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Surface plasmon resonance (SPR) of Ag nanoparticles (NPs), and its emission enhancement properties are investigated by time-resolved photoluminescence spectroscopy using tris(8-hydroxyquinolinato)aluminium (Alq3), which is generally applied in organic light-emitting diode, as the emitter. 5-nm-thick Ag island-films were fabricated, and annealed at various temperatures to vary the size of the Ag NPs. The peak position of the SPR band in the absorption spectra of Ag NPs blue-shifts with increasing annealing temperature, that is, the SPR frequency is controlled by the NP size. Comparison of the photoluminescence (PL) spectra of Alq3 with and without Ag NPs annealed at 150 °C indicates 1.2-fold enhancement of PL for Alq3 with Ag NPs compared to the reference Alq3. From the temperature dependence of the PL intensity and lifetime of Alq3 with Ag NPs, we evaluated the degree of enhancement of the radiative recombination rate in the presence of the localized surface plasmon of Ag NPs, in comparison with the competitive non-radiative quenching process.

We report the ellipsometric and photoluminescence (PL) properties of Indium zinc oxide (IZO) films, which were grown by radio frequency sputtering under Ar and O2 atmospheres. IZO films grown under an O2 atmosphere (IZO (O2)) showed enhanced PL properties when compared to the films grown under an Ar atmosphere (IZO (Ar)), particularly with respect to the band-edge emission. The enhancement of band-edge emission can be attributed to the reduction in the non-emissive defect states related to oxygen vacancies, which were repaired by sputtering under O2 atmosphere, whereas the PL enhancement in green region is probably due to the formation of the different types of defects under the excess oxygen environment. This was also supported by the results of time-resolved PL measurements, where the band-edge emission of IZO (Ar) showed rapid decay with a 50 ps lifetime, which indicates the dominance of the relaxation pathway to underlying defect states. In contrast, the PL decay profiles of IZO (O2) for band-edge and emissive defect states showed moderate decay with time-constants of 2.3 ns and 5.7 ns, respectively. The exciton relaxation dynamics were sensitive to the presence and its kinds of defect states, which were controlled by the growth conditions.

Amorphous rhodium (Rh) oxide thin films ranging in thickness from 50 to 400 nm were prepared by reactive sputtering at −20 °C in either an oxygen (O2) or water (H2O) vapor atmosphere. Their electrochemical and electrochromic (EC) properties were investigated in an aqueous KOH electrolyte solution. The transferred charge density increased linearly with increasing film thickness, and a 400 nm-thick H2O-deposited film displayed the highest transferred charge density of 60 mC/cm2. Electrochemically active Rh atoms comprised approximately 20% and 50% of the Rh atoms in the O2- and H2O-deposited films, respectively. Transmittance by the bleached and colored films decreased with increasing film thickness in accordance with Lambert's law. The 400 nm-thick H2O-deposited film exhibited the largest change in transmittance (57%) at 700 nm. In contrast, the maximum change in transmittance by an O2-deposited film (16%) was observed at a thickness of 200 nm. The molar absorption coefficients of the bleached H2O-deposited films were much smaller than those of the O2-deposited films. However, the molar absorption coefficients of the colored H2O- and O2-deposited films were very similar. The Rh oxide thin films prepared by sputtering in a H2O vapor atmosphere exhibited low molar absorption coefficients in the bleached state and exhibited excellent EC properties and stable transmittance through 25,000 cyclic voltammetry cycles.

The use of water vapor as a reactive gas under metallic mode for high rate sputter deposition of chromium oxide thin films have been studied in the course of this research. Chromium oxide (Cr2O3) thin films were deposited by an RF magnetron sputtering system with chromium metal as a target and argon (Ar) and water vapor (H2O) as the sputtering gas. Water was injected to the target or substrate surface at an H2O flow ratio of H2O/(H2O + Ar), varied from 0 to 100%. A liquid nitrogen cold trap was placed in the sputtering chamber to adsorb non-reacted H2O molecules. When the cold trap was inactive, the deposition rate and discharge voltage dropped and the transmittance of the films increased above an H2O flow ratio of 10%. Discharge voltage and plasma emission measurements showed that Cr2O3 films were deposited under compound target mode. In contrast, when the cold trap was active, the deposition rate increased with increase in H2O flow ratio and also a gradual increase in the transmittance of the films was observed. Hence, the target surface was considered to be almost in a metallic state and the oxidation proceeded gradually. Results of this study indicate that H2O sputtering using cold trap is a promising method for the formation of chromium oxide thin films at high deposition rates under metallic target mode.

