Preparation and properties of r.f.-sputtered polymer-metal thin films

The ability to produce polymer-metal thin films by co-sputtering from a composite target was investigated using polytetrafluoroethylene (PTFE) (Teflon) and Ekonol polymers. The preparation of PTFE-metal thin films by sputtering was found to be limited by target cross-contamination possibly caused by negative ion re-sputtering processes. The Ekonol-metal films were found to have microstructure and conductivity properties similar to other metal-insulator composites.     

X-ray reflectivity study of r.f.-sputtered thin SiO2 films

X-ray reflectivity investigations have been performed on thin amorphous SiO₂ films obtained by r.f.-sputtering of fused quartz onto Si single crystals in an argon atmosphere.This is a non-destructive technique to determine thickness and density as well as the interface and surface roughness. For the SiO₂/Si system (small differences in density) the X-ray reflectivity is sufficiently sensitive to provide precise information on the occurence of an intermediate layer we obtained only on well-polished silicon wafers.The thickness of the films is compared with that obtained from ellipsometry data and mechanical scanning measurements (stylus method).     

Atomic defects and stresses in r.f.-sputtered SiO2 thin films

The influence of a number of technological factors on the optical and dielectric properties of thin amorphous SiO₂ films obtained by r.f. sputtering of fused quartz in an argon atmosphere was investigated.Using IR spectroscopy and the measurement of the a.c. conductivity the films obtained are shown to have the radiation defects of the C₁^- type induced by the high energy particle bombardment during sputtering.The observed shift in the main IR absorption band of the films as a function of their thicknesses is related to the stresses due to the difference in thermal expansion coefficients of the film and the substrate as well as their structural disparity.     

Characterization of r.f.-sputtered ZnO thin films by X-ray diffraction and scanning electron microscopy

Thin films of ZnO, ranging in thickness from 0.08 to 6 μm, have been prepared by r.f. sputtering on substrates of either quartz or glass under various deposition conditions and subsequently characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results from XRD indicate that the grain size increases from 0.01 to 0.5 μm as the film thickness is increased from 0.08 to 6 μm for deposition at 65 °C and increases from 0.1 to 0.3 μm as the deposition temperature is increased from 65 to 480 °C for a constant film thickness of 2 μm, whereas the lattice strain and dislocation density decrease slightly under similar conditions. Results from SEM indicate that the particle size parallel to the plane of the film is approximately equal to the mean grain size perpendicular to the plane of the film, suggesting that growth proceeds by the nucleation of new grains rather than by the elongation of columnar grains in the growth direction. General observations indicate that microstructural parameters, such as grain size, grain shape and lattice strain, depend sensitively on the exact nature of the deposition conditions.     

Characterization and properties of r.f.-sputtered thin films of the alumina–titania system

Thin films of the aluminum oxide (Al₂O₃)–titanium oxide (TiO₂) system including Al₂O₃, TiO₂, and Al₂O₃/TiO₂ were prepared by radio-frequency (r.f.) magnetron sputtering using ceramic targets of Al₂O₃, TiO₂, and Al₂O₃/TiO₂ composites with different Al₂O₃/TiO₂ ratio. These films were studied at different substrate temperatures, r.f. powers, and annealing temperatures. Composition, microstructure, thermomechanical property of internal stress, and mechanical property of scratch adhesion, were evaluated. A thin film with a dielectric constant of 62 and a loss tangent of 0.012 was obtained at 500 °C from a 10/90 target. This thin film remained the high dielectric constant of TiO₂, but had an improvement in the dielectric loss tangent. Al₂O₃-containing films had a higher resistivity and breakdown field, which was improved further by annealing. Optical properties, such as refractive index and optical transmittance, were also investigated.     

Electrical and optical properties of r.f.-sputtered amorphous V2O5-CaO-MoO3 films

Amorphous films of the V₂O₅-CaO-MoO₃ system are fabricated by r.f.-sputtering and the d.c. conductivity and optical properties are studied. The conductivity of 1200–1400 nm thick amorphous V₂O₅-CaO-MoO₃ films with different film compositions ranges from 4.7 × 10^–4 to 1.1 S cm^–1 at 458 K. The films are n-type semiconducting. The conduction of the films is attributed to adiabatic small polaron hopping and is primarily due to hopping between V⁴⁺ and V⁵⁺ ions. The films are optically transparent in the visible range. The optical band gap energy is evaluated to be between 2.90 and 2.39 eV. The Urbach tail analysis gives the width of localized states between 0.40 and 0.58 eV. A feasibility study reveals the films to be applicable as transparent film thermistors.     

