Showing papers on "Evaporation (deposition) published in 1989"

XeCl Excimer Laser Annealing Used to Fabricate Poly-Si TFT's

Abstract: Polycrystalline silicon thin-film transistors (poly-Si TFT's) with a high carrier mobility were fabricated at low processing temperatures of 150 and 250°C. A hydrogenated amorphous silicon (a-Si:H) film was successfully crystallized at room temperature by multistep irradiation of XeCl-308 nm excimer laser pulses without explosive evaporation of hydrogen. The poly-Si TFT's fabricated by the 250°C process had a carrier mobility of 54 cm2/Vs and a low potential barrier height at a grain boundary of 0.01 eV.

Ion-assisted deposition of mixed Tio2-Sio2 films

Abstract: Mixed thin films of TiO2 and SiO2 were produced by coevaporation from separate electron‐beam sources and simultaneous bombardment of the growing film with oxygen ions. The optical properties of the films were determined during growth by in situ ellipsometry and the surface composition of the deposited films studied by in situ ion scattering spectroscopy, ex situ x‐ray photoelectron spectroscopy, and energy filtered electron diffraction. The correlation between the optical and surface characterization is presented. There is evidence of local variations in the relative concentrations of TiO2 and SiO2. The position of the Si 2p binding energy depends on the TiO2 content in the film, indicating the possible formation of an intimate mixture.

Metalorganic Deposition (MOD): A Nonvacuum, Spin-on, Liquid-Based, Thin Film Method

Abstract: There are many methods of depositing thin film materials: thermal evaporation, sputtering, electron or laser beam evaporation, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE). A good survey of many of the deposition methods appears in the 1988 November and December issues of the MRS BULLETIN. One method not included in that survey, however, is metalorganic deposition (MOD), a powerful method for depositing a variety of materials.Metalorganic deposition is not to be confused with metalorganic chemical vapor deposition (MOCVD), which is a gaseous deposition method. MOD is a nonvacuum, liquid-based, spin-on method of depositing thin films. A suitable organic precursor, dissolved in solution, is dispensed onto a substrate much like photoresist. The substrate is spun at a few thousand revolutions per minute, removing the excess fluid, driving off the solvent, and uniformly coating the substrate surface with an organic film a few microns thick. The soft metalorganic film is then pyrolyzed in air, oxygen, nitrogen, or other suitable atmosphere to convert the metalorganic precursors to their constituent elements, oxides, or other compounds. Figure 1 shows a schematic of the deposition process including a prebake and annealing (if necessary).

Laser-induced forward transfer: A new approach for the deposition of high T c superconducting thin films

Abstract: We propose in this work a new approach, named laser-induced forward transfer, for the rapid deposition and patterning in a clean environment of high {ital T}{sub {ital c}} superconducting thin films. A stoichiometric high {ital T}{sub {ital c}} compound is initially deposited in a thin layer on an optically transparent support by laser evaporation or another more conventional technique. By irradiating under vacuum or in air the precoated layer with a strongly absorbed single laser pulse through the transparent support, we are able to remove the film from its support to be transferred onto a selected target substrate, held in contact to the original film. Using this technique, we have successfully transferred with one single pulse, provided by an excimer or a Nd:YAG laser, YBaCuO and BiSrCaCuO precoated thin films on various substrates. The Rutherford backscattering spectrometry experiments do not show any strong modification in the composition of the transferred layer against the source material, and the superconducting phases for the two types of compounds were obtained after subsequent thermal annealing carried out in a furnace around 850--900 {degree}C in O{sub 2}. For the BiSrCaCuO films transferred onto MgO, substrates we have measured an onset critical temperature of about 90more » K with a zero resistance at 80 K.« less

In situ growth of superconducting YBaCuO using reactive electron-beam coevaporation

Abstract: Conditions required for in situ growth of YBaCuO thin films by reactive electron-beam evaporation have been explored. Three sources of activated oxygen (atomic oxygen from microwave discharge, plasma generated by electron beams, and an ion beam) were compared. The best results so far were obtained with atomic oxygen. Epitaxial films with high critical currents were grown on SrTiO/sub 3/ [100] and [110], Al/sub 2/O/sub 3/ (1102), and MgO [100] at 600 degrees C. Evaporation rates were controlled with a rate monitor using atomic absorption. >

High-quality optical and epitaxial Ge films formed by laser evaporation

Abstract: High‐quality thin films of Ge were deposited by pulsed laser evaporation of molten Ge. Films deposited on 300 °C substrates showed very smooth morphologies and single‐crystal grain structures. Energetic ions in the vapor stream, generated by the laser‐induced plasma, were observed to affect nucleation and bulk‐film growth. Films deposited on ambient temperature substrates by laser evaporation were denser, harder, and exhibited higher values of refractive index and lower levels of intrinsic stress than the films deposited by thermal evaporation.