Recently, we found that Ag thin films with low electrical resistivity could be produced by DC sputtering using Kr gas, whose atomic mass is closer to that of Ag than Ar gas is. In contrast, sputtering using Ar caused trapping of Ar atoms in the film, leading to higher resistivity. In addition, the films sputtered using Kr gas had a much larger crystallite size than those sputtered using Ar gas. In the present study, we clarified the relation between the resistivity and crystallite size by data fitting using an equation proposed in the literature. Ag thin films with a thickness of 150 nm were deposited on glass substrates via DC magnetron sputtering in Ar or Kr gas at a pressure of 2 mTorr. The sputtering voltage was varied from 300 to 1000 V. By fitting the experimental data, we found that the model curves reproduced the experimental results for films sputtered in either Ar or Kr gas, and the electron reflection coefficient at the grain boundaries was the same for both types of film. Thus, the resistivity depends on the crystallite size, and the electron scattering behavior is basically the same for both films. Therefore, it is considered that the main reason for the lower resistivity of the film produced by sputtering in Kr is enhanced grain growth due to suppression of energetic neutral Kr bombardment of the film surface. Although it is known that the Ar gas pressure affects the characteristics of thin films, the effects of pressure have not been well investigated for Kr gas. In the present study, we examined the effect of the Kr gas pressure on the resistivity and crystallite size for sputtered Ag films. The results indicated that there was no significant effect.

We demonstrated that the sequential structural control of nanoparticles of an open-framework coordination polymer, copper hexacyanoferrate (CuHCF). The structural control has been achieved by addin...

Improvement of the color-switching response of an electrochromic device (ECD) is achieved using nanoparticles of Prussian blue (iron hexacyanoferrate, FeHCF-NPs) and of zinc hexacyanoferrate (ZnHCF-NPs) using size-control of ZnHCF-NP by the nanoparticle classification. Using the centrifuge method, ZnHCF is classified into three groups with average particle sizes of 59 nm, 71 nm, and 214 nm. The maximum transmittance contrast Δ T max of a FeHCF/ZnHCF ECD is blue-to-colorless with -ca. 60%, irrespective of the ZnHCF-NP used. However, the response time for coloration of the ECD with the smallest ZnHCF-NPs is only 13% of that of other ECDs with the largest ZnHCF-NPs, although the response time of the electrode with the smallest ZnHCF-NP electrode remains 65 % and 79 % of the largest case for oxidation and reduction, respectively. Because the applied voltage is limited to avoid the side reaction in the coloration of the ECD, the acceleration of the electrochemical response by the downsizing of ZnHCF-NPs leads the drastic change in the coloration speed.

Nickel oxide is a promising electrochromic (EC) material, and it is a material that changes color upon undergoing electrochemical oxidation and reduction. In this study, we prepared nickel oxide thin films by sputtering a nickel metal target using water vapor (H2O) as a reactive gas, and investigated the effects of substrate cooling and water vapor flow ratio in the atmosphere of argon (Ar) gas, R H2 O = H2O/(Ar + H2O). High and constant target voltage and plasma emission peaks of Ni atoms were obtained up to R H2 O = 75% at ‒80 °C, indicating that the Ni target maintained a metallic state. The deposition rate increased with increasing R H2 O when the substrates were cooled, and a maximum deposition rate of 34.6 nm min−1 was obtained at R H2 O = 50%. The nickel oxide thin films that were formed in the metallic target mode showed high transmittance in the as-deposited state and good EC properties.

Fluorocarbon thin films were formed by radio-frequency magnetron sputtering using a polytetrafluoroethylene target with different substrate temperatures in the range −5 to 200 °C. Using X-ray diffraction and Fourier transform infrared spectroscopy, it was confirmed that the films were amorphous and contained C–F bonds. X-ray photoelectron spectroscopy measurements indicated that the amount of cross-linking in the films increased with increasing substrate temperature. Corresponding to the change in the molecular structure, the adhesion strength of the films to the Si substrate, estimated by micro-scratch testing, improved with increasing substrate temperature.

Hydrated ZrO 2 thin films were prepared by reactive sputtering in O 2 , H 2 O, and H 2 O + H 2 O 2 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 O 2 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 O 2 gas. It was indicated that the higher ion conductivity of the films was caused by lower film density and higher water content.

Hydrated ZrO 2 thin films were prepared by reactive sputtering in H 2 O atmosphere at different substrate temperatures. The crystal structure, chemical bonding state, film density, refractive index, surface morphology and ion conductivity of the films were investigated. The intensity of the absorbance peaks due to hydrogen bonded OH groups increased and the film density decreased with decreasing substrate temperature. Correspondingly, the ion conductivity increased with decreasing substrate temperature and a maximum ion conductivity of 6×10 −6 S/m was obtained for the film deposited at the lowest substrate temperature of −30 °C. We considered that the addition of H 2 O in the reactive gas and substrate cooling were very effective in increasing the H 2 O content and decreasing film density, which resulted in the high proton conductivity of the films.

