Properties of reactively sputtered Mo1−x O x films

Molybdenum oxide (Mo_1–xO_x) films were prepared by reactive rf sputtering of a Mo target in O₂/Ar plasma. The dependence of film properties on various sputtering parameters is investigated. The atomic percentage of oxygen (x) in the Mo_1–xO_x films decreases with sputtering power and increases with the partial pressure of oxygen. Mo_1–xO_x films that exhibit metallic conductivities can be obtained over a wide range of sputtering conditions. The intrinsic film stress of conducting Mo_1–xO_x is compressive. Such M_1–xO_x films were shown by backscattering spectrometry to be excellent diffusion barriers between Al and Si up to 600 °C annealing for 30 min.     

Deposition of nanostructured crystalline and corrosion resistant alumina film on bell metal at low temperature by rf magnetron sputtering

Aluminium oxide films deposited by rf magnetron sputtering for protective coatings have been investigated. The alumina films are found to exhibit grainy surface microstructure. The grain size, structure and density depend on different system parameters such as argon and/or oxygen flow rate and applied rf power etc. The effect of transition of the discharge from metallic to reactive mode on the surface characteristics of the alumina film is studied. X-ray diffractometry reveals that in poisoned mode of sputtering and under optimized power and pressure, crystalline alumina film can be grown. Different system conditions are optimized for corrosion resistant aluminium oxide films with good adhesion properties. Nanostructured alumina film is obtained at lower pressure (8 × 10⁻⁴ to 9 × 10⁻⁴ Torr) by rf reactive magnetron sputtering.     

Studies on bombardment-enhanced conductivity. IV: IV. On the chemical state of oxygen-bombarded Nb2O5

It is now a well-established result that an increased oxygen content in bombarded metal targets influences the yields of secondary ions or photons. A similar influence appears to have been identified also for a decreased oxygen content in the case of bombarded oxide targets. The chemical state of targets which have gained or lost oxygen is less often specified and the present work was therefore undertaken to determine this state in a particular system, oxygen-bombarded Nb₂O₅. The results relate to conductivity, annealing, and electron diffraction. Specifically, intermediate doses $\text{(? 4 × 10}\text{ions}\text{cm}{}^2\text{)}$ of 35 keV oxygen ions led, as with many other substances, to amorphization with unchanged conductivity. Doses in excess of $\text{2 × 10}{}^{17}\text{ions}\text{cm}{}^2$, however, caused an increase in the bulk conductivity of a factor of about 4 × 10⁸ as well as a corresponding stoichiometry change such that Oxygen was lost and a thin layer of crystalline NbO was formed. These changes persisted when bombarded specimens were heated in vacuum at 150–800 °C. The results are discussed from the standpoint of three mechanisms, namely thermal-spike induced vaporization, internal precipitation, and preferential sputtering. Vaporization could be excluded on the basis of the oxygen partial pressures for the process $\text{Nb}{}_2\text{O}{}_5\text{(1) = 2}\text{NbO}\text{(1) +}\text{3}\text{2}\text{O}{}_2\text{(g)}$ being too low, while precipitation could be tentatively excluded on the basis of the vacuum annealings. There were no obvious objections, however, to a model for oxygen loss based on preferential oxygen sputtering even if the details of the model were unclear.     

Deuteron d-state effects for the reactions 117Sn(d, p)118Sn and 119Sn(d, p)120Sn

Angular distributions of the differential cross section and the three tensor analyzing powers were measured for the reactions ¹¹⁷Sn($\text{d}$, p)¹¹⁸Sn and ¹¹⁹Sn($\text{d}$, p)¹²⁰Sn at E_d = 12 MeV. In addition, excitation functions of the tensor analyzing power T₂₀ were measured at proton lab angles of 0° and 5° for energies ranging from 10 to 12 MeV. At forward angles, the tensor analyzing powers for the ground state (l_n = 0) transitions are more than an order of magnitude larger than the predictions of distorted-wave calculations which neglect the deuteron D-state. Qualitative agreement with the measurements is obtained when the D-state is included.     

