Microstructures of ITO films deposited by d.c. magnetron sputtering with H2O introduction

ITO films were deposited by d.c. magnetron sputtering with/without H₂O introduction. The structural and optoelectrical properties of the films were analyzed in detail. The films deposited with H₂O introduction exhibited an entirely amorphous structure, whereas the as-deposited films deposited without H₂O introduction exhibited a polycrystalline In₂O₃ structure. The amorphous ITO films deposited under the high H₂O partial pressure were confirmed to contain a much higher concentration of hydrogen inside the films by secondary ion mass spectroscopy, which remained after post-annealing at 350 °C. The crystallization temperature of the films subjected to post-annealing was increased to higher than 220 °C. These stable amorphous ITO films had a wet-etching rate in oxalic acid solution two orders of magnitude higher than that of the films deposited without H₂O introduction.     

Preparation and characterization of diamond films

Diamond films were deposited by magnetron sputtering of vitreous carbon disc and also by plasma CVD technique using C₂H₂ + H₂ or CO₂ + H₂ gas mixtures. The films were characterized by measuring the electrical, optical and microstructural properties. FTIR and Raman studies were carried out to study the effect ofsp ² andsp ³ bonds present in the films. The films had a high mechanical stress which was determined from the broadening of the optical absorption tail in the films.     

Mid-frequency deposition of a-C:H films using five different precursors

The plasma-enhanced chemical vapour deposition (PECVD) of amorphous hydrogenated carbon films from pulsed discharges with frequencies in the range from 50 kHz to 250 kHz was investigated. Five different hydrocarbons (acetylene C₂H₂, isobutene C₄H₈, cyclopentene C₅H₈, toluene C₇H₈ and cycloheptatriene C₇H₈) were probed as film growth precursors. In addition, two types of pulse-generators with somewhat different waveforms were used to power the discharges in the so called mid-frequency range. The a-C:H films deposited in a parallel-plate reactor were characterised for their thickness/deposition rate, hardness and hydrogen content. The hydrogen concentration in the films varied between 19 at.-% and 37 at.-%. With the substrate temperature held constant, it is roughly in inverse proportion to the hardness. The film with the highest hardness of 25 GPa was formed at a deposition rate of 0.8 μm/h in the C₂H₂ discharge at the lowest investigated pressure of 2 Pa. With increasing molecular mass of the precursor mostly weaker films were deposited. Relatively high values of both deposition rate and hardness were achieved using the precursor isobutene: a hardness of 21 GPa combined with a deposition rate of 4.1 μm/h. From the probed precursors, isobutene is also most advantageous for a-C:H deposition at higher pressures (up to 50 Pa investigated). But, as an over-all trend, the a-C:H hardness decreases with increasing deposition rate.     

Mid-frequency deposition of a-C:H films using five different precursors

The plasma-enhanced chemical vapour deposition (PECVD) of amorphous hydrogenated carbon films from pulsed discharges with frequencies in the range from 50 kHz to 250 kHz was investigated. Five different hydrocarbons (acetylene C₂H₂, isobutene C₄H₈, cyclopentene C₅H₈, toluene C₇H₈ and cycloheptatriene C₇H₈) were probed as film growth precursors. In addition, two types of pulse-generators with somewhat different waveforms were used to power the discharges in the so called mid-frequency range. The a-C:H films deposited in a parallel-plate reactor were characterised for their thickness/deposition rate, hardness and hydrogen content. The hydrogen concentration in the films varied between 19 at.-% and 37 at.-%. With the substrate temperature held constant, it is roughly in inverse proportion to the hardness. The film with the highest hardness of 25 GPa was formed at a deposition rate of 0.8 μm/h in the C₂H₂ discharge at the lowest investigated pressure of 2 Pa. With increasing molecular mass of the precursor mostly weaker films were deposited. Relatively high values of both deposition rate and hardness were achieved using the precursor isobutene: a hardness of 21 GPa combined with a deposition rate of 4.1 μm/h. From the probed precursors, isobutene is also most advantageous for a-C:H deposition at higher pressures (up to 50 Pa investigated). But, as an over-all trend, the a-C:H hardness decreases with increasing deposition rate.     

