Showing papers on "Thin film published in 1973"

How thin is a thin bed

Abstract: Based on reflective properties, a thin bed may be conveniently defined as one whose thickness is less than about λb/8 where λb is the (predominant) wavelength computed using the velocity of the bed. The amplitude of a reflection from a thin bed is to the first order of approximation equal to 4πAb/λb, where b is the thickness of the bed and A is the amplitude of the reflection if the bed were to be very thick. The equation shows that a bed as thin as 10 ft has, for typical frequency and velocity, considerably more reflective power than is usually attributed to it.

Optical and photoelectric properties and colour centres in thin films of tungsten oxide

Abstract: Thin films of Wo3 deposited on quartz substrates at room temperature have been shown to be amorphous in structure. The optical absorption spectra of the amorphous and crystalline films have been measured in the temperature range 110° to 500°K. The fundamental absorption edge of an amorphous film occurs at 3800 A which on crystallization moves to 4500 A. On the high-energy side of the absorption edge several absorption peaks are resolvable in both types of film. The frequency dependence of the absorption coefficient below 104 cm−1 is described by an expression of the form K (v, T) = K 0 exp[− (β/kT) (E 0 − hv)] and above 104 cm−1 it follows a square law dependency. The temperature coefficient of the band edges was found to be − 5.0 × 10−4 eV/°K and the estimated band gaps at 0°K were found to be 3.65 and 3.27 eV for the amorphous and crystalline films, respectively. The electrical conductivity of a thin film has been measured in the temperature range 298–573°K and the activation energy was found t...

Electrical conduction in concentrated disordered transition metal alloys

Abstract: Results are presented of an investigation on the origin of the low temperature coefficient of resistance in NiCr thin films. It is shown that this low temperature coefficient is an intrinsic property of the alloy. Besides NiCr a large number of disordered alloys containing transition metals have similar conduction properties, both in bulk and as a thin film. For these materials a correlation has been found between the resistivity and its temperature coefficient. These anomalous conduction properties are probably caused by the very small electron mean free path in these materials.

Amorphous metallic films for magneto-optic applications

Abstract: It has been demonstrated that perpendicular uniaxial anisotropy and compensation points in the vicinity of room temperature can be obtained in amorphous thin films of rare‐earth—transition‐metal alloys. The magneto‐optic properties of these films are reported, and it is shown that a remarkably good signal‐to‐noise ratio can be obtained in a thermomagnetically written film.

Depolarization-Field-Induced Instability in Thin Ferroelectric Films-Experiment and Theory

Abstract: The existence of depolarization fields in thin ferroelectric films is experimentally demonstrated by investigating an unconventional electrode-ferroelectric configuration consisting of a triglycine sulphate (TGS) film sandwiched between a gold and a doped-silicon electrode. Due to nonidentical electrodes, the compensating-charge distribution for opposite polarization directions is asymmetric and consequently depolarization fields cannot be sufficiently reduced by domain formation. These depolarization fields manifest themselves by reducing the intrinsic polarization in thin ferroelectric films with respect to the bulk value and this aspect is experimentally confirmed. For a sufficiently thin film, depolarization fields become too strong and a polarization instability is observed. These effects are simulated by altering the compensation-charge extension in the silicon electrode by photoillumination. Other causes, like impurities, and structural defects, which can lead to reduction of polarization, are ruled out. Theoretical model calculations including the depolarization field are reported. The calculation predicts an intrinsic polarization reduction in thin ferroelectric films and is in good agreement with experiments reported here.

Phase Transition, Stability, and Depolarization Field in Ferroelectric Thin Films

Abstract: It is shown that the polarization in a thin ferroelectric film, which is sandwiched between semiconducting electrodes, is compensated incompletely The associated depolarization fields are size dependent and change the magnitude of the polarization, transition temperature, coercive field, and the order of the phase transition Thermodynamic considerations give stability requirements for thin films, which are different from the bulk The properties of a thin ferroelectric film, which in bulk form exhibits a second-order phase transition, are investigated as a function of thickness, temperature, biasing potential, and electrode properties Numerical results are presented for triglycinesulfate

ir‐laser‐addressed thermo‐optic smectic liquid‐crystal storage displays

Abstract: Thermally induced optical storage and erasure (local and nonlocal) of scattering centers in thin films of smectic liquid crystals has been demonstrated. These new thermo‐optic and electrothermo‐optic effects provide the basis for what is believed to be the first practical application of smectic liquid crystals, an infrared‐laser‐addressed light valve for the recording, storage, and display of high‐resolution graphic images.

