Growth of thin Ag films produced by radio frequency magnetron sputtering

Thin Ag films in the thickness range D = 14–320 nm were deposited by radio frequency magnetron sputtering on glass substrates at room temperature inside a vacuum chamber with base pressure of about 5 × 10^− 6 Pa. The growth of the films was studied via X-ray diffraction and atomic force microscopy experiments. The two techniques are complementary and give us the opportunity to study the surface roughness, the statistical distribution and the average value of the grain size, as well as the texture of the samples. It is shown that the film roughness increases negligibly within the first 60 atomic layers of growth. The thicker films (D 300 nm) develop a nanocrystalline structure with a root mean square roughness of about 2.5 nm. The grain size evolves linearly with the thickness from 9.4 nm at D = 54 nm to 31.6 nm at D = 320 nm.     

Structure and dielectric properties of sputtered bismuth magnesium niobate thin films

The Bi_1.5MgNb_1.5O₇ (BMN) thin films were prepared on platinum coated sapphire by rf magnetron sputter deposition. Effects of substrate temperature, sputter pressure and O₂/(O₂ + Ar) mixing ratio on phase structures and dielectric properties of thin films were investigated. The results indicated that sufficiently high substrate temperature and low sputter pressure would facilitate the formation of cubic pyrochlore in BMN thin films. Meanwhile, the appropriate O₂/(O₂ + Ar) mixing ratio of sputter atmosphere was required. The deposited Bi_1.5MgNb_1.5O₇ cubic pyrochlore thin films with (222) oriented texture exhibited large tunability of ~ 50% at a maximum applied bias field of 1.5 MV/cm, with low dielectric loss of ~ 0.007. The temperature and frequency dependent dielectric measurements indicated that no noticeable dielectric dispersion was detected in BMN cubic pyrochlore thin films.     

Residual stress of graded-index-like films deposited by radio frequency ion-beam sputtering

In this study, Ta₂O₅-SiO₂ composite films with various proportions of Ta₂O₅ were prepared by radio frequency ion-beam sputtering deposition. The residual stress of each composite film was analyzed. The residual stresses of different graded-index-like layers made of composite films were studied. The results show that the residual stress of a single layered composite film was lower than that of pure SiO₂ or a pure Ta₂O₅ film. Furthermore, when the composite film was made graded-index-like, the residual stress was reduced.     

Properties of TaSiN thin films deposited by reactive radio frequency magnetron sputtering

TaSiN is a promising material for application as electrically conductive diffusion barrier for the integration of high permittivity perovskite materials in integrated circuits. TaSiN thin films were deposited by reactive radio frequency magnetron sputtering using TaSi and TaSi_2.7 targets in an Ar/N₂ atmosphere. The sputter power was varied in order to achieve different TaSiN compositions. The stoichiometry of as-deposited films was estimated using Rutherford backscattering spectroscopy. The as-deposited TaSiN thin films are amorphous. Their crystallization temperature is above 700 °C and increases with higher nitrogen content. They have metallic conduction and ohmic behavior. The resistivity of as deposited films is in the range from 10^− 6 Ω m up to 10^− 3 Ω m and increases with nitrogen content. It was found that p⁺⁺-Si/Ta₂₁Si₅₇N₂₁ develops unacceptable high contact resistance. Introducing an intermediate Pt layer the stack p⁺⁺-Si/Pt/Ta₂₁Si₅₇N₂₁ had a good conductive properties and good thermal stability at 700 °C.     

Indium tin oxide films deposited on polyethylene naphthalate substrates by radio frequency magnetron sputtering

Indium tin oxide (ITO) thin films were deposited on unheated polyethylene naphthalate substrates by radio-frequency (rf) magnetron sputtering from an In₂O₃ (90 wt.%) containing SnO₂ (10 wt.%) target. We report the structural, electrical and optical properties of the ITO films as a function of rf power and deposition time. Low rf power values, in the range of 100-130 W, were employed in the deposition process to avoid damage to the plastic substrates by heating caused by the plasma. The films were analyzed by X-ray diffraction and optical transmission measurements. A Hall measurement system was used to measure the carrier concentration and electrical resistivity of the films by the Van der Pauw method. The X-ray diffraction measurements analysis showed that the ITO films are polycrystalline with the bixbite cubic crystalline phase. It is observed a change in the preferential crystalline orientation of the films from the (222) to the (400) crystalline orientation with increasing rf power or deposition time in the sputtering process. The optical transmission of the films was around 80% with electrical resistivity and sheet resistance down to 4.9 × 10^- 4 Ωcm and 14 Ω/sq, respectively.     

