Showing papers on "Thin film published in 1984"

Thin film transistor

Abstract: PURPOSE:To obtain a transparent thin film transistor having a large ON-current and a memorizing property by a method wherein a transition metal oxide is used as a semiconductor layer. CONSTITUTION:A gate 2 is formed on a substrate 1, then an SiO2 film 3 is deposited on the whole surface, a semiconductor layer 4 is formed, and a source electrode 5 and a drain electrode 6 are formed. Then, an SiO2 film 7 is provided in such a manner that it will not be formed on the electrode 6, and a thin film transistor TFT is formed. In this constitution, a transition metal oxide which is WO3 in other words is used. When WO3 is used for the film 4, its ON-current is approximately two figures higher when compared with the TFT whereon an amorphous semiconductor layer is used. Also, as the WO3 is transparent, a transparent TFT is obtained when a transparent electrode is used for electrodes 2, 5 and 6. Besides, a WO3 thin film can maintain the donor position in the film and the width of a depletion layer for a fixed period even after voltage is cut off, and a memorizing property can also be given to the film.

Highly Conductive and Transparent Aluminum Doped Zinc Oxide Thin Films Prepared by RF Magnetron Sputtering

Abstract: Highly conductive films of Al-doped ZnO have been prepared by rf magnetron sputtering of a ZnO target with Al2O3 dopant of 1–2 wt% in content added. Films with resistivity as low as 2×10-4 Ωcm and transmittance above 80% at the wavelength between 400 and 800 nm can be produced on low temperature substrate with a relatively high deposition rate. It is shown that a stable resistivity for use in various ambients at high temperature can be attained for the films. The characteristic features of Al-doped ZnO films are their high carrier concentration and low mobility in comparison with non-doped ZnO films.

The preparation of cross‐section specimens for transmission electron microscopy

Abstract: The structure and chemistry of thin solid films are best studied by transmission electron microscopy (TEM) when they are viewed in cross-section—that is, when the surface normal of the film is made perpendicular to the electron beam. In this orientation, the substrate, the thin film layers, and the interfaces between them can be imaged either simultaneously or individually. Further, information from each of these regions remains distinct from that obtained from the others, eliminating the problems of superimposition that are a consequence of viewing a layered structure in the conventional manner (i.e., parallel to the surface normal). A technique for fabricating TEM specimens that can be viewed in cross-section is described here. Although the majority of our work is with silicon-based materials, the technique can be readily adapted to the study of other systems.

Coatings on glass

Abstract: Introduction and history composition, structure and properties of inorganic and organic glasses nature of a surface cleaning of substrate surfaces glass and thin films film formation methods film thickness properties of thin films applications of coatings on glass.

Modification of the optical and structural properties of dielectric ZrO2 films by ion‐assisted deposition

Abstract: Low‐energy bombardment by argon and oxygen ions has been used in the deposition of thin dielectric films of ZrO2. The film packing density has been improved from 0.83 to unity with a corresponding increase in the refractive index from 1.84 to 2.19. The highest stable refractive index measured was 2.23 for oxygen ion‐assisted deposition of ZrO2 on a substrate heated to 300 °C. Ion bombardment during condensation of evaporated ZrO2 on a room temperature substrate results in crystallization into the cubic phase which is consistent with previous studies of ion impact crystallization by thermal‐spike processes. At elevated substrate temperatures the monoclinic phase is also present.

Multiple determination of the optical constants of thin-film coating materials

Abstract: The seven participating laboratories received films of two different thicknesses of Sc2O3 and Rh. All samples of each material were prepared in a single deposition run. Brief descriptions are given of the various methods used for determination of the optical constants of these coating materials. The measurement data are presented, and the results are compared. The mean of the variances of the Sc2O3 refractive-index determinations in the 0.40–0.75-nm spectral region was 0.03. The corresponding variances for the refractive index and absorption coefficient of Rh were 0.35 and 0.26, respectively.

Electrical and optical properties of zinc oxide thin films prepared by rf magnetron sputtering for transparent electrode applications

Abstract: Zinc oxide films were prepared on unheated glass substrates by rf magnetron sputtering under an applied external dc magnetic field in pure argon gas, and electrical and optical properties of the deposited films were investigated. Highly transparent films with resistivity as low as 10−4 Ω cm, which were weakly oriented perpendicular to the substrate surface(c‐axis orientation), could be produced with a relatively high deposition rate on the substrate suspended perpendicular to the target surface by controlling the sputtering gas pressure and the external dc magnetic field, without any postdeposition preparative treatment. The Hall mobility of the film with the highest conductivity was about 120 cm2/V sec, which was the highest yet reported for thin films on ZnO. The increase in the conductivity was related to the increase in Hall mobility which was caused by the decrease of carrier scattering from grain boundaries due to the grain growth resulting from the improvement of crystallization. The improvement of...

