Nd photoluminescence study of Nd-doped Si-rich silica films obtained by reactive magnetron sputtering

Nd³⁺-doped silicon-rich silicon oxide (SRSO) thin films have been fabricated by reactive magnetron sputtering of a pure silica target topped with Nd₂O₃ chips. The concentration of Nd ions in the deposited layers is controlled by the number of Nd₂O₃ chips, whereas the incorporation of silicon excess is monitored by the hydrogen partial pressure, P_H2, introduced in the Ar plasma, owing to the ability of hydrogen to reduce the oxygen released by the sputtering of the silica target. Photoluminescence (PL) experiments were made at room temperature using a nonresonant excitation line from an Ar laser. The influences of Nd³⁺ content and P_H2 have been studied to optimize the Nd³⁺ emission. PL spectra reveal a two order of magnitude enhancement of the Nd³⁺ emission around both 0.9 and 1.1 μm, when Si nanoclusters (Si-nc) are formed in the same Nd³⁺-doped matrix. The dependence of the Nd³⁺ PL with P_H2 and Nd concentration is indicative of the occurrence of an efficient energy transfer from the Si-nc to the rare earth ions. The radiative lifetime is also deduced and commented in the light of Nd³⁺-Si-nc coupling.     

Superconducting MgB2 films obtained by magnetron sputtering

Superconducting MgB₂ films with a superconducting transition temperature of 24 K were obtained by magnetron sputtering. The high homogeneity of the films was demonstrated by the magneto-optical imaging of the magnetic flux penetration.     

Superhard Nb-Si-N composite films synthesized by reactive magnetron sputtering

By means of the reactive magnetron sputtering method, a series of Nb-Si-N composite films with different Si contents were deposited in an Ar, N₂ and SiH₄ mixture atmosphere. These films’ chemical composition, phase formation, microstructure and mechanical properties were characterized by the energy dispersive spectroscopy, X-ray diffraction, transmission electron microcopy, atomic force microscopy and nanoindentation. The experimental results showed that the silicon content in the Nb-Si-N composite films can be conveniently controlled by adjusting the SiH₄ partial pressure in mixed gas. The hardness and elastic modulus of the Nb-Si-N films were remarkably increased with a small amount of silicon addition and reached their maximum values of 53 and 521 GPa, respectively, at 3.4 at.% Si. Such an obvious enhancement of mechanical properties is related to the increment of crystal defects in the Nb-Si-N films. With silicon content increasing in the films further, the mechanical properties decreased gradually to somewhat a bit lower than those of the NbN film.     

磁控反应溅射制备择优取向氮化铝薄膜

以氮气为反应气体，采用磁控反应溅射方法制备了择优取向的氮化铝薄膜．通过XRD测试发现．靶基距、溅射气压影响薄膜的择优取向：大的靶基距及高的溅射气压利于（100）面择优取向，小的靶基距和低的溅射气压利于（002）面择优取向．通过对沉积速率的分析发现．高的沉积速率利于（002）面择优取向，低的沉积速率利于（100）面择优取向．研究结果表明：沉积速率影响了核在衬底表面的生长方向，从而影响了各晶面的生长速度．最终决定薄膜的择优取向．     

Gadolinia-doped ceria films deposited by RF reactive magnetron sputtering

Gadolinia-doped ceria (GDC) films were prepared by RF reactive magnetron sputtering from a Gd-10 at.% Ce alloy target in reactive O₂/Ar gas mixtures and annealed at 700 °C for 2 h. Material characteristics and chemical compositions of GDC films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Electrical behaviors were measured by AC impedance in the range of 500–700 °C at OCV for air condition. The microstructure of GDC films was found to be an assembly of columnar crystallites with a cubic fluorite structure. The total conductivity of 700 °C-annealed GDC (GDC-1) with the obtained composition of (Ce_0.911Gd_0.089)O_1.938 was higher than that of bulk yttria-stabilized zirconia (YSZ), but smaller than bulk GDC. The governing mechanism of conduction of sputtered-GDC electrolyte films was mainly governed by a grain boundary process, which resulted in a blocking effect and the lower conductivity of thin films than that of bulk GDC samples. Our results suggested that sputtered-GDC films with a comparable conductivity can be used as solid electrolyte layers for a solid oxide fuel cell (SOFC) system as compared to the well-known YSZ.     

