Oxygen Content In Films Research Articles

Oxygen content and disorder of a-axis YBaCuO films with very high crystallinity studied by resonant Rutherford backscattering

Highly crystalline a-axis films were deposited by the hybrid sputtering method, and the conventional DC-template sputtering method. The films prepared by hybrid sputtering have very low T c while those prepared by the DC-template method have T c close to 90 K. The oxygen contents and disorder were studied by the resonant RBS method. We found that the oxygen contents of the films deposited by hybrid sputtering depended on the deposition temperature. Oxygen deficiency can be the reason for the poor superconducting properties of those films deposited by hybrid sputtering. A highly crystalline film deposited by DC-template sputtering had T c close to 90 K but was found to be off-stoichiometric and to have depth-dependent oxygen disorder. The disorder at the Ba and O sublattices of those highly crystalline a-axis films was found to be uncorrelated.

Femtosecond reflectivity of 60 K Y-Ba-Cu-O thin films

We report systematic studies of the femtosecond transient reflectivity at 2 eV in partially oxygen-depleted Y-Ba-Cu-O thin films exhibiting the resistive superconducting transition at 60 K. Our measurements, performed at room temperature, reveal that in 60 K films, the Fermi level in the Cu-O2 plane lies approximately 2 eV above the filled copper d9/d10 band. By mapping the transient optical response across a 1 cm2 film, we show that the position of the Fermi level is very sensitive to the apparent local variations of the film oxygen content, which gives rise to dramatically different transient optical responses. We also observe a strong transient reflectivity dependence on intensity, which can be attributed to the shift of the Fermi level caused by nonequilibrium hole heating.

ガスフロースパッタ法による多結晶Ｆｅ膜成長に及ぼす低エネルギーイオン衝撃の効果

The effects of ion bombardment during deposition on the structures and magnetic properties of Fe films were investigated by a bias-sputtering technique. In order to control the energy of incident ions at low bias voltages, a gas-flow-sputtering method was used in which effective deposition of films was possible even at 1-Torr pressure. Some marked influences on the grain structure and coercive force Hc of polycrystalline films were observed at bias voltages higher than -20V. The growth of crystal grains was promoted at low bias voltages in the range of -30V. In contrast, the crystallinity of films was suppressed at voltages around -100 V. The value of Hc was decreased by applying a substrate bias, and had a minimum value of 4 Oe when the bias was about -30 V. It was also observed that the oxygen content in films was decreased by bias-sputtering, as has been generally observed.

Internal Stress for Sputtered Sendust Films

It has become clear that the internal stress (?) of thermally treated sendust films changes depending on the treatment temperature, the thermal expansion coefficient (?) of the substrate, and the film oxygen content. The measured value for low-oxygen-content sendust film is 169×10?7. Values of calculated using the value of for Sendust film show good agreement with measured values.

Deposition of Thin Film SrFeO2.5+x by Pulsed Laser Ablation

ABSTRACTPulsed laser ablation has been used to deposit thin perovskite films based on the formula: SrFeO2.5+x (x = 0 to ≈ 0.5). Good quality films have been deposited on (1102) and AT cut quartz substrates at temperatures ranging from 300 to 1130 K. Films grown below 770 K showed little or no preferential crystallinity. Temperatures around 913 K produced films predominantly oriented (200), while temperatures greater than 1000 K produced films with (110) orientation. Films were grown from pellets of two compositions (SrFeO2.5, and SrFeO≈3). The former had a higher ablation threshold than the latter. The atmosphere during cooling had a greater effect on the film's oxygen content than the growth atmosphere. Films cooled in vacuum had the brownmillerite structure (x=0), whereas films cooled in 53.3 kPa oxygen had the cubic perovskite structure (x≈0.5).

