Nm-thick Thin Film Research Articles

Highly conductive RuO2 thin films from novel facile aqueous chemical solution deposition

Ruthenium dioxide (RuO2) thin films were synthesized by Chemical Solution Deposition (CSD) on silicon substrates using only water and acetic acid as solvents. The microstructure, phase purity, electrical and optical properties as well as the thermal stability of the thin films have been characterized. The microstructure of the thin films strongly depends on the annealing temperature: A smooth thin film was achieved at an annealing temperature of 600 °C. Higher annealing temperatures (800 °C) led to radial grain growth and an inhomogeneous thin film. A very low resistivity of 0.89 µΩm was measured for a 220 nm-thick thin film prepared at 600 °C. The resistivity of the thin films increases with temperature, which indicates metallic behavior. Phase purity of the thin films was confirmed with X-ray Diffraction (XRD) measurements, X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. Transmission and reflectivity measurements indicate that RuO2 efficiently blocks the UV-VIS and IR wavelengths. The optical constants determined via spectroscopic ellipsometry show high absorption in the near-IR region as well as a lower one in the UV-VIS region. The thermal stability was investigated by post-annealing, confirming that the thin films are stable up to 750 °C in synthetic air.Graphical

Evolution of the Ni0.9Pt0.1/Si system under annealing via nano-crystalline textured phases

The reaction of a Ni0.9Pt0.1 7 nm-thick thin film with the underlying Si(001) substrate as a function of the annealing temperature was studied using in situ XRD techniques as well as ex situ advanced XRD and TEM imaging on quenched samples. It was found that the Ni0.9Pt0.1/Si system initially evolves accordingly to diffusion controlled reactions via the development of nano-crystalline Ni-rich Ni1−x(Pt)Six phases that combine the ability of fast kinetic growth and texture inheritance. The system remains then stable over some tens of degrees before Ni(Pt)Si nucleation occurs, once the related energetic barrier is overcome. It was additionally found that this newly observed phase sequence remains valid up to Ni0.9Pt0.1 deposited layer thicknesses of about 16 nm, which is remarkable for such systems.

Study of uniaxial deformation behavior of 50 nm-thick thin film of gold single crystal using in situ X-ray pole figure measurements

In this paper, in situ measurements of synchrotron x-ray pole figure have been performed during incremental uniaxial deformation test on a single-crystal gold foil. The 50 nm thick Au thin film was elaborated by ion sputtering at 400 °C on NaCl single crystal as a template. The resulting film consists of a single-crystal gold foil containing a small density of thin and small {111} growth twins (few nm thick and few tens of nm long) revealed by x-ray pole figure measurement. The as-deposited gold single crystal was then transferred onto flexible polyimide substrates for deformation test. This work focuses on the relative evolution of the diffracting volume related to growth twins during a loading-unloading tensile test. Macroscopic applied deformations and x-ray pole figures were measured in situ during a uniaxial tensile test in the Au [110] direction. X-ray pole figures clearly evidenced the relative evolution of the diffracting volumes related to the (111) and 1¯1¯1 twins which exhibit a huge increase of about 450% at a uniaxial applied true strain of about 4%. The concomitant variation of diffracting volumes related to the two other twin variants (namely 1¯11 and 11¯1 twins) shows a relatively low decrease of 25%. The results open out onto a true strain-twinning volume hysteresis curve, indicative of the deformation mechanisms of gold thin films that can be interpreted as a twinning-detwinning mechanism.

Structural properties of glancing angle deposited nanostructured surfaces for enhanced boiling heat transfer using refrigerant R-141b

