Vacuum-deposited Metal Films Research Articles

Microstructure and Electrical Resistivity of Ink-Jet Printed Nanoparticle Silver Films under Isothermal Annealing

【Interest in use of ink-jet printing for pattern-on-demand fabrication of metal interconnects without complicated and wasteful etching process has been on rapid increase. However, ink-jet printing is a wet process and needs an additional thermal treatment such as an annealing process. Since a metal ink is a suspension containing metal nanoparticles and organic capping molecules to prevent aggregation of them, the microstructure of an ink-jet printed metal interconnect 'as dried' can be characterized as a stack of loosely packed nanoparticles. Therefore, during being treated thermally, an inkjet-printed interconnect is likely to evolve a characteristic microstructure, different from that of the conventionally vacuum-deposited metal films. Microstructure characteristics can significantly affect the corresponding electrical and mechanical properties. The characteristics of change in microstructure and electrical resistivity of inkjet-printed silver (Ag) films when annealed isothermally at a temperature between 170 and $240^{\circ}C$ were analyzed. The change in electrical resistivity was described using the first-order exponential decay kinetics. The corresponding activation energy of 0.44 eV was explained in terms of a thermally-activated mechanism, i.e., migration of point defects such as vacancy-oxygen pairs, rather than microstructure evolution such as grain growth or change in porosity.】

Ultra-smooth metal surfaces generated by pressure-induced surface deformation of thin metal films

We present a mechanical pressing technique for generating ultra-smooth surfaces on thin metal films by flattening the bumps, asperities, rough grains and spikes of a freshly vacuum deposited metal film. The method was implemented by varying the applied pressure from 100 MPa to 600 MPa on an e-beam evaporated silver film of thickness 1000 A deposited on double-polished (100)-oriented silicon surfaces, resulting in a varying degree of film smoothness. The surface morphology of the thin film was studied using atomic force microscopy. Notably, at a pressure of ∼600 MPa an initial silver surface with 13-nm RMS roughness was plastically deformed and transformed to an ultra-flat plane with better than 0.1 nm RMS. Our demonstration with the e-beam evaporated silver thin film exhibits the potential for applications in decreasing the scattering-induced losses in optical metamaterials, plasmonic nanodevices and electrical shorts in molecular-scale electronic devices.

Surface Deformation of Metal Films Under Controlled Pressure for Generating Ultra-flat Metal Surfaces

ABSTRACTWe present a technique to generate ultra-smooth surfaces and direct pattern imprinting on thin metal films by flattening the bumps and spikes of a freshly vacuum deposited metal film. The technique was implemented by using a small footprint mechanical imprint press that has the capability to vary the applied pressure from 100MPa to 600MPa. The mechanical press was incorporated with a tactile force sensor that enabled direct monitoring of the applied pressure. We demonstrated the feasibility of the technique on an e-beam evaporated silver (Ag) metal film with thickness ranging from 150Å (optically thin) to 1000Å (optically thick). The film was deposited on double-polished (100)-oriented silicon surface and double-polished borosilicate glass, resulting in a varying degree of film smoothness. The surface morphology of the pressed thin film was then studied using atomic force microscopy and SEM. Our demonstration with the e-beam evaporated silver thin film exhibits the potential for applications in decreasing the scattering-induced losses in optical metamaterials, plasmonic nanodevices and electrical shorts in molecular-scale electronic devices.

Effect of a vacuum-deposited metal film on the CV of the Li insertion/extraction reaction at a graphitized carbon fiber electrode

A metal film of silver, copper, or gold was vacuum-deposited on the surface of mesophase pitch-based carbon fiber prepared at 3100 °C, and the Li insertion/extraction behaviour was examined by measuring the cyclic voltammogram (CV) for various film thicknesses in a non-aqueous electrolyte containing 1 M LiClO 4. The peak height of the CV was examined in detail for the deposited silver film. The peak height increased at first with increasing film thickness up to 150 Å, but then began to decrease. At around 200 Å, a minimum peak height which was nearly the same as that of the pristine sample was observed. The peak height then increased again up to a film thickness of 400 Å, where it was two times higher than that of pristine sample, then decreased gradually. Such a complicated CV could not be observed with a gold or copper film where the enhancing effect was monotonous and more remarkable with a thinner film. X-ray diffraction patterns of the silver film deposited on the carbon fiber showed a strong crystal orientation to the carbon substrate like epitaxial growth, which was found to be dependent on both the thickness and the deposition rate. The CV peak height correlated well with the silver crystal orientation, implying that the electrochemical reaction rate differs on different crystal faces. Such could not be found in the case of gold or copper. The peak enhancing effect and the cycle behaviour were elucidated in view of the nature of solid electrolyte interphase (SEI), conductivity, and the effect of alloy formation.

