Showing papers on "Evaporation (deposition) published in 1986"

Evaporated Sn‐doped In2O3 films: Basic optical properties and applications to energy‐efficient windows

Abstract: We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...

Noble‐metal‐based transparent infrared reflectors: Experiments and theoretical analyses for very thin gold films

Abstract: Very thin gold films were prepared on glass by ion plating (IP) and by conventional evaporation (CE). Below a certain thickness—∼9 nm for IP and ∼15 nm for CE—the films comprised a metal network; above this thickness we found uniform films. Optical properties were recorded by spectrophotometry. Conspicuous near‐infrared transmittance plateaus were seen in network films. This effect is conducive to high solar transmission. The spectral features were explained from effective medium theories based on the film structure. The uniform films were consistent with the Drude theory, provided that an anomalously large frequency dependence of the relaxation energy was invoked. Significant induced transmission was found in calculations on dielectric/gold/dielectric coatings. Our results lead to improved noble‐metal‐based transparent infrared reflectors for potential use on energy efficient windows.

Oxidation temperature dependence of the dc electrical conduction characteristics and dielectric strength of thin Ta2O5 films on silicon

Abstract: Tantalum pentoxide thin films (60–80 nm thick) on silicon were prepared by thermal oxidation at 430–675 °C of electron‐beam evaporated Ta. The tantalum layers had been deposited by electron‐beam evaporation onto the Si substrates held at room temperature (RT) or heated to 150 °C during Ta evaporation. The dc conduction properties and the dielectic strength of the Ta2O5 films were studied employing Al/Ta2O5/Si capacitors. The smallest conductivity was found for Ta2O5 films formed from Ta deposited onto Si held at RT during evaporation and oxidized at 490 °C for 1 h in dry O2. This minimum conductivity corresponds to a leakage current of 1×10−7 A/cm2 at an applied field of 1 MV/cm (Al negative on p‐type Si substrates). The dc conduction characteristics can be interpreted by assuming Poole–Frenkel conduction. For Ta2O5 formed from Ta which had been deposited onto Si substrates held at 150 °C during evaporation, the conductivity is smallest for a film which had been oxidized at 430 °C for 1 h (lowest oxidatio...

Adhesion of evaporated titanium films to ion‐bombarded polyethylene

Abstract: Ti films were deposited onto high‐density polyethylene (HDPE) samples by electron‐beam evaporation. Prior to film deposition the samples were in situ pretreated by Ar ion bombardment using a sputter ion gun. The adhesion of the films, determined as the pull strength required for film failure, was measured as a function of ion dose. HDPE substrates processed at two different temperatures were examined. The adhesion of the Ti films to HDPE samples processed at ≊150 °C increased with the ion dose to a steady‐state value corresponding to the cohesive strength of the HDPE substrate. The adhesion to the samples processed at ≊200 °C increased to a maximum and then decreased for further ion bombardment to a level of the same order as that for films deposited onto as‐prepared samples. The effects of the ion bombardment upon the HDPE surface chemistry were examined by means of x‐ray photoelectron spectroscopy (XPS). The ion bombardment resulted in dehydrogenation and cross linking of the surface region and for prol...

Magnetic properties of iron nitride thin films with high corrosion-resistance

Abstract: Magnetic properties of Fe x N thin films prepared using ion-beam technique is reported. During the oblique incidence of iron, iron films were nitrized by nitrogen ions beam. A low energy broad-beam ion source (Kaufman type) was used for ionizing nitrogen. Magnetic properties of the films were studied static measurements and Mossbauer spectroscopy. It was found that the composition of the films consists mainly of α-Fe and e-Fe 2-3 N whose composition ratio were depend on ion current during the evaporation. The film prepared at ion current of 0.47 A/m2had squareness ratio of 0.85 and the saturation magnetization of 4200 gauss. It is emphasized that those obtained thin films show remarkable corrosion-resistance. Little corrosion was observed after the film was placed in a 5 % saline solution for a month.