Pseudomorphic growth of GexSi1−x on silicon by molecular beam epitaxy

Abstract: GexSi1−x layers are grown on Si substrates over the full range of alloy compositions at temperatures from 400–750 °C by means of molecular beam epitaxy. At a given growth temperature films grow in a smooth, two‐dimensional manner up to a critical germanium fraction xc. Beyond xc growth is rough. xc increases from 0.1 at 750 °C to 1.0 at ∼550 °C. Rutherford ion backscattering measurements indicate good crystallinity over a wide range of growth conditions. Transmission electron microscopy reveals that in thin films, the lattice mismatch between the GexSi1−x and Si layers can be accommodated by lattice distortion rather than by misfit dislocation formation. This pseudomorphic growth condition can persist to alloy thicknesses as large as l/4 μm.

Supercritical fluid molecular spray film deposition and powder formation

Abstract: Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. Upon expansion and supersonic interaction with background gases in the low pressure region, any clusters of solvent are broken up and the solvent is vaporized and pumped away. Solute concentration in the solution is varied primarily by varying solution pressure to determine, together with flow rate, the rate of deposition and to control in part whether a film or podwer is produced and the granularity of each. Solvent clustering and solute nucleation are controlled by manipulating the rate of expansion of the solution and the pressure of the lower pressure region. Solution and low pressure region temperatures are also controlled.

High‐efficiency electroplated heterojunction solar cell

Abstract: Over 9% efficiency is demonstrated in electroplated CdS/CdTe thin film solar cells. Processing of the devices is described. A brief heat treatment step first anneals out the deep lifetime killer centers in the material then converts the originally n‐type film into solar cell grade p‐CdTe.

Ion–surface interactions during thin film deposition

Abstract: The interactions of ion beams with surfaces are strongly dependent on the incident kinetic energy and the amount of ionic charge. Fundamental effects of ion bombardment by atomic and cluster ion beams have been elucidated in terms of kinetic energy of the ion beams. These fundamental effects include enhancement of adatom migration, desorption of physically absorbed atoms, displacement of the surface atoms, sputtering, shallow ion implantation, and trapping of impinging atoms. The importance of low energy ion beams for film formation is shown by taking into account the binding energies of the atoms in a solid. Emphasis has been placed on interactions of ionized cluster beams (ICB) during film formation because ICB offers unique capabilities for deposition due to the properties of the clusters and also to characteristic low energy ion beam transport over a range from thermal energy to a few hundred eV.

Structural and morphological investigation of the development of electrical conductivity in ion-irradiated thin films of an organic material

Abstract: Thin films of 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA) develop low electrical resistivity ( 5×1...

Preparation of ferroelectric PZT films by thermal decomposition of organometallic compounds

Abstract: Transparent PZT thin films with perovskite structure were successfully obtained by thermal decomposition of organometallic compounds at the temperatures of 500 to 700° C. The films deposited on platinum substrates were smooth and uniform, but microcrackings were observed in the films deposited on fused silica substrates. The ratio of metal composition in the PZT film agreed with that in the mixture of starting materials. Films obtained at 700° C on platinum substrate showed a hysteresis loop. A spontaneous polarization was 35.65μC cm−2, a saturation remanent polarization was 30.56μC cm−2 and a coercive field was 45 kV cm−1. Dielectric constant and dielectric loss angle were about 300 and 0.05, respectively.

Impurity trapping, interface structure, and luminescence of GaAs quantum wells grown by molecular beam epitaxy

Abstract: A correlation has been demonstrated between impurity trapping and the interface structure in GaAs quantum well (QW) superlattices and single quantum well structures grown by molecular beam epitaxy (MBE) on (100) GaAs. Using low‐temperature cathodoluminescence, photoluminescence, and transmission electron miscroscopy, we have shown that interface roughness in QW superlattices is related to trapped impurities at interfaces. We have observed that impurities originate from either the substrate or from the GaAlAs MBE layers. A new getter smoothing effect associated with QW structures is shown to produce efficient impurity trapping and yield higher quality GaAs QW with atomically smooth interfaces.