Crystal structures and transformation of Cu-Se and Ag-Te in solid-solid reactions

Cu-Se and Ag-Te crystals which grew by solid-solid reactions of vacuum-deposited metal and chalcogen films were investigated with a JEM 200-CX electron microscope (Cs= 1.2 mm), with the aid of image simulation and optical diffraction.Fig. 1 shows an image of a slender crystal observed 10 days after an amorphous Se film was mounted on a holey Cu film. The image in A matches with a calculated image shown in Fig. 2a. The calculation was carried out for a CuSe crystal (P63/mmc, a=0.394, c=1.725 nm) 20 nm thick, with the a-axis relatively tilted at 1° about the [012] axis to the incident electron beam, at an underfocus of Δf=50 nm. The optical diffractogram from the image of the area A was used for the calibration of the distance in the optical diffractograms from the other areas B∼ E. The crystal in B formed before the formation of the CuSe crystal.

Characterization of the topography of vacuum-deposited films 2: Ellipsometry

In many technologies a means of characterizing the surfaces of vacuum-deposited metal films would be desirable. Following the first part of this work, which dealt with light scattering, we have assessed ellipsometry as a possible tool. For surfaces with a root-mean-square roughness smaller than 40 nm the influence of roughness on ellipsometric parameters ψ and Δ was observed to be very small (<0.02°/nm) at a wavelength of 632.8 nm. These surfaces however had a different morphology as shown by a scanning electron microscope. Rougher surfaces showed a dominant decrease in ψ and a relatively smaller decrease in Δ with increasing roughness. Besides the influence of surface roughness, the particular morphology of the surface and the constitution of the residual gas atmosphere during evaporation of the Al thin film were shown to be also of significance. For this reason, together with the inability to discriminate between roughness values in the 0–40-nm range, ellipsometry at 632.8 nm wavelength is less suitable for measuring surface roughness of vacuum-deposited films.

Windows with heat mirrors for energy conservation

Detailed calculations have shown that radiation heat losses through double-pane windows can be substantially reduced by the application of a thin, transparent film, reflective to long-wave radiation (‘heat mirror’). The comparative analysis of different types of ‘heat mirror’ has been carried out, and a tin oxide layer deposited by spray has been recognized as the most suitable for large-scale production. A tin oxide film has been deposited on glass by a spray method using ordinary commercial materials for the substrate, the solvent and the solution. The optical properties of the tin oxide films obtained have been compared with those measured on films deposited by more sophisticated methods; results are as follows: in comparison with vacuum-deposited metallic films or vacuum-deposited SnOx, films, our sprayed SnOx, films have similar or better transmissivity for visible spectra and somewhat (10–30 per cent) lower reflectivity for the infrared portion of the spectrum, but at the same time the prices of material and/or production costs are several orders of magnitude lower.

Air-exposure effect on the resistivity of thin bismuth films

A survey of previous studies on vacuum deposited metal films shows that in high frequency measurements, explicit reference to the effect of air-exposure is not made. The present work on bismuth films (in-situ and air-exposed) at dc and rf frequencies, carried out mainly to study the air-exposure effect, shows that in-situ dc and rf and exposed rf all show nearly the same resistivity for thick continuous films. But air-exposed dc film resistances, when compared to in-situ dc resistances, show that the grain boundary reflection coefficient, R gin Mayadas-Shatzkes model changes from 0·2 to 0·6. This is shown to be due to the grain boundary oxidation. The result is substantiated by rf measurements.

Comparative studies of the contact angle as a measure of adherence for photoresist

A non-destructive method of determining the adhesion of Shipley AZ 1350J photoresist on various vacuum-deposited metal films is reported. The correlation between the water contact angle and the adherence of Shipley photoresist on metal films is also reported.