Characterisation of SiOxCyHz thin films deposited by low-temperature PECVD

SiO_xC_yH_z thin films were deposited from hexamethyldisiloxane (HMDSO)/O₂ mixtures in a parallel plate, capacitively coupled, RF plasma reactor. Polyethylene terephthalate (PET), Si(1 0 0) wafers and KBr tablets were chosen as substrates. Effect of HMDSO/O₂ ratio, total treatment pressure and power input on the properties of the deposited films were investigated. The structure and bondings were studied by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Wettability characteristics of the deposited thin films were investigated by means of water droplet contact angle measurements. Surface morphology was investigated with atomic force microscopy. Barrier properties of the SiO_xC_yH_z thin films were investigated by measuring the water vapour transmission rate of the coated PET substrates. Correlations between the characteristics of the deposited film and their barrier properties were discussed.     

Plasma-enhanced chemical vapor deposition of molybdenum

The plasma-enhanced chemical vapor deposition of molybdenum films from Ar-Mo(CO)₆ gas mixtures and H₂-Mo(CO)₆ gas mixtures was studied. Films deposited from the former mixture contain large quantities of carbon and oxygen before and after annealing, while their sheet resistance remained beyond the range of the four-point probe used here. As-deposited films from the latter mixture contain carbon, but oxygen is present apparently in the form of a hydroxide. On annealing, the resistivity reaches a minimum of 7.5 μΩ cm and oxygen is no longer present in the film.     

Polycrystalline silicon film growth in a SiF4/SiH4/H2 plasma

The growth of polycrystalline silicon (polysilicon) films from SiF₄/SiH₄/H₂ gas mixtures is reported. The polysilicon films have been deposited in a multi process reactor by a PECVD process. The effect of r.f. power, chamber temperature and gas flow ratios on grain size and deposition rate have been determined. The fluorine concentration and the grain sizes of the films have been determined by SIMS and atomic force microscopy (AFM), respectively. Grain sizes in excess of 900 Å are reported for layers deposited at 300°C.     

A comparative analysis of a-C:H films deposited from five hydrocarbons by thermal desorption spectroscopy

Thermal induced gas evolution studies were performed on hydrogenated amorphous carbon (a-C:H) films deposited by plasma enhanced chemical vapour deposition (PECVD). The hydrocarbon-argon discharges were powered by asymmetric bipolar voltage pulses. Five different hydrocarbons (acetylene C₂H₂, isobutene C₄H₈, cyclopentene C₅H₈, toluene C₇H₈ and cycloheptatriene C₇H₈) were compared as film growth precursors.The films were heated in vacuum upto 1000 °C and at the same time the gaseous effusion products were measured with a quadrupole mass spectrometer (QMS). The release of hydrogen, water, argon and different hydrocarbons from CH₄ upto C₇H₈ was proved. Large hydrocarbons were detected only when heating up soft films. When annealing hard films, they almost only lost hydrogen - mainly as H₂ but also in remarkable portion as H₂O. Possibly, the water in the a-C:H films contains the main fraction of hydrogen unbounded to carbon.The characteristic temperatures for the onset of gas evolution of the molecular gases and of argon were found to be strictly correlated with the film hardness - independent of the film growth precursor. The threshold temperature for the release of the dominating effusion product, molecular hydrogen, is significantly higher than that of argon only for films with hardness below about 13 GPa.     

The influence of argon addition on the deposition and properties of Si:H,Cl films prepared in a glow discharge

Thin silicon films produced in r.f. glow discharges fed with SiCl₄-H₂ mixtures are studied. The effect of argon addition to the feed is examined. Emission spectroscopy and laser interferometry were used to correlate some kinetic parameters, such as the deposition rate, with chemical, optical and structural properties of the deposited material. An overall film growth mechanism is suggested in which chemisorbed species and hydrogen atoms play an important role.     

Effects of hydrogen dilution on CNx film properties deposited using rf PECVD from a mixture of ethane,nitrogen and hydrogen

Carbon nitride (CN_x) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf PECVD) from a mixture of ethane (C₂H₆), nitrogen (N₂) and hydrogen (H₂) gases. The C₂H₆ and N₂ flow rates were kept constant, while the H₂ flow rate was varied. The effects of hydrogen dilution on the growth rate and structural properties of the films were studied. It was found that a significant increase in the films growth rate was observed with the introduction of H₂ at as low as 25 standard cubic centimeters per minute (sccm). A set of CN_x films deposited from C₂H₆:N₂ mixture without any inclusions of H₂ were also presented in this work as a reference to compare the differences between those two sets and to understand the roles of H₂ to the films properties. At highest H₂ flow rate, the structure of the films changed from polymeric to graphitic and the quenching of PL was observed. Furthermore, higher N incorporation with lower E_g was obtained for these films compared to those of C₂H₆:N₂ films. The change in the structure of the films corresponds to changes in their chemical bonding. As N incorporation increased, the porosity of the films increases and thus affects the disorder in the film structures.     

