Liquid Phase Deposition Technique Research Articles

Characterization of methylene blue/TiO 2 hybrid thin films prepared by the liquid phase deposition (LPD) method: Application for fabrication of light-activated colorimetric oxygen indicators

Methylene blue (MB)/TiO 2 hybrid nanocomposite material has been successfully deposited on both bare glass and indium tin oxide (ITO) covered glass by the liquid phase deposition (LPD) technique. LPD method is applied to one-step hybrid dye/TiO 2 deposition. An optimized amount of MB is added to the fluoride titania precursor aqueous solution in order to entrap this dye within the growing thin film of TiO 2, yielding a MB/TiO 2 nanocomposite material. Stable, well-adhered, intense blue-colored and optically transparent coatings have been obtained. The formation of the material can be explained by electrostatic interaction between negative charge density at the fluorinated surface of TiO 2 and the cationic dye. MB/TiO 2 nanocomposite material has been characterized by ATR-FT-IR, UV–vis spectroscopy, SEM, TEM, grazing angle XRD and cyclic voltammetry (CV). Deposited hybrid films exhibit photochemical activity: MB is photobleached upon UVA irradiation, using triethanolamine (TEOA) as mild sacrificial electron donor. Moreover, light-activated oxygen indicators with high optical transparency and delayed response can also be satisfactory fabricated by spin-coating a solution of TEOA with an encapsulating polymer (hydroxyethyl cellulose) over the MB/TiO 2 hybrid films.

Alternative fluoride scavengers to produce TiO2films by the liquid phase deposition (LPD) technique

TiO2 films have been deposited on bare glass and on glass coated with indium tin oxide (ITO) by the liquid phase deposition (LPD) method, using Al(III) nitrate and Fe(III) chloride as alternative fluoride scavengers. Films were characterized by grazing angle X-ray diffraction, scanning electron microscopy, UV-vis spectra, X-ray photoelectron spectroscopy and photoluminescence. Results are compared with those obtained using boric acid, which is commonly used as a scavenger in the LPD technique. Well adhered films, 250–450 nm thick, were obtained after 3 h of deposition process at 80 °C (353 K). While Al(III) is not significantly incorporated on the film, in the case of Fe(III) considerable incorporation of this element is observed. When Al(III) nitrate is used as a scavenger instead of boric acid, the deposition rate is nearly doubled. Furthermore, the effect of the substrate on the TiO2 crystal growth has been addressed. On bare glass, the low number of nucleation sites, slightly influenced by the scavenger nature, causes a partial coverage of the substrate. Glass pretreatment for 30 min with a H2TiF6 aqueous solution at 80 °C noticeably increases the nucleation site density, leading to continuous transparent film deposition. Coherent films were deposited on ITO surfaces as this substrate favors the nucleation of TiO2.

Fabrication silver film inside silica capillary

To study hollow waveguides for CO2 laser transmission, a liquid-phase deposition technique is applied to form a silver film inside silica capillary based on the method of silver mirror reaction. Using this fabrication method, the optimum combination of different parameters is gained and hollow waveguides have been made successfully with a bore size of 1mm and a guide with length of as long as 2m on self-producing apparatus. To meet quality silver film, a relative high temperature, low flowing speed and long time are adopted on the basis of low reactant concentration. The maximum transmission efficiency of hollow-core fiber without dielectric coating can be up to 85 percent and loss can be low to 0.5dB/m, maximum output power is 53W for stable 20 mintues.

P-42: Development of CNT Cathodes for Field-Emission FPDs by Liquid-Phase Fabrication

Fabrication of CNT pattern by liquid-phase based deposition technique has been studied in Xintek for several years. By using this technique, we successfully fabricated sealed CNT field emission display prototypes with diode structures. The CNT panel size has been scaled up from 4 inch to 8 inch. Patterned CNT cathode was made by incorporating photolithography techniques into the liquid-phase deposition process. CNT pattern size of 50 um was achieved on our standard (unpolished) display substrates. A simple substrate polishing process could reduce the CNT pattern size down to 20 um. It indicates that high-resolution displays are possible by improving the surface smoothness of the substrates. The patterned CNT cathodes demonstrated good field emission characteristics including low turn-on field and high emission current density. However, the emission uniformity remains to be a major concern. The global emission uniformity of the CNT panels can be improved through more engineering efforts. We believe that the emission uniformity in pixel can be enhanced by optimization of the liquid-phase deposition process and CNTs concentration, distribution as well as morphology in the cathodes. Liquid-phase deposition technique can also deposit CNTs into preformed triode structures with the aid of photolithography techniques.