Phase formation and characteristics of r.f.-sputtered barium-strontium titanate thin films on various bottom layers

(Ba_0.7Sr_0.3)TiO₃ thin films were deposited by r.f.-magnetron sputtering on Pt/Ti/Si, Pt/TiSi₂/Si and Pt/Ti/SiO₂/Si substrates, respectively, and annealed at 650 C for 30s by Rapid Thermal Annealing (RTA). XRD (X-ray diffraction) patterns revealed that the BST films had perovskite structure without preferred orientation. Auger depth profiles of barium-strontium titanate (BST) films on various substrates were performed. In the Pt/Ti/Si and Pt/TiSi₂/Si structures, Si diffused into the BST film, but in the Pt/Ti/SiO₂/Si structure, the diffusion of Si into the BST film was prevented and the interface between the BST film and the electrode was stable. The dielectric constants were about 310–260 (100 kHz–1 MHz).     

Some properties of r.f.-sputtered hafnium nitride coatings

Hafnium nitride coatings were deposited by reactive r.f. sputtering from a hafnium target in nitrogen and argon gas mixtures. The rate of deposition, the composition, the electrical resistivity and the complex index of refraction were investigated as functions of the target-to-substrate distance and the nitrogen fraction f_N2 in the sputtering atmosphere. It was found that the relative composition of the coatings is independent of f_N2 for values above 0.1. The electrical resistivity of the hafnium nitride films changes over 8 orders of magnitude when f_N2 changes from 0.10 to 0.85. The index of refraction is almost constant at 2.8(1?0.3i) up to f_N=0.40 then decreases to 2.1(1?0.1i) for higher values of f_N2.     

The effect of ion implantation on r.f.-sputtered TiB2 films

Films of TiB₂ were deposited onto various substrates by r.f. sputtering in argon and in an ArBF₃ mixture. The stoichiometric composition of the films was studied by Rutherford backscattering and nuclear reaction techniques. After film deposition, the effect of ion implantation with boron and krypton ions was studied. In the last case a substantial increase in the adhesion of the film to the substrate and in the microhardness was observed.     

Preparation and characterization of Ce-doped BaTiO3 thin films by r.f. sputtering

Ce-doped BaTiO₃ thin films prepared on silicon-platinium by r.f. sputtering has been investigated. BaTiO₃ doped with 5.5 mol%CeO₂ thin film was deposited at 550°C substrate temperature in an Ar atmosfere. The crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy with EDAX. Analysis by X-ray diffraction patterns show that the crystalline film with a cubic structure of BaTiO₃, was obtained. The surface morphology (roughness, the grain size and the droplet size) of the thin film surface was examined by atomic force microscopy (AFM). The grain size is about 160 nm, the droplet size is about 0.675 m and the roughness is 36.88 nm. EDAX analysis established a composition of the film to be identical with that of the target (BaTiO₃ doped with 5.5 mol%CeO₂). The broad peak in the capacitance versus temperature curve at the Curie point indicate that the r.f. sputtered Ce-doped BaTiO₃ film is ferroelectric. The values of the capacitance of the thin film at 1 KHz were found to be 86 pF and the loss dielectric was tan = 0.0875. The film exibits a dielectric anomaly peak at 23°C showing ferroelectric to paraelectric phase transition.     

Preparation of Fe-N films by r.f. sputtering

Fe-N films over a wide compositional range have been prepared by the reactive sputtering method. Fe-N sputtered films were composed of a single or two phases such as-Fe₂N,-Fe_3.02N,-Fe_3.82N,-Fe₄N and-Fe; however, an unknown phase was observed at a higher nitrogen pressure. A remarkable preferred orientation of the-Fe_3.02N (110) plane parallel to the film surface was observed. The Curie temperature of the sputtered -Fe_3.82N sample was 490° C, which was almost the same as that of-Fe₄N prepared by metal nitriding. The saturation magnetization, _s, of the sputtered Fe-N samples decreased from 151.8 to 42.4 e.m.u.g^–1 with increasing nitrogen content from 7.94 to 24.87 at%, and its coercive force,₁ H _c was found to lie in the range 150 to 600 Oe in the powder form at room temperature.     