Growth of lithium tantalate thin films by radio-frequency magnetron sputtering with lithium enriched target

LiTaO₃ thin films were deposited by radio-frequency magnetron sputtering with a Li enriched target composed of Li₂O₂/Ta₂O₅ (55:45 at.%). Morphology, crystallinity, dielectric and pyrolectric properties of thin films of LiTaO₃ are studied according to the temperature of deposition and the nature of the back electrode (Ru/RuO₂ and RuO₂). In order to develop thermal microsensors containing pyrolectric thin layers deposited on membranes of SiN_x ensuring the thermal isolation of the device, the final aim is to improve the pyroelectric coefficient for infrared pyroelectric detectors applications. The best pyroelectric coefficient of LiTaO₃ thin films (400 nm), obtained for a growth temperature of 620 °C and a pressure of 0.67 Pa, is equal to 40 µC/m² K.     

Characterization of the silicon oxide thin films deposited on polyethylene terephthalate substrates by radio frequency reactive magnetron sputtering

Transparent silicon oxide films were deposited on polyethylene terephthalate substrates by means of reactive magnetron sputtering with a mixture of argon and oxygen gases. The influences of process parameters, including the oxygen flow ratio, work pressure, radio frequency (RF) power density and deposition time, on the film properties, such as: deposition rate, morphology, surface roughness, water vapor/oxygen transmission rate and flexibility, were investigated. The experimental results show that the SiO_x films deposited at RF power density of 4.9 W/cm², work pressure of 0.27 Pa and oxygen flow ratio of 40% have better performance in preventing the permeation of water vapor and oxygen. Cracks are produced in the SiO_x films after the flexion of more than 100 cycles. The minimum transmission rates of water vapor and oxygen were found to be 2.6 g/m² day atm and 15.4 cc/m² day atm, respectively.     

Epitaxial (Pb,La)(Zr,Ti)O3 thin films on buffered Si(100) by on-axis radio frequency magnetron sputtering

In this study, we discuss the case for integration of epitaxial (Pb,La)(Zr,Ti)O₃ (PLZT) thin films with silicon for electro-optic device applications. PLZT films, approximately 500 nm thick, were grown by on-axis radio frequency magnetron sputtering on CeO₂/YSZ-buffered Si(100) substrate with a SrRuO₃ electrode layer embedded between CeO₂ and PLZT. The structural properties and surface topography of the different oxide layers were examined with X-ray diffraction analysis and atomic force microscopy. The perovskite thin films were predominantly (001)-oriented, with a (002) rocking curve halfwidth of approximately 0.3° and a surface roughness compatible with requirements for application in optical devices. The PLZT cation stoichiometry was assessed from quantitative X-ray photoelectron spectroscopy. These measurements uncovered a substantial depletion of lead in the film surface for layers deposited at substrate temperatures above ~ 600 °C, whereas the surface concentration of La, Zr and Ti remained virtually unaffected over a wide range of growth temperatures.     