Fabrication technique for filling-factor tunable titanium dioxide colloidal crystal replicas

Filling-factor tunable titanium dioxide replicas of colloidal crystals were fabricated by using a liquid phase deposition (LPD) technique. Ammonium hexafluorotitanate [(NH4)2TiF6] was used as a precursor, which was converted slowly to titanium dioxide by hydrolysis with boric acid. After the oxide was formed in voids of latex colloidal crystals, the latex was removed by calcination. By applying the LPD process to the replica again, the filling factor of the replica could be increased in a controllable fashion. With 203 nm template spheres, the peak shift in the ∼490 nm stop band depended linearly on the deposition time for the first 20 min, at a rate of 4.4 nm/min. Thus the position of the Bragg reflection peak could be adjusted precisely by controlling the filling factor of the replica structure.

A review of thin-film crystalline silicon for solar cell applications. Part 1: Native substrates

Approximately half the cost of a finished crystalline silicon solar module is due to the silicon itself. Combining this fact with a high-efficiency potential makes thin-film crystalline silicon solar cells a growing research area. This paper, written in two parts, aims to outline world-wide research on this topic. The subject has been divided into techniques which use native substrates and techniques which use foreign substrates. Light trapping, vapour- and liquid-phase deposition techniques, cell fabrication and some general considerations are also discussed with reference to thin-film cells.

Optical properties of fluorinated silicon oxide films by liquid phase deposition for optical waveguides

Optical properties of fluorinated silicon oxide (SiOF) films for optical waveguide in optoelectronic devices were investigated. The SiOF films are formed at 25/spl deg/C by a liquid phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H/sub 2/SiF/sub 6/) aqueous solution. Two main absorption peaks corresponding to Si-O and Si-F bonds were observed at the wavenumbers of 1090 and 930 cm/sup -1/ in Fourier transform infrared (FTIR) spectrum, respectively. The LPD-SiOF films show very little content of water components such as Si-OH bonds and OH group. Although the transmittance for 600-nm-thick LPD-SiOF film gradually decreased from the wavelength around 700 nm, the relative transmittances to quartz glass are over 98% in the wavelength region from 350-2500 nm. The concentration of fluorine atoms in the LPD-SiOF film was about 5%, and the calculated composition was SiO/sub 1.85/F/sub 0.15/. The calculated refractive index from the polarizability for LPD-SiOF film was 1.430, and agrees very well with the measured value at the wavelength of 632.8 nm by ellipsometry. The dispersion of refractive index was evaluated and fitted to a three-term Sellmeier's dispersion equation. The zero dispersion wavelengths for the LPD-SiOF and thermally grown SiO/sub 2/ films were 1.271 and 1.339 /spl mu/m, respectively.

Optical properties of small-bore hollow glass waveguides

Hollow glass waveguides with a 250-µm i.d. have been fabricated with a liquid-phase deposition technique that uses silica tubing as a base material. The losses of the 250-µm-bore guide measured at CO(2) laser wavelengths are as low as 2.0 dB/m. The straight losses for the hollow guides are in good agreement with theoretically predicted losses as a result of the nearly ideal structure of the guides. It is also shown that the guides have low bending losses, a nearly pure-mode delivery, and good high-power laser transmission. By proper design of the dielectric thickness, the guide is also able to deliver Er:YAG laser energy with a low loss of 1.2 dB/m for the 320-µm-bore waveguide. Because the hollow glass waveguide is very flexible and robust, it is quite suitable for medical applications.