Reactive sputtering is one of the most commonly used techniques for the fabrication of compound thin films, and the critical condition for target mode transition from metal mode to oxide mode is very important. We investigated the effects of total gas flow rate and sputtering power on the critical condition in Al-O2 reactive sputtering. It was found that the ratio of the number of sputtered Al atoms (NAl) to the number of supplied O atoms (NO) at the critical condition was almost constant, and the ratio of NAl to NO was close to the stoichiometric ratio of Al2O3 (2 to 3). It is thought that the introduced oxygen is gettered by Al atoms almost completely and the target remains in the metal mode below the critical condition. By increasing the amount of supplied O atoms above the stoichiometric ratio of Al2O3, the oxygen supply overcomes the gettering effect. Then, oxygen concentration in the plasma increases abruptly and the target mode changes from metal mode to oxide mode., application/pdf

Reactive sputtering is a very useful and widely used technique for preparing compound thin films, however, the target surface state is not fully understood. In this study, a Si wafer was used as a model sputtering target, and the thickness of the oxide and nitride layers formed on the target surface after sputtering in Ar+O2 and Ar+N2 mixed gases, respectively, was measured by ellipsometry. The maximum thicknesses of oxide and nitride layers were found to be approximately 7 nm in pure O2 gas and 4 nm in pure N2 gas, respectively. The oxidation rate of Si in oxygen plasma was thought to be higher than the nitridation rate of Si in nitrogen plasma.

We have investigated the epitaxial growth of (1 1 1)ZrN films on (1 1 1)Si substrate at a relatively low temperature using an ultrahigh vacuum DC magnetron sputtering system. The film quality obtained and the epitaxial relationship were evaluated on the basis of analyses of X-ray diffraction (XRD) patterns, X-ray pole figures, and grazing incidence angle X-ray reflectivity (GIXR), transmission electron microscopy (TEM) and atomic force microscopy (AFM) results. It was found that (1 1 1)ZrN films were grown epitaxially on (1 1 1)Si at a substrate temperature of 500 ∘ C with the directional relationship ZrN(1 1 1)[1 1 0] ∥ Si(1 1 1)[1 1 0]. GIXR and AFM results also revealed that the epitaxial (1 1 1)ZrN film has a high film density comparable to that of bulk ZrN and a fairly flat surface morphology with an average surface roughness of approximately 0.25 nm.

We have expected that the epitaxial growth of (111)Rh and (001)Rh films with a thickness of 100 nm can be controlled on (11 2 0) sapphire by changing sputtering parameters using an ultrahigh-vacuum sputtering system, because the lattice mismatches between the two-dimensional superlattice cells of (111)Rh/(11 2 0) sapphire and (001)Rh/(11 2 0) sapphire systems are the same. Thus, the effect of rf sputtering power (Prf) on each epitaxial growth was examined, and the crystal quality, surface morphology, resistivity and temperature coefficient of resistivity (TCR) of the prepared Rh films were evaluated. As a result, it is revealed that both the (111)Rh and (001)Rh films can be grown epitaxially on (11 2 0) sapphire by adjusting only the values of Prf (deposition rate: Rd) under the condition of the substrate temperature (Ts) of 500 °C. In addition, it is confirmed that the average surface roughness of these epitaxially grown Rh films is below approximately 1.2 nm, and resistivity of approximately 5.6 ×10-6 Ω cm is obtained.

We have investigated the influence of N 2 addition to the Ar sputtering gas on the crystal orientation of sputtered Ru films. An rf magnetron sputtering apparatus with a Ru target (99.9%) and a glass substrate heated to 100 °C or 300 °C was used for the deposition. The crystal structure, chemical composition and electrical properties of the resultant films were investigated. X-ray diffraction (XRD) revealed the dominant orientation at 0% N 2 to be the c -axis. With increasing proportion of N 2 in the sputtering gas at a substrate temperature of 100 °C, the intensity of the (002) peak decreased, finally disappearing at 50% N 2 . This c -axis-suppressed Ru film sputtered at 50% N 2 was found to contain nitrogen by Auger electron spectroscopy (AES), but by annealing the film in vacuum at 400 °C, the nitrogen in the film was completely removed. The film orientation remained the same as before annealing. Thus, we have demonstrated a new method for depositing Ru films with a controlled preferential orientation of either c -axis oriented or c -axis suppressed.