R.f.-sputtered SiO2 films for optical applications

We investigated the refractive index variation of r.f.-sputtered SiO₂ films in the direction normal to the substrate surface as a function of some important deposition conditions. As confirmed by Rutherford backscattering measurements the impurity content and its distribution over the film thickness profoundly affect the optical homogeneity and the UV absorption of SiO₂ films. Homogeneous SiO₂ films with refractive indices and transmission properties close to those of fused silica can be prepared by judicious selection of the substrate temperatures. This is possible even under such rough mutual contamination conditions as occur in the fabrication of multilayer stacks.     

ZnO:Ga透明导电膜的低温制备及特性研究

采用射频磁控溅射法在玻璃衬底上低温制备出高质量的镓掺杂氧化锌(ZnOGa)透明导电膜,对薄膜的结构和光电特性以及制备参数对薄膜性能的影响进行了研究.制备的ZnOGa是具有六角纤锌矿结构的多晶薄膜,最佳择优取向为(002)方向.薄膜的最低电阻率达到了3.9×10-4Ωcm,方块电阻～4.6Ω/□,薄膜具有良好的附着性,在可见光区的平均透过率达到90%以上.     

Optical and structural characterization of r.f. sputtered CeO2 thin films

The optical and structural properties of r.f. sputtered CeO2 thin films deposited on Pyrex substrates have been studied as a function of substrate temperature during deposition. The refractive index, n, extinction coefficient, k, and bandgap of the films were calculated from reflectance, R, and transmittance, T, spectra in the wavelength range 340–900 nm. The refractive index of CeO2 films at 550 nm comprises values from about 2.25–2.4 depending on the substrate temperature during deposition. The extinction coefficient was negligible for wavelength values higher than 400 nm. The value obtained for the bandgap was 3.1 eV. The X-ray diffraction patterns showed the same (f c c) cubic structure with preferential orientation depending on substrate temperature during deposition. The scanning force microscope measurements showed that the roughness and grain size of the CeO2 films increase with increasing substrate temperature. This revised version was published online in November 2006 with corrections to the Cover Date.     

Deposition of B4C/BCN/c-BN multilayered thin films by r.f. magnetron sputtering

Thin films of cubic boron nitride (c-BN) and B₄C/BCN/c-BN multilayers, were deposited by r.f. (13.56 MHz) multi-target magnetron sputtering from high-purity (99.99%) h-BN and a (99.5%) B₄C targets, in an Ar (90%)/N₂ (10%) gas mixture. Films were deposited onto silicon substrates with (100) orientations at 300 °C, with r.f. power density near 7 W/cm². In order to obtain the highest fraction of the c-BN phase, an r.f. substrate bias voltage between − 100 and − 300 V was applied during the initial nucleation process and − 50 to − 100 V during the film growth. Additionally, B₄C and BCN films were deposited and analyzed individually. For their deposition, we varied the bias voltage of the B₄C films between − 50 and − 250 V, and for the BCN coatings, the nitrogen gas flow from 3% to 12%. A 300-nm-thick TiN buffer layer was first deposited to improve the adhesion of all samples. X-ray diffraction patterns revealed the presence of c-BN (111) and h-BN phases. FTIR spectroscopy measurements indicate the presence of a peak at 780 cm^− 1 referred to as “out-of-plane” h-BN vibration mode; another peak at 1100 cm^− 1 corresponds to the c-BN TO mode and the “in-plane” vibration mode of the h-BN at 1400 cm^− 1. BN films deposited at 300 °C at a pressure of 4.0 Pa and under − 150 V of nucleation r.f. bias, applied for 35 min, presented the highest c-BN fraction, near 85%. By using 32 layers, it was possible to deposit a 4.6-μm-thick c-BN film with adequate mechanical properties and good adhesion to the substrate.     

Preparation of BN films by r.f. thermal plasma chemical vapour deposition

Boron nitride films were prepared at 1 atm by r.f. thermal plasma chemical vapour deposition from the gas systems of Ar-BF₃-N₂ (or NH₃, NF₃)-H₂, Ar-BCl₃-N₂ (or NH₃, NF₃)-H₂, and Ar-B₂H₆-N₂ (or NH₃)-H₂. The appearance and the deposition rate of the films changed drastically with the composition of the feed gas. Only from the Ar-BF₃-N₂(-NF₃) gas, were transparent and smooth films obtained, while from other gas systems, white flaky or powder-like deposits formed. The structure of these films was basically sp²-bonded turbostratic BN, and the formation of cubic BN was not confirmed.