Evaluation of ion conductivity of ZrO2 thin films prepared by reactive sputtering in O2, H2O, and H2O + H2O2 mixed gas

Hydrated ZrO₂ thin films were prepared by reactive sputtering in O₂, H₂O, and H₂O + H₂O₂ mixed gas, and the effect of the sputtering atmosphere on ion conductivity of the films was investigated. The results showed that the films deposited in O₂ gas exhibited poor ion conductivity; however, the ion conductivities of the films deposited in the other two kinds of atmosphere were similar and 300-500 times higher than that of the films deposited in O₂ gas. It was indicated that the higher ion conductivity of the films was caused by lower film density and higher water content.     

Simple way for preparation of ZnO films by surfactant mediated spray pyrolysis

Nanocrystalline porous ZnO films are deposited onto alumina foil substrates by polyvinyl alcohol (PVA) modified spray pyrolysis. Water and ethanol–water mixture were used for preparation of the sols. The effect of polyvinyl alcohol on the morphological and photocatalytical properties of ZnO films was studied. It was found that the polyvinyl alcohol plays important role in formation of porous films structure with ganglia like morphology. Relatively compact granular morphology was observed for the ZnO samples, grown without organic surfactant. The X-ray diffraction patterns revealed the formation of phase-pure ZnO thin films. The FTIR spectra and DTA-TG analyses of the precursor mixtures: Zn(CH₃COOH)₂·2H₂O and Zn(NO₃)₂·6H₂0 with PVA revealed that ZnO is formed before the final decomposition of the polymer at 350 °C.     

Electrodeposition of CuInSe2 absorber layers from pH buffered and non-buffered sulfate-based solutions

CuInSe₂ (CIS) thin films were deposited on Mo/glass substrates by one-step electrodeposition from aqueous baths containing CuSO₄, In₂(SO₄)₃ and SeO₂ with Li₂SO₄ electrolyte. The quality of the electrodeposited films depended on the presence of pH buffer in the bath. CIS films deposited from non-pH buffered baths showed pronounced (112) orientation, while films exhibiting more random orientation were obtained from pH buffered baths. Denser, smoother samples were obtained from non-pH buffered baths, though with no difference in film composition. As-deposited films exhibit low crystallinity and require recrystallization by annealing in H₂Se. Best devices, ∼ 9%, were obtained with CuInSe₂ films deposited from non-pH buffered baths.     

Atomic layer deposition of HfO2 thin films and nanolayered HfO2–Al2O3–Nb2O5 dielectrics

Smooth, 4–6-nm thick hafnium oxide films were grown by atomic layer deposition from HfI₄ or HfCl₄ and H₂O on SiO₂/Si(1 0 0) substrates at 300 °C. Non-uniform films were obtained on hydrogen-terminated Si(1 0 0). The stoichiometry of the films corresponded to that of HfO₂. The films contained small amounts of residual chlorine and iodine. The films deposited on SiO₂/Si(1 0 0) were amorphous, but crystallized upon annealing at 1000 °C. In order to decrease the conductivity, the HfO₂ films were mixed with Al₂O₃, and to increase the capacitance, the films were mixed with Nb₂O₅. The capacitance–voltage curves of the Hf–Al–O mixture films showed hysteresis. The capacitance–voltage curves of HfO₂ films and mixtures of Hf–Al–Nb–O were hysteresis free.     

Polymer film formation in C2F6H2 discharges

Thin fluoropolymer films deposited in an r.f. discharge fed with C₂F₆H₂ mixtures were studied. The effect of the electrical characteristics, the substrate temperature and the feed composition on both the chemical structure of the film and on the growth mechanism were analysed.It was found, in particular, that the structure of the film is affected by the H₂ concentration in the feed and by the discharge voltage and current values and that the polymerization rate decreases with temperature after a threshold.     