Thermally Stimulated Currents in Semiconductors and Insulators Having Arbitrary Trap Distributions

Abstract: The theory is developed for thermally stimulated currents (TSC) that flow in optically or electrically excited insulators and semiconductors in which the field is sufficiently high and the (active) region in which the free carriers are generated is sufficiently thin (e.g., reverse-biased junctions, thin films, etc.) so that recombination rate of the free carriers is negligible. Closed-form solutions are obtained for the TSC characteristics for semiconductors and insulators containing arbitrary trap distributions. Using various ad hoc trapping distributions, it is shown that the approximate high-field TSC characteristics correlate extremely well with the exact characteristics that were computed numerically. More important, however, it is shown that the shape of the observed TSC characteristic is a direct reflection of the sum of the trap distribution in the upper half and the lower half of the band gap. The technique is potentially a powerful means of characterizing trap distributions in defect semiconductors and insulators, in that it permits the direct determination of the trap distribution without requiring an a priori knowledge of the trap parameters and without the need for laborious analyses.

Loss Measurements in Thin-Film Optical Waveguides

Abstract: An apparatus for the measurement of attenuation of light in thin-film waveguides is described. It involves a prism that rides on a liquid film along the guide and couples the light out of the guide. A spatial resolution of ~0.5 mm and an accuracy of 0.02 dB/cm were achieved.

Sputtering and Backscattering of keV Light Ions Bombarding Random Targets

Abstract: Range and damage distributions have been calculated for light ions slowing down in heavy targets in the energy region where electronic stopping is dominating and approximately proportional to velocity. Following Schi⊘tt's approach, well-known integral equations for spatial moments were approximated by differential equations, and the latter solved by numerical integration. Moments over the two distributions up to third order have been obtained, and the distributions were constructed by use of the Edgeworth expansion. From the profiles, backscattering coefficients and relative sputtering yields were determined. Comparison is made with previous theoretical results, computer simulation and experimental results. An improved calculation of the sputtering yield of light ions bombarding a thin film is also presented.

Chemical Vapor Deposition of Thin‐Film Platinum

Abstract: Chemical vapor deposition of platinum for microelectronic applications has been studied with the aim of avoiding the radiation damage to dielectrics caused by sputter or e‐gun deposition. Two known CVD methods—the pyrolysis of Pt acetylacetonate and the reduction of —were tried and judged unsatisfactory for either purity or adherence. A novel method of Pt deposition using the trifluorophosphine complex is reported. The process is simple and reliable, and produces adherent bright films of crystals on a variety of substrates at 200°–300°C in 1 atm hydrogen. The Pt contains small amounts of residual phosphorus, mostly concentrated at the surface. Resistivity of 750Aa films is 1.8 times that of bulk Pt. MOS capacitors with CVD Pt field plates on both and alone have shown good stability under bias‐temperature aging. CVD Pt and Si interdiffuse readily to form ohmic or Schottky diode contacts.

High molecular weight, thin film piezoelectric transducers

Abstract: A transducer for converting electrical energy into mechanical or acoustic energy or vice versa using a converting means made of a thin film of high molecular weight polymer piezo-electric organic compound having orientated molecules and having electrodes bonded or deposited onto both surfaces thereof. When an electric current is applied to the electrodes, the thin film is extended or contracted in a direction different from the direction of orientation of the molecules. when the angle between these two directions is 45*, the extent of the extension or contraction of the thin film is at a maximum and the best converting efficiency can be obtained.

Reaction kinetics of tungsten thin films on silicon (100) surfaces

Abstract: The rate of reaction between Si (100) surfaces and tungsten films deposited by rf diode sputtering depends on the preparation of the silicon surface. If rf substrate bias is used to clean the silicon, then the rate of reaction in the temperature range 700–850 °C is independent of time, with an activation energy of 3 eV/mole W. The native oxide layer between the silicon and tungsten, that exists when sputter cleaning is not used, can act as a barrier to WSi2 formation. In this case, the time‐independent region is preceded by a period when the reaction rate increases with time. The rate is then controlled by two‐dimensional spreading of discontinuous WSi2 regions that originate at sites where the reaction barrier can be penetrated. After a continuous WSi2 layer is formed, additional growth can produce a stage where the increased path length for silicon diffusion causes the transport step to control the over‐all rate of the reaction. Quantitative models are presented for each of the three stages in the reaction. The models explain some of the macroscopic observations made on reacted layers.

