Showing papers on "Layer by layer published in 1994"

Layer-by-Layer Assembly of Alternate Protein/Polyion Ultrathin Films.

Abstract: Layer-by-layer assembly of multilayer films was realized by means of alternate adsorption of positively charged globular proteins (myoglobin or lysozyme) and anionic poly(styrenesulfonate). Regular growth during at least 20 alternate adsorption cycles was proved by means of UV spectroscopy and quartz crystal microbalance. Superlattices containing alternate layers of both myoglobin and lysozyme were similarly prepared.

Origin of oxygen induced layer-by-layer growth in homoepitaxy on Pt(111).

Abstract: Whereas on the clean (111) surface Pt grows in a multilayer (3D) mode at 300 and 400 K, preadsorption of an ordered p(2\ifmmode\times\else\texttimes\fi{}2) oxygen overlayer leads to a high quality layer-by-layer (2D) growth with the oxygen floating on the film. In contrast to other surfactants oxygen can be completely removed from the film surface at the growth temperature. It is demonstrated that the presence of oxygen reduces the barrier height for the motion of PT adatoms across step edges. This facilitates the interlayer mass transport and thus the layer-by-layer growth.

Atomic-scale mechanisms for surfactant-mediated layer-by-layer growth in homoepitaxy.

Abstract: Atomic-scale mechanisms for surfactant-mediated layer-by-layer growth in homoepitaxy are investigated theoretically. Starting with minimal assumptions on relative bond strengths, we demonstrate that four possible mechanisms can be operative in enhancing layered growth: (1) a high density of islands at the initial growth stage of each layer, (2) a reduced activation barrier for atoms to cross steps, (3) incorporation into a growing island, and (4) an effective increase in the migration rate on top of the island. We assess the relative importance of these processes by computer simulations.

Change in the electronic states of graphite overlayers depending on thickness

Abstract: Electronic states of graphite overlayers formed on the TaC(111) surface have been investigated with the use of scanning tunneling microscopy and photoelectron spectroscopy. The graphite film grows on the substrate layer by layer. The thickness of the overlayer has been adjusted precisely to be either one or two monolayers. The physical properties of the monolayer graphite film are modified by chemical bonding at the interface. This interfacial bonding becomes weak upon the formation of the second layer of graphite, which makes the properties of the double-layer graphite film similar to those of bulk graphite.

Surface-treated substrate and process for its production

Abstract: A surface-treated substrate consisting essentially of a substrate having at least two treated surface layers wherein the first layer constituting the outermost layer among the treated surface layers is a layer formed by treating with a treating agent containing a compound (I) capable of forming a surface having a contact angle of at least 70° against water, and the second layer constituting an underlayer in contact with the outermost layer is a thin film layer of a heat resistant polymer formed by treating with a treating agent containing a compound (II) capable of forming a thin film of a heat resistant polymer and fine particles of a polymer, to form a thin film and heating the thin film to thermally decompose the fine particles of a polymer.

Deposition of multiple layer thin films using a broadband spectral monitor

Abstract: A method is provided for monitoring and controlling the deposition of multiple layer thin films using a broadband spectral monitor and a generalized model of the film. A design specification, including the number of layers and the material, refractive index, and thickness of each layer, is provided for the desired thin film. A target optical thickness is computed for the end point of each layer using correction factors based on the generalized model, preferably a single layer model, of the multilayer thin film. A monitor chip, such as a silicon substrate, is used for monitoring the multiple layers of film deposition. During deposition of the film, a broadband spectral monitor (BBSM) comprising a source of broadband light is directed onto the monitoring chip. Light reflected by the monitoring chip is received by a photosensor that provides a broadband reflectance spectrum to a computer. The BBSM reflectance spectrum is fit to the generalized model to produce an output corresponding to the optical thickness of the deposited film. When the broadband spectral monitor optical thickness measurement equals the target optical thickness at the end point of the layer, deposition of that layer is terminated and deposition of the next layer may commence. This process is repeated during the deposition of each successive layer until the entire multiple layer thin film is complete.

Thin film semiconductor device for display and method of producing same.