Electron microprobe compositional analysis of sputtered tantalum-aluminium films

In the present paper the methods for measurement of the composition of two or more component tantalum-based thin sputtered films are summarized. The influence of the target construction on the composition of the films is discussed. The Ta-Al films were sputtered from composite Ta-Al targets. The composition of films was measured by means of the electron microprobe technique. From results it follows that using the composite targets for sputtering in argon at a pressure of 2×10^?2 torr and in its mixture with nitrogen (10^?3 torr), the composition of Ta-Al films is proportional to the ratio of the Ta and Al exposed surfaces on the target. The proportionality factor equals to the ratio of “effective” sputtering yields of target components measured at given sputtering conditions. The presence of nitrogen in sputtering gas decreases the value of Ta yield 2.2 times. If a small Al surface is sputtered together with much larger Ta surface, the sputtering yield of Al remains unchanged. In Ta-Al films the occluded argon was qualitatively determined. The presence of nitrogen was not proved. This seems to be caused by the absorption of nitrogen characteristic radiation in the investigated films.     

Analyzing powers of valence and inner neutron-hole states in 115Sn via the 116Sn(d, t) reaction

The reaction ¹¹⁶Sn($\text{d}$, t)¹¹⁵Sn up to 7.5 MeV excitation energy has been studied at 40 MeV incident energy using a vector polarized deuteron beam. The measured analyzing power reveals strong J-dependence effects and has been used to clearly assign the spin of a number of low-lying states in the ¹¹⁵Sn nucleus. At higher excitation energy, a broad and fragmented bump is observed between 3.7 and 6.0 MeV in ¹¹⁵Sn. This work reports on one of the first attempts to determine the spin of such structure through polarization measurements. The analyzing power data indicates a mixing of spins $\text{J =}\text{9}\text{2}\text{,}\text{1}\text{2}$, in agreement with the excitation of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{and}\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ inner neutron-hole strengths in the ¹¹⁵Sn nucleus. In addition, some $\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ components are observed around ~ 4.6 MeV excitation energy.     

Effect of O2 gas partial pressure on structures and dielectric characteristics of rf sputtered ZrO2 thin films

Amorphous and polycrystalline zirconium oxide thin films have been deposited by reactive rf magnetron sputtering in a mixed argon/oxygen or pure oxygen atmosphere with no intentional heating of the substrate. The films were characterized by high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and capacitance versus voltage (C-V) measurements to investigate the variation of structure, surface morphology, thickness of SiO₂-like interfacial layer as well as dielectric characteristics with different oxygen partial pressures. The films deposited at low oxygen partial pressures (less than 15%) are amorphous and dense with a smooth surface. In contrast, the films prepared at an oxygen partial pressure higher than 73% are crystallized with the microstructure changing from the mixture of monoclinic and tetragonal phases to a single monoclinic structure. The film structural transition is believed to be consequences of decrease in the oxygen vacancy concentration in the film and of increase of the energetically neutral particles in the plasma due to an increased oxygen partial pressure. SE measurements showed that significant interfacial SiO₂ growth has taken place above approximately 51%. The best C-V results in terms of relative dielectric constant values are obtained for thin films prepared at an oxygen partial pressure of 15%.     

Mesure de la conductivite electrique totale du protoxyde de cobalt en fonction de sa composition definie par des electrodes d'alliage cobalt-platine,entre 1000 et 1400 K

The total electrical conductivity of cobaltous oxide has been measured from 1000 to 1400 K as a function of its composition, especially in the range of low oxygen pressures up to the limit of equilibrium with cobalt. These measurements have been carried out with monocrystalline samples of oxide placed between cobalt-platinum alloy electrodes; oxide composition is fixed by the activity of cobalt in the alloy which is also the activity of cobalt in oxide. Results are given by isotherm curves of the logarithm of conductivity versus the logarithm of oxygen pressure. The slope of these isotherms shows a regular variation between $\text{1}\text{4}$ and less than $\text{1}\text{6}$; this fact can only be explained by the successive effects of the formation of vacancies V″_Co, V′_Co and of intrinsic conductivity by electrons and free holes.     

A kinetic study of the initial oxidation of the Ni(001) surface by RHEED and x-ray emission

Nickel (001) surfaces were prepared by a combination of high temperature oxidation, argon ion bombardment and hydrogen reduction. The oxidation of this surface in pure C₂ to form NiO was studied by reflection high energy electron diffraction (RHEED) and X-ray emission. On exposure to oxygen the “clean” surface was found to chemisorb oxygen to produce a coverage of 0.014 $\text{micro}\text{g}\text{cm}{}^2$ in an ordered c(2 × 2) structure. Within this film there appears to exist a number of nucleation sites dependent on temperature and step density. Growth is by oxygen capture at the periphery of these sites to produce oxide islands approximately three oxygen planes thick which spread to cover the surface. At room temperature this film does not thicken with additional oxygen exposure.     