Thin‐film LiNbO3 electro‐optic light modulator

Abstract: An out‐diffused planar optical waveguide in LiNbO3 has been used to produce an efficient broad‐band electro‐optic phase modulator. The ratio of modulation index η and voltage is 0.13 V−1, the maximum base bandwidth with 50‐Ω load is 3.2 GHz, and the modulating power per unit bandwidth for η=1 rad is 0.2 mW/MHz.

Superconducting properties, electrical resistivities, and structure of NbN thin films

Abstract: Superconducting properties and electrical resistivities of NbN thin films have been studied as a function of sputtering parameters, film structure, and composition. A good correlation exists between superconducting Tc's and film structure and composition regardless of the sputtering conditions used to achieve this structure. The most important parameters affecting Tc are lattice parameter, crystal structure, island structure, and impurity content. Substrate temperature, Ar/N2 ratio, and impurity content are the principal sputtering parameters affecting film structure, and thus Tc.

MnBi films for magnetooptic recording

Abstract: Progress made during the past years in the area of magnetooptic data storage by the computer industry has been most impressive. Many material media and physical phenomena have been developed for this particular application. It now appears that a large capacity ( \gsim 10^{10} bits) magnetooptic data store possessing major advantages over the conventional recording techniques could be developed. Of the many materials and techniques advanced to date, the use of thin films of MnBi for thermomagnetic writing, erasing, and magnetooptic reading has received particularly intensive study because of the many unique properties of this film medium. In order to provide an assessment of the potential of this medium for optical memory application, we have included in this review the pertinent material physical properties of MnBi; the memory characteristics in regard to read, write, and erase operation; the physical process involved in the writing and erasure by thermomagnetic technique; the technique for detection of written information; and the utilization of this medium for magnetic holographic storage. Emphasis is given to the material properties and physical phenomena, rather than the systems considerations in using MnBi films for optical memory.

An analysis of carrier‐facilitated transport

Abstract: The physical and mathematical characteristics of carrier-facilitated transport in a liquid film are examined for a reaction scheme of the form A + B ⇄ AB, in which A is the permeating species and B and AB are diffusable species which are constrained not to leave the film. For thin films, a solution is developed as a perturbation from purely physical diffusion and is expressed as a second-order power series. For thick films, a solution is developed as a perturbation from a state in which the species concentrations at any one point within the film are related by an equilibrium constraint. This development utilizes the techniques of matched asymptotic analysis. Taken together, these solutions provide an excellent estimate of the facilitation for a film of any thickness, as shown by comparison with numerical results.

Method of depositing thin film utilizing a lift-off mask

Abstract: A method for use in depositing thin films in the fabrication of integrated circuits which avoids edge tearing of the films. The method involves depositing a non-photosensitive organic polymeric material on a substrate, and forming on said polymeric layer a masking layer of an inorganic material, preferably metal, having openings in a selected pattern. Then, forming, by reactive sputter etching, utilizing the metallic mask as a barrier, openings through the polymeric layer extending to the substrate, the openings in the polymeric layer being aligned with and laterally wider than the corresponding openings in the metallic masking layer. The thin film to be deposited is then applied over the structure; it is, thereby, deposited on the substrate in said openings. Then, the remaining polymeric layer is removed, lifting off the masking layer and the thin film above the polymeric layer to leave thin film deposited in a selected pattern in the openings.

Optical constants of ice in the infrared

Abstract: The normal-incidence spectral reflectance of ice at −7° C has been measured in the range 300–5000 cm−1. A Kramers–Kronig phase-shift analysis of the measured spectral reflectance has been employed to provide values of the real and imaginary parts of the refractive index. The resulting values of these optical constants are suitable for use in Mie-theory computations of scattering by ice particles in planetary atmospheres. The optical constants of ice at −7° C are compared in detail with those of liquid water at several temperatures and with those recently determined for ice at −170° C.