Titanium dioxide (TiO2) coated nanostructured surfaces for nucleate pool boiling heat transfer were experimentally studied. A 600 nm thick TiO2 nanostructured coating over a TiO2 intermediate layer (100 nm-thick thin film) was fabricated with two different azimuthal rotations 120 rpm and 460 rpm on two separate copper heating surfaces using the glancing angle deposition (GLAD) technique. A nanostructure with 600 nm-thick coating without an intermediate layer was synthesized on a copper heating surface at an azimuthal rotation of 460 rpm by applying the same technique. Pool boiling experiments were performed on all the surfaces, including the one natural copper surface and one treated surface at atmospheric pressure using R-141b to analyze the boiling heat transfer performance. The TiO2 nanostructured surface with the intermediate layer provided higher heat transfer activities than the surface without the intermediate layer. The modified 600 nm thick TiO2 nanostructured surface using 460 rpm azimuthal rotation of GLAD technique with the 100 nm thick TiO2 intermediate layer surface had a significantly enhanced boiling heat transfer performance compared to that of the 600 nm thick TiO2 nanostructured surface using 120 rpm azimuthal rotation of GLAD technique with the 100 nm thick TiO2 intermediate layer surface, treated surface, and natural copper surfaces. The surface fabrication technique would alter the thermodynamic performance of a surface, especially in the case of energy conversion devices, to expedite the heat transfer.

Skew scattering dominated anomalous Hall effect in Cox(MgO)100−x granular thin films

We investigated the mechanism(s) of the anomalous Hall effect (AHE) in magnetic granular materials by fabricating 100 nm-thick thin films of Cox(MgO)100−x with a Co volume fraction of 34 ⩽ x ⩽ 100 using co-sputtering at room temperature. We measured the temperature dependence of longitudinal resistivity () and anomalous Hall resistivity () from 5 K to 300 K in all samples. We found that when x decreases from 100 to 34, the values of and respectively increased by about four and three orders in magnitude. By linearly fitting the data, obtained at 5 K, of anomalous Hall coefficient () and of to , we found that our results perfectly fell on a straight line with a slope of 0.97 ± 0.02. This fitting value of in clearly suggests that skew scattering dominated the AHE in this granular system. To explore the effect of the scattering on the AHE, we performed the same measurements on annealed samples. We found that although both and significantly reduced after annealing, the correlation between them was almost the same, which was confirmed by the fitted value, = 0.99 ± 0.03. These data strongly suggest that the AHE originates from the skew scattering in Co–MgO granular thin films no matter how strong the scattering of electrons by the interfaces and defects is. This observation may be of importance to the development of spintronic devices based on MgO.

Fabrication of yttrium-doped barium zirconate thin films with sub-micrometer thickness by a sol–gel spin coating method

Abstract A modified sol–gel process was developed for the fabrication of sub-micrometer scale yttrium-doped barium zirconate (BZY) thin film at much lower processing temperatures. The film was fabricated by direct spin-coating of the sol on a Si3N4 passivated Si substrate, followed by low temperature thermal annealing at 1000 °C, and single BZY phase without barium carbonate residue was obtained. A 200 nm-thick thin film without obvious through-film cracks was fabricated with optimized process parameters of sol concentration and heating rate. The stoichiometry of the BZY thin film was well-controlled and no Ba evaporation was observed due to the low processing temperature. The combination of sol–gel and spin coating method can be a promising alternative to vacuum-based thin film deposition techniques for the fabrication of sub-micrometer scale BZY thin film.

Lamellar orientation of polyamide 6 thin film crystallization on solid substrates

We studied the lamellar orientation of polyamide 6 (PA6) thin films with the thickness ranged from ∼5 μm to ∼20 nm on different solid substrates. The lamellar morphology was observed using atomic force microscopy and transmission electron microscopy, and the lamellar orientation was characterized using two-dimensional (2D) grazing incidence wide-angle X-ray diffraction (GI-WAXD) and selected area electron diffraction (SAED). The 2D GI-WAXD results indicate that in the films thicker than ∼50 nm PA6 lamellae of the α-form are preferentially edge-on with the ab-planes (b is the chain axis) parallel to the substrate. Decrease of film thickness leads to higher order of the orientation. This edge-on orientation is insensitive to the surface properties of the substrates changed from hydrophilic to hydrophobic, suggesting that the low energy hydrogen bonded sheets of PA6 are prone to lying down in the film. For the films on the hydrophilic substrate with thickness less than ∼50 nm, the edge-on orientation remains. On the other hand, on a more hydrophobic substrate, flat-on lamellae can be detected by SAED when the film thickness is reduced to be less than 50 nm. An unexpected result is that in the ∼30 nm-thick thin films the strong confinement effect can result in flat-on lamellae of PA6's γ-form, although the crystallization temperature applied did not favor the γ-form formation. We consider that in comparison with that of the α-form lamellae with a lath-like shape, the growth of more symmetrical lamellae of the γ-form with large lateral dimensions can reduce more the free energy of the very thin film.

