Films Of Various Metals Research Articles

EDDY CURRENT METHOD FOR STUDYING INHOMOGENEITIES AND DEFECTS IN THIN METAL FILMS

The variety of structure and specific properties associated with the small thickness of thin metal films lead to the fact that their physical characteristics differ significantly from the characteristics of the same materials in the bulk state. To determine the characteristics of thin metal films, the development of new non-destructive research methods is relevant. The article substantiates the advantages of the eddy current testing method for studying the surface of thin metal films of various metals. The design of a subminiature eddy current transducer designed to study the electrical conductivity, thickness and degree of damage of thin metal films is presented, and a hardware and software complex is designed that allows the control of the developed transducer. The study of metal films made it possible to show the inhomogeneity of the distribution of the substance over the surface of the substrate. The dependence of the signal amplitude of the developed transducer on the film thicknesswas also determined. To verify the results obtained, studies of the light transmittance of the films were carried out using the photometric method. Comparison of the measurement results obtained by the two methods showed a high degree of agreement betweenthe two developed methods for studying films.

Acoustoelectronic interaction in metal island films

The interaction of surface acoustic waves with conduction electrons of island films of various metals was investigated. Island films were formed on the surface of piezoelectric crystalline substrates: Lithium Niobate, Bismuth Germanate, and Piezoquartz. It is experimentally obtained that the surface acoustic wave attenuation as a function of film resistance has a characteristic maximum, and that the velocity changes from the velocity at the free surface of the substrate to that at the metallized surface.

Scalable and Versatile Fabrication of Metallic Nanofoam Films with Controllable Nanostructure Using Ar-Assisted Thermal Evaporation

A scalable and versatile method is proposed for the fabrication of nanofoam films of various metals, such as Ag, Au, Cu, and Pd, based on modified vacuum thermal evaporation, wherein an inert Ar ga...

Investigation of Optical Transmission in Thin Metal Films

Thin metal films have recently attracted large interest due to their practical application in photo-detectors, solar cells and quantum electronics. It is known that thin films of noble metals such as Au, Ag, and Cu have a maximum optical transmittance in the shorter part of spectrum. In our work, optical properties of thin metals films deposited by thermal evaporation and low pressure (1.33·10 -5 - 1.33·10 -4 Pa) DC plasma sputtering were investigated. Such low pressure is provided by triode sputtering method which supports a ballistic type of mass transfer between the sputtering target and the substrate. This method enables fine control of the film thickness and its density. Comparison of the films deposited by mentioned above two methods on glass substrates shows significant differences in their optical and electrical properties. Thin films of following metals: Sn, Al, V, Ti, Ni, Mo, Ta, W, Au, Ag, and Cu were deposited on glass and their optical and electrical properties were studied. The transmission spectra of thin films of various metals have significant differences. In our paper we discuss the causes of these differences.

Picosecond-Laser 4-Beam-Interference Ablation as a Flexible Tool for Thin Film Microstructuring

Interference of laser beams with the high pulse energy opens an opportunity of direct structuring over large areas. We report results of the laser beam interference ablation of thin metal films on glass using an infrared picosecond laser. The laser beam was split into four beams by a diffractive optical element, and 4F imaging system was used to produce interference pattern on the surface of the metal film. Regular structures with a period of 5μm were produced in thin films of various metals. A variety of periodical patterns can be formed using the method by controlling the process parameters.

Conducting and reflecting properties of nanometer-width films of various metals

The conducting and reflecting properties of silver, gold, nickel, iron, chromium, and titanium films are investigated. It is shown that a low conductivity of films relative to bulk materials results from the amorphism of the films and the porosity of their substrates. Two different techniques for measuring the film conductivity are compared: a contact technique and a reflection technique. It is shown that the conductivity values obtained via the two techniques are of the same order of magnitude but may differ by a factor of up to 4.