Deposition and dielectric properties of CaCu3Ti4O12 thin films deposited on Pt/Ti/SiO2/Si substrates using radio frequency magnetron sputtering

Polycrystalline CaCu₃Ti₄O₁₂ thin films were deposited on Pt(111)/Ti/SiO₂/Si substrates using radio frequency magnetron sputtering. The phase formation and the physical quality of the films were crucially dependent on the substrate temperature and oxygen partial pressure. Good quality films were obtained at a substrate temperature of 650 °C and 4.86 Pa total pressure with 1% O₂. The dielectric constant (∼ 5000 at 1 kHz and 400 K) of these films was comparable to those obtained by the other techniques, eventhough, it was much lower than that of the parent polycrystalline ceramics. For a given temperature of measurements, dielectric relaxation frequency in thin film was found to be much lower than that observed in the bulk. Also, activation energy associated with the dielectric relaxation for the thin film (0.5 eV) was found to be much higher than that observed in the bulk ceramic (0.1 eV). Maxwell-Wagner relaxation model was used to explain the dielectric phenomena observed in CaCu₃Ti₄O₁₂ thin films and bulk ceramics.     

Chemical states of carbon in amorphous boron carbide thin films deposited by radio frequency magnetron sputtering

Boron carbide thin films were deposited by radio frequency (RF) magnetron sputtering and characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high resolution transmission electron microscopy. The results reveal that the structure of thin films deposited at substrate temperatures lower than 350 °C is amorphous. We found that there are four chemical states for carbon in amorphous boron carbide thin films deposited by RF magnetron sputtering. One is the segregated carbon in form of the graphitic inclusions in the thin film identified by Raman spectroscopy and Raman mapping using two strong peaks at ~ 1360 cm^− 1 and ~ 1590 cm^− 1, but the XPS results show that the graphitic inclusions do not connect to the substrate directly. On the surface the carbon forms C=O bonds characterized by the peak of C1s core level at 285.0 eV besides B-C bonds in the boron carbide with the peak of C1s being at 282.8 eV. The detailed analysis of B-C bonds in the boron carbide shows that there are two states for carbon atoms in B-C bonds: in the C-B-C models with C1s peak at 282.3 eV and in the icosahedra with C1s peak at 283.3 eV.     

Optical, electrical and structural properties of Cu2Te thin films deposited by magnetron sputtering

Thin films of Cu₂Te were deposited, at room temperature, on glass substrates by magnetron sputtering from independent Cu and Te sources. This work presents the effect of annealing temperature on the optical, structural, and electrical properties of sputtered Cu₂Te films. Annealing above 300 °C resulted in stoichiometric and near stoichiometric Cu₂Te phases, whereas temperatures above 400 °C yielded films with single Cu₂Te phase. In contrast, annealing at temperatures of 250 °C and below resulted in mixed phases of CuTe, Cu₇Te₅, Cu_1.8Te, and Cu₂Te. Analyses of transmittance and reflectance measurements for Cu₂Te indicate that photon absorption occurs via indirect band transitions for incident photons with energy above the band gap energy and free carrier absorption below the band gap energy. The determined indirect band gap was 0.90 eV and its associated phonon energy was 0.065 eV. Optical phonon scattering was identified as the mechanism through which the momentum is conserved during absorption by free carriers. Electrical measurements show p-type conductivity and highly degenerate semiconducting behavior with a hole carrier concentration p = 5.18 × 10²¹ cm^− 3.     

The roles of B-site ions in lead strontium zirconate titanate thin films for electrically tunable device applications

B-site modification lead strontium zirconate titanate Pb_0.4Sr_0.6Zr_xTi_1 − xO₃ (PSZT, x = 0-0.7) thin films were prepared on Pt/TiO₂/SiO₂/Si substrates by a sol-gel method. The XRD results indicate that paraelectric PSZT thin films at room temperature are obtained as x approaches 0.2. The temperature-dependent dielectric and hysteresis loop measurements reveal that the thin films have diffuse phase transition characteristics and relaxor-like behavior with nano-polar regions in the paraelectric films at room temperature. The Curie temperature of the PSZT thin films varies with the Zr contents, exhibiting a complex trend. This can be attributed to two competitive factors: higher mobility of Ti⁴⁺ than Zr⁴⁺ and smaller open space left for the displacement of Ti ions with the increase of Zr content. The further increase of the Zr contents leads to the simultaneous decrease of dielectric constant, dielectric loss and tunability. PSZT (x = 0.4) thin film shows the largest figure of merit of 24.3 with a moderate tunability of 55.8% and a dielectric loss of 0.023. This suggests that B-site ions have different roles in modifying the electrically tunable performance of PSZT thin films for tunable microwave device applications.     