Thin Film Growth of YBa 2 Cu 3 O 7− x by ECR Oxygen Plasma Assisted Reactive Evaporation

Abstract: A new apparatus equipped with an ECR oxygen plasma source, a co-evaporation system of Y, Ba and Cu and a differential pumping system was developed. YBa2Cu3O7-x superconducting films were obtained at a substrate temperature of 450–500°C. The critical temperatures of films deposited on SrTiO3, MgO and Si substrates were 87 K, 80 K and 63 K, respectively. These properties were closely related to the crystallinity of the film.

Angular‐selective optical properties of Cr films made by oblique‐angle evaporation

Abstract: Thin Cr films were made by oblique‐angle evaporation onto glass. Electron microscopy showed an inclined columnar microstructure. Spectrophotometry yielded a strongly angular‐selective p‐polarized transmittance, consistent with recent theoretical notions, of potential interest for energy‐efficient windows.

In situ reflection high energy electron diffraction observation during growth of YBa2Cu3O7−x thin films by activated reactive evaporation

Abstract: Epitaxial growth of (001) oriented YBa2Cu3O7-x (YBCO) on SrTiO3(100) and MgO(100) by activated reactive evaporation was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED observation of the YBCO films on both the substrates demonstrated the formation of the perovskite structure even at initial deposit. A sharp streak in every deposition stage revealed the layer-by-layer growth. The initial deposit on the substrate of MgO with the large mismatch of 9% kept the same in-plane lattice spacing as MgO. The lattice spacing converted from the bulk value of MgO to that of YBCO when the layer became thicker than 12 A.

Crystallographic characteristics and electrical properties of Al‐doped ZnO thin films prepared by ionized deposition

Abstract: Aluminum‐doped ZnO thin films were prepared by ionized deposition on glass substrates. The crystallinity and electrical properties of Al‐doped ZnO films prepared by ionized evaporation depend on the deposition conditions. The c‐lattice constant of ZnO films increases with ionization current and acceleration voltage. The spacing distribution of c‐lattice planes varies inversely with the orientation distribution of the c axis, when deposition conditions such as ionization current, acceleration voltage, and substrate temperature are changed; the line width B002 of a (002) diffraction peak increases while the FWHM of rocking curve ΔΘ50 decreases. These changes of crystallographic characteristics cause a decrease in Hall mobility, and defects in the film resulting from ion bombardment cause a decrease in carrier concentration. Therefore, an increase in resistivity is observed in Al‐doped ZnO films grown by ionized deposition. Ion bombardment during deposition must be minimized to avoid degradation of Al‐doped ...

Effects of substrate temperature on absorption edge and photocurrent in evaporated amorphous SnS2 films

Abstract: The optical gap Eo and photocurrent peak Ep were investigated in amorphous SnS2 films evaporated onto glass substrates kept at a temperature from 294 to 609 K. For substrate temperatures up to 343 K, the film grew into an amorphous state with Eo=1.05+or-0.1 eV and Ep=2.1+or-0.05 eV. With increasing temperature, Eo increased markedly to 1.93 eV, while Ep decreased to 1.50 eV. By considering the results of radial distribution function obtained from the analysis of X-ray diffraction, the increase of Eo was explained in terms of a transition from an amorphous to a polycrystalline state. The substrate temperature dependence of the density of states was discussed including the result of two-step activation processes of electrical conductivity.

Method of making mixed metal oxide coated substrates

Abstract: In a reactive ion plating process utilizing radio frequency power, the rate of evaporation of a noble metal such as ruthenium or iridium, the rate of evaporation of a valve metal such as titanium, and the partial oxygen pressure are adjusted to produce electrically conductive mixed metal oxide ceramic coating on a valve metal substrate. The noble metal constitutes 10-20 percent of the metal atoms in the coating. The coated substrate can sustain 150 amperes per square meter of exposed coating surface in fresh water electrolyte for at least 20 hours, and preferably at least 75 hours, without an excessive increase in the voltage level required to maintain that current density.

Method of producing carbon-containing materials by electron beam vacuum evaporation of graphite and subsequent condensation

Abstract: A method of producing carbon-containing materials, residing in that, prior to electron-beam vacuum evaporation of graphite, on the surface of the graphite there is disposed a transition metal of Groups VI-VIII of the Periodic System or a mixture of at least two transition metals of said Groups, ensuring a higher rate of evaporation of graphite with respect to said metals or mixture, the metal or mixture is melted by an electron beam (10), evaporation of the graphite proceeding through the resulting melt (11) with subsequent condensation of the graphite on a support (4). In the course of gradual consumption of the graphite and said metal or mixture their supply into the resulting melt (11) is effected in such a manner that the consumed surface of the graphite should be completely overlapped by the melt (11).