Reactive sputtering is one of the most widely used techniques for preparing compound thin films. In this study, a Ti model target, a 1 μm thick Ti film sputter deposited on a Si wafer, was used as the sputtering target. The thickness of the oxide layer formed on the surface of the model target after sputtering in an Ar+O_2 mixed gas atmosphere was measured by ellipsometry under various varying processing parameters including oxygen flow ratio, sputtering time, rf power, and total gas pressure. The oxide layer thickness was varied from a few nanometers to approximately 100 nm by changing the parameters, and a nonuniform oxide layer thickness was observed on the target surface., application/pdf

The influence of adding N_2 to the sputtering gas on the crystal orientation of metal films was investigated. We observed a crystal orientation change of Ni films from (111) to (100) upon the addition of N_2 into the sputtering gas. The increase of substrate temperature resulted in higher degree of orientation of Ni films. Applying a similar deposition condition, Ag and Cu films were also deposited. However, no change was observed for Ag films. Cu films deposited at room temperature showed orientation change but the crystallinity became poor due to the incorporation of nitrogen. It is considered that the difference in the influence of N_2 addition is a result of the strength of interaction between nitrogen and metals. We must determine the suitable deposition conditions for the orientation change., application/pdf

Ag oxide thin films were grown on glass substrates by sputtering an Ag target in an Ar+O_2 mixed gas. Effects of O_2 flow ratio on resistivity, reflectance and transmittance of the Ag oxide films were studied. Crystal structure and chemical binding state of the films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. Ag films with a resistivity of 4 μΩcm and a reflectance of 98% were obtained at O_2 flow ratios below 5%. The increase of resistivity and the decrease of reflectance were observed with increasing O_2 flow ratio due to the formation of mixed films of Ag and Ag oxide. Above an O_2 flow ratio of 40%, the transmittance of the films increased and semitransparent Ag_2O films with resistivity of an order of 10^8Ωcm were formed., application/pdf

Ti and TiO_2 films were deposited by RF reactive sputtering using a mixed gas of Ar and O_2. TiO_2 films were found to be formed at oxygen flow ratios above 7%. At the critical O_2 flow ratio, the amount of supplied Ti atoms was found to agree with that of O_2 molecules. Above the critical O_2 flow ratio, the amount of supplied O_2 molecules exceeded the gettering effect of the sputtering Ti atoms and oxygen density in the plasma began to increase. As a result, the surface of the Ti target was oxidized and TiO_2 films were formed. The thickness of the oxide film formed on the Ti target increased with increasing oxygen flow ratio and a maximum thickness of 5-6 nm was obtained at oxygen flow ratios of 40-100%., application/pdf

Thin films of noble metals are considered to be important materials for microelectronics applications. In this study, Ru thin films were deposited on SiO2/Si substrates by RF magnetron sputtering using a mixture of Ar and O2 gases, and the effects of O2 flow ratio, substrate temperature and film thickness on the crystal orientation and surface roughness of the films were studied. Single orientation (001) Ru thin films were formed under appropriate conditions, such as O2 flow ratios lower than that required for RuO2 formation and high substrate temperatures. A minimum full-width at half-maximum of 1.2° was obtained for the rocking curve of the Ru (002) X-ray diffraction peak. The average surface roughness (Ra) of the single orientation films was estimated to be approximately 1 nm by atomic force microscopy. The oxygen introduced during sputtering was thought to play a role as a surfactant.

(001)-oriented Ru films were prepared on SiO2/Si substrates by rf magnetron sputtering using a mixed gas of Ar and O2 with an appropriate O2 flow ratio which was lower than that required for RuO2 formation. Oxygen atoms are believed to play a role as a surfactant and to enhance single oriented growth of Ru films. Next, highly (100)-oriented RuO2 films were deposited on the Ru films by reactive sputtering. The (100)-oriented growth of the RuO2 films is thought to originate from local epitaxial growth on (001)-oriented Ru grains because the mismatch between superlattices of Ru (001) and RuO2 (100) planes is small. Full-widths at half maximum (FWHMs) of 1.8° and 2.1° were obtained for the X-ray diffraction (XRD) rocking curves of Ru (002) and RuO2 (200) peaks, respectively. The highly textured RuO2/Ru electrodes are expected to be useful for dynamic random access memory (DRAM) and ferroelectric random access memory (FeRAM) technologies.

Polycrystalline HfO2 thin film capacitors were prepared by anodizing sputter-deposited Hf films, and their capacitor and leakage current properties were studied. Electrical measurements were performed for the parallel-plate Hf anodized capacitors with an Al–HfO2–Hf (metal–insulator–metal) structure, and high capacitance density (0.6 µF/cm2) and low dielectric loss (0.0095) were obtained for a very thin-oxide capacitor anodized at 10 V. In addition, the leakage current density of this capacitor was about 5 ×10-9 A/cm2 at an applied voltage of 5 V. The leakage current density (J) of HfO2 capacitors as a function of applied electric field (E) was investigated for several capacitors with different oxide thicknesses, by plotting ln (J) vs E1/2 curves. As a result, it was revealed that the conduction mechanism is due to Schottky emission, irrespective of the oxide thickness.

