Comparison between rf-sputtered and electron beam evaporated thin electrode and electrolyte films for application in rechargeable lithium microbateries

The electrochemical performance of ion conducting thin films depends strongly on the deposition method. This provides a possibility of tailoring thin films with new functional properties. A comparative study was made between rf-sputtering and electron beam evaporation which are the two most commonly employed methods for the preparation of thin films. For this purpose, thin films of Li_3±xPO_4±yN_z were rf-sputtered and electron beam evaporated and investigated with regard to the electrochemical properties. It was found that solid thin films of the electrolyte Li_3±xPO_4±yN_z may be sputtered, but not electron beam evaporated. Compared to rf-sputtered Li_1±xCoO_2±y and C thin films, electron beam evaporated Li_1±xCoO_2±y and C thin films show chemical diffusion coefficients which are at least one order of magnitude higher. Paper presented at the 4^th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Influence of self-assembly monolayers on the characteristics of copper phthalacyanine thin film transistor

Self-assembly monolayers (SAMs) of octadecyltrichlorosilane (OTS) on a silicon dioxide substrate were formed in solution, or by vacuum vapor methods, and characterized by Fourier transform infrared (FTIR) spectroscopy. We found that the OTS SAMs on SiO₂ substrates greatly affect the order and connectivity of evaporated copper phthalocyanine (CuPc) thin films, as confirmed by an atomic force microscopy (AFM) and X-ray diffraction analysis. The performance of the organic CuPc thin film transistor comprising OTS SAMs interposed between a gate dielectric and an organic semiconductor layer could be effectively enhanced as a result of improvements in the quality both of the organic/dielectric interface and the evaporated CuPc thin films. The deposition of an OTS SAM leads to a mobility of 1.48×10^-3 cm²/Vs, 1–2 orders higher than that of bare silicon dioxide. PACS 73.61.Ph; 85.30.Tv; 78.66.Tr     

Untersuchungen an dünnen Alkalimetallschichten V

At 10^?8 mm Hg thin potassium films are evaporated on a quartz target by means of a potassium atomic beam in a reproducible manner. The big change of the optical absorption and of the electrical conductivity of such films on targets which are either “unbekernt” or “bekernt” is measured as a function of target temperature and film thickness.     

An electrochromic device (ECD) cell characterization on electron beam evaporated MoO3 films by intercalating/deintercalating the H+ ions

Thin films of molybdenum oxide (MoO₃) is one of the most interesting layered intercalation materials because of its excellent application in solid state batteries, large-area window and display systems. In recent years there has been considerable interest in variable transmittance electrochromic devices (ECD) based on Li⁺, H⁺ and K⁺ intercalation in transition metal oxide (MoO₃) thin films. In the present investigation, thin films of MoO₃ were prepared by electron beam evaporation technique on microscopic glass and fluorine doped tin oxide (FTO) coated glass substrates for the application in electrochromic device cells. The compositional stoichiometry of the films was studied by X-ray photoelectron spectroscopy (XPS). The electrochromic nature of the films has been analyzed by inserting H⁺ ions from the H₂SO₄ electrolyte solution using the cyclic-voltammetry (CV) technique. We studied the electrochromic device cells (ECD) incorporating an evaporated MoO₃ thin films as electrochromic layers. The devices exhibit good optical properties with low transmittance values in the colored state, which make them suitable for large-area window applications. The maximum coloration efficiency of the cell was observed at about 70 cm²/C.     

Adhesion and stress of magnesium oxide thin films: Effect of thickness, oxidation temperature and duration

Nanoscale magnesium oxide thin films have been deposited on glass substrate by thermal oxidation (in air) of vacuum evaporated magnesium films. X-ray diffraction (XRD) showed orientation along (2 0 0) and (2 2 0) directions. The mechanical properties of the MgO thin films were found to be the function of thickness (300, 450 and 600 nm), oxidation temperature (573, 623 and 673 K) and oxidation duration (90 and 180 min). As oxidation temperature and oxidation duration increases, adhesion and intrinsic stress were found to increase. Intrinsic stress decreased whereas adhesion increased due to increase in thin film thickness. The value of intrinsic stress was in range 28.902-73.212 (×10⁷ N/m²) and that of adhesion was 12.1-27.4 (×10⁴ N/m²) for the thin film of thickness 300 nm.     

Raman Scattering of amorphous selenium films

First order Raman scattering measurements are presented for thin film evaporated a-Se. High temperature films yield polarized and depolarized spectra that are very similar to those of bulk a-Se. Low temperature in situ studied films indicate increased disorder and a considerable reduction in the intensity of the ring attributed 112 cm^?1 peak. The Raman spectra of higher temperature films are consistent with a small number of rings and ordered chains that arise from constraints on the dihedral angle. Films deposited at low temperature suggest a reduction in chain order and ring population as might arise from a weakening of constraints on the dihedral angle.     