Features of the mechanoluminescence of thin metal films excited by long and short laser pulses

We have studied the strain-induced luminescence from thin fine-grained films of various metals under the action of short (subnanosecond) and long (millisecond) laser pulses. The possible mechanism of luminescence excitation is considered, according to which the emission is due to the interaction between grain boundary dislocations and impurities occurring in the intergranular region.

Critical currents of strongly disordered ultra-thin superconducting films

Quench-condensed films of various metals are well known systems for studying the superconducting state in presence of strong disorder. Critical currents of superconducting films of Bi and Sn with sheet resistance <500 Ω were found to vary with temperature according to the relation I c( T)= I c(0)(1−( T/ T c) 4). The result was found to be independent of the substrate used. The observed dependence implies a variation of the superconducting gap Δ( T)∼(1−( T/ T c) 4) 1/2, near T c. This is different from the behaviour of a BCS type gap near T c but consistent with some existing measurements on fabricated 2-D Josephson junction arrays. The I– V characteristics of these films also show hysteresis, indicating the presence of underdamped intergrain Josephson coupling. The values of the intergrain resistances and capacitances are estimated from the ratios of the observed retrapping and critical currents.

Macroparticle-free thin films produced by an efficient vacuum arc deposition technique

Macroparticle-free films of various metals and diamond-like carbon have been obtained by a pulsed vacuum arc deposition technique. An axial magnetic field (100–200 mT) generated by the discharge current itself was used to focus the plasma produced by the cathode spots and to guide the plasma flow through a macroparticle filter. The films were characterized by scanning electron microscopy, atomic force microscopy, and Rutherford backscattering spectrometry. They were found to be macroparticle-free. The total efficiency of the combined gun-filter plasma source is even higher than a standard nonfiltered vacuum arc plasma source in terms of deposited film thickness per discharge, because the plasma losses in the filter are overcompensated by the focused plasma injection into the filter.

Surface States and Barrier Height at Metal-GaAs Interface

Metal GaAs Schottky barriers have been prepared by vacuum deposition of films of various metals onto chemically etched n-type GaAs substrates. The diodes exhibit nearly ideal C-V and I-V characteristics with n values of 1.1 or less. The barrier height values derived from the I-V characteristics of the various contacts are found in agreement with those obtained from the C-V measurements only when the measured value of ideality factor n is also included in the expression for the saturation current Is. An estimate of the surface state density and the position of the neutral level at the metal-GaAs interface has been made from the observed dependence of barrier height on the metal work function φM employing the most recent values of φM. Surface states play a dominant role in the formation of the barrier and their density is 3.4×1014 eV-1cm-2 on the etched surfaces of GaAs.

Schottky barriers on p-type silicon

Measurements have been made of the electrical characteristics of Schottky barriers made by evaporating films of various metals (Al, Pb, Ni, Au, Ag, Cu) onto p-type silicon. The barriers were generally lower than on n-type silicon, and in the case of Au the barrier was so low as to provide an effectively ohmic contact at room temperature. The truly exponential portion of the forward I– V characteristic was restricted to a comparatively small voltage range. Within this range ‘ n’ values of about 1.10 were obtained. The reverse characteristics could be explained in terms of generation in the depletion region. The variation of barrier height with metal work-function indicates that the surface-state parameters (density of states and position of neutral level) are essentially the same for p-type as for n-type silicon. This is confirmed by the fact that, for a given metal, the sum of the barrier heights on n-type and p-type silicon is approximately equal to the band-gap.

Ultrahigh vacuum station for thin film and residual gas analysis studies

A bakeable, sputter-ion pumped ultra-high-vacuum system capable of in situ residual gas analyses before, during, and after the deposition of thin films by evaporation, sputtering or sublimation has been constructed. The system is readily modified, capable of rapid sample changes and daily cycling from atmospheric to pressures below 10 −10 torr. Thin films of various metals, semiconductors and compound materials have been grown. The nature of the residual background gases under various vacuum conditions has been determined with a partial pressure analyzer. Initial results on the pumping background of gases during film growth by getter sputtering are also presented.

