Textured tetragonal ZrO2 film grown on (100) silicon surface by DLI metal-organic chemical vapor deposition

Zirconia (ZrO2) thin films with micronic layer thickness are deposited on Si(100) substrates by MOCVD in a cold wall reactor using direct injection (DLI-CVD) process with Zr2(OiPr)6(thd)2 precursor diluted in cyclohexane. The effects of experimental parameters such as substrate's temperature, injection frequency, oxygen partial pressure in the reactive chamber and deposition duration of the process are investigated in order to produce a strongly textured tetragonal ZrO2 film. The films crystalline structure and crystallite size (several nm) are identified by Grazing incidence X-ray diffraction (GIXRD); the microstructure and morphology are observed with the use of FEG-SEM. GIXRD patterns showed the predominance of nano-crystallized tetragonal phase (or cubic) in the films. Pole figures have been analysed for both {111}(t-c) and {200}(t-c) planes in order to evaluate the relationship binding the preferential crystallographic orientation to the column-like growth structure. Besides, the internal stresses levels (with the use of sin2 psi method) within zirconia layers varied from a compressive to a tensile state depending on the experimental deposition conditions and are related to phase orientation and/or transformation into monoclinic one. It is demonstrated that high temperature, low pressure and low deposition time enhanced the tetragonal phase quality that became highly (200)t textured.     

Nanocrystallized tetragonal metastable ZrO2 thin films deposited by metal-organic chemical vapor deposition for 3D capacitors

ZrO₂ is a potential candidate for the realization of 3D capacitors on silicon for future Systems-on-Chip. This paper reports on the deposition of ZrO₂ thin films by metal-organic chemical vapor deposition on planar and 3D structures. Physico-chemical as well as electrical properties of the films are investigated. It is shown that the change of phase and microstructure of the film due to annealing at 900 °C under O₂ impacts directly on the electrical performance of the capacitors. Capacitance densities are 2 nF/mm² for planar capacitors and reach 8 nF/mm² for capacitors with pores etched in silicon with a 4:1 aspect ratio.     

Growth of epitaxial sodium-bismuth-titanate films by metal-organic chemical vapor phase deposition

The liquid-delivery spin metal-organic chemical vapor phase deposition method was used to grow epitaxial sodium-bismuth-titanate films of the system Bi₄Ti₃O₁₂ + xNa_0.5Bi_0.5TiO₃ on SrTiO₃(001) substrates. Na(thd), Ti(OⁱPr)₂(thd)₂ and Bi(thd)₃, solved in toluene, were applied as source materials. Depending on the substrate temperature and the Na/Bi ratio in the gas phase several structural phases of sodium-bismuth-titanate were detected. With increasing temperature and/or Na/Bi ratio, phase transitions from an Aurivillius phase with m = 3 to m = 4 via an interleaved state with m = 3.5, and, finally, to Na_0.5Bi_0.5TiO₃ with perovskite structure (m = ∞) were established. These phase transitions proceed at remarkably lower temperatures than in ceramics or bulk crystals for which they had been exclusively observed so far.     

Thin cobalt oxide films for catalysis deposited by plasma-enhanced metal-organic chemical vapor deposition

The plasma-enhanced metal-organic chemical vapor deposition was used to prepare thin films of cobalt oxide starting with cyclopentadienyldicarbonyl-cobalt(I) (CpCo(CO)₂) mixed with argon and oxygen. The films were characterized by Raman and Fourier transform infrared spectroscopies, electron diffraction, and energy dispersive X-ray microanalysis. Their thickness was estimated by ellipsometric measurements. Catalytic properties of the films were tested in oxidation of n-hexane. It has been found that spinel-type Co₃O₄ nanoclusters with a crystallite size of 4-6 nm are formed in the deposits. Amorphous carbon and amorphous CoO_x phases are also observed in the films. The content of these phases depends on the molar fraction of oxygen in the gas mixture. Preliminary catalytic tests have shown that precalcined Cr-Al steel carrier covered by the plasma-deposited films reveals much higher catalytic effect then the non-deposited substrate.     

Photoluminescence and structure of ZnO films deposited on Si substrates by metal-organic chemical vapor deposition

The structure and photoluminescence (PL) at room temperature of ZnO films deposited on Si(111) substrates by metal-organic chemical vapor deposition (MO-CVD) using diethylzinc (DEZ) and CO₂ was investigated. It was found that these properties strongly depend on growth temperature and pressure. ZnO films can be deposited only at low pressure and in the temperature region of 500–650°C. The samples grown at certain conditions can generate stronger luminescence of ZnO. When the growth temperature increased to 650°C, the ZnO₂ phase was observed in X-ray diffraction (XRD) patterns of the samples. This characteristic became evident after the samples annealed. Appearance of a ZnO₂ phase results in production of a new emission band centered at 575 nm in the PL spectrum at room temperature, and the green emitting band also disappears.     

Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH₃)₄) diluted in H₂ as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co₂Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.     

Investigation of alumina-silica films deposited by pulsed injection metal-organic chemical vapour deposition

This work is devoted to deposition of alumina-silica films using an innovative pulsed injection metal organic chemical vapour deposition technique and aluminium tri(iso-propoxide) (Al(i-OPr)₃) and tetraethoxysilane (TEOS) as precursors. The deposited aluminium silicate films have been characterised by scanning electron microscopy, infrared spectroscopy, X-ray diffractometry and capacitance-voltage (C-V) measurements. The investigation of the deposition at different Si/Al ratios and substrate temperatures has shown that the growth rate increases with the increase of Al(i-OPr)₃ proportion in solution and decreases as the proportion of TEOS increases. We have also shown that aluminium content in the film increases at lower deposition temperatures while silicon content increases at higher temperatures. The permittivity of the films determined from C-V measurements decreases with increasing substrate temperature. It was found that films deposited at substrate temperatures of 600 or 700 °C and with the highest Si/Al ratio have the lowest dielectric permittivity. This research should be useful for further development of MOCVD technology for the deposition of aluminosilicate-based dielectric materials with controlled dielectric permittivity.     

Characterization of MgZnO films grown by plasma enhanced metal-organic chemical vapor deposition

MgZnO (magnesium-zinc-oxide) films were grown on (11-20) sapphire substrates and Zn-polar ZnO substrates by plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) employing microwave-excited plasma. Structural, electrical and optical properties were investigated by X-ray diffraction, atomic force microscope, Hall, transmittance and photoluminescence measurement. The c-axis lattice constant decreases proportionally to an increase in the Mg content of Mg_xZn_1 − xO films. Therefore, this indicates that Mg atoms can be substituted in the Zn sites. Mg contents in films on ZnO substrates increase up to 0.11. In addition, Ga doped ZnO films were grown on (11-20) sapphire substrates. The resistivity of the films on (11-20) sapphire is controlled between 1.2 × 10^− 3 Ω cm to 1 Ω cm by changing the process conditions. The overall results indicate the promising potential of this PE-MOCVD method for related (Zn, Mg)O films formation because of the reactivity of the radicals, such as oxygen radicals (O?).     

Nitrogen doped ZnO thin films prepared by photo-assisted metal-organic chemical vapor deposition

Nitrogen-doped ZnO (ZnO:N) films were prepared by photo-assisted metal-organic chemical vapor deposition technique using NH3 as N doping source. The effects of in-situ light irradiation on the properties of ZnO:N films were studied by Hall measurements, X-ray diffraction, Raman scattering, and X-ray photoelectron spectroscopy. The results show that stable p-type ZnO:N films with a hole concentration of 3.61 x 10(17) cm(-3) was successfully achieved. Moreover, introducing proper in-situ light irradiation during the growth process can not only effectively improve the crystalline quality of ZnO films, but also enhance the activity of (N)o (N occupies O site) acceptors by removing the undesirable hydrogen atoms from ZnO:N films. Both effects are benefit for the p-type conductivity formation. Our results indicate that photo-assisted MOCVD maybe an effective technology to realize device-quality p-type ZnO:N films.     

Epitaxial growth of RuO2 thin films by metal-organic chemical vapor deposition

Conductive RuO₂ thin films were epitaxially grown on LaAlO₃(100) and MgO(100) substrates by metal-organic chemical vapor deposition (MOCVD). The deposited RuO₂ films were crack-free, and well adhered to the substrates. The RuO₂ film is (200) oriented on LaAlO₃ (100) substrates at deposition temperature of 600°C and (110) oriented on MgO(100) substrates at deposition temperature of 350°C and above. The epitaxial growth of RuO₂ on MgO and LaAlO₃ is demonstrated by strong in-plane orientation of thin films with respect to the major axes of the substrates. The RuO₂ films on MgO(100) contain two variants and form an orientation relationship with MgO given by RuO₂(110)//MgO(100) and RuO₂[001]//MgO[011]. The RuO₂ films on LaAlO₃(100), on the other hand, contain four variants and form an orientation relationship with LaAlO₃ given by RuO₂(200)//LaAlO₃(100) and RuO₂[011]//LaAlO₃[011]. Electrical measurements on the RuO₂ thin films deposited at 600°C show room-temperature resistivities of 40 and 50 μΩ cm for the films deposited on the MgO and LaAlO₃ substrates, respectively.     