Synthesis of titanium nitride films by ion-beam- enhanced-deposition

Titanium nitride films have been prepared by simultaneous vacuum deposition of titanium from an electron gun evaporation source and nitrogen ion beam bombardment with an ion energy of 40 keV. The pressure of the target chamber during processing was 6.5 × 10 -4 Pa. The atomic arrival ratio of implanted nitrogen ions to deposited titanium atoms varied from 0 to 0.5. Rutherford backscattering analysis showed that nitrogen ion bombardment can apparently reduce the oxygen concentration in films. The component ratio N:Ti in films prepared at low temperature was greater than that in films prepared at high temperature. At the same atomic arrival ratio, the component ratio N:Ti in the film decreased with increasing titanium deposition rate. These facts are considered to arise from the situation that the composition in the films is strongly affected by the adsorption of nitrogen. X-ray diffraction analysis showed that films formed by ion-beam- enhanced deposition (IBED) were mainly composed of titanium nitride of NaCl- type structure. The mechanical properties of the films have been investigated. The titanium nitride films prepared by IBED exhibited high hardness on improved wear resistance. The adhesion of IBED titanium nitride films to the substrate was superior to that of films obtained by chemical or physical vapour deposition.

Growth and properties of TiN and TiO xN y diffusion barriers in silicon on sapphire integrated circuits

The usefulness of titanium nitride thin films deposited under different sputter deposition conditions as a diffusion barrier in silicon-to-aluminum contacts was examined. In particular, the effect of oxygen in the barrier film was investigated. The films were r.f. sputter deposited from a titanium target in an Ar-N 2 or Ar-N 2-O 2 gas mixture under varying conditions of applied d.c. substrate bias voltage. The variations in film oxygen content, resistivity, film stress and deposition rate are presented as functions of nitrogen and oxygen partial pressures, and applied substrate bias. The diffusion barrier properties of dark brown films (B films) deposited under no-bias conditions, bright golden films (G films) deposited under proper substrate bias, and oxygen-containing golden films (Ox films) were tested by Rutherford backscattering spectrometry and optical measurements at temperatures of 450–600°C. Cross-bridge Kelvin resistor contact resistance structures were formed on the sapphire wafers for electrical characterization of these films. It was found that the G films are much better diffusion barriers than our B films, and show very low contact resistance in an Al/TiN/Ti/Si metallization scheme. Addition of oxygen in the G films increases the contact resistance, but at the same time decreases the failure rate of the contacts during heat-treatment cycles.

The formation of buried oxide layers by ion implantation

An experimental system has been developed, capable of producing buried oxide layers by high dose oxygen ion implantation. A Whickham Engineering implanter has been used with hybrid beam scanning and infra-red pyrometry to produce buried oxide layers. A new spinning disc target chamber, which can handle large wafer batches is described. Nuclear reaction analysis has been used to assess the dose and uniformity of the oxide layers. The technique has been shown to be capable of accurately measuring the oxygen content of films by comparison with ellipsometric measurements.

Effects of the angle of deposition on short-range order in amorphous germanium

A comparison of the atomic arrangements in germanium films deposited at normal and oblique incidence is made. It is shown that the parameters of short-range order are sensitive to the angle ϕ of deposition. The oblique incidence effects manifest themselves both in the intensity function and in the radial distribution function (RDF). The RDF of a film deposited at oblique incidence has an additional correlation peak at r 0 = 0.174 nm which is not observed for normal incidence. Its location corresponds to the length of the GeO bond. It arises because of the increase in the oxygen content of the filn with increasing obliqueness. The coordination number consistent with the GeO correlations is proportional to the oxygen content of the film as estimated by Auger electron spectroscopy. The incorporated oxygen and the structural anisotropy of obliquely deposited films also influence the shape of the second structural peak of the RDF. The reasons for the different oxygen contents in films prepared under the same vacuum conditions are discussed.

アモルファスＣｏ‐Ｔｉ膜の軟磁気特性

Amorphous Co-Ti films of about 1 μm in thickness have been prepared by r.f. co-sputtering technique. The coercivity of Co-Ti films is found to depend strongly on the sputtering conditions such as the substrate bias and the argon pressure. Soft magnetic films with the coercivity less than 50 mOe are obtained at the substrate bias Vb of −30∼ −50 V. Through the negative bias, the oxygen content in films decreases from 4at.% (Vb = 0V) to less than 1 at.% (Vb = −30∼ −50 V) and further the columner structure observed in the films at Vb = 0V disappears in those at Vb = −30V. When the films are annealed in a magnetic field, the coercivity is almost constant up to 400°C, while the uniaxial magnetic anisotropy is induced above 200°C.