Electrophysical properties of zinc-sulfide films obtained by high-frequency magnetron sputtering

The structure and electrophysical properties of zinc-sulfide films obtained by high-frequency magnetron sputtering are investigated. It is shown that the electrical strength of the films is no less than 10⁶ V·cnr^–1, the width of the forbidden band is 3.2–3.3 eV, and the refractive index is 1.8. The films are tested as electroluminescent layers in thin-film electroluminescent emitters. Luminescence with a brightness of 150 cd/m² is obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 29–32, June, 1990.It remains to thank A. A. Miller for perfecting the electron-microscope investigations.     

Surface characterization of TiO2 thin films obtained by high-energy reactive magnetron sputtering

This paper presents the results of surface characterization of TiO₂ thin films deposited on different substrates by the use of high-energy reactive magnetron sputtering. Structural investigations carried out by X-ray diffraction (XRD) and atomic force microscopy (AFM) have shown a strong influence of both the substrate type, and its placement in the deposition chamber (relative to the sputtering target), on the structural properties of the films. In all cases, there is evidence for pseudoepitaxial growth. XRD examination showed existence of TiO₂-rutile phase with preferred (1 1 0) orientation and AFM measurements revealed nanocrystalline structure directly after deposition. X-ray photoelectron spectroscopy analysis showed that the TiO₂ films have stoichiometric composition.     

Cu-In-O composite thin films deposited by reactive DC magnetron sputtering

Cu-In-O composite thin films were deposited by reactive DC magnetron sputtering at room temperature. The samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV/vis spectrophotometer, four-probe measurement and Seebeck effect measurement, etc. The samples contain Cu, In and O. The ratios of Cu to In and O to In increase with increase in O₂ flow rates. The ratio of Cu to In is over 1 and this suggests that Cu is in excess. The obtained Cu-In-O thin films are very possibly made of rhombohedral In₂O₃ and monoclinic CuO. Transmittance of the films decreases with increase in O₂ flow rate. The decrease in transmittance results from increase in Cu content in the films. The optical band gap of all the samples is estimated to be 4.1-4.4 eV, which is larger than those of In₂O₃ and CuO. The sheet resistance of the films decreases with increase in O₂ flow rate. Conductivity of the films is a little low, due to the addition of Cu and the poor crystalline quality of the film. The conduction behavior of the films is similar to that of In₂O₃ and the conduction mechanism of Cu-In-O thin films is through O vacancy.     

Nanocrystalline titanium carbide thin films deposited by reactive magnetron sputtering

We investigated the structure and composition of titanium carbide thin films deposited by the reactive magnetron sputter ion plating process as a function of deposition parameters. The films were sputtered onto unheated glass substrates by means of an unbalanced planar d.c. magnetron equipped with a titanium target using a mixture of argon and methane. The deposition parameters ranged from 0.05 Pa to 2 Pa for total working gas pressurep _T, from 10% to 60% (volume) for relative methane concentration in the working gas mixture, from 45 mm to 85 mm for the substrate-to-target distanced _s-t and from −50V to −800V for the substrate biasU _S. It was found that the crystallinity of the thin films strongly decreases with increasingp _T,d _s-t andU _S. The experiments described show the conditions necessary to obtain sputter-deposited nanocrystalline titanium carbide films. This work has been partially supported by the Grant Agency of the Czech Republic under Grant No. 106/96/K245 and by the Ministry of Education of the Czech Republic under Grant No. VS96 059.     

Magnetic properties of Er-doped ZnO films prepared by reactive magnetron sputtering

All Zn_1−x Er _x O (x=0.04, 0.05, and 0.17) films deposited on glass substrates by radio-frequency reactive magnetron sputtering exhibit the mixture of ferromagnetic and paramagnetic phases at room temperature. The estimated magnetic moment per Er ion decreases with the increase of Er concentration. The temperature dependence of the magnetization indicates that there is no intermetallic ErZn buried in the films. The ferromagnetism is attributed to the Er ions substitution for Zn²⁺ in ZnO lattices, and it can be interpreted by the bound-magnetic-polaron model.     

Kinetic properties of TiN thin films prepared by reactive magnetron sputtering

Results of investigations of kinetic properties of TiN thin films prepared by dc reactive magnetron sputtering are presented. It is established that the TiN thin films are polycrystalline and possess semiconductor n-type conduction. The carrier concentration is ～10²² cm^?3, while electron scattering occurs at ionized titanium atoms.     