Annealing and partial pressure ratio effects on ZnO films grown by metal-organic chemical vapor deposition using tert-butanol as oxidant

ZnO films were deposited by metal-organic chemical vapor deposition on (0001) sapphire substrates at various partial pressure ratios of oxygen and zinc precursors (R_VI/II). The annealing and the R_VI/II ratio effects on the vibrational and optical properties of ZnO films have been investigated by Micro-Raman scattering and low temperature photoluminescence (PL) spectroscopy. As confirmed by characterizations used in this study, the quality of the ZnO films was improved by thermal annealing at 900 °C in oxygen ambient. Raman spectra of the as-deposited films show a broad band (BB) centered at about 518 cm⁻¹ whose intensity increases when the R_VI/II ratio decreases. After annealing, the intensity ratio of the BB to the E₂ high (E₂^H) peak decreases rapidly with increasing the annealing time (t_an). The vibrational properties of the annealed films grown at R_VI/II = 1 need only 1 h to be improved in contrast to those of films grown in Zn-rich condition, which need 4 h. From the E₂^H mode frequency, the residual stress in both the as-grown and the annealed films has been estimated. Micro-Raman measurements show that as-grown films are under a compressive stress which vanishes upon annealing and is not strongly dependent on t_an for t_an up to 1 h. PL spectra show that sharp donor bound exciton and A-free exciton emissions are observed for the as-deposited films grown at R_VI/II ≥ 0.5 and are enhanced after annealing for 1 h. However, in ZnO films grown in Zn-rich condition these emissions are absent and a t_an = 4 h is needed to annihilate non-radiative recombination centers and improve their luminescent efficiency.     

Low-temperature growth and orientational control in RuO2 thin films by metal-organic chemical vapor deposition

For growth temperatures in the range of 275°C to 425°C, highly conductive RuO₂ thin films with either (110)- or (101)-textured orientations have been grown by metal-organic chemical vapor deposition (MOCVD) on both SiO₂/Si(001) and Pt/Ti/SiO₂/Si(001) substrates. Both the growth temperature and growth rate were used to control the type and degree of orientational texture of the RuO₂ films. In the upper part of this growth temperature range ( 350°C) and at a low growth rate (< 3.0 nm/min.), the RuO₂ films favored a (110)-textured orientation. In contrast, at the lower part of this growth temperature range ( 300°C) and at a high growth rate (> 3.0 nm/min.), the RuO₂ films favored a (101)-textured orientation. In contrast, higher growth temperatures (> 425°C) always produced randomly-oriented polycrystalline films. For either of these low-temperature growth processes, the films produced were crack-free, well-adhered to the substrates, and had smooth, specular surfaces. Atomic force microscopy showed that the films had a dense microstructure with an average grain size of 50–80 nm and a rms. surface roughness of 3–10 nm. Four-probe electrical transport measurements showed that the films were highly conductive with resistivities of 34–40 μΩ-cm (at 25°C).     

Adherent amorphous hydrogenated carbon films on metals deposited by plasma enhanced chemical vapor deposition

This paper reports the findings of a study of the structural, mechanical, and tribological properties of amorphous hydrogenated carbon (a-C:H) coatings for industrial applications. These thin films have proven quite advantageous in many tribological applications, but for others, thicker films are required. In this study, in order to overcome the high residual stress and low adherence of a-C:H films on metal substrates, a thin amorphous silicon interlayer was deposited as an interface. Amorphous silicon and a-C:H films were grown by using a radio frequency plasma enhanced chemical vapor deposition system at 13.56 MHz in silane and methane atmospheres, respectively. The X-ray photoelectron spectroscopy technique was employed to analyze the chemical bonding within the interfaces. The chemical composition and atomic density of the a-C:H films were determined by ion beam analysis. The film microstructure was studied by means of Raman scattering spectroscopy. The total stress was determined through the measurement of the substrate curvature, using a profilometer, while micro-indentation experiments helped determine the films' hardness. The friction coefficient and critical load were evaluated by using a tribometer. The results showed that the use of the amorphous silicon interlayer improved the a-C:H film deposition onto metal substrates, producing good adhesion, low compressive stress, and a high degree of hardness. SiC was observed in the interface between the amorphous silicon and a-C:H films. The composition, the microstructure, the mechanical and tribological properties of the films were strongly dependent on the self-bias voltages. The tests confirmed the importance of the intensity of ion bombardment during film growth on the mechanical and tribological properties of the films.     