Study of the nonstoichiometric composition op zinc oxide

The x values in the nonstoichiometrie chemical formula Zn_1+xO have been measured in the temperature range from 400 to 1200°C under oxygen pressures from 1 to 10^?6 atm, and also 1 atm of air. The x values varied between 0.00824 and 0.06370 under the various oxygen pressures. The enthalpies of formation of excess zinc in zinc oxide were in general less than 7.40 kcal/mole under the above conditions, all positive values representing an endothennic process. The plots of log x vs log P_o2 (or log x = 1/n log P_o2) are linear, and the 1/n values from the slopes of the plots are $\text{?1}\text{14.0}\text{to}\text{?1}\text{11.1}$ in the temperature range 400–900°C. Many physical properties of zinc oxide such as electrical conductivity, catalytic effects and defects can be explained on the basis of the x values and the mechanism of formation of the nonstoichiometric compositions of the oxide.     

射频反应性溅射沉积的Cd2SnO4薄膜物理性质与缺陷特性研究

在Ar+O₂混合气氛中射频反应性溅射Cd-Sn合金靶制备了透明导电Cd₂SnO₄(简称CTO)薄膜。用X射线衍射测量了CTO膜的结构。实验结果表明,这种薄膜的电学和光学性质依赖于混合气体中的氧浓度、衬底温度以及沉积后的热处理。获得的CTO膜最低电阻率为1.74×10^-6Ω·cm,可见光光谱区最高透射率为95％。对于氧浓度为6％、衬底温度为400℃时沉积的CTO膜,经热处理后,其光隙能由热处理前的2.37eV增大为2.6 关键词：     

X-ray photoelectron spectroscopy of TiO2 and other titanate electrodes and various standard Titanium oxide materials: Surface compositional changes of the TiO2 electrode during photoelectrolysis

Surface compositional changes were observed for TiO₂ single crystal electrodes used for photoelectrolysis of water. Surface stoichiometries of several types of TiO₂, SrTiO₃ and BaTiO₃ electrodes were characterized by XPS and compared with a variety of titanium, titanium oxide and titanium hydride standard materials. Reduction of the electrode surface in a hydrogen atmosphere results in an oxygen deficient surface composition. Photoelectrolysis at current densities of $\text{10–15}\text{mA}\text{cm}{}^2$ for periods up to 8 h appears to return the electrode surface to a nearly stoichiometric oxygen-to-metal ratio. Reduction of the titanium oxide surfaces was also observed by exposure to an argon ion beam. Analysis of the electrode surface by a combination of XPS and ion-sputter profiling was still possible by simultaneous analysis of standard materials.     

The quadrupole moments of the 5− states in 116Sn, 118Sn and 120Sn

The quadrupole interaction frequencies $\text{ω}{}_0\text{=}\text{3eQ}{}_1\text{V}{}_{\mathrm{zz}}\text{41(21-1)}\text{h}\text{?}$ in the 5^? state of ¹¹⁸Sn have been measured by time differential perturbed angular correlation technique in Sn, Sb and (95% Sn+5% Sb) environments. The ω₀ for ¹¹⁶Sn was determined in Sn environment only. With the help of the known electric field gradient ¹) of Sn in a Sn lattice the quadrupole moments have been deduced as $\text{Q(5}{}^{\mathrm{?}}\text{,}{}^{118}\text{Sn}\text{) = ±0.10(4) b}\text{and}\text{Q(5}{}^{\mathrm{?}}\text{,}{}^{116}\text{Sn}\text{) = ±0.165(60)}\text{b}$. These values together with the known²) quadrupole moment of the analogous 5^? state in ¹²⁰Sn are interpreted in terms of the pure single-particle model. The data exhibit the expected strong systematic variation of Q_I with the number of particles in the h_{$\text{11}\text{2}$}. subshell which is being filled with 1, 3 and 5 neutrons in ¹¹⁶Sn, ¹¹⁸Sn, and ¹²⁰Sn, respectively.     