A W target was sputtered in a mixture gas of Ar and O 2 , and influences of the oxygen flow ratio and substrate temperature on electrical and optical properties and crystal structure of the WO x films were studied. The formation process of the WO x films was studied based on the changes in the deposition rate, plasma emission spectra and the total pressure in the chamber, and was divided into the following three classes. (1) In the low O 2 flow ratio region (below 10%), W and W 3 O films are formed, (2) In the intermediate O 2 flow ratio region (about 20%), WO x (2≤x

RhO2 belongs to the family of conducting platinum group metal oxides, which have attracted attention as new capacitor electrode materials for dynamic random access memories (DRAMs) and nonvolatile ferroelectric random access memories (FeRAMs). Rh, Rh2O3, and RhO2 thin films were prepared by sputtering and their XPS spectra were collected with a monochromatic Al Kα x-ray source. This report includes XPS spectra of Rh 3d and O 1s core regions for these films.

Iridium oxide is an anodic electrochromic material, which takes on a blue-black color through electrochemical oxidation and turns to transparent via reduction. Hydrated amorphous Ir oxide thin films with various thicknesses from 20 to 400 nm were prepared by reactive sputtering in a H2O atmosphere, and their transmittance spectra in both the bleached and colored states as well as their response times were examined in this study. The bleached and colored transmittances decreased with increasing film thickness according to Lambert’s law, and the absorption coefficients in the bleached and colored states were estimated to be 3.2 ´ 103 and 1.1 ´ 105 cm-1, respectively, at a wavelength of 600 nm. The results point to almost all the Ir atoms being electrochemically active and contributing to the color change. A maximum transmittance change of 81% was obtained for the 400 nm-thick film. Further, there was a trade-off between the response speed and the transmittance change. The response speed slowed down with increasing the film thickness, while the coloring and bleaching response time for the thick films was several tens of seconds.

In order to investigate the effect of the vacuum conditions on the process of initial formation of Mo silicides, Mo/Si systems were subjected to heat treatment under high vacuum and clean ultrahigh vacuum, after which we compared and analyzed the behavior of interfacial solid-phase reactions by means of X-ray analysis, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. Results of investigation suggest that the temperature at which the initial silicide formation takes place in the ultrahigh vacuum is lower than that in the high vacuum. However, no differences in the formation phase were found under the different vacuum conditions. It was established that the initial formation processes under both high vacuum and ultrahigh vacuum conditions involve multiphase silicides consisting of Mo3Si, Mo5Si3, and MoSi2, and the film growth continues also as the multiphase silicides. During this time, the main phase is MoSi2, but since the dominant diffusing species are different for various vacuum conditions, during the sputtering under high vacuum the dominant diffusing species is Si, while under the ultrahigh vacuum, Si diffusion begins at a lower temperature simultaneously with Mo. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(3): 71–78, 2001

Reactive sputtering techniques have been widely used for forming compound thin films. In this study, the time-dependent variation of the target mode of an Al–O 2 system was investigated by measuring the target voltage for various reactive O 2 gas flow ratios and presputtering (i.e., sputtering in pure Ar gas to clean the target surface) times. The Al target remains in metallic mode for a certain period of time after being exposed to an Ar–O 2 plasma before it begins to be oxidized. This period increases with decreasing O 2 flow ratio and with increasing the presputtering time. It is considered that the period is caused by the gettering of O 2 gas by Al films deposited on the substrate and the chamber wall during presputtering.

Ni–N thin films are prepared by reactive sputtering in an rf diode sputtering system. Deposition parameters, such as nitrogen flow ratio, substrate temperature and substrate holder potential were changed and their effects were investigated. When the substrate was heated at 220°C, Ni and Ni3N phases were observed by XRD. In the case of substrate temperature being room temperature (RT), Ni2N phase also appeared and characteristic nitrogen incorporation into Ni lattice was seen. In addition, when the substrate holder was set to the float potential, nitrogen content of the film which is thought to be lower than the case of ground potential, caused stronger resputtering effect. Because it was observed that the formation phase and nitrogen content of the film depend on the substrate temperature, the nitrogenizing reaction on the deposit surface was considered to rule the film formation. This was also supported by the results on the target surface analysis after sputtering and plasma emission spectroscopy measurements.

Ru and RuO2 thin films are considered to be new electrode materials for dynamic random access memories (DRAMs) and ferroelectric nonvolatile memories because of their low resistivity and good thermal and chemical stabilities. In this study these thin films were pepared by reactively sputtering a Ru metal target (99.9% purity) in an argon and oxygen atmosphere. XPS spectra were collected with a PHI 1600 spectrometer equipped with a monochromatic Al Kα x-ray source and a multichannel detector. This report includes XPS spectra of Ru 3d and O 1s core regions for these samples. The binding energy of Ru 3d5/2 is determined as 280.0 and 280.8 eV for Ru and RuO2 films, respectively. The presence of a small amount of Ru with higher oxidation states, such as Ru6+ and Ru8+, is shown at the surface of the RuO2 thin film.