Abstract: An LDD structure of a thin film transistor for pixel switching is realized on a large glass substrate by low-temperature processes. A thin film semiconductor device for display comprises a display part and a peripheral driving part formed on a glass substrate (0). Pixel electrodes (9) and NchLDD-TFTs are arranged in a matrix in the display part. Thin film transistor PchTFTs and NchTFTs which constitute circuit elements are formed in the peripheral driving part. Each thin film transistor consists of a gate electrode (1), an insulating film (2) formed on the gate electrode (1), a polycrystalline semiconductor layer (3) formed on the insulating layer (2), and a high concentration impurity layer constituting a source (4) and a drain (7) formed on the polycrystalline semiconductor layer (3). Further, an NchLDD-TFT thin film transistor for switching has an LDD structure in which a low concentration impurity layer (8) is interposed between the polycrystalline semiconductor layer (3) and the high concentration impurity layer (7).

Thin film semiconductor device for active matrix panel

Abstract: A thin film semiconductor device comprising a thin film transistor (TFT) having a thin film semiconductor on an insulation substrate to define an element region, and a hygroscopic interlayer dielectric which covers the element. A hydrogenation treatment which comprises the interlayer dielectric provided thereon a cap film for blocking hydrogen diffusion, so that water entrapped by the interlayer dielectric may be decomposed to generate hydrogen which is allowed to diffuse into the thin film transistor provided on the side opposite to that of the cap film.

Method of depositing crystalline carbon-based thin films

Abstract: Crystalline carbon-based thin film structures are formed in which a compositionally-graded intermediate layer is first deposited on a substrate, and a crystalline carbon-based thin film such as silicon carbide or diamond is deposited thereafter on the intermediate layer. The compositionally-graded intermediate layer has a carbon content which increases in a direction away from the substrate. The compositionally-graded intermediate layer is effective in reducing problems associated with the lattice mismatch between the thin film and the substrate which hamper conventional hetero-epitaxial growth of high quality crystalline carbon-based thin films.

Artificially engineered pyroelectric Sr1−xBaxTiO3 superstructure films

Abstract: Artificially engineered superstructure films of SrTiO3/BaTiO3 were deposited layer by layer via pulsed laser deposition onto substrates of sapphire with and without Pt/Ti electrodes. Secondary‐ion‐mass‐spectroscopy and x‐ray diffraction measurements were performed to explore the nature of the multilayered structure. Dielectric measurements versus temperature revealed a broad peak near the extrapolated Curie temperature.

Synchronous modulation bias sputter method and apparatus for complete planarization of metal films

Abstract: A method for producing planarized metal films on a substrate which includes the steps of depositing a thin film of a metal onto the substrate; after the thin film is deposited, generating vacancies in the deposited thin film of metal to increase the mobility of the metal atoms of the deposited thin film; after generating vacancies within the deposited thin film of metal and before depositing any more metal, heating the surface of the deposited thin film to cause a reflow of the metal in the thin metal film; and repeating the above sequence of steps until a metal layer is formed having a predetermined thickness.

H2 sensors using Fe2O3-based thin film

Abstract: This paper describes the fabrication procedure as well as the sensing properties of new hydrogen sensors using Fe2O3-based thin film. The film is deposited by the r.f. sputtering technique; its composition is Fe2O3, TiO2(5 mol%) and MgO(0–12 mol%). The conductance change of the film is examined in various test gases. The sensitivity to hydrogen gas is enhanced by treating the film in vacuum at 550 °C for 4 h and then in air at 700 °C for 2 h. The sputtered film is identified to be polycrystalline α-Fe2O3 based on X-ray diffraction patterns. However, the surface layer is considered to be changed to Fe3O4 after heating in vacuum and then to γ-Fe2O3 after heating in air. The film is thus a multilayer one with a thin γ-Fe2O3 layer on a α-Fe2O3 layer. The sensing mechanism is discussed based on measurements of the physical properties of the film, such as the temperature dependence of the sensor conductance, X-ray diffraction pattern, surface morphology, RBS (Rutherford back-scattering) spectrum and optical absorption spectrum.

Structure of Polycrystalline Silicon Thin Film Fabricated from Fluorinated Precursors by Layer-by-Layer Technique

Abstract: We observed the structure of polycrystalline silicon (poly-Si) fabricated from fluorinated precursors, SiFn Hm (n+m≤3), by repeated deposition of very thin layers, 10 nm thick, and atomic hydrogen treatment (H-treatment). The surface views and the cross-sectional views of poly-Si were observed using a field-emission scanning electron microscope (FE-SEM) and transmittance electron microscope (TEM), respectively. Poly-Si was made up of columnar crystalline grains of which diameters were 200 nm or more. These columnar crystalline grains grew perpendicularly on the amorphous layer grown directly on the glass substrate. Crystalline nuclei were formed within the amorphous layer and grew into crystalline grains with the aid of H-treatment. The thickness of this incubation layer was dramatically reduced by extending the period of H-treatment.