952. Operational experience with ultra-high-vacuum, sputter-ion pumped resistance furnaces: J S Hetherington,Trans Vac Metall Conference, 1964, Amer Vac Soc, Boston, Mass, (1965), pp 251–257

A bakeable, sputter-ion pumped ultra-high-vacuum system capable of in situ residual gas analyses before, during, and after the deposition of thin films by evaporation, sputtering or sublimation has been constructed. The system is readily modified, capable of rapid sample changes and daily cycling from atmospheric to pressures below 10−10 torr. Thin films of various metals, semiconductors and compound materials have been grown. The nature of the residual background gases under various vacuum conditions has been determined with a partial pressure analyzer. Initial results on the pumping background of gases during film growth by getter sputtering are also presented.

947. Vacuum equipment in microelectronics: R P Riegert, SCP and Sol Stat Tech, July 1965,8 (7), 17.

A bakeable, sputter-ion pumped ultra-high-vacuum system capable of in situ residual gas analyses before, during, and after the deposition of thin films by evaporation, sputtering or sublimation has been constructed. The system is readily modified, capable of rapid sample changes and daily cycling from atmospheric to pressures below 10−10 torr. Thin films of various metals, semiconductors and compound materials have been grown. The nature of the residual background gases under various vacuum conditions has been determined with a partial pressure analyzer. Initial results on the pumping background of gases during film growth by getter sputtering are also presented.

948. An analysis of physical adsorption isotherms in ultra-high-vacuum range: A B Huang,J Vac Sci & Tech,2 (1), Jan–Feb 1965, 6–11

A bakeable, sputter-ion pumped ultra-high-vacuum system capable of in situ residual gas analyses before, during, and after the deposition of thin films by evaporation, sputtering or sublimation has been constructed. The system is readily modified, capable of rapid sample changes and daily cycling from atmospheric to pressures below 10−10 torr. Thin films of various metals, semiconductors and compound materials have been grown. The nature of the residual background gases under various vacuum conditions has been determined with a partial pressure analyzer. Initial results on the pumping background of gases during film growth by getter sputtering are also presented.

Electrical Properties of Thin Polymer Films. Part I. Thickness 500–2500 Å

The current I through silicone polymer films formed by electron-beam bombardment in the thickness range 500–2500 Å has been measured as a function of voltage and temperature between 4° and 300°K. The electrodes were vapor-deposited films of various metals. The electron transport is nonlinear and depends on voltage and thickness only through the electric field E when the applied voltage is greater than 5 V. At and below five volts, a negative resistance phenomenon similar to that described by Hickmott is sometimes observed which is voltage dependent rather than field dependent. The high-field electron transport depends rather strongly on temperature. The negative resistance phenomenon is not temperature dependent. The field-dependent current changes with time as a result of the diffusion of oxygen into the film, and this change appears to be correlated with a change in electron spin resonance absorption. The effect of free radicals on the electron transport which is thereby suggested, is further confirmed by the increased current observed as a result of a relative increase in the electron beam intensity used in the film formation. A hysteresis observed in the electron transport may be due to high-field polarization of the dielectric. The capacity of the specimens also changes with time, as a result of the diffusion of water into the dielectric. The usual theoretical expressions for field emission or Schottky emission do not completely fit the electron transport data although log I varies as E1/2.

Thin films of separated isotopes by cathodic sputtering

The construction and use of a chamber for the production of thin films from milligram quantities of separated isotopes by cathodic sputtering are described. It is adapted for the coating of thin substrates supported on frames suitable for use as accelerator targets or beta spectroscopy sources. Typical operating conditions yield films of various metals, up to opacity in thickness, in one to twelve hours. Details are included for the sputtering of osmium.

Graphical Method for Estimation of Contrast in Electron Microscopy

In the preparation of shadowed specimens for electron microscopic examination, it is often required to estimate the contrast to be expected with different thicknesses of films of various metals, different aperture angles, and beam potentials. This communication describes a graphical method for this purpose.