Hydrogen-containing Ta2O5 (Ta2O5:H) thin films are considered to be a candidate for a proton-conducting solid-oxide electrolyte. In this study, Ta2O5:H thin films were prepared by reactively sputtering a Ta metal target in an O2 + H2O mixed gas. The effects of sputtering power and post-deposition heat treatment on the ion conducting properties of the Ta2O5:H thin films were studied. The ionic conductivity of the films was improved by decreasing the RF power and a maximum conductivity of 2 × 10−9 S/cm was obtained at an RF power of 20 W. The ionic conductivity decreased by heat-treatment in air, and no ion-conduction was observed after treatment at 300 °C due to the decrease in hydrogen content in the films.

Hydrogen-containing Ta2O5 (Ta2O5:H) thin films, which are considered to be candidates for proton-conducting solid electrolytes, were prepared by reactive sputtering in H2O atmosphere. The substrate temperature during sputter deposition was changed from -20 to 70 °C because the equilibrium vapor pressure of water depends strongly on temperature. The chemical composition of the films was characterized by Rutherford backscattering (RBS) and hydrogen forward scattering (HFS), and it was found that the H/Ta atomic ratio increased with decreasing substrate temperature, and a maximum ratio of 2.2 was obtained at -20 °C. The ion conductivity measured at room temperature also increased with decreasing substrate temperature and a maximum conductivity of 4 ×10-8 S/cm was obtained at -20 °C. It is considered that the desorption rate of H2O molecules from the growing film surface was decreased by the substrate cooling, which resulted in the increase in the hydrogen content and the improvement of the ion conductivity.

application/pdf, Reactive sputtering is one of the widely used techniques to prepare compound thin films. In this study, Al and Al2O3 films were deposited by RF magnetron sputtering using mixed gas of Ar and O2. The formation process of the Al2O3films was studied by plasma emission spectroscopy and target voltage measurements. Al2O3films with transmittance above 95% and refractive index of 1.50-1.66 were found to be formed at O2 flow ratios above 8%. Plasma emission peaks of O atoms (777nm) were clearly seen at oxygen flow ratios above 8%, and target voltage decreased drastically at O2 flow ratios above 8%. It is thought that the surface of Al target was changed from metallic mode into oxide mode at the O2 flow ratios of 8%. The relationship between the amount of sputtered Al atoms and the amount of supplied O2molecules was studied, and the atomic ratio of sputtered Al atoms to supplied oxygen atoms was found to be approximately 2:3 at the critical O2flow ratio of 8%.

Hydrogen-containing tantalum oxide (Ta2O5) thin films are considered to be a candidate for proton-conducting solid-oxide electrolytes. Hydrogen-containing Ta2O5 thin films were prepared by reactively sputtering a Ta metal target in O2+H2O mixed gas. The effects of the H2O flow ratio and sputtering power on the hydrogen content in the films were studied by Fourier transform infrared spectroscopy (FTIR) and secondary ion mass spectrometry (SIMS). The hydrogen content in the films deposited in O2+H2O mixed gas was approximately three times as large as that deposited in O2 gas, and a maximum hydrogen content of 3.5×1021 atoms/cm3 was obtained.

TiN thin films are prepared by sputtering method using Ti and TiN targets to compare their properties. Stoichiometric TiN films are obtained using both Ti and TiN targets, and the lowest values of resistivity for them are found to be 30.8 μΩ cm and 45.6 μΩ cm, respectively. In the change of film resistivity with N 2 flow ratio, a remarkable difference is seen between two cases and the reason is discussed in the view point of formation mechanism : on the sputtering of Ti target, nitriding reaction of the target surface followed by deposition of TiN is predominant but at the same time the reaction at the substrate also makes important role. On the sputtering of TiN target, however, possibility of the nitriding reaction at the substrate is almost excluded because the target is already TiN. Merits and demerits for each film preparation are also summarized.

In general, the presence of a reactive gas in the sputtering atmosphere must be avoided to prevent the formation of any other phases during the preparation of metal films. However, we hypothesized that films of metals, which do not form a nitride phase, could be prepared even in 100% nitrogen. Ag films were sputter-deposited in nitrogen and characterized. We found that it is feasible to obtain pure Ag films by rf sputtering in a nitrogen discharge. No other phase but Ag was detected by X-ray diffraction (XRD) analysis and nitrogen was not detected in the film by Auger electron spectroscopy. Electrical resistivity was also as low as 2.8 I?Ic cm. Moreover, we found that Ag films thus deposited at a substrate temperature of 100 A°C exhibited preferential orientation of (100), though that of (111) is generally observed in films sputtered in Ar. At other substrate temperatures, the degree of (100) orientation decreased. Consequently, we have found that sputter-deposition by the present method is useful for preparing pure Ag films with texture controlled by selecting the appropriate conditions., NOTICE: This is the author's version of a work accepted for publication by Elsevier. Changes resulting from the publishing process, including peer review, editing, corrections, structual formatting and other quality control mechanisms , may not be reflected in this document. Changes may have been to this work since it was submitted for publication., application/pdf