The growth of AuGa2 thin films on GaAs(001) to form chemically unreactive interfaces

Abstract: Thin AuGa2 films were grown by codeposition from separate Au and Ga evaporation sources on clean GaAs(001) substrates in ultrahigh vacuum, and were studied by Auger electron spectroscopy, electron energy-loss spectroscopy, low-energy electron diffraction, scanning electron microscopy, and x-ray diffractometry. The morphology and crystallinity of the AuGa2 were highly dependent upon the film deposition and annealing history. Films grown on room-temperature substrates were continuous, specular, and polycrystalline, but the dominant orientation was with the (001) planes of the crystallites parallel to the substrate surface. Annealing to temperatures between 300°and 480°C caused the film to break up and coalesce into rectangular crystallites, which were all oriented with (001) parallel to the surface. An anneal to 500°C, which is above the AuGa2 melting point, resulted in the formation of irregular polycrystalline islands of AuGa2 on the GaAs(001) substrate. No interface roughening or chemical reactions between the film and substrate or interface were observed for even the highest-temperature anneals.

Manufacture of thin film transistor

Abstract: PURPOSE:To perform stable operation characterized by high mobility, by using a silicon film made by thermal CVD of high-order silane such as trisilane or higher as a channel semiconductor film of a thin film transistor. CONSTITUTION:On an insulating substrate 1, a gate 2 comprising Ni, W, Mo and the like is formed by evaporation, sputtering and the like. A gate insulating film 3 such as a silicon oxide film and silicon nitride film is laminated by a CVD method and the like on the gate 2. A silicon film 4 of high-order silane such as trisilane or higher is formed by a thermal CVD method on the film 3. A source 5 and a drain 6, which have doublelayer structure of a P-or N-type low resistance semiconductor film and a metal film, are formed. An inverted staggered type thin film transistor is formed. The silicon film 4 is formed as follows: the substrate is heated to a temperature of about 400 deg.C; the high order silane such as the trisilane or higher is introduced in a chamber 7; and the film 4 is formed on the surface of the substrate by thermal decomposition reaction on the substrate.

Method for making graded I-III-VI2 semiconductors and solar cell obtained thereby

Abstract: Improved cell photovoltaic conversion efficiencies are obtained by the simultaneous elemental reactive evaporation process of Mickelsen and Chen for making semiconductors by closer control of the evaporation rates and substrate temperature during formation of the near contact, bulk, and near junction regions of a graded I-III-VI 2 , thin film, semiconductor, such as CuInSe 2 /(Zn,Cd)S or another I-III-VI 2 /II-VI heterojunction.

Epitaxial growth of superconducting niobium thin films by ultrahigh vacuum evaporation

Abstract: A series of thin films of niobium have been grown on various orientations of single crystal sapphire by e‐beam evaporation in an ultrahigh vacuum molecular beam epitaxy system. The films were grown at temperatures between 600 and 950 °C and at growth rates from 0.1 to 10 A/s. The films were single‐crystal as determined by both in situ reflection high energy electron diffraction patterns and by Read photographs. The best films had rocking curve widths of the order of 1/10 of a degree. The superconducting transition temperature was measured as a function of film thickness and crystal orientation and ranged up to 9.35 K for a thick sample grown on [1102] sapphire.

Effects of oxygen on the growth of vapor‐deposited aluminium films

Abstract: Aluminium films were grown by evaporation at different oxygen partial pressures. The oxygen partial pressure has a marked effect on the growth, the morphology, and the physical properties of the aluminium films. At low oxygen pressures homogeneous, faceted layer was grown. At oxygen partial pressures of about 1×10−5 Pa an inhomogeneous layer was obtained, which consists of rather large hillock‐like grains and small grains. The latter are covered by an oxide layer, on which secondary nuclei are found. At high oxygen partial pressures a fine‐grained, smooth surface is obtained. From a comparison with the results of a previous study it was concluded that oxygen and water affect the growth of aluminium films, by different mechanisms.

Variation of the nucleated products in ultrathin films of Ti-Co on Si substrates with processing changes

Abstract: The purpose of this study is to investigate solid‐state nucleation and growth in Ti/Co/Si and Co/Ti/Si thin‐film ternary systems, and to compare results under a variety of preparation conditions. The deposition methods used were rf sputtering and e‐beam evaporation. The nucleated compounds are determined by transmission electron microscopy and diffraction. CoTi2 is the first nucleated compound in the Ti/Co/Si ternary systems prepared by e‐beam evaporation irrespective of substrate temperature, thickness, or other factors. This is in contrast to the films produced by rf sputtering where this phase was not observed. Experimental findings also show that in thin‐film ternary systems, the first‐phase nucleation temperature and subsequent compounds could be altered as the intermediate metal layer becomes less than 20 A. This is an indication that interference between interfaces begins to play a significant role at about this thickness, so that the reaction paths and the first nucleated phases are determined not...