Preparation and structure of carbon film deposited by a mass‐separated C+ ion beam

Abstract: Carbon films were deposited using mass‐separated C+ ions of 300 and 600 eV. The films have diamond‐like characteristics such as transparency in the visible spectral region with wavelengths longer than about 650 nm and in the infrared, and high electrical resistivity. Transmission electron diffraction analysis shows that the film is amorphous and does not contain graphitically bonded carbon atoms. Kα x‐ray emission spectrum of the carbon in the film agrees well with that of diamond. In the x‐ray photoemission spectrum of the film, no characteristic energy loss due to π plasmon was observed. The atomic density of the film calculated from the energy loss due to the plasma oscillation of valence electrons is 1.7×1023 atoms/cm3, which is in good agreement with that of diamond. These results indicate that the film deposited using C+ ion beam consists of tetrahedraly bonded carbon atoms.

Ferrite plating in aqueous solution: New technique for preparing magnetic thin film

Abstract: This paper describes the principle and performance of a new technique which facilitates the formation of crystalline spinel film at low temperature (T<80 °C) without a heat treatment. For a substrate, not only a metal but also oxides and organic compounds can be used. Various transition metals (M=Ni, Co, Mn, Cu, Zn, etc.) are incorporated into the spinel. Hydrolyzed metal ions FeOH+ and MOH(n−1)+ in an aqueous solution (pH=6∼11,T=40∼80 °C) are adsorbed on a substrate surface which react into spinel film associated with anodic or air oxidation of the FeOH+ ion. We have plated Fe3O4 and CoFe2O4 films on a substrate of Cu, polyethylene terephthalate, and stainless steel. They are polycrystalline with no preferred orientation, and exhibit no magnetic anisotropy. The polar Kerr rotation of these films has been measured.

Measurements of adherence of residually stressed thin films by indentation. II. Experiments with ZnO/Si

Abstract: Indentation‐induced delamination between thin films of ZnO and Si substrates is examined. Delamination occurs by the growth of lateral cracks, either along the interface or within the film adjacent to the interface. The crack path is determined by the indenter load and the film thickness, as well as by residual stresses formed during deposition. A change in crack path from the interface to the film, accompanied by an increase in crack radius, is observed and is interpreted as a buckling‐induced stress intensification. The interface fracture toughness is estimated from the relative crack lengths in the buckled and unbuckled films.

CuInSe2 thin film solar cell with thin CdS and transparent window layer

Abstract: A thin film photovoltaic device having first layer of copper indium selenide, a second layer of cadmium sulfide having a thickness less than 2500 angstroms, and a third layer of conducting wide bandgap semiconductor such as zinc oxide. The transparent third layer allows good transmission of blue light to the junction region while fully depleting the junction area to improve device voltage.

Ion-assisted deposition of optical thin films: low energy vs high energy bombardment

Abstract: Oxygen ion-assisted deposition of SiO2 and TiO2 has been investigated as a function of ion energy (30–500 eV) and current density (0–300 μA/cm2) at the optic. It is shown that both low and high energy ion bombardment improve SiO2 film stoichiometry, although slightly greater improvement is realized for the low energy case. For TiO2 films, low energy bombardment improves stoichiometry, while high energy bombardment is clearly detrimental. A reduction in H content by a factor of 10 is observed in SiO2 films deposited with high energy ion bombardment. Durable films are produced at low substrate temperatures (50–100°C). Film stress characteristics are discussed.

Wide spectrum antireflective coating for fused silica and other glasses.

Abstract: A method of forming a laser damage resistant wide-spectrum antireflective coating on fused silica and other glasses has been developed. The single-layer graded-index coating is deposited from a specific polymer solution which is converted to a porous SiO2 film. The size of the pores in the film is first reduced by heat treatment to prevent eventual UV scattering. Refractive-index gradation is achieved by grading this non-scattering porosity using a mild etching agent to a depth which is sufficient to smooth the density transition from air to the substrate glass. The resultant coating provides antireflectivity over the entire transmission range of silica extending to wavelengths as short as 250 nm. Laser damage thresholds as high as 9 J/cm2 at 350 nm have been demonstrated for this coating on fused silica substrates, which makes it particularly suitable for the optics of high-power lasers.

Microstructure of vapor-deposited optical coatings.

