Showing papers on "Evaporation (deposition) published in 1993"

Atomic force microscopy and surface-enhanced Raman spectroscopy. I. Ag island films and Ag film over polymer nanosphere surfaces supported on glass

Abstract: The surface roughness and nanometer scale structure of Ag films used for surface‐enhanced Raman scattering (SERS) are characterized using atomic force microscopy (AFM). Two important types of thin film based SERS‐active surface have been examined in this study: (1) Ag island films (AgIF’s) on smooth, insulating substrates and (2) thick Ag films evaporated over both preroughened and smooth substrates. AFM is demonstrated to be capable of quantitatively defining the three‐dimensional (3D) structure of these roughened surfaces. The effects of mass thickness, dm, and thermal annealing on the nanostructure of AgIF’s are studied in detail. Particle size histograms are calculated from the AFM images for both ‘‘as‐deposited’’ and annealed IF’s with dm=1.8 and 3.5 nm. Quantitative measurements of the SERS enhancement factor (EF) are coupled with the AFM data and interpreted within the framework of the electromagnetic theory of SERS. AFM images for thick evaporated Ag films over a monolayer of polymer nanospheres (AgFON) shows the clear presence of ‘‘random substructure roughness’’ reducing their utility as controlled roughness surfaces. Similar roughness structures are observed for thick evaporated Ag films on smooth, insulating substrates. Nevertheless, AgFON surfaces are demonstrated to be among the most strongly enhancing thin film based surfaces ever studied with EF’s comparable to those found for electrochemically roughened surfaces. Applications of FON surfaces to ultrahigh sensitivity SERS, anti‐Stokes detected SERS, and surface‐enhanced hyper‐Raman spectroscopy (SEHRS) are reported.

Structures and properties of electron-beam-evaporated indium tin oxide films as studied by x-ray photoelectron spectroscopy and work-function measurements

Abstract: Indium tin oxide (ITO) films deposited on single‐crystal Si wafers by the electron‐beam‐(EB) evaporation method have been investigated by x‐ray photoelectron spectroscopy (XPS) together with work‐function and resistivity measurements. The XPS studies suggest that all the ITO films consist of crystalline and amorphous phases. The amount of the crystalline phase with respect to the amorphous phase for the ITO films, deposited with the incident angle of the ITO vapor to the Si substrate θi at 0°, is smaller than that for the ITO films deposited at θi=45°. The amount of the crystalline phase hardly depends on the conditions of postdeposition heat treatments, while that of the amorphous phase increases by raising the temperature of the heat treatments. Metal indium present in the films deposited at θi=0° is transformed into amorphous indium oxide by heating at 450 °C in air. Metal tin is also present near the ITO/Si interface for the ITO films deposited at θi=0°. The work function of the ITO films deposited at...

Laser Ablation and the Production of Polymer Films

Abstract: The formation of high-quality thin films of polytetrafluoroethylene (PTFE) is important in many applications ranging from material reinforcement to molecular electronics. Laser ablation, a technique widely used to deposit a variety of inorganic materials, can also be used as a simple and highly versatile method for forming thin polymer films. The data presented show that PTFE films can be produced on various supports by the evaporation of a solid PTFE target with a pulsed ultraviolet laser. The composition of the ablation plume suggests that PTFE ablation and subsequent film formation occur by way of a laser-induced pyrolitic decomposition with subsequent repolymerization. The polymer films produced by this method are composed of amorphous and highly crystalline regions, the latter being predominantly in a chain-folded configuration with the molecular axis aligned parallel to the substrate surface.

Quenching of porous silicon photoluminescence by deposition of metal adsorbates

Abstract: Various metals were deposited on luminescent porous silicon (PS) by immersion in metal ion solutions and by evaporation. The photoluminescence (PL) was quenched upon immersion in ionic solutions of Cu, Ag, and Au but not noticeably quenched in other ionic solutions. Evaporation of 100 A of Cu or 110 A of Au was not observed to quench PL. Auger electron spectroscopy performed on samples quenched and then immediately removed from solution showed a metallic concentration in the PS layer of order 10 at.%, but persisting to a depth of order 3000 A.

Pulsed laser deposition of thin metallic alloys

Abstract: The pulsed KrF excimer laser ablation was applied for the preparation of thin metallic alloys. Above an ablation threshold of about 5 J/cm2, an explosive evaporation of the target material occurs leading to high deposition rates of up to 3 nm/s and a stoichiometry transfer between the target and the deposited film. The surfaces of the grown amorphous and polycrystalline films are smooth except for a small number of droplets. The pulsed laser ablation was found to be an attractive alternative to other film deposition techniques, not only for high‐temperature superconductors, semiconductors, and insulators, but also for metallic alloys.