Tunable diode laser measurements of the band strength and collision halfwidths of nitric oxide

The strength of the fundamental absorption band of nitric oxide at 5.3 μm and collision halfwidths of nitric oxide lines broadened by nitrogen, argon, and combustion gases were measured in absorption cell, flat flame and shock tube experiments using a tunable diode laser. Room temperature absorption measurements were made in an absorption cell filled with NO/N₂ or NO/Ar mixtures or with probe-extracted combustion gases. High temperature (to 2500 K) absorption measurements were performed for NO in N₂ and NO in Ar using a shock tube, and for NO in combustion gases using a flat flame burner.Absorption measurements were made on lines from 1860–1925 cm^?1, ($\text{Ω=}\text{1}\text{2}$ and $\text{3}\text{2}$,P($\text{5}\text{2}$-R ($\text{29}\text{2}$)) resulting in a band strength of 123±8 cm^-2 atm^?1 at 273.2 K. Collision halfwidth dependencies for each broadening species were examined as a function of rotational quantum number and temperature.     

The application of tailored modulation techniques to depth profiling with auger electron spectroscopy

Tailored modulation techniques (TMT) are applied to depth profiling to eliminate errors in signal strength measurements caused by Auger line shape changes. The application of TMT is illustrated by profiling through Al₂ O₃Al interfaces. When peak-to-peak heights in first derivative spectra $\text{n}$⁽¹⁾_m (E) are used for profiling, the measured Al KL_2,in3L_2,3 signal strength shows a large decrease near the interface. This artifact is reduced when peak heights in $\text{n}$_m (E) are used but can be eliminated only when Auger area values are used for profiling. The peak heights in $\text{n}$_m (E) and Auger area values can both be obtained in real time with TMT and plotted automatically with conventional multiplexing equipment. Some features of Auger spectra obtained using TMT are illustrated, and a comparison of depth profiles obtained using peak-to-peak heights in $\text{n}$¹_m (E), peak heights in $\text{n}$_m (E) and Auger area values demonstrates the usefulness of TMT in depth profiling.     

Structural and Magnetic Characteristics of Nanogranular Co–Al2O3 Single- and Multilayer Films Formed by the Solid-State Synthesis

The results of structural and magnetic investigations of nanogranular Co–Al₂O₃ films formed from Co₃O₄/Al thin-film layered structures upon vacuum annealing are reported. The Co₃O₄/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O₂ gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al₂O₃ single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.

     

Effects of defects on the quantum efficiency of Eu2+ -doped aluminates with the magnetoplumbite-type crystal structure

The luminescence of SrAl₁₂O₁₉ : Eu²⁺ phosphors can be quenched by substitution of a small amount of Mg for Al, or by preparing samples with excess Al₂O₃. It is most probable that oxygen vacancies near the Eu²⁺ activator ions act as the radiationless sinks of the excitation energy. In CaAl₁₂O₁₉ : Eu²⁺ the quenching of the luminescence by the introduction of defects is much less effective, so that less oxygen vacancies are supposed to be formed. In view of the fact that the stability of CaAl₁₂O₁₉, with respect to less oxygen containing phases, is higher than that of SrAl₁₂O₁₉, this is a reasonable assumption. The homogeneity range of $\text{La}{}_{\mathrm{1?x}}\text{Al}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext><mtext>3\; +\; x</mtext>}}\text{O}{}_{19}\text{: Eu}{}^{\mathrm{2+}}$ is at such values of x that a large number of Al vacancies exist. Quenching of its luminescence by the introduction of oxygen vacancies was not observed. In LaMgAl₁₁O₁₉ : Eu²⁺ phosphors Al³⁺ interstitials rather than oxygen defects seem to play a dominate role in achieving charge neutrality.     

Electrical conduction and bipolar switching properties in transparent vanadium oxide resistive random access memory (RRAM) devices

In this study, the electrical conduction and bipolar switching properties in transparent vanadium oxide thin films are investigated and discussed. (110)-oriented vanadium oxide thin films were well deposited onto transparent ITO substrates for the possible development of applications in the structure of system-on-panel devices. For the as-deposited vanadium oxide thin films, they were prepared for 1 h by a rf magnetron sputtering method of rf power 130 W, chamber pressure 10 mTorr, substrate temperature 550 °C, and different oxygen concentrations. In addition, the Al/V₂O₅/ITO device presents reliable and bipolar switching behavior. The on/off ratio and switching cycling of two stable states are found and discussed. We suggest that the current–voltage characteristics are governed by ohmic contact and Poole?Frankel emission transport model mechanisms in low- and high-voltage regions, respectively.