, the magnitude of SEE yield for the thin insulating layer is strongly related to the detailed mechanism of electron supply, which is determined by the thickness of the insulating layer and the applied bias voltage to the sample during the SEE process.

Cladding and characteristics of LiNbO3 single crystal fibre

A magnesium ion indiffusion process is applied to LiNbO3 single crystal fibres deposited with MgO thin film on their surface. A core–cladding waveguide structure with different refractive index profile is formed in LiNbO3 single crystal fibres by selecting suitable diffusion parameters such as diffusion temperature, diffusion time and MgO film thickness. An electron probe microanalysis was used to measure the Mg-ion concentration distribution of the Mg diffused layer. The propagation loss of the clad crystal fibre (Mg-diffused crystal fibre) is measured to be 14 times lower than that of the unclad crystal fibre and the transmission modes were observed. The microstructural characteristics of the Mg diffused crystal fibres were also characterized by using Laue X-ray diffraction and scanning electron microscopy. It was shown that a good starting single crystal of the Mg diffused crystal fibres can be preserved by controlling suitable diffusion parameters and matching suitable crystal fibre diameter.

Characteristics of junctions and resistors fabricated using an all-NbN superconductor integrated circuit foundry process

Trilayer NbN/MgO/NbN tunnel junctions and Mo and NbN/sub x/ resistors fabricated over a NbN ground plane form the basis of a high performance, 10 K, superconductor integrated circuit foundry process. To produce high yield LSI and VLSI superconductor integrated circuits requires predictable device characteristics, stable, well-characterized, thin film deposition processes, and control of critical dimensions (CD). In this paper, we discuss improvements in thin film deposition processes, device characteristics, and CD control. Repeatable trilayer characteristics have been achieved through the use of feedback control of critical MgO and NbN sputtering parameters. Run-to-run variations in MgO film thickness have been reduced to less than /spl plusmn/1.0% (1/spl sigma/) using a novel computer feedback control technique. Improvements in MgO deposition uniformity and CD control of junction size have reduced across wafer I/sub c/ nonuniformity to less than /spl plusmn/10% (3/spl sigma/) and 100 junction array I/sub c/ nonuniformity on 0.5 cm chips to /spl plusmn/2% (1/spl sigma/). We report on the electrical characteristics of junctions and resistors and on component spreads and stability of our NbN foundry process.

Films grown by laser ablation on Si(100) and GaAs(100) substrates with and without MgO buffer layers

films have been grown by laser ablation on (100) oriented Si and GaAs substrates. Optimal growth of was obtained at a substrate temperature of 450C in a molecular oxygen atmosphere of Torr. X-ray measurements show these films to be (111) oriented, with the growth direction random in the plane of the film. The introduction of (100) oriented, epitaxial MgO buffer layers as thin as 10 Å on the substrates results in the growth of (100) oriented, epitaxial films. X-ray pole-figure measurements on these films indicate that both the and the MgO films are oriented cube on cube on the Si and GaAs substrates, namely . Room-temperature magnetization measurements of the (111) oriented films show that there is good agreement between the magnetic properties of the films grown on Si and on the GaAs substrates. Similar agreement is found for the magnetization measurements of the (100) oriented epitaxial films grown with a MgO buffer layer. Moreover, the hysteresis loops for the (111) and (100) oriented films are very similar, indicating that the epitaxy has not significantly improved the magnetic properties of the . In fact, a small decrease of the high-field magnetization is observed with increasing MgO film thickness.

Ultimate TEM Observation of Tungsten Clusters on MgO(001) Surfaces

The surface diffusion process of tungsten (W) atoms and clusters on MgO(001) surfaces was successfully studied by time-resolved high resolution electron microscopy (TRHREM) in the time resolution of 1/60 s. The observation was realized by optimizing the thickness of MgO films and by using a special imaging technique, such as the off-Bragg HREM method. During the observation, W clusters composed of four and five atoms adsorbed on MgO(001) surfaces were detected in images reproduced from the videotape images. The multislice image simulation for the interpretation of the image contrast showed a possibility of discrimination of the atomic configuration of clusters such as "bcc," "on-top" or "fcc" type clusters, from the image contrast at the center of the clusters. The reason for the discrimination was clarified through the multislice image simulation, suggesting that the lattice mismatch between the clusters and the MgO lattice was a key factor in determining the image contrast.

Deposition of in-plane textured MgO on amorphous Si3N4 substrates by ion-beam-assisted deposition and comparisons with ion-beam-assisted deposited yttria-stabilized-zirconia

We report the growth of in-plane textured (100) MgO on amorphous Si3N4 substrates by ion beam assisted deposition (IBAD). The textured MgO can be used as a structural template for subsequent epitaxial thin film deposition. The results are compared with IBAD of (100) and (111) yttria-stabilized-zirconia (YSZ). Based on transmission electron microscopy (TEM) and in situ reflection high energy-electron diffraction (RHEED), we find that MgO texturing is a nucleation-controlled process and the alignment is a function of nuclei size and density. This differs greatly from the evolutionary-type texturing process observed for IBAD (100) YSZ. Consequently, we are able to make 100 Å thick MgO films with 7° in-plane alignment, whereas IBAD (100) YSZ films need to be thicker than 5000 Å to achieve in-plane alignment better than 13°. This has important implications for the economical application of IBAD induced alignment in real manufacturing processes, including high Tc superconductor (i.e., YBCO) coated tapes, photovoltaics, magnetic thin films, and semiconductor devices.