Preparation of superconducting Tl-Ca-Ba-Cu thin films by chemical deposition

Abstract: A chemical deposition process for the preparation of superconducting thin films of Tl2CaBa2Cu2O8 (2122) and Tl2Ca2Ba2Cu3O10 (2223) has been developed. Oriented, superconducting 2122 and 2223 thin films have been successfully fabricated on single‐crystal yttria‐stabilized zirconia and magnesium oxide substrates (〈100〉 orientation). Epitaxial films have been prepared on magnesium oxide. Chemical analysis of the film composition by energy dispersive x‐ray analysis is in agreement (2122 vs 2223) with the phases indicated by powder x‐ray diffraction. The thin films of these compounds exhibited superconducting transition temperatures above 105 K as determined by variable‐temperature resistivity and ac magnetic susceptibility measurements. In addition, microwave surface resistance measurements at 150 GHz show that these films have very low losses at 77 K (1 mΩ).

Superconducting properties of laser evaporated epitaxial YBaCuO thin films

Abstract: Thin films of YBa 2 Cu 3 O 7 − x have been deposited on 〈100〉 SrTiO 3 by an excimer laser evaporation process from a stoichiometric 123 target with a substrate temperature between 720 and 780 °C and an oxygen partial pressure during the deposition in the range from 0.1 to 0.3 mbar. After the deposition the films were cooled to ambient temperature in situ within 1 h in flowing oxygen gas. X-ray analysis and transmission electron microscope investigations of the film-substrate interface indicate that the films did grow epitaxially in c axis orientation. The full-width half-maximum of the rocking curves of the (005) reflection is less than 0.65°. Susceptibility measurements and four-probe resistivity measurements show complete diamagnetism and zero resistance at 90 K, with a transition width of 2 K. At 100 K a resistivity of about 60 μΩ cm is observed. In films patterned by photolithography, critical current densities up to 5.2 × 10 6 A cm −2 in zero magnetic field and 3.0 × 10 5 A cm −2 at 2 T and 77 K are obtained.

Reactive deposition of hard coatings

Abstract: The reactive deposition of thin films is analyzed by means of a microphysical model. This model shows the way in which to (i) eliminate the hysteresis effect and (ii) control the deposition process. Special attention is devoted to physical parameters, such as fluxes of ions v i , metallic particles v m and reactive gas particles v r , the energy of particles bombarding the growing film and the substrate temperature which play a fundamental role in the deposition process, and to deposition systems with enhanced ionization. A correlation between (i) process parameters, (ii) microstructure, texture, phase and chemical composition of films, and (iii) resulting film properties is discussed in detail for Ti−N films. A comparison of arc evaporation and magnetron sputtering is also given. The need for equipment providing independent control of the deposition rate and ion bombardment of films is emphasized.

Evaporating and sputtering: Substrate heating dependence on deposition rate

Abstract: The deposition of copper into the through holes and vias of printed wiring boards (PWB’s) has been done using vacuum processing techniques such as evaporation and sputtering. One of the most important limiting factors for any deposition process is the substrate heating. The temperature of epoxy‐glass PWB’s should not exceed 180 °C (350 °F). For evaporation, there are two major contributions, the heat of condensation and radiant heating, with the heat of condensation dominating at deposition rates >2 μm/min. The radiant heating is very dependent on α e, the product of the substrate absorptivity and the source emissivity. Sputter deposition has two main sources of substrate heating: the heat of condensation and the kinetic energy of the incident atoms and ions. The experimental apparatus used to measure the power absorbed by a PWB substrate is described. Data are presented for the power absorbed by the substrate as a function of deposition rate for sputtered copper. These data are compared with the results ...

Structure and properties of c-BN film deposited by activated reactive evaporation with a gas activation nozzle

Abstract: This paper describes the structure and properties of cubic boron nitride (c-BN) film deposited using activated reactive evaporation with a gas activation nozzle. c-BN films deposited directly on various substrates showed very poor adhesion. It was found that a hexagonal phase of a few hundreda˚ngstroms thick was formed before the c-BN phase appeared and this resulted in poor adhesion. The adhesion characteristics of the c-BN film to the substrate were significantly improved by inserting silicon nitride interlayer. The micro Vickers hardness of a c-BN film of thickness 1.5μm was 5500– 6300 kg mm-2. As verified by a scratch test, a high substrate temperature effected good adhesion. The coefficient of friction for the c-BN film in contact with stainless steel was about 0.35 in air at ambient temperature, whereas at 1.7 × 10-3 Pa at 400 °C it was extremely low, 0.02.