Preparation of Tl-Ba-Ca-Cu-O thin films by diffusion of Tl into laser evaporated Ba2Ca2Cu3Ox films

Preparation of superconducting Tl-Ba-Ca-Cu-O thin films by diffusion of Tl into laser evaporated Ba₂Ca₂Cu₃O_x thin films is reported. From a sintered Ba₂Ca₂Cu₃O_x bulk sample we prepared using a pulsed Nd:YAG laser, Ba-Ca-Cu-O thin films on sapphire and SrTiO₃ single-crystal substrates. Subsequently the films were loaded with Tl by simultaneously annealing the films together with a sintered Tl₂Ba₂Ca₂Cu₃O₁₀ sample both enclosed in a small stainless steel box; in our procedure Tl contamination was reduced to a minimum. T_c values near 100 K and critical currents of 5·10³ A/cm² at 77 K were obtained.     

Electron microscope study of aluminium films evaporated on air-cleaved sodium chloride

The article deals with the structure of thin aluminium films evaporated on air-cleaved NaCl substrates. The effect of the substrate temperature and the film thickness on the structure, the orientation and the grain size of the films was studied at a deposition rate of 10 Å/see (ev. 50 Å/see) in a vacuum of about 7. 10^–5 torr. The optimum temperature for epitaxial growth was found to be about 420°C. An almost regular arrangement of grains was found in the thickness region of 90–150 Å.     

Effects of the compliance current on the resistive switching behavior of TiO2 thin films

Nanocrystalline TiO₂ thin films were fabricated on Pt(111)/Ti/SiO₂/Si substrates by the thermal oxidation of evaporated Ti films. Effects of the compliance current on the resistive switching behavior of the Pt/TiO₂/Pt sandwich structures were studied in detail. The reset current increased when the compliance current increased from 10 mA to 20 mA. When the compliance current exceeded 20 mA, the switching behavior disappeared, which could be attributed to the change of the conducting behavior in the low-resistance state. A resistance change ratio of as high as 10² was obtained between the high-resistance state and the low-resistance state. The study of the effect of compliance current contributes to obtaining stable and reliable resistive switching behavior for nonvolatile memory applications.     

Lattice defects and its influence on hyperfine interactions on EuS evaporated thin films

In a study of the Mössbauer effect on¹⁵¹Eu in bulk EuS and evaporated thin films the influence of lattice defects on the hyperfine interactions has been investigated by variation of the substrate temperature during evaporation. The changes in the hyperfine and the lattice parameters with lattice defects are similar to the changes in those parameters observed in substances exhibiting an increasing portion of covalency.     

Dämpfung von Hyperschall in dünnen Silberschichten bei 9 GHz

The attenuation of longitudinal hypersonic waves (8.4–10.0 GHz) in thin polycrystalline silver films has been measured in the temperature range from 4 to 26 ?K. The silver films with thicknesses between 0.2 and 3.0 Μ. were evaporated on the optically flat polished end surface of a cylindrical quartz transducer. The measured value of the attenuation coefficient α=1.5·10⁴ dB cm^?1 is much higher than the theoretically predicted value due to electron-phonon interaction. Furthermore the measured value α is independent of temperature and increases with the square of frequency. Presumably this attenuation of hypersonic waves in polycrystalline silver films is due to scattering processes at lattice defects.     

Absorption bistability in evaporated ZnSex thin films

Intrinsic absorption bistability in ZnSe_1.36 thin films, produced by thermal evaporation is observed. The influence of laser pulse duration and resonator mirror reflectivity is studied experimentally and theoretically. Compared to ZnSe elements prepared by other methods, the evaporated films allow a longer operation wavelength of 514 nm, a low threshold power of 10 mW and a smaller element size below 10 m³.     

Electrochromic phenomena in transition metal oxide thin films prepared by thermal evaporation

We present an experimental study on the electrochromic properties of MoO₃, WO₃ and mixed WO₃-MoO₃ thin films prepared by thermal evaporation. We have constructed symmetric and quasi-symmetric electrochromic cells incorporating the evaporated oxide films as electrochromic layers. Li⁺ doped V₂O₅ films served as ion storage layers. The symmetric cells were found to exhibit significantly improved optical properties compared to the quasi-symmetric ones, with very low luminous transmittance values in the colored state, which makes them suitable for large-area window applications. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Corrosion of Ultrathin Iron Layers and Titanium Nitride Coated Iron

In this paper results are presented on the corrosion resistance against SO₂-polluted atmospheres of ultrathin Fe layers (<2.5 nm) deposited on SiO₂/Si wafers by two methods: vacuum evaporation and Langmuir–Blodgett (LB) technique. It is shown that the corrosion resistance of the evaporated films is similar to that shown by massive iron while the corrosion resistance of the LB films is remarkably higher. We also show that the corrosion resistance of iron evaporated films can be greatly enhanced by using TiN coatings. Results on the influence of the SO₂ concentration, the atmospheric relative humidity and the exposure time on the corrosion behaviour of thin (30 nm) TiN layers deposited onto evaporated Fe films on SiO₂/Si wafers are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Densification and nanocrystallisation of sol-gel ZrO 2 thin films studied by surface plasmon polariton-assisted Raman spectroscopy

