Effects of assisting and sputtering ion current on ion beam assisted deposition textured yttria stabilized zirconia buffer layers of coated conductors

Biaxially textured yttria stabilized zirconia (0 0 1) thin films were fabricated on untextured hastelloy substrates by ion beam assisted deposition method. The effects of assisting beam current density J_a and sputtering beam current density J_s on the textures of the films were studied. The results indicate that as J_a or J_s increase, both the out-of-plane and the in-plane textures are improved initially, and then degrade. The results can be attributed to anisotropic damage and selective sputtering effect of assisting ions. At the same ion-to-atom arrival ratio r, which is reflected with J_a/J_s value, lower deposition rate can enhance the biaxial texture.     

Oxygen assisted deposition of Sr2FeMoO6 thin films on SrTiO3(1 0 0)

Epitaxial thin films of Sr₂FeMoO₆ (SFMO) were prepared by pulsed laser deposition on SrTiO₃(1 0 0) substrate. Thin films have been grown under different gas environments and they were structurally characterised by XRD. In contrast to previous reports, deposition carried out in the presence of a small amount of O₂ with Ar yields high-quality SFMO films with a saturation magnetic moment of 3.8 μ_B. These SFMO films were strained in such a way that they were elongated along the c-axis and compressed in the ab-axes directions. The large low-field magnetoresistance seen in these films has been attributed to the tunneling across the antisite boundaries.     

电子束、离子辅助和离子束溅射三种工艺对光学薄膜性能的影响

运用电子束、离子辅助和离子束溅射三种镀膜工艺分别制备光学薄膜,包括单层氧化物薄膜和增透膜,然后采取一系列测试手段,如Zygo轮廓仪、原子力显微镜、表面热透镜技术和X射线衍射等技术,来分析和研究不同的工艺对这些薄膜性能的不同影响,以判断合理的沉积工艺。     

电子束、离子辅助和离子束溅射三种工艺对光学薄膜性能的影响

 运用电子束、离子辅助和离子束溅射三种镀膜工艺分别制备光学薄膜，包括单层氧化物薄膜和增透膜，然后采取一系列测试手段，如Zygo轮廓仪、原子力显微镜、表面热透镜技术和X射线衍射等技术，来分析和研究不同的工艺对这些薄膜性能的不同影响，以判断合理的沉积工艺。     

Structural and magnetic properties of thin epitaxial Fe films on (1 1 0) GaAs prepared by metalorganic chemical vapor deposition

Iron films have been grown on (1 1 0) GaAs substrates by atmospheric pressure metalorganic chemical vapor deposition at substrate temperatures (T_s) between 135°C and 400°C. X-ray diffraction (XRD) analysis showed that the Fe films grown at T_s between 200°C and 330°C were single crystals. Amorphous films were observed at T_s below 200°C and it was not possible to deposit films at T_s above 330°C. The full-width at half-maximum of the rocking curves showed that crystalline qualities were improved at T_s above 270°C. Single crystalline Fe films grown at different substrate temperature showed different structural behaviors in XRD measurements. Iron films grown at T_s between 200°C and 300°C showed bulk α-Fe like behavior regardless of film thickness (100–6400 Å). Meanwhile, Fe films grown at 330°C (144 and 300 Å) showed a biaxially compressed strain between substrate and epilayer, resulting in an expanded inter-planar spacing along the growth direction. Magnetization measurements showed that Fe films (>200 Å) grown at 280°C and 330°C were ferromagnetic with the in-plane easy axis along the [1 1 0] direction. For the thinner Fe films (⩽200 Å) regardless of growth temperature, square loops along the [1 0 0] easy axis were very weak and broad.     