Fluorinated interlayer dielectric films in ULSI multilevel interconnections

Fluorinated interlayer dielectric films for ultra large scale integrated circuit (ULSI) multilevel interconnections are investigated. The interlayer dielectric film properties and their formation techniques have to meet three requirements such as: (1) a high planarization capability, (2) a low dielectric constant and (3) a low deposition temperature. To satisfy the three requirements, the technologies such as (i) a fluorinated spin-on-glass (SOG) film by fluorotrialkoxysilane vapor treatment (FAST-SOG), (ii) a fluorinated SiO 2 (SiOF) film by room temperature chemical vapor deposition (RTCVD-SiOF) using fluorotrialkoxysilane (FTAS) and pure water as gas sources, (iii) a room temperature liquid phase deposition (LPD) SiO 2 film, and (iv) fluorinated polyimide siloxane (F-PSI) films are desirable. The RTCVD, FAST and LPD techniques have shown the possibility to reduce the film formation temperature to room temperature by catalytic reactions. The dielectric constant for SiO 2 films can be reduced to 3.7 at 1 MHz by using the RTCVD and LPD techniques. The dielectric constant of 2.7 at 1 MHz can be achieved for the F-PSI films, and is lower than those for conventional polyimide films (3.2–3.5) and SiO 2 films (3.9–4.2). Although the FAST-SOG, RTCVD-SiOF and F-PSI films cannot achieve full planarization, the LPD technique can achieve both global and local planarization because this technique has high capability for selective SiO 2 film deposition. The fluorinated films have other good properties such as low residual stress, low residual OH contents and low moisture absorption, which can enlarge the fabrication margins of multilevel interconnections. These other properties are also very effective for improving the ULSI devices performance.

Fluorinated SiO2 Films For Interlayer Dielectrics In Quarter-Micron Ulsi Multilevel Interconnections

AbstractFluorinated SiO2 films for use as interlayer dielectrics in ULSI multilevel interconnections are investigated. The interlayer dielectric film properties and their formation techniques have to meet the following requirements: (1) a low dielectric constant, (2) a high planarization capability, (3) a high capability for narrow gap filling, and (4) a low deposition temperature for low residual stress. To satisfy these requirements, three technologies have been investigated. They are: (i) a fluorinated SiO2 (SiOF) film by room temperature chemical vapor deposition (RTCVD-SiOF) using fluorotrialkoxysilane (FTAS) and pure water as gas sources, (ii) a room temperature liquid phase deposition (LPD) SiO2 film, and (iii) a fluorinated spin-on-glass (SOG) film by fluorotrialkoxysilane vapor treatment (FAST-SOG). The dielectric constant for SiO2 films can be reduced to 3.7 at 1 MHz by the RTCVD and LPD techniques. Although the FAST and RTCVD techniques cannot achieve full planarization, the LPD technique can achieve both global and local planarization because this technique has high capability for selective SiO2 film deposition. The RTCVD, FAST and LPD techniques have shown the possibility to reduce the film formation temperature to room temperature by catalytic reactions, resulting in low residual stress. Other properties of the RTCVD-SiOF, LPD-SiO2 and FAST-SOG films are good enough for the interlayer dielectric film application. The LPD-SiO2 film shows higher endurance properties to moisture than the RTCVD-SiOF and FAST-SOG films.

Planarization of amorphous silicon thin film transistors by liquid phase deposition of silicon dioxide

A planarized device structure was developed for amorphous silicon thin film transistors to overcome the gate leakage problem. Utilizing the liquid phase deposition technique, a silicon oxide film with thickness exactly equal to the gate height was grown around the gate to planarize the surface for the fabrication of inverted staggered thin film transistors. The planarized thin film transistor has smaller leakage current and better performance, i.e., field effect mobility, subthreshold swing, etc. This novel process has a potential to improve the yield of large area liquid crystal display.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Properties of liquid-phase-deposited SiO 2 films for interlayer dielectrics in ultralarge-scale integrated circuit multilevel interconnections