Evaluation of Microstructure Characteristics of Lithium Niobate Single‐Crystal Fiber with Magnesium‐Ion‐Indiffused Cladding

A magnesium ion indiffusion process is applied to lithium niobate single–crystal fibers. Electron probe microanalysis shows that magnesium ions have diffused into the bulk of the crystal fibers and the magnesium ion concentration in the magnesium–diffused layer has an approximately parabolic profile, which corresponds to that of theoretical simulation. It is shown by conventional X–ray diffraction and scanning electron microscopy that a good starting single crystal of the magnesium–diffused crystal fiber can be preserved by controlling suitable diffusion parameters such as diffusion temperature, diffusion time, and MgO film thickness, etc., to ensure the completeness of magnesium ion indiffusion, but the magnesium–diffused region etches differently from virgin‐region crystals.

Microbeam RBS on flat panel displays

We have demonstrated the utility of microbeam-Rutherford BackScattering (μ-RBS) in spatially resolved studies of operational plasma effects on the interior surfaces of plasma flat panel displays manufactured by Photonics Imaging. The experiments were performed at the Sandia Nuclear microprobe using a 2.8 MeV He beam with an average beam spot size of less than 8 μm. The interior surface of the top panes of the flat panels is composed of approximately 800 nm of MgO on top of a 2000 nm thick PbO layer. μ-RBS of sample panels operated under varying conditions measured changes in the surface MgO film thickness due to plasma erosion and redeposition as accurately as ± 1.5 nm. The high accuracy in the MgO thickness measurement was achieved by inferring the MgO thickness from the shift of the Pb front edge in the RBS spectrum. An estimate for the thickness accuracy as a function of the acquired statistics is presented. The surface of the flat panels' bottom panes is also comprised of MgO on top of PbO. However, troughs ∼ 100 μm wide by 10 μm deep were partially filled with phosphor and cover the entire width of the surface. This leaves only 100 μm long sections of MgO within the trough exposed. Using μ-RBS, we were able to analyze the surface composition of these regions.

Pulsed laser deposition of /MgO bilayered films on Si wafer in waveguide form

Strontium barium niobate (SBN) thin films were grown on Si (111) substrates coated with MgO buffer by the pulsed laser deposition (PLD) technique. The thickness of SBN and MgO films were of the order of 1200 nm and 840 nm respectively. X-ray energy dispersive spectrometry (XREDS) showed that SBN films have stoichiometric composition identical to the target material, and no Si diffusion into the SBN film was found. X-ray diffraction (XRD) scans indicated that MgO films were highly (111) textured, but the SBN films were polycrystalline without preferential orientation. The surface of the SBN film was smooth, dense and crack-free and no large droplets were observed when studied under a scanning electron microscope (SEM). A favourable optical waveguiding property of the bilayered films was demonstrated by a prism coupler method.

Surface modification investigation of lithium niobate single crystal fiber

Abstract In this paper, a Mg-ion indiffusion process is applied to LN single crystal fiber with MgO thin film deposited on its surface. After a large number of exploring experiments, we conclude that a core-cladding waveguide structure of crystal fiber with different refractive index profile can be obtained by selecting suitable diffusion parameters such as diffusion temperature, diffusion times and MgO film thickness. Other optical characteristics of the cladded fibers are investigated.

ＡＣ‐ＰＤＰ用ＭｇＯ印刷保護層の膜質に対するＭｇＯバインダ添加効果

The effect of liquid binder on the film properties of screen-printed MgO film for the protective layer for AC-PDP has been studied. The liquid binder is a stabilized magnesium diethoxide solution which changes to MgO after firing and binds the MgO particles. After drying, the MgO film thickness increases with increasing MgO liquid binder content. However, after firing, the MgO film thickness decreases with increasing MgO liquid binder content, because the MgO powder content decreases with increasing liquid binder content. When liquid binder content is less than 10 wt%, surface roughness of the MgO film increases and film density decreases with increasing liquid binder content. This is caused by a gas generated by the liquid binder. When liquid binder content is more than 10 wt%, the surface roughness of the MgO film decreases and film density increases with increasing liquid binder content. This is caused by the liquid binder combining powders. Therefore, it is concluded that the optimization of liquid binder content is very important for improving film properties.

MBE growth and HR-TEM observations of several-nm MgO film on the cleavage plane of Bi2Sr2CaCu2Ox single crystals

Pinhole-free, several-nm thick MgO films were fabricated for the first time on the cleavage plane of Bi2Sr2CaCu2Ox single crystals by the MBE method, and confirmed by direct HR-TEM observation of the MgO/BSCCO interface. A superconducting energy gap with BCS-like behavior was clearly observed from tunneling spectroscopy for Nb/MgO/BSCCO.

Ａｌ‐Ｍｇ合金溶湯の酸化の抑制に及ぼすＣＯ２の作用について

A role of CO2 in suppresing oxidation of molten Al-Mg alloys in air-CO2 atmosphere was studied. The surface film on the molten Al-Mg alloys in air-CO2 atmosphere is composed of MgO with a slight amount of carbon. Carbon does not form carbon compounds such as MgCO3. CO2 functions more effectively for the molten metal on which a thick MgO film covers, but does ineffectively for the molten metal on which thin MgO and/or MgAl2O4 films cover. The protecting ability of surface film depends on the concentration of CO2 at the film forming period, but does not on the gas applying time in the period. This phenomenon is attributed to prevention of O2 diffusion into the molten metal by the MgO film which adsorbs CO2 gas.