Very thin ZrO ₂ films (few nanometers) have been prepared by sol-gel process. These films were deposited onto a stack of a thin silver layer evaporated on a glass substrate for Surface Plasmons Resonance (SPR) experiments. The first aim of this work is to study the high densification of the sol-gel films followed by the refractive index and thickness accurate measurements at each step of the annealing procedure, using an optical set-up based on SPR. Secondly, SPR excitation coupled with micro-Raman experiment has also been performed to determine the thin films structure depending on layer thickness. Finally, Conventional Transmission Electron Microscopy (CTEM) and High Resolution (HRTEM) studies have been conducted to check and complete Raman spectroscopy results. A discussion compares the optical results and the Transmission Electron Microscopy observations and shows that ultra thin layers structure is strongly depends on films thickness. Received 14 May 2001 and Received in final form 2 January 2002     

Self-assembled monolayers of decanethiol on Au(111)/mica

We report here a preparation for thin gold films on mica substrates. We have investigated the influence of the substrate temperature and the evaporation rate on the morphology of the films. After careful outgasing of the substrate, 100 nm of Au is evaporated onto the mica surface maintained at high temperature. After slow cooling, ex situ characterizations are performed using AFM and STM. For our purposes, the best compromise between roughness and grain size is found to occur for an evaporation rate of 2 ?s^-1 onto a mica substrate maintained at 460 C. We have used these substrates for STM and AFM study of decanethiol self-assembled monolayers (SAMs). We present results for gold samples immersed for a few seconds in decanethiol solutions, revealing an incomplete organization of the films. The organization process is discussed through comparison between AFM and STM data recorded on the SAMs. Then we present molecular resolution STM pictures of ordered SAMs for longer immersion times. Received 25 May 1999     

Highly uniform electrochromic tungsten oxide thin films deposited by e-beam evaporation for energy saving systems

In the last few decades, there has been a surge of interest in using tungsten oxide thin films as an active layer of electrochromic device. These devices have several practical applications such as smart window of buildings and automobile glazing for energy saving. The main objective of this work was to construct highly homogeneous and uniform e-beam evaporated amorphous WO_3-x based films into electrochromic devices, which were fully characterized for switching speed, coloration efficiencies and cycling voltammetry responses. Fabricated devices contain indium doped transparent oxide coated glass as the transparent conductive electrode, ～200?nm thickness of WO_3-x as the cathodically coloring material and a lithium perchlorate based conducting gel electrolyte. X-ray diffraction patterns indicate that all as-deposited films are amorphous. Experimental results showed that both solid and liquid electrolyte electrochromic devices are initially very transparent that exhibit perfect optical modulation and coloration efficiency (up to 68.7?cm²/C and 52.6?cm²/C at 630?nm, respectively) due to easier intercalation of the Li⁺ within their structure. One of the more significant findings to emerge from this study is that e-beam coated electrochromic devices based on tungsten oxide thin films showed superior performance among to other coating methods. Therefore, excellent reversibility of color change behavior is attractive for pertinent use in electrochromic energy storage devices.     

Preparation of CuInGeSe4 thin films by selenization method using the Cu-In-Ge evaporated layer precursors

CuInGeSe₄ quaternary compounds are known to have a chalcopyrite-like structure and have band gaps of about 1.3 eV, suitable for optimum conversion efficiency for solar cells. We have prepared the CuInGeSe₄ thin films by the selenization method using the Cu-In-Ge evaporated layer precursors. The analyses of X-ray diffraction show that the single phase of CuInGeSe₄ is obtained by the selenization of precursors at 450-500 °C. The SEM observation of film surface shows that the grain sizes are in the order of 1-2 μm. The band gaps of selenized films close to 1.6 eV are wider than that of bulk crystals (about 1.3 eV). These films have p-type conduction and higher electrical resistivities than more 10⁵ Ω cm at room temperature.     

Proton beam enhanced adhesion of iron films

Depth-selective surface Mössbauer and adhesion measurements were pertormed on as evaporated and proton bombarded⁵⁷Fe and⁵⁶Fe/⁵⁷Fe films supported by glass and fused silica. The results contribute to the understanding of the mechanism responsible for adhesion enhancement of metallic films induced by ion bombardment in the electronic stopping region.     

CEMS studies of Sn−O thin films prepared by thermal evaporation

Thermal evaporated thin Sn?O films subjected to annealing treatments in air in the range 473–1173 K and in Ar in the range 473–773 K followed by annealings in air up to 1373 K were studied by CEMS (Conversion Electron Mössbauer Spectroscopy). Complementary Mössbauer and X-ray measurements were also performed on SnO powder that underwent the same series of annealings. The presence of the intermediate oxide Sn₃O₄ was detected. A temptative hyperfine characterization for the Sn²⁺ site in Sn₃O₄ is given.