Photovoltaic Characteristics Of Thin Films Of Cu2SnS3

Abstract: We report for the first time the optical absorption and photovoltaic characteristics of thin films of Cu2SnS3,. Films obtained by the direct evaporation of the synthesised compound were observed to be deficient in copper, while those grown in an atmosphere of copper vapour were observed to be more stoichiometric. Both sets of films are characterised by indirect and direct absorption edge properties. The indirect absorption edges are at 1.O65 and 1.5O0 eV, while the direct band edges are at 1.658 and 1.770 eV for the copper deficient and stoichiometric films respectively. The stoichiometric film is characterised by p-type semiconducting properties while schottky type solar cell developed from it is observed to have promising photovoltaic characteristics.

Surface reforming method for inorganic coating film

Abstract: PURPOSE: To decrease the affinity of water and the impurities in the water and to prevent generation of a burnt deposit by bringing silicon functional type silyl isocyanate and/or silicon functional type silyl thioisocyanate into reaction or adsorption with an inorg. coating film. CONSTITUTION: The cause for generation of the burnt deposit on the surface of the inorg. coating film lies in that the components in water drops adhere as evaporation residues on the surface of said film. The components of the evaporation residues consist mainly of Si, have high affinity to the inorg. coating film consisting of SiO 2 or the like and adhered securely to the surface of the coating film. The silicon functional type silyl isocyanate and/or silicon functional type silyl thioisocyanate is, therefore, brought into reaction with the inorg. coating film or is adsorbed thereon in order to prevent the generation of the burnt deposit, by which the adhesive strength of the evaporation residues is weakened and the light wiping away of the residues remaining on the surface with a cloth or the like is permitted. Furthermore, water repellency is provided so that the water drops themselves are made hardly adherable on the surface and the generation of the burnt deposit is decreased. COPYRIGHT: (C)1988,JPO&Japio

Raman scattering and x-ray diffraction characterization of amorphous semiconductor multilayer interfaces

Abstract: Raman spectroscopy (RS) and low-angle x-ray diffraction (LAXRD) have been used to characterize semiconductor multilayer interfaces. In the present study a model for Raman spectra of multilayers is developed and applied to the specific case of the interfaces of a-Si/a-Ge multilayers. Quantification of the “blurring” of interfaces is possible because peak heights in the Raman spectra of thin films are proportional to the number of scatterers, thus RS is capable of directly “counting” the total number of chemical bonds of a given type in the film. Multilayers, prepared by various deposition techniques, are compared. The relative roles of LAXRD and RS in investigating interfaces are contrasted. Several a-Si/a-Ge multilayers deposited by ultra-high vacuum (UHV) evaporation (MBD) are found to exhibit very regular periodicities and exceptionally sharp interfaces (<1.0 A intermixing).

Mass spectrometer controlled electron beam evaporation synthesis of multilayered materials

Abstract: A UHV apparatus equipped with two high‐power electron guns is extended with a multichannel quadrupole mass spectrometer which accurately controls the deposition rate. A rotating substrate holder is used for deposition of multilayers at room temperature; a fixed substrate holder enables one to prepare layered structures at liquid N2 temperature. A home‐built load lock in combination with an extended travel sample manipulator permits a rapid change of the samples without breaking vacuum. The system has been used to deposit Nb/Cu and Pb/Ge multilayers and preliminary structural measurements indicate the samples are of high quality.

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

Abstract: 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.

A new metallization technique for very large scale integrated structures: Experiments and computer simulation

Abstract: A new metallization process was developed. Grooves and holes with an aspect ratio of up to 1 were completely filled and partially planarized by the combination of high vacuum evaporation and sputter etching in a multiple cycle alternating process. Excellent agreement between experimental and computer simulated groove and hole profiles was achieved.