Ferroelectric thin film with intermediate buffer layer

Abstract: The present invention provides a substrate providing a ferroelectric crystal thin film which includes an electrode formed on a semiconductor single crystal substrate and a ferroelectric crystal thin film of Bi 4 Ti 3 O 12 formed on the electrode through the intermediary of a buffer layer.

Manufacture of thin film solar cell and thin film solar cell

Abstract: PURPOSE:To obtain a method of manufacturing a thin film solar cell, which separates efficiently a semiconductor thin film from a heat-resistant substrate and can use repeatedly the substrate. CONSTITUTION:A peel layer 2 consisting of a silicon oxide film, a semiconductor thin film 3 consisting of a P-type polycrystalline silicon thin film and a cap layer 4 consisting of a silicon oxide film are formed in order on a heat-resistant substrate 1 consisting of a single crystal silicon wafer. Then, a zone melting recrystallization of the thin film 3 is performed. Then, the layer 4 is removed and thereafter, a bonding layer 5 is formed on the upper surface of the thin film 3. Then, through holes 8 to reach the layer 2 are formed in the thin film 3. Then, the layer 2 is etched away through the holes 8 and the thin film 3 is separated from the substrate 1. Then, electrodes are respectively formed on the upper and lower surfaces of the thin film 3.

Method for manufacturing thin film transistor with short hydrogen passivation time

Abstract: In a method for manufacturing a thin film transistor, a polycrystalline silicon layer, a gate insulating layer, a gate electrode layer, a non-doped insulating layer, and a metal connections layer are formed on a substrate, and then, a hydrogen passivation is carried out. The non-doped insulating layer has a thickness of less than approximately 100 nm.

Carrier transport in polycrystalline silicon films deposited by a layer‐by‐layer technique

Abstract: The transport processes in phosphorus‐doped polycrystalline silicon thin films are examined by standard six‐electrode Hall effect and conductivity measurements over a wide temperature range, 100–400 K. These films were deposited by a novel layer‐by‐layer technique at very low substrate temperatures (300–360 °C) using fluorinated precursors, SiFmHn (m+n≤3). The analysis indicated that the grain boundaries are the major barriers to carrier transport. The grain boundary carrier transport is controlled by thermionic emission at high temperatures, whereas at low temperatures, it is dominated by a tunneling process through the barriers. The electrical properties of these films were found to vary as a function of the film thickness. It appears that the grain boundary defects are passivated to a large degree by this novel deposition technique and that the grain boundary barriers are consequently smaller than those in films prepared by other growth schemes.

Articles having diamond-like protective thin film

Abstract: Articles protectively coated with a diamond-like thin film firmly bonded to the substrates are obtained by forming an intermediate layer composed of an amorphous mixture of silicon and carbon on a substrate of a material which has only a slight affinity for such a diamond-like thin film, and forming a diamond-like thin film further thereon.

Depth Profiling Analysis of Aluminum Oxidation During Film Deposition in a Conventional High Vacuum System

Abstract: The oxidation of aluminum thin films deposited in a conventional high vacuum chamber has been investigated using x‐ray photoelectron spectroscopy (XPS) and depth profiling. The state of the Al layer was preserved by coating it with a protective MgF2 layer in the deposition chamber. Oxygen concentrations in the film layers were determined as a function of sputter time (depth into the film). The results show that an oxidized layer is formed at the start of Al deposition and that a less extensively oxidized Al layer is deposited if the deposition rate is fast. The top surface of the Al layer oxidizes very quickly. This top oxidized layer may be thicker than has been previously reported by optical methods. Maximum oxygen concentrations measured by XPS at each Al interface are related to pressure to rate ratios determined during the Al layer deposition.

Method of fabricating semiconductor thin film and a Hall-effect device

Abstract: A method of fabricating a semiconductor thin film is initiated with preparing a substrate having a surface consisting of a single crystal of Si. The surface has an oxide film. Then, the oxide film is removed. The dangling bonds of the Si atoms on the surface are terminated with hydrogen atoms. An initial layer is formed on the substrate of the single crystal of Si terminated with the hydrogen atoms, of at least one selected from the group consisting of Al, Ga, and In. A buffer layer containing at least In and Sb is formed on the initial layer. A semiconductor thin film containing at least In and Sb is formed on the buffer layer at a temperature higher than the temperature at which the buffer layer is started to be formed. There is also disclosed a method of fabricating a Hall-effect device. This method is initiated with forming a semiconductor thin film by making use of the above-described fabrication method. Then, electrodes are attached to the thin film.