Crystalline diamond/graphite nanoflake hybrid films

Freestanding crystalline diamond/graphite nanoflake hybrid films have been deposited in H₂/CH₄ gas mixtures using a high pressure (1.3 × 10⁴ Pa) direct current plasma discharge. Sacrificial layers of close-packed silica microspheres were used as a matrix to produce dual gas chemistries on the plasma-facing and reverse sides of the microspheres. A continuous polycrystalline diamond film was formed on the front surface whilst graphite was deposited in the form of nanoflakes as a thinner hemispherical layer on the reverse side of the silica spheres respectively. Chemical etching of the silica matrix yielded crystalline diamond/well-aligned graphite nanoflakes hybrid films.     

Soft Magnetic Properties and Electrochemical Behavior of Nanocrystalline CoFeCu Thin Films Electrodeposited from Citrate-Added Baths

CoFeCu thin films were electrodeposited from baths with natural pH (instead of pH～2.8 used in conventional baths) and containing different sodium citrate dosages. ChemEQL V.3.0 software was employed to study speciation diagrams of citrate-added CoFeCu bath with natural pH. At low sodium citrate dosage, Co⁺⁺, Fe⁺⁺, and Cu⁺⁺ species were dominant in CoFeCu bath with natural pH (around 5.2). However, as dosage of sodium citrate in the bath increased, the concentration of complexed species (especially Co(C₆H₅O₇)^?, Fe(C₆H₅O₇)^?, and Cu(OHC₆H₅O₇)^2?) significantly raised. Cyclic voltammetry (CV) studies showed that the formation of complexed species in the bath shifted reduction potential of metals towards more negative potentials. Moreover, in order to deposit cobalt and iron simultaneously with copper, it was necessary to increase the reverse potential (E _λ ) value gradually with sodium citrate dosage, otherwise, only copper would have deposited from citrate-added CoFeCu bath. Scanning electron micrographs illustrated that using natural pH (about 5.2) remarkably decreased the number of microvoids in the deposited films compared with the film deposited from conventional baths with pH level of 2.8. EDS, XRD, and VSM were also used for characterization of the deposited films. All deposited films exhibited nanocrystalline structures, and increasing sodium citrate into the baths led to reduction in grain sizes (D) and coercivity (H _c) of the CoFeCu thin films. Plotting log(H _c) versus log(D ⁶) demonstrated that films coercivity followed the “D ⁶ law”. There were only two phase structures (FCC (Co) or BCC (Fe)) observed in the X-ray diffraction patterns of the films. In addition, films with double-phase structures (FCC+BCC) showed finer grain sizes and therefore exhibited lower coercivity in comparison with single-phase (FCC or BCC) films. CoFeCu thin films deposited at higher dosages of sodium citrate (>20 g/L) were poor in diamagnetic copper and consequently showed higher saturation magnetizations.     

Silicon nitride films deposited from SiF4/NH3 gas mixtures

Silicon nitride films have been deposited from SiF₄/NH₃/H₂ gas mixtures. The deposition reaction at high pressure (52 torr), takes place only for temperatures above 800°C. In the temperature range 800–1000°C the reaction is controlled by a surface process. The increase in H₂ and SiF₄ partial pressures enhances the deposition rate. The SiF₄ molecules provide a high concentration of available silicon atoms, while the hydrogen molecules inhibit the etching effect of the free fluorine atoms. Finally, the effect of an r.f. plasma in the chemical vapour deposition reaction has been evaluated.     

Preparation of FeN x -TiN films by CVD

FeN _x -TiN films were prepared on fused silica substrates by chemical vapour deposition from the gas mixture of Fe(C₅H₅)₂, TiCl₄, NH₃ and H₂ as starting materials under atmospheric pressure. FeN _x -TiN films were deposited above 500°C and the constituent phase was a mixed phase of FeN _x and TiN. The composition, deposition rate and saturation magnetization of FeN _x -TiN films deposited at 750°C were in good agreement with the estimation made by assuming that FeN _x and TiN phases were independently deposited.     

Micropore density in a-Si:H and a-Si:H:Cl films

a-Si:H films deposited from various silane-containing gas mixtures have been studied regarding their porosity. Micropore densities of 2.O × 10²cm^-2, 5.0 × 10⁴cm^-2 and 5.0 × 10⁴cm^-2 were determined for a-Si:H:C1, a-Si:H(H₂) and a-Si:H(Ar) films, respectively. It is suggested that these values correlate with the structural properties of the films, so that a-Si:H:Cl films seem to be the most uniform on the microstructural scale.