Vanadium(IV) oxide thin films on glass and silicon from the atmospheric pressure chemical vapour deposition reaction of VOCl3 and water

The dual source atmospheric pressure chemical vapour deposition (APCVD) reaction of VOCl₃ and H₂O was used to prepare thin films of vanadium oxides on glass and silicon substrates. The thin films were characterised by X-ray diffraction, Raman spectroscopy X-ray photoelectron spectroscopy and scanning electron microscopy. At reactor temperatures above 600 °C with a gas-phase excess of water over VOCl₃, vanadium(IV) oxide thin films were produced which show a thermochromic transition temperature of 67 °C. The APCVD process is directly compatible with high throughput float-glass production enabling the use of a thin film of VO₂ as an intelligent window coating. With reactor temperatures below 600 °C or with a gas-phase excess of VOCl₃ over water, V₂O₅ thin films were produced. Vanadium(IV) oxide thin films could also be prepared on silicon substrates from the APCVD reaction of VOCl₃ and H₂O, which opens up further technological applications for the APCVD of VO₂ thin films.     

Syntheses, X-ray structures and CVD studies of diorganoalkoxogallanes

Structural studies by X-ray crystallography have been carried out for a range of diorganoalkoxogallanes incorporating donor-functionalized ligands. The compounds [Et₂Ga(μ-OR)]₂ (1, R = CH₂CH₂NMe₂; 2, R = CH(CH₃)CH₂NMe₂; 3, C(CH₃)₂CH₂OMe; 4, R = CH(CH₂NMe₂)₂) adopt dimeric structures with a planar Ga₂O₂ ring, and each gallium atom is coordinated in a distorted trigonal bipyramidal geometry. Low pressure chemical vapor deposition (CVD) of 2 and 4 resulted in the formation of oxygen deficient gallium oxide thin films on glass. However, the reaction of Et₃Ga and ROH (R = CH₂CH₂NMe₂, CH(CH₃)CH₂NMe₂, C(CH₃)₂CH₂OMe, CH(CH₂NMe₂)₂) in toluene under aerosol assisted (AA)CVD conditions afforded stoichiometric Ga₂O₃ thin films on glass. This CVD technique offers a rapid, convenient route to Ga₂O₃, which involves the in situ formation of diethylalkoxogallanes, of the type [Et₂Ga(μ-OR)]₂, the structures of which are described in this paper. The gallium oxide films were deposited at 450 °C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.     

Preparation and Characterization of CuInS2 Thin Films for Solar Cells by Chemical Bath Deposition

Introduction Recent years, chalcopyrite semiconductors have been successfully applied as absorber layers for polycrystalline thin-film solar cells. Among the ternary compound semiconductors, CuInS2 thin films with a direct bandgap of about 1.50 eV and a large absorption coefficient in the range of 104-105cm-1[1] are one kind of the most promising optical absorbers for high efficiency thin film solar cells.To date, CuInS2-based solar cells have shown conversion efficiency of about 12. 5%[2]. They exhibit long-term stability without any signs of degradation.     

Model of electrochromic and related phenomena in tungsten oxide thin films

We have developed a model of electrochromic and related phenomena in tungsten oxide thin films based on the assumption that the constitution of such films is heterogeneous and built up of nanosized particles, pores and adsorbed substances (mainly water). It is discussed why a high-efficiency reversible blue colour is observed in amorphous tungsten oxide films (α-WO₃ films) as well as why such porous thin films with polycrystalline or amorphous constitution and with a variety of particle properties can be easily obtained by a physical vapour deposition process in a low-pressure atmosphere in the presence of water. A substrate temperature in the range 450–550 K corresponds to some plateau on the water desorption curves which divided physically adsorbed water from chemically adsorbed water. Two types of structural units based on tetrahedrally and octahedrally coordinated tungsten ions have the main role in the formation of the film constitution. The tetrahedral structural units have a glass-forming function, but the octahedral ones have a modification function. From the electrochemistry point of view, the internal multiphase interfaces in such films are distributed multiphase electrodes. The adsorbed water together with defects of the oxide particles provide reagents for reversible coloration reactions in the film. The colour centres can be induced thermally (oxygen nonstoichiometry) or electrically (injected ions) or by radiation (photoinjected hydrogen). The electrochromism and related phenomenon of α-WO₃ films can be directly related to ion insertion/extraction processes controlled by external forces. Electronic Publication     

Structure and optical properties of CVD molybdenum oxide films for electrochromic application