Fabrication of high aspect ratio silicon pillars of <10 nm diameter

Abstract: We report the fabrication of high aspect ratio, sub‐10 nm size, structures in silicon without involving any wet chemical etching. A 50 nm thick double layer of low and high molecular weight polymethylmethacrylate resist was exposed with an 80 kV electron beam of diameter smaller than 5 nm. After exposure the resist was developed in 3:7 cellusolve: methanol with ultrasonic agitation during development. A 5 nm thick AuPd film was deposited by ionized beam evaporation and a metal pattern was obtained by liftoff. Sub‐10 nm AuPd dots were recorded with a scanning electron microscope. The AuPd pattern was then used as a mask on the Si substrate which was etched with reactive ion etching. Silicon nanocolumns with diameters ranging from 5 to 7 nm and an aspect ratio of height to diameter of about 7:1 were obtained.

Growth and characterization of (111) and (001) oriented MgO films on (001) GaAs

Abstract: The effects of substrate preparation on the structure and orientation of MgO films grown on (001) GaAs using pulsed laser deposition has been investigated. Textured MgO films displaying a (111)MgO∥(001)GaAs orientation relation with x‐ray rocking curve full width at half maximum (FWHM) values as low as 1.8° were obtained in cases where the native GaAs surface oxide was only partially desorbed prior to growth. Reflection high‐energy electron diffraction, transmission electron microscopy (TEM), and x‐ray pole figure analysis of these films reveals a preferential orientation within the plane of the substrate: [110]MgO∥[110]GaAs and [112]MgO∥[110]GaAs. An interfacial layer (∼5 nm thick) was observed in high resolution TEM analysis, and was attributed to a remnant native GaAs oxide layer. Complete desorption of the native GaAs oxide at ∼600 °C in vacuum prior to MgO growth led to significant surface roughening due to Langmuir evaporation, and resulted in randomly oriented polycrystalline MgO films. Growth o...

On-chip screen type solid state image sensor and manufacturing method thereof

Abstract: A first P-type diffusion layer is formed on a semiconductor substrate. A photodiode is formed thereon. A transfer channel is formed on the semiconductor substrate. Agate insulating film is grown from a silicon oxide film on the semiconductor substrate. A transfer gate electrode is formed on the gate insulating film by patterning polysilicon. A light-shielding film of a metallic evaporation film is formed on the transfer gate electrode so that light cannot enter the transmission channel only to be a smear component. A difference in level of about 2 to 4 μm is formed on the semiconductor substrate of the transfer channel due to the transfer gate electrode and the light-shielding film. An underlying smooth layer is formed to smooth the surface difference in level, and a first light-shielding layer is formed on it. A transparent film is formed on it, and a third light-shielding layer is formed via a second light-shielding layer and a transparent film. Further, a transparent film having the same material and the same film thickness as the above transparent film covers the third light-shielding layer, and then is smoothed. An on-chip lens is formed on it. Thus, a negative influence of a flare light can be prevented.

Refractory metal capped low resistivity metal conductor lines and vias formed using PVD and CVD

Abstract: Capping a low resistivity metal conductor line or via with a refractory metal allows for effectively using chemical-mechanical polishing techniques because the hard, reduced wear, properties of the refractory metal do not scratch, corrode, or smear during chemical-mechanical polishing. Superior conductive lines and vias are created using a combination of both physical vapor deposition (e.g., evaporation or collimated sputtering) of a low resistivity metal or alloy followed by chemical vapor deposition (CVD) of a refractory metal and subsequent planarization. Altering a ratio of SiH₄ to WF₆ during application of the refractory metal cap by CVD allows for controlled incorporation of silicon into the tungsten capping layer. Collimated sputtering allows for creating a refractory metal liner (15) in an opening (14) in a dielectric (11-13) which is suitable as a diffusion barrier to copper based metallizations (16) as well as CVD tungsten. Ideally, for faster diffusing metals like copper, liners are created by a two step collimated sputtering process wherein a first layer is deposited under relatively low vacuum pressure where directional deposition dominates (e.g., below 1mTorr) and a second layer is deposited under relatively high vacuum pressure where scattering deposition dominates (e.g., above 1mTorr). For refractory metals like CVD tungsten, the liner can be created in one step using collimated sputtering at higher vacuum pressures.

Incongruent transfer in laser deposition of FeSiGaRu thin films

Abstract: The laser ablation and deposition of FeSiGaRu is studied. The deposited thin films are analyzed with Auger electron spectroscopy and Rutherford backscattering spectrometry. It is found that the gallium and ruthenium content of the thin films is strongly dependent on the laser fluence. At high laser fluences (6 J/cm2) the thin films are depleted of gallium due to preferential sputtering of the gallium atoms from the thin film. Near the threshold fluence (1.9 J/cm2) the films contain an excess of gallium due to preferential evaporation of gallium from the target. The latter conclusions are based on time‐of‐flight studies of ablated atoms and ions and on measurements of the atoms that are sputtered from the substrate by the incoming flux.