TiN films were prepared by reactive sputtering using a radio-frequency magnetron sputtering system. Ti films containing nitrogen were also formed, depending on nitrogen flow. For all films the crystal structure, chemical binding state and composition were investigated. An abrupt transition occurred in the narrow region between 7% and 8% nitrogen flow. Other phases like Ti2N or amorphous state were not observed in the transition process. The electrical resistivity of TiN prepared at 400°C with 8% of nitrogen flow was 24 μΩ cm, equivalent to that of bulk TiN. Films showed low resistivity at higher nitrogen flow (10% and 12%). Films kept low resistivity (30 μΩ cm) at 50 nm thickness, and the continuity of the film was confirmed even at 5 nm thickness.

Current density-voltage characteristics, luminance, and emission spectra of an organic electroluminescent (EL) cell were measured at temperatures between -160 and 20 o C. An aromatic diamine and 8-hydroxyquinoline aluminum (Alq 3 ) were used as the hole transport and the emitting layers, respectively. The EL luminance at a constant current density of 1 mA/cm 2 was found to decrease with increasing temperature, and the photoluminescence intensity of the Alq 3 powder was also found to show a similar temperature dependence

We have examined the preparation conditions of low-resistivity α-Ta thin films on (001) Si by conventional dc magnetron sputtering without bias sputtering or ion beam radiation. As a result, when the sputtering conditions at substrate temperatures above 400°C and sputtering dc powers above 50 W are satisfied, α-Ta films can be grown in a single-oriented (110) state on (001) Si by conventional dc sputtering to minimize the surface energy.

Hydrated ZrO2 thin films were prepared by reactive sputtering using H2O gas, and these films were heat treated in air at temperatures from 100 to 350 °C. Absorbance peaks due to hydrogen-bonded OH groups for these samples were observed by Fourier transform infrared spectroscopy. The peak intensities were nearly the same before and after heat treatment below 200 °C, but began to decrease at 250 °C, and the absorption peak disappeared at 350 °C. Ion conductivity of the films was evaluated by AC impedance measurements and was found to be about 3 ×10-6 S/m before and after heat treatment at 200 °C; it also decreased after heat treatment above 250 °C. From these results, we considered that protons of OH and/or H2O in the films are the dominant ionic species that contribute to the ion conductivity of the films.

Ni oxyhydroxide (NiOOH) thin films were prepared by reactive sputtering in an atmosphere of H2O gas, and the effects of sputtering gas pressure on their electrochromic properties in KOH aqueous electrolyte were studied. The largest optical density change was obtained for the thin films deposited under high sputtering gas pressures of approximately 6.7 Pa because of their low film density and chemical composition close to NiOOH. Stable transmittance change during coloring and bleaching cycles was obtained for the film from the first cycle up to 100 cycles.

In this study, we have examined the preparation of thin films of Ni oxyhydroxide, which are used for batteries, supercapacitors, and electrochromic devices, by reactive sputtering. Transmittance and resistivity were found to decrease with the incorporation of H2O into the sputtering gas. This indicates that the valence state of Ni atoms in the film changes from Ni2+ to Ni3+. Peaks due to Ni–OH and hydrogen bonded OH were observed by Fourier transform IR (FTIR) spectroscopy of the films sputtered in O2 + H2O mixed gas. From the obtained results, it is confirmed that Ni oxyhydroxide films are formed by reactive sputtering in O2 + H2O mixed gas. An electrochromic coloration efficiency of 29 cm2/C was obtained in 1 M KOH aqueous electrolyte solution for the Ni oxyhydroxide films.

We have prepared an Al–Y anodized capacitor using sputter-deposited Al–Y alloy film with 5 at. % Y atoms, and evaluated the capacitor properties and the leakage current properties before and after heat treatment. In addition, the characterization of Al–Y anodized films was examined by X-ray diffraction, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy analyses. As a result, it is revealed that the thermal stability of an Al–Y anodized capacitor is superior to that of a pure Al anodized capacitor because of its excellent passive nature, and the loss properties can be improved by increasing the heat treatment temperature in air because of the reduction of the equivalent series resistance. Furthermore, it is clarified that the cause of the short-circuited state observed at 550°C is the formation of a narrow capillary-like conduction path of metallic Al atoms as a result of the interdiffusion of Al.

We have prepared (001)ZrN films epitaxially grown on (001)Si substrates by a low temperature process using an ultrahigh vacuum magnetron sputtering system, and evaluated their epitaxial relationships and film qualities, using X-ray diffraction (XRD) analysis, X-ray pole figure, grazing incidence angle X-ray reflectivity (GIXR), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It is clarified that (001)ZrN films grow epitaxially on (001)Si even at room temperature with the directional relationship of ZrN(001)[110]∥Si(001)[110], and the lattice mismatch at the interface between (001)ZrN and (001)Si is relaxed due to the existence of a very thin transition layer. It is also revealed from GIXR and AFM that the epitaxial ZrN films have a high film density and a flat surface morphology, irrespective of substrate temperature.