Vibrational and optical properties of MoO₃ thin films have been studied by Raman and infrared spectroscopy. The films were deposited onto Si substrates at a temperature of 150 °C by chemical vapor deposition of Mo(CO)₆ at atmospheric pressure and different amounts of oxygen in the reactor. The Raman and IR spectral analyses show that the as-deposited films are in general amorphous. Post-deposition annealing at 300 and 400 °C leads to crystallization and the MoO₃ film structure is a mixture of orthorhombic and monoclinic MoO₃ modifications. Transformation of the monoclinic crystallographic modification to a thoroughly orthorhombic layered structure is observed for films heated at temperatures above 400 °C. Electronic Publication     

Luminescence and dielectric properties of c-axis oriented (Bi1.90Eu0.10)(V1−zMoz)O5.5 ferroelectric thin films

(Bi_1.90Eu_0.10)(V_1−zMo_z)O_5.5 (z = 0, 0.05, 0.10, 0.15 and 0.20) thin films with c-axis oriented were prepared on Pt(111)/Ti/SiO₂/Si substrates by using chemical solution deposition method. The effect of Mo⁶⁺ concentration on the structure, luminescence properties and dielectric properties of the thin films were characterized systematically. X-ray diffraction data indicates that the thin films with low Mo⁶⁺-doping content can remain Bi₂VO_5.5 structure. When the Mo⁶⁺-doping content z reaches to 0.15, the thin films are a mixture of diphase with the main phase Bi₂VO_5.5 and secondary phase Bi₂MoO₆. Under UV irradiation, all the thin films emit a bright red or orange emission which origin from Eu³⁺. With increasing Mo⁶⁺-doping content z, the relative intensity of the Red and Orange emissions show obviously change. The value of Red/Orange ratio first decrease, and it reached minimum when z is 0.15, then it recover to the initial value. The variation trend of the Red/Orange ratio reflects the change of the lattice symmetry. Dielectric constant of the thin films increased with the increasing of the Mo⁶⁺ concentration while dielectric loss decreased. The decrease of the quantities of oxygen vacancies and the generation of Bi₂MoO₆ phase are responsible for the improvement of electric properties. These results explain that Eu³⁺ion can be used as an effective luminescent probe in (Bi_1.90Eu_0.10)(V_1−zMo_z)O_5.5 (z = 0, 0.05, 0.10, 0.15 and 0.20) thin films, and the electric properties of the thin films can be improved by Mo⁶⁺ doping.     

Chemical deposition of semiconducting cadmium selenide quantum dots in thin film form and investigation of their optical and electrical properties

Cadmium selenide quantum dots with cubic crystal structure are chemically deposited in thin film form using selenosulfate as a precursor for selenide ions and ammonia buffer with double role: as a ligand and as a pH value controller. The optical band gap energies of as-deposited and thermally treated cadmium selenide thin films, calculated within the framework of parabolic approximation for the dispersion relation, on the basis of equations which arise from the Fermi's golden rule for electronic transitions from valence to conduction band, are 2.08 and 1.77 eV, correspondingly. The blue shift of band gap energy of 0.34 eV for as-deposited thin films with respect to the bulk value is due to the quantum size effects (i.e., nanocrystals behave as quantum dots) and this finding is in agreement with the theoretical predictions. During the thermal treatment the nanocrystals are sintered, the increase of crystal size being in correlation with the decrease of band gap energy. The annealed thin films are practically non-quantized. From the resistance-temperature measurements, on the basis of the dependence of ln(R/Ω) vs 1/T in the region of intrinsic conduction, the thermal band gap energy (at 0 K) of 1.85 eV was calculated.     

Spectroscopic ellipsometry study of CVD molybdenum oxide films: effect of temperature

The optical properties of CVD MoO₃ films were studied by ellipsometry in the spectral range 280–820 nm. The films were deposited on silicon substrates by pyrolytic decomposition at atmospheric pressure of Mo(CO)₆ at 150 and 200 °C. To optimize the film structure, annealing was performed at temperatures of 300 and 400 °C. The refractive index for as-deposited MoO₃ films varies within 1.8–2.2 and the optical band gap energies in the range 2.87–2.98 eV. After annealing, the latter values slightly increase to 2.85–3.05 eV, depending on the annealing temperature. The band gap energies are typical for a polycrystalline material. Peaks in the spectral dependence of the absorption coefficient were observed. Their position and intensity are found to be affected by the process temperature. Electronic Publication     

Dielectric properties of Ca(Zr0.05Ti0.95)O3 thin films prepared by chemical solution deposition

Ca(Zr_0.05Ti_0.95)O₃ (CZT) thin films were grown on Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by the soft chemical method. The films were deposited from spin-coating technique and annealed at 928 K for 4 h under oxygen atmosphere. CZT films present orthorhombic structure with a crack free and granular microstructure. Atomic force microscopy and field-emission scanning electron microscopy showed that CZT present grains with about 47 nm and thickness about 450 nm. Dielectric constant and dielectric loss of the films was approximately 210 at 100 kHz and 0.032 at 1 MHz. The Au/CZT/Pt capacitor shows a hysteresis loop with remnant polarization of , and coercive field of 18 kV/cm, at an applied voltage of 6 V. The leakage current density was about at 3 V. Dielectric constant-voltage curve is located at zero bias field suggesting the absence of internal electric fields.     