Texture control of ZnO films by inductively coupled plasma assisted chemical vapor deposition

ZnO films were grown on Si (100) and quartz substrates by inductively coupled plasma-assisted chemical vapor deposition using diethylzinc, O₂, and Ar. ZnO films with the (002) preferred orientation (PO) were formed at substrate temperatures > 250 °C regardless of any other changes made to process variables, since the (002) plane has the lowest formation energy with the highest number of unsaturated Zn-ZnO or O-ZnO bonds. At temperatures < 250 °C, the a-axis plane PO such as (100), (110), and (101) as well as the c-axis (002) plane PO were able to form by varying the temperature, plasma power, and deposition rate. The a-axis PO was formed when the radio frequency power was high enough to produce a crystalline ZnO film but was insufficient to form a (002) PO. The a-axis PO was also formed at higher deposition rates ≥ 20 nm/min when the radio frequency power was high enough to produce crystalline ZnO film. Since the (002) plane grew slowly, the grain exposing (002) plane was overgrown by the grains of the a-axis plane at higher deposition rates.     

Thin-film transistors deposited by hot-wire chemical vapor deposition

In the past few years hot-wire chemical vapor deposition (HWCVD) has become a popular technique for the deposition of silicon-based thin-film transistors (TFTs). Several groups have been using hot-wire deposited amorphous and microcrystalline silicon as the active layers in TFTs. In such devices either thermal SiO₂ or plasma-deposited silicon nitride was the gate insulator. Recently ‘All-Hot-Wire TFTs’ have been realized, with also the silicon nitride deposited by HWCVD. This paper reviews the characteristics of hot-wire TFTs with amorphous and microcrystalline silicon using plasma- or hot-wire deposited silicon nitride as the gate insulator. It has been shown that hot-wire TFTs have a higher stability upon gate-bias stress as compared to their plasma-deposited counterparts. We present an overview of the stability of hot-wire TFTs deposited at a range of substrate temperatures. The higher stability of hot-wire TFTs that have been deposited at temperatures of 400–500 °C is ascribed to an enhanced structural order, i.e. a higher degree of medium-range order of the silicon network.     

Structure and morphology of titanium nitride films deposited by laser-induced chemical vapour deposition

Results on the deposition of titanium nitride on AISI M2 tool steel-type substrates by pyrolytic laser chemical vapour deposition are reported. Spots of TiN were deposited from a gas mixture of TiCl₄, nitrogen and hydrogen using a continuous wave quasi-TEM_oo CO₂ laser beam. The morphology and the structure of the deposited material were investigated by optical microscopy, scanning electron microscopy and X-ray diffraction. The chemical composition was studied with a scanning electron microscope with an energy dispersive spectrometer, and with an electron probe microanalyser. The topography of the coating was analysed with a stylus profilometer and different thickness profiles were measured depending on the laser-power densities and irradiation times. The morphology of the films showed a strong dependence on the laser-power density, interaction time and partial pressure of TiCl₄.     

Annealing effects on structural and electrical properties of fluorinated amorphous carbon films deposited by plasma enhanced chemical vapor deposition

The annealing effects on the structural and electrical properties of fluorinated amorphous carbon (a-C:F) thin films prepared from C₆F₆ and Ar plasma are investigated in a N₂ environment at 200 mTorr. The a-C:F films deposited at room temperature are thermally stable up to 250 °C, but as the annealing temperature is increased beyond 300 °C, the fluorine incorporation in the film is reduced, and the degree of crosslinking and graphitization in the film appears to be enhanced. At the annealing temperature of 250 °C, the chemical bond structures of the film are unchanged noticeably, but the interface trapped charges between the film and the silicon substrate are reduced significantly. The increased annealing temperature contributes the decrease of both the interface charges and the effective charge density in the a-C:F film. Higher self-bias voltage is shown to reduce the charge density in the film.     

Characterizations of gallium-doped ZnO films on glass substrate prepared by atmospheric pressure metal-organic chemical vapor deposition

Ga-doped zinc oxide (ZnO:Ga) films were grown on glass substrate by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using diethylzinc and water as reactant gases and triethyl gallium (TEG) as an n-type dopant gas. The structural, electrical and optical properties of ZnO:Ga films obtained at various flow rates of TEG ranging from 1.5 to 10 sccm were investigated. X-ray diffraction patterns and scanning electron microscopy images indicated that Ga-doping plays an important role in forming microstructures in ZnO films. A smooth surface with a predominant orientation of (101) was obtained for the ZnO:Ga film grown at a flow rate of TEG = 7.5 sccm. Moreover, a lowest resistivity of 3.6 × 10^− 4 Ω cm and a highest mobility of 30.4 cm² V^− 1 s^− 1 were presented by the same sample, as evaluated by Hall measurement. Otherwise, as the flow rate of TEG was increased, the average transmittance of ZnO:Ga films increased from 75% to more than 85% in the wavelength range of 400-800 nm, simultaneously with a blue-shift in the absorption edge. The results obtained suggest that low-resistivity and high-transparency ZnO films can be obtained by AP-MOCVD using Ga-doping sufficiently to make the films grow degenerate and effect the Burstein-Moss shift to raise the band-gap energy from 3.26 to 3.71 eV.