Ag-N doped ZnO film and its p-n junction fabricated by ion beam assisted deposition

Ag-N doped ZnO film was synthesized by ion beam assisted deposition and its electrical properties and annealing property were investigated. The films remained p-type even after annealing at 400 °C in air for 10 min. While the annealing temperature went up to 500 °C, the conduction type of these films shifted from p-type to n-type. The p-type ZnO film revealed low resistivity (0.0016 Ω cm), low Hall mobility (0.65 cm² V⁻¹ s⁻¹) and high carrier concentration (5.8 × 10²⁰ cm⁻³). ZnO p-n homojunction consisting of a p-type layer (Ag-N doped ZnO film) and an n-type layer (In-doped ZnO film) had been fabricated by ion beam assisted deposition. With electrical measurement, its current-voltage curve had a typical rectifying characteristic with current rectification ratio of 25 at bias ±5 V and a reverse current of 0.01 mA at −5 V. The depletion width was estimated 3.8 nm by using p-n junction equation.     

Morphology and crystallographic properties of rubrene thin films grown on muscovite(0 0 1)

Thin films of the organic semiconductor rubrene were deposited on muscovite (0 0 1) substrates by hot wall epitaxy. The morphology of rubrene thin films in combination with their crystallographic properties was characterized by transmission electron microscopy. The initial growth proceeds in a partially wetting regime where amorphous droplets are formed. Through diffusive interactions the droplets merge together in partially crystalline open networks. At a more advanced growth stage, spherulites are formed and a variety of crystalline morphologies appears. Platelet- and needle-like morphologies can be assigned to the orthorhombic phase of rubrene with the [3 0 1] and [1 1 0] zone axes, respectively.     

A low temperature study of electron transport properties of tantalum nitride thin films prepared by ion beam assisted deposition

Measurement of electrical resistivity in the temperature range of tantalum nitride films prepared by Ion Beam Assisted deposition and pure tantalum films prepared by electron beam evaporation has been carried out. The tantalum film shows a resistivity minimum at T_m=12 K, whereas tantalum nitride shows a decrease in resistivity with an increase in temperature. An attempt has been made to explain such anomalous behavior by using existing theories.     

High temperature scanning tunneling microscopy of purely ion conducting yttria stabilized zirconia (YSZ)

Scanning tunneling microscopy (STM) on wide band gap insulators is generally not possible. Here we demonstrate that ionic insulators with high ion mobility, such as yttria stabilized zirconia, are an exception to this rule. The ion conductivity ensures that the sample maintains a defined potential relative to the STM tip and thus a stable tunnel junction. Consequently, ion conductors provide an opportunity for characterizing wide band gap insulators, and thin films and nanostructures supported on them by STM.     

SBN thin films growth by RF plasma beam assisted pulsed laser deposition

SBN thin films were grown on MgO and Silicon substrates by PLD and RF-PLD (radiofrequency assisted PLD) starting from single crystal Sr_0.6Ba_0.4Nb₂O₆ and ceramic Sr_0.5Ba_0.5Nb₂O₆ stoichiometric targets. Morphological and structural analyses were performed on the SBN layers by AFM and XRD and optical properties were measured by spectroellipsometry. The films composition was determined by Rutherford Backscattering Spectrometry. The best set of experimental conditions for obtaining crystalline, c-axis preferential texture and with dominant 31° in-plane orientation relative to the MgO (100) axis is identified.     

Nucleation, growth and morphology of Co thin films on Ag(1 1 0)

Scanning tunneling microscopy (STM) experiments reveal that Co growth on Ag(1 1 0), at coverages of Co < 1 ML and low substrate temperatures (150 K), involves a concomitant insertion of Co into the top Ag layer and exchange of Ag out onto the surface. At 300 K, coverages of Co > 1 ML gives rise to a 3D nanocluster growth on the surface, with the clusters covered by Ag. Depending slightly on coverage, the clusters have a typical diameter of 3 nm and a height of 0.4 nm. Upon annealing to 500 K, major changes are observed in the morphology of the surface. STM and AES show that there is a reduction of the number of Co islands on the surface, partly due to subsurface Co cluster migration and partly due to sintering into larger clusters.     