Properties of aluminum nitride films by an ion beam and vapor deposition method

Abstract: Aluminum nitride (AlN) films were prepared by evaporation of aluminum and simultaneous irradiation with nitrogen ions in the low energy regions, 200–1000 eV. These films were formed on substrates of fused silicas at room temperature. XPS analysis revealed that the AlN bonding state varied with the composition ratio of aluminum and nitrogen. In films with Al/N > 1, these spectra showed clear peaks and humps due to AlN chemical bonding and metallic aluminum atoms. Properties of the optical transmittance and electrical resistivity depended on the ratio of Al/N. The films prepared with Al/N = 1 indicated that the transmittance was approximately 98% and the resistivity 10 14 Ω cm .

Quick Deposition of ZuS:Mn Electroluminescent Thin Films by Intense, Pulsed, Ion Beam Evaporation

Abstract: Electroluminescent ZnS:Mn thin films have been guickly deposited by a high-density, high-temperature plasma produced by the irradiation of an intense (>GW/cm2), pulsed (~tens of ns) ion beam onto a ZnS:Mn target The films prepared on a glass substrate have a polycrystalline hexagonal structure The temperature of the target plasma was estimated to be ~27 eV, where the plasma was highly ionized The instantaneous deposition rate was estimated to be ~4 cm/s, which is at least five orders of magnitude higher than that of any other conventional evaporation techique We have prepared a ZnS:Mn electroluminescent device with a luminescent layer having a thickness of ~200 nm The device has a threshold voltage of ~80 V0p (zero to peak value) The maximum luminance of 195 cd/m2 has been obtained under 10 kHz sinusoidal excitation at 144 V0p

Layer and director structure in surface stabilized ferroelectric liquid crystal cells with non-planar boundary conditions

Abstract: High resolution X-ray scattering studies of thin smectic C* (SC) samples prepared between solid plates coated with obliquely evaporated silicon monoxide to favor surface director orientation tilted out of the surface plane, reveal a local layer structure which is dependent on the evaporation directions on the plates. Samples with the evaporation directions antiparallel exhibit uniformly tilted layers. Those with parallel evaporation directions exhibit a zig-zag defect free chevron structure of tilted layers.

Tungsten oxide films by reactive and conventional evaporation techniques

Abstract: Tungsten oxide films (WO3) are deposited by thermal evaporation techniques using the starting materials of tungsten (W) and tungsten oxide (WO3). By varying deposition parameters, three main types of WO3 film exhibiting different optical properties form. These are blue, gray, and colorless films. The samples are characterized optically and morphologically. Blue-colored samples exhibit a broad selective absorption peak around 1000 nm. Absorption of gray-colored samples spreads out in the visible region in an exponential form. The refractive indices of samples are between 1.9 and 2.1. The energy gap of blue and colorless samples is 3.32 eV, but that of the gray-colored samples is 3.18 eV and smaller. X-ray diffraction studies reveal that evaporated WO3 films are amorphous. Fourier transform infrared spectra of samples were studied to evaluate bond properties. Colorless near-stoichiometric tungsten oxide films exhibit three absorption peaks in the 1000–600-cm−1 window. These peak locations, in terms of cm−1 window. These peak locations, in terms of cm−1, are 669,737, and 813. In the colored samples, these three absorption peaks split into two peaks ~20 cm−1 apart.

Texture analysis of Al/SiO2 films deposited by a partially ionized beam

Abstract: The preferred crystallographic orientation, or texture, of aluminum films deposited on oxidized silicon by evaporation and by partially ionized beam (PIB) deposition is studied. Texture is quantified by the x‐ray diffraction pole figure technique. The pole figures reveal important details of the crystallite distribution not quantifiable by simply taking the 2θ scan. It is found that the films deposited by the PIB technique possess a very strong {111} fiber texture whose strength can be controlled by deposition conditions. Correlation between the strength of the texture and the electromigration lifetime is discussed.

YBa2Cu3O7 films grown on epitaxial MgO buffer layers on sapphire

Abstract: Epitaxial MgO up to 300 nm thick has been grown on sapphire substrates by electron-beam evaporation in UHV. The most important orientation was MgO(100)‖α-Al 2 O 3 (1 1 02) with [001]||[11 2 0] . It was necessary to anneal the sapphire/MgO bilayers in oxygen at 900°C to restore oxygen to the MgO film which was lost during its evaporation. Superconducting transition temperatures and orientations of crystalline as-deposited YBCO films grown on these buffer layers were comparable to that of films grown directly on MgO(100) single-crystal substrates.