The influence of microstructure on the electrochromic properties of LixWO3 thin films: Part I. Ion diffusion and electrochromic properties

Abstract: The chemical diffusion coefficients of lithium ions in LixWO3 films were investigated as a function of lithium concentration and film porosity. Thin films were deposited with different porosities by thermal evaporation of WO3 powder in various partial water pressures. Our results indicate that diffusion coefficients increase with film porosity and decrease with increasing lithium concentration. Large diffusion coefficients that were found for small lithium concentrations appear to be due to the contribution of protons generated from ion exchange reactions between lithium and water incorporated in the film. Simultaneous electrical and in situ optical measurements were carried out to study the effect of porosity on the electrochromic properties of LixWO3. The coloring efficiency of porous WO3 films increases by approximately 70% when deposited in partial water pressure of 10−4 Torr, but decreases with further increments in water pressure.

Comparative study of titanium dioxide thin films produced by electron-beam evaporation and by reactive low-voltage ion plating

Abstract: Titanium dioxide (TiO(2)) is often used as a high refractive-index material for multilayer optical coatings. However, the optical properties of TiO(2) films depend strongly on the deposition process and its parameters. A comparative study of TiO(2) films fabricated by conventional electron-beam evaporation and by reactive low-voltage ion plating that uses different phases of Ti-O as starting materials is reported. Results on the variability of TiO(2) thin films are analyzed in relation to process parameters. The potential of fabricating high and low refractive-index multilayer stacks with TiO(2) only, by employing two different deposition processes, is presented with a practical example.

Influence of ZnO evaporation on microwave dielectric loss and sinterability of Ba(Zn1/3Ta2/3)O3 ceramics

Abstract: Evaporation of ZnO caused an inhomogeneous and complicated densification process for Ba(Zn 1/3 Ta 2/3 )O 3 ceramics. Densification near the surface was retarded by ZnO evaporation. It was found that homogeneous densification was obtained by sintering with ZnO powder muffling. Formation of an extraphase was suppressed by ZnO muffling. The sinterability of these ceramics was sensitive to preparation conditions. Small deviations in composition from the stoichiometric composition had a significant influence on sinterability. SiO 2 additions were found to improve sinterability.

Multi-phase back contacts for CIS solar cells

Abstract: Multi-phase, single layer, non-interdiffusing M-Mo back contact metallized films, where M is selected from Cu, Ga, or mixtures thereof, for CIS cells are deposited by a sputtering process on suitable substrates, preferably glass or alumina, to prevent delamination of the CIS from the back contact layer. Typical CIS compositions include CuXSe 2 where X is In or/and Ga. The multi-phase mixture is deposited on the substrate in a manner to provide a columnar microstructure, with micro-vein Cu or/and Ga regions which partially or fully vertically penetrate the entire back contact layer. The CIS semiconductor layer is then deposited by hybrid sputtering and evaporation process. The Cu/Ga-Mo deposition is controlled to produce the single layer two-phase columnar morphology with controllable Cu or Ga vein size less than about 0.01 microns in width. During the subsequent deposition of the CIS layer, the columnar Cu/Ga regions within the molybdenum of the Cu/Ga-Mo back layer tend to partially leach out, and are replaced by columns of CIS. Narrower Cu and/or Ga regions, and those with fewer inner connections between regions, leach out more slowly during the subsequent CIS deposition. This gives a good mechanical and electrical interlock of the CIS layer into the Cu/Ga-Mo back layer. Solar cells employing In-rich CIS semiconductors bonded to the multi-phase columnar microstructure back layer of this invention exhibit vastly improved photo-electrical conversion on the order of 17% greater than Mo alone, improved uniformity of output across the face of the cell, and greater Fill Factor.

Transparent Gas Barrier Technologies

Abstract: Transparent gas barriers are receiving considerable attention in the plastics industry for roll coating applications. The three principle vacuum deposition processes, evaporation, sputtering and plasma processing are the focus of transparent gas barrier work at various converters, resin producers and equipment manufacturers. Evaporation produces coatings at very high rates, but plasma processing has reported the best gas barrier results to date [ < 0.06 cc/100 in2/day for single-sided coatings on 0.5 mil polyethylene terephthalate (PET)]. Sputtering rates are lower than evaporation rates, but can produce a wide range of transparent oxides including the material of interest, silica. Evaporated, sputtered and plasma deposited coatings were produced and com pared in terms of oxygen gas transmission and film stoichiometry. The plasma deposted coatings provided the best gas barriers and initial results show that the plasma processed barrier coatings are commercially feasible.