Microstructure and optical properties of Ge films prepared by ion beam assisted deposition

Germanium （Ge） films are prepared on BK7 glass and multispectral zinc sulfide （m-ZnS） substrates by ion beam assisted deposition （IBAD）. The effects of substrate temperature, deposition rate, and ion energy on the microstructure and optical properties of the films are investigated. It can be concluded that Ge film deposited with higher rate or ion energy has more optical absorption, while ion energy below 150 eV helps to reduce film absorption. Film refractive index increases with film deposition rate and bombardment ion energy while it is below 300 eV. And higher growth rate or bombardment ion energy can weaken film diffraction intensity.     

A PdO(1 0 1) thin film grown on Pd(1 1 1) in ultrahigh vacuum

We present experimental results demonstrating that a high quality PdO(1 0 1) thin film can be grown on Pd(1 1 1) in ultrahigh vacuum by oxidizing the metal at 500 K using an oxygen atom beam, followed by annealing to 675 K. Low energy electron diffraction (LEED) images show that the [0 1 0] direction of the PdO(1 0 1) thin film aligns with the [−1 1 0] direction of the Pd(1 1 1) substrate, and that the PdO film grows in three degenerate domains, rotated 120° relative to one another. Based on excellent agreement between the experimental and simulated LEED patterns, we conclude that the surface structure of the PdO thin film deviates minimally from bulk-terminated PdO(1 0 1). Recent temperature programmed desorption (TPD) experiments also provide evidence that the PdO(1 0 1) thin film on Pd(1 1 1) is terminated by the stoichiometric surface in which half of the Pd atoms are coordinatively unsaturated (cus), corresponding to a cus-Pd atom density equal to about 35% of the surface density of Pd(1 1 1). The ability to generate a well-defined PdO(1 0 1) surface in ultrahigh vacuum should provide new opportunities for conducting model surface science studies of PdO, particularly studies aimed at elucidating the reactivity of PdO(1 0 1) toward species important in commercial applications of Pd catalysis.     

First-principles calculation of Mg(0 0 0 1) thin films: Quantum size effect and adsorption of atomic hydrogen

We have carried out first-principles calculation of Mg(0 0 0 1) free-standing thin films to study the oscillatory quantum size effect exhibited in the surface energy, work function, interlayer relaxation, and adsorption energy of the atomic hydrogen adsorbate. The quantum well states have been shown. The calculated energetics and interlayer relaxation of clean and H-adsorbed Mg films are clearly featured by quantum oscillations as a function of the thickness of the film, with oscillation period of about eight monolayers, consistent with recent experiments. The calculated quantum size effect in H adsorption can be verified by observing the dependence of H coverage on the thickness of Mg(0 0 0 1) thin films gown on Si(1 1 1) or W(1 1 0) substrate which has been experimentally accessible.     

Optical properties of Cr/Fe(t)/MgO (0 0 1) thin films

In this work we report on the optical properties of single-crystalline iron thin films. For this, Cr-capped Fe films with thickness, t, in the range 30–300 Å were prepared on MgO (0 0 1) by DC magnetron sputtering, and then studied by optical absorption technique within the range from 1.0 to 3.6 eV. All measurements were carried out at room temperature using a fiber optics spectrophotometer. The intensity of the transmitted light decreases with increasing film thickness. The optical constants of the films are deduced from a model that considers the transmission of light by two absorbing films on an absorbing substrate. The absorption coefficient of the Fe films is also calculated from the transmission data. The absorption spectra show the following characteristics: (i) two large absorption peaks centered at about 1.20 and 2.65 eV; and (ii) a sharp step near 1.40 eV. These structures are associated with conventional interband transitions of the iron film.     

Characterization of hydrogenated amorphous carbon thin films by end-Hall ion beam deposition

Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24 eV to 48 eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5-0.8 nm for α-C:H and 0.35 nm for α-C:H:N films. When the ion energy was increased from 24 eV to 48 eV, the fraction of sp³ bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8 GPa to 12.5 GPa, and the Young's modulus increased from 100 GPa to 130 GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145 GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.     