Surface diffraction on a ψ-circle diffractometer using the χ-axis geometry

The restricted volume above and below the sample on a six-circle diffractometer can limit the size and complexity of sample environments used in surface diffraction studies. An alternative configuration of the diffractometer, where the sample normal is aligned parallel to the χ axis, allows for ample space above and below the χ circle for instrumentation. The merits of this approach are outlined and angles are derived for the diffraction condition for constant-incident-angle, constant-sample-azimuthal-angle and specular geometries. Using a version of this code written forSPEC(http://www.certif.com/content/spec/), sample specular and nonspecular crystal truncation rods measured from a 5 nm-thick thin film are presented.

Anomalous thermal conductivity by surface phonon-polaritons of polar nano thin films due to their asymmetric surrounding media

The surface phonon-polaritons contribution to the thermal conductivity of a nano thin film of silicon dioxide is investigated based on the Maxwell equations and the Boltzmann transport equation. It is shown that: (1) a small difference between the permittivities of the substrate and superstrate of the film can generate giant propagation lengths and therefore remarkably enhances its thermal conductivity with respect to values obtained for a freestanding one. (2) The propagation of surface phonon-polaritons is present in a broad band of frequencies and exhibits its largest propagation lengths at the frequency where the absorption of energy is minimal. (3) The increase of the thermal conductivity of the film as its thickness decreases is higher when it is deposited on potassium bromide instead of being suspended in air. The difference in the thermal conductivity for these two systems increases with increasing temperature and reducing the film thickness. A thermal conductivity as high as 2.5 W/m K is obtained for a 30 nm-thick thin film at room temperature, which is about 1.8 times larger than its bulk phonon value. The obtained results show that the propagation of surface phonon-polaritons has the potential not only to offset the reduction of the phonon thermal conductivity of a nano thin film, when its sizes are scaled down, but also to enhance it, by choosing properly the permittivity of its substrate.

Analytical solution for temperature oscillation in the heater/thermometer film in 3ω method and its application to thermal conductivity measurement of micro/nanometer-films

Analytical solution in terms of series for temperature oscillation in the heater/thermometer film is derived for 3ω measurements. The complex temperature solution is seperated into the real and imaginary parts. Analysis is performed to show the effect of the combined parameters of ac frequency, heater width and sample thermal properties on the temperature oscillation. The mathematical model for the measurement is corrected based on the solution. Accordingly, a 3ω setup is developed to determine thermal conductivity of 500 nm-thick thin film on Si substrate. Uncertainty analysis and comparison with the results of differential-3ω methods and published values are made, the results show good mutual agreement. The thermal conductivities of SiO2 film and Si substrate are determined simultaneously with the series solution and by extension to high frequency. The method is also employed to measure the thermal conductivity of the multi-layer antireflective coating of ZrO2/SiO2 deposited on Nd:YAG surface. The ZrO2 film has a thermal conductivity smaller than the volume value. The established 3ω setup and analytical method can be applied to investigate the thermal performance of thin film-substrate structures for use with micro-systems such MEMS.

Sputter deposition of nm-thick films for passivation of organic pellicles

Pellicles are critical to the 157 and 193 nm lithography technology. The polymeric pellicles are prone to contamination of environment, which may shorten their lifetimes. In this paper, authors passivated pellicles with various nm-thick thin films deposited by the room-temperature sputtering method. The pellicles were investigated for its light transmission efficiency and surface bond structure change. The environmental influence test was carried out by exposing the pellicle to a high-humidity, high-temperature condition. The result showed that a proper coating layer could protect the pellicle from environmental contamination while keeping the light transmittance loss low.