Properties of a new fluorinated SiO 2 film for interlayer dielectrics in multilevel interconnections of ultralarge-scale integrated circuits (ULSIs) are investigated. The fluorinated SiO 2 films are formed at 35 °C by a liquid phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H 2SiF 6) aqueous solution. The LPD SiO 2 film surface profiles on polysilicon and aluminum wirings are flat enough, indicating that the LPD technique has good capability for the surface planarization of interlayer dielectric films. The compositions of as-deposited LPD SiO 2 films and those annealed at 400 and 900 °C are SiO 1.85F 0.15, SiO 1.85F 0.15 and SiO 1.90F 0.10 respectively. The LPD SiO 2 film deposition mechanism is explained as follows: (i) fluorosilanols [F n Si(OH) 4− n ] formation; (ii) fluorosilanol oligomer formation by a catalytic reaction in the solution; (iii) oligomer adsorption onto the substrate surface; (iv) oligomer polymerization by a catalytic reaction. The absorption peak position, full width at half-maximum (FWHM) and absorption coefficient for the Si-O bond in the Fourier transform infrared spectra for the as-deposited LPD SiO 2 films are 9.17 micrometer, 0.83 micrometer and 1.19 × 10 6 m -1, respectively, indicating that the films are formed by tightly bonded Si-O networks. The as-deposited LPD SiO 2 films have a refractive index of 1.433, a density of 2.19 × 10 3 kg m -3, an etching rate (measured using 1:30 buffered hydrofluoric acid (HF) solution) of 83 nm min -1, and a residual stress of 20 MPa (tensile). The film shrinkages after annealing at 400 and 900 °C are 0.8% and 2.0% respectively. Although these properties are changed by annealing at 400 and 900 °C, these values are still better than those of SiO 2 films deposited by chemical vapor deposition (CVD) at 400 °C for use as interlayer dielectric films. The LPD SiO 2 films have better electrical properties, such as lower leakage current, higher dielectric breakdown strength (> 6.3 × 10 8 V m -1) and lower dielectric constant (< 3.9 at 1 MHz), than the CVD SiO 2 films.

Spatially resolved photoluminescence investigation of optical damage induced by SiNx deposition in InGaAs

Spatially resolved photoluminescence (SRPL) was used as a tool to study the effect of SiN x deposition by plasma-enhanced chemical vapor deposition on n-type InGaAs layers grown on InP substrates by liquid phase and metal-organic chemical vapor deposition techniques. With the SiN x deposition parameters fixed, the “recovery” of the photoluminescence (PL) signal (band edge) was monitored as a function of thermal annealing and incident laser beam power, therefore investigating the optical damage induced by the SiN x deposition and the effect on the damage of the annealing process. Successive etchings of the InGaAs epilayer followed by PL measurements suggest that the depth of the optical damage (as indicated by PL intensity signal recovery) is a function of the epilayer crystal quality and depends critically on the thermal annealing. Samples with no thermal annealing showed a fast recovery of the PL signal, indicating a very shallow damaged layer.

A Selective SiO2 Film‐Formation Technology Using Liquid‐Phase Deposition for Fully Planarized Multilevel Interconnections

A selective film‐formation technology using liquid‐phase deposition (LPD) around room temperature for fully planarized multilevel interconnections is developed. The LPD technique utilizes supersaturated hydrofluosilicic acid aqueous solution as a source liquid. The films can be selectively formed on chemical vapor deposition (CVD) underlayers in the trenches between photoresist patterns or tungsten wiring with photoresist as mask. For polysilicon patterns with photoresist masks, the films creep along the polysilicon and photoresist sidewalls. The selective deposition mechanism can be explained as siloxane oligomers, which are formed in the supersaturated aqueous solution, have different chemical reactivity between the photoresist and substrate surface. Global planarization of trenches between tungsten wiring is achieved, using the selective deposition technique. A fully planarized double‐level tungsten interconnection is realized using both selective film deposition and selective tungsten CVD via filling. Low contact resistance of ca. 0.3 Ω/unit is achieved for via holes 0.8 μm in diam.

Liquid and vapour phase deposition techniques for powder coating: B.V. Nita et al (Rensselaer Polytechnic Inst, Troy, New York, USA)

Liquid and vapour phase deposition techniques for powder coating: B.V. Nita et al (Rensselaer Polytechnic Inst, Troy, New York, USA)