Formation of High-quality Advanced High-k Oxide Layers at Low Temperature by Excimer UV Lamp-assisted Photo-CVD and Sol-gel Processing

IntroductionOne of the most critical challenges for deepsubmicron silicon researches is the technologicallimit to the use of silicon dioxide as the gate dielec-tric. For sub- 0 .1μm CMOS technology roadmapspredict the need for a sub- 2 nm Si- oxide gate di-electric[1,2 ] . Off- state tunnelling effects for transis-tors with gate oxide thickness below 2 nm lead tohigh leakage current densities of1 _ 1 0 A/cm2 [3 ] ,which become a serious obstacle for transistors,particularly for the rapidly …     

Recent advances in studies of bubble-solid interactions and wetting film stability

Research in the area of bubble-solid interactions is reviewed and highlighted, with a focus on studies of wetting film drainage using theoretical approaches and experimental (interferometric) approaches, and also studies probing the stability of wetting films, where the stability has been affected by physical and chemical modification/factors. Significant advances have been made in recent years in the area of interferometry and force measurement of bubble-surface encounters, with multiple light wavelengths used to improve accuracy and certainty with regard to thickness of wetting films, as well as high speed interferometry. These advances have been accompanied with improvements to models to describe nonequilibrium aspects of opposing interfaces. Experimental studies of the influence of air bubbles and surface roughness have highlighted the importance of dissolved gas and surface condition in determining whether wetting films are stable. Finally, many new studies on the influence of polymer layers on wetting film stability and rupture have been published, and these are described in relation to the increase in our understanding of the role of adsorbed polymers in altering surface chemistry and physics of the underlying substrate.     

Microstructure and electrical properties of BaTiO<Subscript>3</Subscript> and (Ba,Sr)TiO<Subscript>3</Subscript> ferroelectric thin films on nickel electrodes

Nickel thin films have been sputtered on standard Si/SiO₂ substrates with TiO₂ as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates were used for deposition of BaTiO₃ and (Ba,Sr)TiO₃ dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates under identical conditions but crystallized in an oxygen atmosphere.     

Molecular dynamics method in studies of molecular film growth processes

This review is an attempt to analyze some of the experimental problems arising in the course of growth of orientated molecular films using metal monophthalocyanine (MPc) films as an example and to demonstrate the possibilities of molecular dynamics simulation of these processes for solving experimental problems. Examples of theoretical simulation of adsorption processes are given; formation of a molecular monolayer is considered for copper phthalocyanine films as an example.     

Electrical,Optical, and Structural Properties of SnO2: F Films as a Function of Fluoride Precursor Concentration and Temperature

Atmospheric pressure chemical vapor deposition (APCVD) employing the precursor system of tin tetrachloride, ethyl formate, and 2,2,2‐trifluoroethyl trifluoroacetate vapors that were transported to hot glass substrates to deposit fluorine doped tin dioxide thin films. The system is optimized with respect to the substrate deposition temperature and to the amount of fluoride added to the precursor stream and the resultant structural, electrical and optical properties compared. Increasing the substrate temperature from 360 °C to 610 °C resulted in an approximately linear increase in thickness of the tin dioxide films. However, the resistivity decreased from 1.8 × 10^–2 Ω · cm at 360 °C to a minimum of 5.9 × 10^–4 Ω · cm at 560 °C and increased to 9.4 × 10^–4 Ω · cm at 610 °C. While maintaining a substrate temperature of 560 °C different amounts of fluorine precursor was introduced into the carrier stream, from 0 mL · h^–1 to 5 mL · h^–1, resulting in a decrease in resistivity (ρ) from 5.3 × 10^–2 Ω · cm at 0 mL · h^–1 to a minimum of 5.9 × 10^–4 Ω · cm at 2 mL · h^–1 and then increased to 1.0 × 10^–3 Ω · cm at 5 mL · h^–1. As the amount of fluoride is increased a concommittent increase in carrier concentration results until the point of overdoping the film produces an increase in scattering sites that increases resistivity. Best films were deposited at 560 °C and when the fluoride precursor flow rate was 2 mL · h^–1.     