Abstract: The microstructure of thin films applied by conventional physical vapor deposition for use as optical coatings is columnar for most of the materials commonly used. This has been established for about a decade through numerous experimental observations employing microfractographical replication for use with high resolution transmission electron microscopes. Scanning electron microscopes are more useful investigating coating defects, the most remarkable of these defects being known as nodules. From fundamental considerations of nucleation and growth of thin films, the origin of both columns and nodules and the dependence of their appearance on the deposition conditions are discussed in some detail. A simple 2-D simulation model assuming limited surface mobility of adatoms or admolecules shows striking similarities to peculiar properties of both columnar and nodular growth seen in actual investigations. Conclusions are drawn as to how the two types of microstructure influence general film properties and, in particular, how they influence possible laser damage mechanisms.

Emergent Process Methods for High-Technology Ceramics

Abstract: The present conference covers colloidal processing of advanced ceramics, novel power-forming and powder-processing methods, the derivation of ceramics by polymer processing, chemical vapor deposition techniques, ion beam deposition methods, the laser and ion beam modification of surfaces, hot isostatic pressing and dynamic compaction, shock conditioning and subsequent densification of ceramics, and very high pressure processing methods. Specific attention is given to the preparation of shaped glasses by the sol-gel method, the synthesis of powders and thin films by laser-induced gas phase reactions, the plasma sintering of ceramics, laser chemical vapor deposition, the microstructure and mechanical properties of ion-implanted ceramics, a computer simulation of dynamic compaction, shock-induced modification of inorganic powders, and diamond anvil technology.

High‐temperature electrical properties of 3C‐SiC epitaxial layers grown by chemical vapor deposition

Abstract: Electrical properties of 3C‐SiC layers, epitaxially grown on silicon by chemical vapor deposition, have been investigated at the temperatures between room temperature and 850 °C. In this temperature range, the electron mobility changes with temperature as μH∼T−1.2∼−1.4. The weaker temperature dependence of mobility and the larger mobilities compared with other polytypes of SiC suggest that 3C‐SiC is a promising material for devices operated at high temperatures.

Growth of epitaxial films by chemical vapor deposition utilizing a surface cleaning step immediately before deposition

Abstract: A method and apparatus for low temperature deposition of epitaxial films using low pressure chemical vapor deposition (CVD) with and without plasma enhancement. More specifically, the process enables CVD of epitaxial silicon at temperatures below 800° C. by use of an in situ argon plasma sputter cleaning treatment of the silicon substrate prior to deposition.

Organic‐on‐inorganic semiconductor contact barrier diodes. II. Dependence on organic film and metal contact properties

Abstract: We discuss the effects of organic film thickness, film crystalline texture, contact metal, and temperature on the current‐voltage characteristics (I‐V) of organic‐on‐inorganic (OI) semiconductor contact barrier diodes, where the prototypical compound; 3, 4, 9, 10‐perylenetetracarboxylic dianhydride (PTCDA) serves as the organic thin film. The results presented can be fully understood in terms of the thermionic emission‐space‐charge‐limited (TE‐SCL) current model introduced in previous papers. Studies of the I‐V characteristics suggest the presence of a trap distribution centered at Δe=0.20 eV above the PTCDA valence band edge. Also, we have found a correlation between the hole mobility (μeff) and PTCDA crystalline texture, and obtain a mobility as high as μeff=1.4 cm2/V s for highly ordered crystalline thin films. Finally, the general criteria which must be fulfilled by an organic compound used to achieve high‐performance OI devices are outlined. The properties of several such devices using various organi...

Electrical transport properties of CoSi2 and NiSi2 thin films

Abstract: Transport studies have been performed on thin films of CoSi2 and NiSi2 in the temperature range 1–300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room‐temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiessen’s rule is obeyed over a remarkable range of bombardment doses.

Polycrystalline thin-film CuInSe 2 /CdZnS solar cells

Abstract: The fabrication and properties of polycrystalline, CuInSe 2 thin-film solar cells based upon a heterojunction device structure of P-type CuInSe 2 and N-type CdS or mixed CdZnS are described. A photovoltaic conversion efficiency of 11 percent is reported for a CuInSe 2 / CdZnS cell of 1-cm2area when tested under simulated AM1 illumination (ELH lamp). While the highest efficiency cells have been prepared on Mo-metallized, polycrystalline alumina substrates, good cell performance is also presented for cells fabricated on low-cost glass substrates. The vacuum deposited selenide and sulfide films are reported to exhibit strong columnar growth features throughout the critical junction region. The spectral response of the cells is described as being relatively flat from 1100 to 600 nm with very high quantum yields(> 0.8). Photoluminescence emission data on the CuInSe 2 thin-film excited with a He-Ne laser is presented. In general, selenide films producing a good cell performance are reported to exhibit spectra with two or three major broad-band emissions.