Changing the crystal orientation of Ni films by the effect of reactive gas is attempted. It is known that (111)-oriented Ni film is usually obtained by sputtering in pure Ar gas. However, we report that almost single-oriented (100) Ni films are prepared by rf sputtering when a small amount of N2 (1% < N2 flow ratio < 7%) is mixed with Ar gas. By electrical resistivity measurement and Auger electron spectroscopy (AES), the presence of nitrogen in the (100) Ni films is not observed. Consequently, it is found that nitrogen influences the crystal orientation at the growing film surface but is not incorporated into the films. This enables us to prepare Ni films with either (111) orientation or (100) orientation by sputtering in a controlled manner without a postannealing process.

C-axis-oriented Ru thin films were deposited on glass substrates by sputtering a Ru target in Ar and O2 gas mixture with O2 flow ratios which were lower than that required for RuO2 formation. A minimum value of 3.5° was obtained for the full-width at half maximum (FWHM) of the rocking curve of a Ru (002) peak for the Ru film deposited at a substrate temperature of 500°C and O2 flow ratio of 4%. The c-axis-oriented Ru films were observed to be formed from the initial stage of crystal growth and became continuous even at a film thickness of 3 nm. Two-dimensional crystal growth of the single-axis-oriented Ru films was suggested.

We investigated whether the Cu(111) single-oriented state having excellent electromigration resistance could be realized on SiO2/Si and Si wafers by annealing Cu–Zr alloy films in vacuum. It was revealed that the Cu(111) single-oriented state could be realized on both substrates of SiO2/Si and 7059 glass, when Cu–Zr films were annealed at 500°C for 5 min. The obtained resistivities of the Cu–Zr films after annealing above 400°C were lower than those (3–3.5 µΩcm) of Al alloy systems. Next, we examined the thermal stability of the Cu–Zr/ZrN/Zr/Si contact system, and compared it with that of the Cu/ZrN/Zr/Si system. As a result, although the thermal stability of the former was somewhat inferior to that of the latter, the system was sufficiently stable up to 550°C, maintaining the single-oriented state of the Cu(111) overlayer and the ZrSi2 region with the lowest contact resistivity at the Si interface.

Thin films of RhO2, which belongs to the family of conducting platinum group metal oxides, were prepared by reactive sputtering. Influences of sputtering parameters, such as rf power and substrate temperature, and postdeposition annealing on crystallinity, chemical bonding state and resistivity of the deposited films were studied, in order to obtain low-resistivity RhO2 thin films. The resistivity of the deposited films decreased with decreasing rf power. Plasma emission measurement suggested that oxidation of Rh proceeded under the low rf power condition. Poorly-crystallized conducting RhO2 thin films with resistivity of 300–500 µΩcm were prepared at substrate temperatures below 150°C; the resistivity of the films increased with increasing substrate temperature above 150°C due to the formation of semiconducting Rh2O3. After postdeposition annealing in oxygen atmosphere at up to 700°C, well-crystallized RhO2 films were formed, and the minimum resistivity of 80 µΩcm was obtained.

We have investigated the preparation conditions of single-oriented (002) Zr film on n-(001) Si by varying the sputtering parameters during deposition using an ultrahigh-vacuum dc magnetron sputtering system. The crystallinity and preferential orientational plane of Zr film on Si were examined by X-ray diffraction analysis, and the chemical nature at the Zr/Si interface was evaluated by X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses. We found that the Zr film with the single-oriented (002) plane grew on (001) Si under the conditions of sputtering power above 50 W and substrate temperature range of 350–400°C. For this reason, it is speculated that a thin interdiffusion layer, which consists of elementary atoms (Zr and Si) and Zr silicide, formed at the Si interface plays the role of a buffer layer to relax the misfit between Zr and Si.

As a preliminary examination for improving the reliability of the Cu metallization system of Si-LSI, we prepared Cu/Hf/Si, Cu/CuHf2/Hf/Si and Cu/HfN/Hf/Si contact systems, and compared their thermal stabilities. The change in crystal structure and the interdiffusion behavior were investigated by X-ray diffraction and Auger electron spectroscopy, respectively. In the case of Cu/CuHf2/Hf/Si, its thermal stability was slightly superior to that of Cu/Hf/Si without the CuHf2 layer. However, slight outdiffusion of Si to the Cu surface was also observed, similar to the case of Cu/Hf/Si. On the other hand, the Cu/HfN/Hf/Si system was satisfactorily stable up to 630°C. In addition, it was revealed that Hf silicide containing Hf3Si2 that has the lowest contact resistivity can be maintained at the Si interface up to 630°C.