Strength of glass with vacuum-deposited metal films: Cr, Al, Au and Ag

Fracture strength of acid-etched glass with vacuum deposited metal films is investigated. The strength of the etched glass having an initial value of 1696±39 MN m−2 reduces to 265±10 MN m−2 with 69 nm thick Cr film coating. Al film coating also causes the strength reduction, but the reproducibility of the strength is not found even under strictly controlled evaporation conditions. In ambient air, the strength of Au- and Ag-coated glasses maintains the initial high strength value and slightly increases with film thickness. From strength reduction behaviour of Cr-coated glass and dynamic fatigue characteristics for Ag-coated glass, it is highly probable that rupture of the metal film takes place before fracture of the glass occurs, and the flaw formed in the film propagates under loading into the glass to act as a Griffith crack.

Strength of glass with vacuum-deposited metal films: Cr, Al, Au and Ag

Strength of glass with vacuum-deposited metal films: Cr, Al, Au and Ag

Determination of specimen thickness by continuum integration

A simple method has been developed which allows an accurate determination of the thickness of any thin specimen microvolume irradiated by an electron beam. The determination of the thickness of such an irradiated region is based upon a single measurement of the generated continuum X-radiation in a standard. When this continuum integral is placed in ratio with the calculated energy loss suffered by the primary electron beam traversing the standard, the ratio may be employed as a correction factor for a given set of electron optical parameters (keV, beam current etc.). A suitable standard for this method is an evaporated metal film. Provided the thickness of the standard employed is known (or can be calculated), the correction can be considered absolute. If the absolute thickness of the standard is not accurately known this method is still applicable, and in this case the thickness calculations can be considered relative, one to another. This technique has been successfully applied in a series of measurements using vacuum deposited metal films at both low and high accelerating voltages (20–100keV) in a variety of electron microscopes equipped with X-ray analytical capabilities.

Determination of noble metals by carbon furnace atomic-absorption spectrometry. Part 1. Atom formation processes

Evidence is presented to support the theory that the formation of atoms of noble metals during carbon furnace atomisation proceeds via direct evaporation of the metal. The evidence includes (i) thermogravimetric investigation of noble metal salts and their aqueous solutions in an argon atmosphere, (ii) X-ray diffraction studies of the residues formed on heating aqueous solutions of some noble metal salts in a carbon furnace atomiser and in the microfurnace of a thermobalance, (iii) measurements of the appearance temperatures of noble metals in a carbon furnace atomiser using aqueous solutions and vacuum-deposited metal films and (iv) activation energies, Ea, and vapour pressure data relating to noble metals at elevated temperatures.Experimental conditions giving the best sensitivity for the determination of seven noble metals (osmium was not detected) in the Perkin-Elmer HGA-74 carbon furnace atomiser are presented. On the basis of a 20-µl sample volume these gave sensitivities (1% absorption) of 0.019, 0.0058, 0.0045, 0.00021, 0.038, 0.023 and 0.00089 µg ml–1 for ruthenium, rhodium, palladium, silver, iridium, platinum and gold, respectively.

Sputtering of Vacuum Deposited Metal Films by Oxygen Ion Bombardment

Sputtering of Vacuum Deposited Metal Films by Oxygen Ion Bombardment

Internal Friction of Vacuum-Deposited Metal Films

Internal Friction of Vacuum-Deposited Metal Films

Quantitative analysis of the mass of thin vacuum-deposited metallic films by colorimetry

Quantitative analysis of the mass of thin vacuum-deposited metallic films by colorimetry

Mechanical properties of vacuum-deposited metal films—I. Copper films

As the first stage in a series of experiments to assess the mechanical properties of single crystal Cu-Ni composite films, the mechanical behavior of vacuum-deposited polycrystal and single crystal Cu films in the thickness range from 3000 to 20,000 Å have been determined. As-deposited polycrystalline films were found to have a high breaking stress of 55 kg/mm 2. Contrary to some observations reported in the literature, the breaking stress did not depend on thickness over the thickness range tested. Single crystal films exhibited much lower breaking stress (18 kg/mm 2) and smaller plastic strain at fracture than polycrystalline films. Creep at room temperature was observed for all films as has been reported previously. Electron microscopy and electron diffraction investigations of the films are reported.

Mechanical properties of vacuum-deposited metal films II: nickel films

Mechanical properties of vacuum-deposited metal films II: nickel films

Mechanical properties of vacuum-deposited metal films III: layered Cu and Ni single crystal composites

Mechanical properties of vacuum-deposited metal films III: layered Cu and Ni single crystal composites

Mechanical properties of vacuum-deposited metal films I: copper films

Mechanical properties of vacuum-deposited metal films I: copper films