Influence of sputtering parameters and nitrogen on the microstructure of chromium nitride thin films deposited on steel substrate by direct-current reactive magnetron sputtering

Chromium nitride thin films were deposited on SA-304 stainless steel substrates by using direct-current reactive magnetron sputtering. The influence of process conditions such as nitrogen content in the fed gas, substrate temperature, and different sputtering gases on microstructural characteristics of the films was investigated. The films showed (200) preferred orientation at low nitrogen content (< 30%) in the fed gas. The formation of Cr₂N and CrN phases was observed when 30% and 40% N₂ were used, with a balance of Ar, respectively. Field emission scanning electron microscopy and atomic force microscopy were used to characterize the morphology and surface topography of the thin films, respectively. Microhardness tests showed a maximum hardness of 16.95 GPa for the 30% nitrogen content.     

Fabrication of YbAl3 film via annealing amorphous Yb-Al film deposited by RF magnetron sputtering

YbAl₃ single-phase bulk alloy was synthesized by melting at 1258 K using raw Yb and Al metals in the ratio of 1:2.2. A sputtering YbAl₃ target was prepared using the precursor YbAl₃ bulk alloy with the spark plasma sintering process. An amorphous Yb-Al film was fabricated by RF magnetron sputtering using the YbAl₃ target, and a single-phase crystalline YbAl₃ film was fabricated by annealing the amorphous Yb-Al film at temperatures higher than 923 K in Ar atmosphere.     

Effect of sputtering power on the properties of Cd1 − xZnxTe films deposited by radio frequency magnetron sputtering

Cd_1 − xZn_xTe films were prepared by radio frequency (r.f.) magnetron sputtering from Cd_0.9Zn_0.1Te slices target with different sputtering power (60-120 W). The effects of sputtering power on the properties of Cd_1 − xZn_xTe films were studied using X-ray diffraction (XRD), energy dispersive X-ray (EDX), atomic force microscopy (AFM), ultraviolet spectrophotometer and Hall effect measurements. The composition of the deposited films was determined by EDX. The Cd content was found always to be higher than the Te content, regardless of sputtering power. This behavior may be explained by the preferential sputtering of cadmium atoms in the target. XRD studies suggest that ZnTe secondary phases were coexisted in Cd_1 − xZn_xTe films. The origin of the secondary phase is ascribed to the lowest sticking coefficient of Zn atom. AFM micrographs show that the grain size increases with the sputtering power. The optical transmission data indicate that shallow absorption edge occurs in the range of 750-850 nm, and the sputtering power does not have a clear effect on the optical absorption coefficient. In Hall Effect measurements, the sheet resistivities of the deposited films are 1.988 × 10⁸, 8.134 × 10⁷, 8.088 × 10⁷ and 3.069 × 10⁷ Ω/sq, respectively, which increase with the increasing of sputtering power.     

陶瓷靶射频磁控溅射TiO2薄膜的制备和光催化特性

Transparent titania thin films were prepared on glass substrates by radio frequency magnetron sputtering from TiO2 ceramic target. The structure and morphology of those films with different sputtering power and substrate temperature has been measured with X-ray diffractometer (XRD) and atomic force microscope (AFM). It was found that the films were anatase and a mix of anatase-rutile with different condition. The transmission of the films has been studied by using UV-VIS-NIR spectrometer. It shows absorption edge has a little red shift with the increase of sputtering power and substrate temperature. The photocatalytic activity of the films was tested on the degradation of Rhodamine B solution. T.he highest degradation efficiency in our experiment was obtained in the film deposited at 550℃ and 130W.     

Growth of FeSb2 thin films by magnetron sputtering

The detailed growth of FeSb₂ films formed on quartz (0001) substrates by magnetron sputtering is reported. FeSb₂ films with different orientations and compositions can be produced by adjusting the Ar working gas pressure and the substrate temperature. By employing FeSb₂ thin layers produced at different substrate temperatures as templates, < 101>-, < 120>- and < 002>-textured FeSb₂ films were produced under identical growth conditions. The thermoelectric properties of film samples grown at different temperatures were measured and the effects of Sb and FeSb impurities were investigated.     