Advances in cathodic arc technology using electrons extracted from the vacuum arc

Abstract: The cathodic arc, as used in vacuum deposition equipment, generates a highly ionized metal vapor. In current industrial practice, this is used for heating and ion etching the substrate, as well as for the actual deposition process. Electrons generated at the same time as the metal ions can be used to modify and extend the process technology. This paper discusses the basic physical principles of utilizing these electrons through the application of subsidiary electrical fields. Thee types of application are discussed: substrate heating by electron impact; ion sputter cleaning using gas ions generated with an arc-enhanced glow discharge; anodic evaporation of metals in reactive and non-reactive gas atmospheres.

Properties of chromium nitride coatings deposited by cathodic arc evaporation

Abstract: CrN coatings deposited at 200–230°C (low temperature) and 480–540°C (high temperature) onto high speed steel were investigated by determining the microhardness, surface roughness and adhesion, as well as using scanning electron microscopy and X-ray diffractometry. It was found that the coatings deposited at lower temperatures exhibit higher hardnesses than those produced at higher deposition temperatures. Both coatings exhibit good adhesion and a dense structure morphology. Bulk X-ray diffraction studies show that, in both cases, the prevalent crystallographic orientation is [220].

Tungsten Films with the A15 Structure

Abstract: Influence of the atmosphere on the crystal structure of thin tungsten films produced by the evaporation method in vacuum was studied. While the crystal structure of the films produced in a high vacuum (e.g., 10-6 Pa) was bcc, the films took on an A15 structure in oxygen and nitrogen atmospheres (e.g., 10-4 Pa). This phenomenon did not occur with the introduction of inert gases such as helium and argon.

Silver‐gold compound metal island films prepared by using a two‐step evaporation method

Abstract: A silver‐gold compound metal island film prepared by using a two‐step evaporation method is demonstrated for the first time. Silver and gold islands have been completely alloyed by heating the film at 300 °C. The resonance wavelength of the compound metal island film exists between those of pure silver and pure gold island films. It is shown that the resonance wavelength can easily be controlled by selection of the mixture ratio of silver and gold.

Solid‐state bonding of accurately oriented metal/ceramic bicrystals in ultrahigh vacuum

Abstract: A machine is described which allows bicrystals of metals and ceramics to be made by pressure bonding at temperatures up to 1500 °C in ultrahigh vacuum (UHV). The mutual orientation of the two component crystals can be adjusted to within 0.1°. The surfaces to be bonded can be sputter cleaned with Ar ions while monitoring by Auger electron spectroscopy, and dopants can be applied by evaporation in a separate chamber. The machine allows the production of bicrystals with interfaces of precisely defined crystallography and chemistry. The specimen size is sufficient for fracture mechanical characterization of interface strength. The performance of the machine is illustrated with data for niobium‐sapphire bicrystals. The machine has been shown to produce bicrystal interfaces whose purity is not measurably impaired by atmospheric contaminants. Fracture resistant levels of Nb‐Al2O3 interfaces bonded at 1700 °C in ordinary high vacuum are reached in the UHV machine already at 1000 °C. Going to temperatures around 1...

Process for making thin polymer film by pulsed laser evaporation

Abstract: A process for producing thin film of a first addition polymer on a substrate comprising bombarding a target, consisting essentially of a second addition polymer, with radiation from a pulsed laser in a vacuum or gas atmosphere to form a plume of components of said second polymer; and depositing said plume on a substrate, whereby a film of said first polymer is formed. The first and second addition polymer may be identical or different and in both cases may be fluoropolymer.

CdSxTe1-x films: preparation and properties

Abstract: CdSxTe1-x films (0

X‐ray photoelectron spectroscopy study of the polypropylene–magnesium interface after in situ plasma and ion treatment: Sticking, bonding, and film growth

Abstract: A study on a model system for polymer–metal interface formation after surface treatment is presented. We discuss a comparative x‐ray photoelectron spectroscopy analysis of in situ plasma and ion‐treated polypropylene surfaces with an evaporated magnesium overlayer. The different surface treatments are found to enhance the sticking probability of the metal vapor on the polymer surface considerably. Depending on the kind of surface treatment, different types of bonding of the Mg with the polymer are observed. The analysis of the excited plasmons is used to gain information about the interface formation. The experimental results suggest an island growth mode of the Mg.

Arc-enhanced glow discharge in vacuum arc machines

Abstract: Vacuum cathodic arc evaporation is well established for the industrial deposition of a variety of hard and metallic coatings for different applications. The standard heating and ion-cleaning processes are easily carried out by the metal ion bombardment generated by the vacuum arc. A novel method for heating and ion cleaning based on a dense argon plasma produced by the electrons from the vacuum arc is presented, namely the arc-enhanced glow discharge (AEGD). In addition to selected plasma parameters, some characteristics features of TiN coatings deposited by AEGD surface conditioning are presented.