Identification of iron oxide phases in thin films grown on Al2O3(0 0 0 1) by Raman spectroscopy and X-ray diffraction

We report on the identification of Fe₃O₄ (magnetite) and α-Fe₂O₃ (hematite) in iron oxide thin films grown on α-Al₂O₃(0 0 0 1) by evaporation of Fe in an O₂-atmosphere with a thickness of a few unit cells. The phases were observed by Raman spectroscopy and confirmed by X-ray diffraction (XRD). Magnetite appeared independently from the substrate temperature and could not be completely removed by post-annealing in an oxygen atmosphere as observed by X-ray diffraction. In the temperature range between 400 °C and 500 °C the X-ray diffraction shows that predominantly hematite is formed, the Raman spectrum shows a mixture of magnetite and hematite. At both lower and higher substrate temperatures (300 °C and 600 °C) only magnetite was observed. After post-annealing in an O₂-atmosphere of 5 × 10^?5 mbar only hematite was detectable in the Raman spectrum.     

Stabilization of the (1 1 0) tetragonal zirconia surface by hydroxyl chemical transformation

Different hydroxyl coverages on the (1 1 0) and (1 0 1) surfaces of tetragonal zirconia have been studied with periodic density functional theory. The tetragonal zirconia (1 1 0) surface is polar and intrinsically unstable. It is however very efficiently stabilized by hydroxyl formation which decreases the effective charge of surface oxygen atoms and hence avoids the electrostatic instability. The hydroxylation induces a strong stabilization of the (1 1 0) surface with respect to the non-polar (1 0 1) termination, and explains why the (1 1 0) surface of ZrO₂ can be found in some catalytic preparations. Surface chemical transformation appears to be a more efficient way to stabilize the (1 1 0) surface in comparison with the surface reconstruction processes.     

Growth and annealing of zinc-blende CdSe thin films on GaAs (0 0 1) by molecular beam epitaxy

CdSe thin films have been grown on GaAs (0 0 1) substrates by molecular beam epitaxy (MBE). The effects of substrate temperature and annealing treatment on the structural properties of CdSe layers were investigated. The growth rate slightly decreases due to the accelerated desorption of Cd from CdSe surface with an increase in the temperature. The sample grown at 260 °C shows a polycrystalline structure with rough surface. As the temperature increases over 300 °C, crystalline CdSe (0 0 1) epilayers with zinc-blende structure are achieved and the structural quality is improved remarkably. The epilayer grown at 340 °C displays the narrowest full-width at half-maximum (FWHM) from (0 0 4) reflection in double-crystal X-ray rocking curve (DCXRC) and the smallest root-mean-square (RMS) roughness of 0.816 nm. Additionally, samples fabricated at 320 °C were annealed in air for 30 min to study the films’ thermal stability. X-ray diffraction (XRD) results indicate that the zinc-blende structure remains unchanged when the annealing temperature is elevated to 460 °C, meaning a good thermal stability of the cubic CdSe epilayers.     

Li–N dual-doped ZnO thin films prepared by an ion beam enhanced deposition method

Li–N dual-doped ZnO films [ZnO:(Li,N)] with Li doping concentrations of 3 at.%–5 at.% were grown on a glass substrate using an ion beam enhanced deposition(IBED) method. An optimal p-type ZnO:(Li,N) film with the resistivity of 11.4 Ω·cm was obtained by doping 4 at.% of Li and 5 sccm flow ratio of N2. The ZnO:(Li,N) films exhibited a wurtzite structure and good transmittance in the visible region. The p-type conductive mechanism of ZnO:(Li,N) films are attributed to the Li substitute Zn site(LiZn) acceptor. N doping in ZnO can forms the Lii–NOcomplex, which depresses the compensation of Li occupy interstitial site(Lii) donors for LiZnacceptor and helps to achieve p-type ZnO:(Li,N) films. Room temperature photoluminescence measurements indicate that the UV peak(381 nm) is due to the shallow acceptors LiZnin the p-type ZnO:(Li,N) films. The band gap of the ZnO:(Li,N) films has a red-shift after p-type doping.