Conductivity and dielectric properties of silicon nitride thin films prepared by RF magnetron sputtering using nitrogen gas

Silicon nitride is an important material in very-large-scale integration fabrication and processing. Recent work on films prepared by radio frequency magnetron sputtering using nitrogen gas have shown that the relative permittivity is typically 6.3 and that aluminium forms an ohmic contact to this material. Under direct current (DC) bias the films exhibited space-charge-limited conductivity with a bulk trap density of the order of 2×10²⁴ m⁻³. In the present work alternating current electrical measurements were made on identical samples as a function of frequency and temperature. Conductivity appeared to be by hopping at lower temperatures, giving way to a free-band conduction process with activation energy of typically 0.44 eV at higher temperatures. Over a limited range of frequency and temperature the model of Elliott was applicable, and yielded a value of 2.87×10²³ m⁻³ for the density of localised states, in reasonable agreement with our estimate of the trap density from DC measurements. As in the DC measurements capacitance followed a geometric relationship with relative permittivity 6.3, and showed a moderate decrease with increasing frequency and an increase with increasing temperature, tending towards a constant value at high frequencies and low temperatures. The loss tangent showed a minimum in its frequency dependence, which appeared to shift to higher frequencies with increasing temperature. The measurements are consistent with the model of Goswami and Goswami for samples having ohmic contacts, and are typical of results obtained on other insulating thin film structures.     

Overview about the optical properties and mechanical stress of different dielectric thin films produced by reactive-low-voltage-ion-plating

Thin films of Ta₂O₅, Nb₂O₅, and HfO₂ were deposited by reactive-low-voltage-ion-plating (RLVIP) on unheated glass and silicon substrates. The film thickness was about 200 nm. Optical properties as well as mechanical film stress of these layers were investigated in dependence of various deposition parameters, i.e. arc current and oxygen partial pressure. For an arc current in the range between 40 and 50 A and an oxygen partial pressure of at least 11 · 10^− 4 mbar good results were obtained. The refractive index and film thickness were calculated from spectrophotometric transmission data using the Swanepoel theory. For example at 550 nm wavelength the refractive index for thin RLVIP-Nb₂O₅-films was found to be n₅₅₀ = 2.40. The optical absorption was obtained by photo-thermal deflection spectrometry. For the investigated materials absorption coefficients in the range of k = 5 · 10^− 4 at 515 nm wavelength were measured. The mechanical film stress was determined by measuring the difference in bending of silicon substrates before and after the deposition process. For dense films, i.e. no water vapour sorption on atmosphere, the mechanical film stress was always compressive with values of some hundred MPa. In case of films deposited with higher arc currents (I_arc > 60A) and lower oxygen pressure (< 15 · 10^− 4 mbar) the influence of a post deposition heat treatment at 350 °C for 4 h on air was also investigated. For these films the properties could clearly be improved by such treatment. However, by using lower arc currents and higher oxygen partial pressure during the ion plating process, immediately dense and environmental stable films with good optical as well as mechanical properties could be achieved without post deposition heat treatment. All the results obtained will be presented in graphs and diagrams.     

Study on ZnO thin films deposited on sol-gel grown ZnO buffer by RF magnetron sputtering

ZnO thin films with preferential C-orientation and dense microstructure have been prepared using RF magnetron sputtering method by the insertion of a sol-gel grown ZnO buffer layer. The XRD results show that the C-orientation of the film deposited on ZnO buffer is obviously better than that deposited directly on lime-glass substrate. With an increase of the RF power from 100 to 380 W, C-orientation of the films with ZnO buffer improves and the grain size increases. When the RF power equals 550 W, the orientation of the film changes to (1 0 0) and the grain size decreases. The crystalline and microstructure quality of the films can be improved after annealing, however, the grain size is not much dependent on the annealing temperature in the range of 560-610 °C.