Cuprite, paramelaconite and tenorite films deposited by reactive magnetron sputtering

Copper oxides films (Cu₂O, Cu₄O₃ and CuO) have been deposited by magnetron sputtering of a copper target in various Ar–O₂ reactive mixtures. The films are characterized by X-ray diffraction, scanning electron microscopy, four-point probe method and UV-Vis spectrometry. The three defined compounds in the Cu---O binary system can be deposited by varying the oxygen flow rate introduced into the reactor. All the films are crystallized with a mean crystal size ranging from 10 to about 35 nm. They are highly resistive and present a direct optical band gap higher than 2 eV. The application of a bias voltage during the deposition phase modifies the texture of the Cu₂O films and also induces a preferential resputtering of oxygen from the Cu₄O₃ ones. This resputtering phenomenon leads firstly to the occurrence of the cuprite phase mixed with the paramelaconite one and secondly to the amorphisation of the films. Finally, the thermal stability in air of cuprite, paramelaconite and tenorite films has been investigated. The results show that the stability of Cu₂O and Cu₄O₃ films in air is influenced by the thickness and/or the texture of the films. Tenorite films with a low optical band gap (1.71 eV) can be formed after air annealing at 350 °C of an unbiased cuprite film.     

反应磁控溅射法制备的氟化类金刚石薄膜的XPS结构研究

采用射频反应磁控溅射法用高纯石墨作靶、三氟甲烷(CHF₃)和氩气(Ar)作源气体制 备了氟化类金刚石（FDLC）薄膜，通过XPS光谱结合拉曼光谱、红外透射光谱和紫外 可见光光谱研究了源气体流量比等工艺条件对薄膜中键结构、sp2/sp3杂化比以及光学带隙等性能的影响.结果表明在低功率(60W)、高气压(2.0Pa)和适当的流量比(Ar/CHF₃=2∶ 1)下利用射频反应磁控溅射法可制备出氟含量高且具有较宽光学带隙和超低介电常数的FDLC薄膜. 关键词： 反应磁控溅射 氟化类金刚石薄膜 红外透射光谱 XPS光谱     

On the theory of stoichiometric binary compound films by reactive magnetron sputtering

The theoretical model of reactive sputtering of binary compounds has been improved; the model makes it possible to calculate the stoichiometry condition for these compounds by taking into account the adhesion of molecules of the reacting gas at the regions of the surface occupied by a binary compound, followed by their diffusion to free titanium atoms. It is shown that surface diffusion of reacting gas molecules facilitates the formation of a stoichiometric binary compound, stabilizes the sputtering process, increases its rate, and makes the synthesis of the binary compound on a getter prevailing over cathode sputtering of this compound.     

Characteristics of a cylindrical magnetron and reactive sputtering of binary compound films

The characteristics of a cylindrical magnetron, such as the dependences of the discharge voltage, chamber pressure, and plasma radiation intensity on the reactive gas flow rate and discharge current, are studied. In this magnetron, titanium nitride (TiN) and titanium dioxide (TiO₂) films are obtained by reactive magnetron sputtering. The transmission and reflection spectra of the films in the visual range are taken. From the transmission data for the TiO₂ films, their refractive index and absorption factor in the wavelength range 350–800 nm, as well as the porosity, are found by the Valeev method. The variation of the fundamental absorption edge with film thickness is determined with the Urbach formula.     

ALNx thin films produced by d.c. reactive magnetron sputtering

Conclusion Aluminium nitride is the very promising thin film material for piezoelectric /2,3/ and microelectronic /4,5/ applications. The high microhardness of AlN_X films, verified in our experiment, opens new possibilities of practical utilization of these films.We wish to thank O.Pártl of the Department of Materials of the Faculty of Nuclear Science and Physical Engineering in Prague for help with microhardness measurements.     

Optical band gap of zinc nitride films prepared on quartz substrates from a zinc nitride target by reactive rf magnetron sputtering

Polycrystalline zinc nitride films have been synthesized onto quartz substrates from the zinc nitride target and the nitrogen working gas by reactive rf magnetron sputtering at room temperature. X-ray diffraction study indicates that polycrystalline zinc nitride films are of cubic structure with the lattice constant a = 0.979(1) nm and have preferred orientations with (3 2 1) and (4 4 2). Its absorption coefficients as well as the film thickness are calculated from the transmission spectra, which are measured with a double beam spectrophotometer. The optical band gap has been determined from the photon energy dependence of absorption coefficient, an indirect transition optical band gap of 2.12(3) eV has been obtained.