Control of retention and fatigue-free characteristics in CaBi4Ti4O15 thin films prepared by chemical method

Ferroelectric CaBi₄Ti₄O₁₅ (CBTi144) thin films were deposited on Pt/Ti/SiO₂/Si substrates by the polymeric precursor method. The films present a single phase of layered-structured perovskite with polar axis orientation after annealing at 700 °C for 2 h in static air and oxygen atmosphere. The a/b-axis orientation of the ferroelectric film is considered to be associated with the preferred orientation of the Pt bottom electrode. It is noted that the films annealed in static air showed good polarization fatigue characteristics at least up to 10¹⁰ bipolar pulse cycles and excellent retention properties up to 10⁴ s. On the other hand, oxygen atmosphere seems to be crucial in the decrease of both, fatigue and retention characteristics of the capacitors. Independently of the applied electric field, the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.     

Surface layer-by-layer chemical deposition reaction for thin film formation of nano-sized metal 8-hydroxyquinolate complexes

The feasibility of a novel and simple layer-by-layer chemical deposition method for the preparation of nano-sized metal 8-hydroxyquinolate complexes has been investigated and reported. Uniform nanocrystalline films have been synthesized via dipping a substrate alternately in metal ion solution followed by ligand solution. The stoichiometry of the as-grown anhydrous Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complex crystals were confirmed from the metal analysis and molar stoichiometric ratio of metal ion to 8-hydroxyquinoline. This was characterized as 1:2 for the Co(II), Ni(II), Cu(II) and Zn(II)–quinolate complexes. The Fe(III)–quinolate thin film was found to exhibit a 1:3 ratio. Electron impact-mass spectra (EI-MS) of all the synthesized thin film metal quinolate complexes were recorded and the results refer to the existence of the molecular ion peak at the corresponding m/z values. Confirmation of such stoichiometric 1:2 and 1:3 ratios were also evident from the (EI-MS) study. The deposited thin films were also subjected to analysis by a scanning electron microscope (SEM) and a particle size ?50 nm was detected. FT-IR and UV–Vis spectroscopy were further used to confirm the structure of the metal 8-hydroxyquinolate complexes. Thermal gravimetric analysis (TGA) was also used to follow up the possible thermal decomposition steps and to calculate the thermodynamic parameters of the nano-sized metal complexes.     

Thin film growth of TiO2 and Ti2O3 by the new method of liquid injection CVD investigated using optical interferometry,XRD and AFM

The method of liquid injection chemical vapour deposition (LICVD) is a new technique, which is being developed for its potential to allow new material compositions and simpler and more flexible deposition schemes. The potential advantage of this technique is that it is possible to fix the precursor composition(s) in the injection solvent, permitting a simpler injection scheme compared to the current need for bubblers or gaseous precursors in CVD. In our system the precursor solution is rapidly volatilised into a carrier gas stream, which is then passed over the heated substrate. In this initial study we use the single component titanium tetraisopropoxide (TTIP) dissolved in THF for the injection solution, and investigate the behaviour of the deposition with in situ optical reflectometry and ex situ XRD and AFM. The data gained gives information on the growth rate, morphology and crystalline properties of the films. The characteristics of our deposition system are that we find a flux controlled growth mode, changes in the rate of deposition as a function of thickness, which are related to the surface morphology and the growth of Ti₂O₃ at temperatures above 450 °C. Copyright © 2006 John Wiley & Sons, Ltd.     

Utilization of iron oxide film obtained by CVD process as catalyst to carbon nanotubes growth

Thin films of Fe₂O₃ were obtained on silica glass substrates through the thermal decomposition of ferrocene in air. These films were characterized by Raman spectroscopy and X-ray diffractometry (XRD), and subsequently used as catalyst on the growth of carbon nanotubes, using benzene or a benzene solution of [Fe₃(CO)₁₂] as precursor. A great amount of a black powder was obtained as product, identified as multi-walled carbon nanotubes by XRD, Raman spectroscopy and transmission electron microscopy. The carbon nanotubes formed through the pyrolysis of the [Fe₃(CO)₁₂] solution were identified as structurally better than the one obtained by the pyrolysis of pristine benzene.     

化学气相沉积法制备ZnO纳米结构薄膜及其SERS活性研究

提供了半导体作为光、电和生物等功能材料的表面和界面信息, 同时也为SERS的研究开拓了新的领域.