Bulk Resistivity Values Research Articles

Arrays of multilayered nanowires (invited)

Multilayered Co/Cu wires with a diameter of 80 nm and a length of 6 μm were produced by electrodeposition in nanoporous polycarbonate membranes. Their magnetoresistance has been measured in a geometry where the current was perpendicular to the layer plane. The anisotropic part of the magnetoresistance was limited to 1.5%. The study, for layer thicknesses ranging from 3 to 100 nm interpreted in terms of the Valet and Fert model, gave estimates of the spin dependent bulk and interface resistivities and their change with temperature. The large Co bulk resistivity value, caused by a large amount of Cu impurities, limited the magnetoresistance in our samples to 20% at room temperature and 30% at 20 K. The Cu spin flip mean free path was found to be temperature independent and determined by scattering at Co impurities in the Cu layer. It was measured for two sets of samples with different amounts of Co impurities.

Stress of Platinum Thin Films Deposited by Dc Magnetron Sputtering Using Argon/Oxygen Gas Mixture

AbstractPt thin films were deposited by a DC magnetron sputtering with Ar/O2 gas mixtures. Due to the oxygen incorporation into the Pt films, deposition rate and resistivity of as-deposited Pt thin films increased with oxygen fraction in the sputtering gas. No peaks from crystalline Pt oxides were observed by x-ray diffraction (XRD) and excessive oxygen incorporation into Pt lead to an amorphous Pt oxide formation. More oxygen could be incorporated in the Pt thin films deposited at lower temperatures and at higher total pressures. Incorporated oxygen was completely removed after an annealing at 800 °C for an hour in air ambient, as the resistivity of the Pt thin films recovered their bulk resistivity values. Tensile stress of the Pt films decreased with oxygen incorporation, and approached a saturation level at high resistivity of the films, presumably due to the formation of amorphous Pt oxides.

FMR of powder La 0.7Ca 0.3MnO 3

We report the observation of ferromagnetic antiresonance and resonance in powder La 0.7Ca 0.3MnO 3 at microwave frequencies of 22 GHz, 32 GHz and 36 GHz in the temperature range 77K–350 K. Using different grain sizes we are able to place an upper limit on the resistivity of the grain and estimate the grain resistivity ϱ grain ≤ 1 m Ω cm in the neighbourhood of the peak resistivity where the reported bulk resistivity values are ϱ bulk ≈20 m Ω cm − 50 m Ω cm . This indicates that the grains appear to be atleast an order of magnitude more conducting than the bulk.

Tribological properties of thin silver films sputter-deposited on superalloy substrates

Thin silver films have been deposited on superalloy (alacrite) substrates with an average roughness of 0.2–0.3 micrometer by radio frequency magnetron sputtering of a silver target in argon atmosphere. The silver films, of 0.4–20 μm thickness, exhibited a crystallographic structure preferentially oriented in the (111) direction, with grain sizes of 150 nm. The compressive residual stresses in these films were as low as -0.05 GPa. Argon-free silver films deposited on silicon substrates at the floating potential possessed an electrical resistivity similar to the bulk-resistivity value. The tribological tests were carried out with an alumina ball-on-disk apparatus operating under loads of 9.8, 2.9 and 1 N at room temperature and 500 °C with a sliding velocity of 0.02 m s −1 for 5000 to 90 000 cycles, i.e. for an average sliding distance varying from 385 m to 7 km. After an initial stage of about 1000 cycles, the friction coefficient of silver-coated alacrite disks was essentially independent of the number of cycles. The average friction coefficient values were in the range 0.14 to 0.42, depending upon film thickness and test temperature. After 5000 cycles under loads of 2.9 and 1 N, the bottom of the wear tracks exhibited a periodic sequence of bumps and hollows. The periodicity of these undulations was dependent on the load and test temperature. The formation of these undulations probably resulted from the adhesive friction mechanism of silver films. Under a load of 9.8 N, the bottom of the wear tracks was flat and the wear of silver films was caused by a ploughing mechanism. The variation of the average friction coefficient of silver-coated alacrite disks with film thickness at room temperature was interpreted on the basis of a mechanism of friction proposed for soft metal films deposited on steel substrates when sliding against hard antagonists.

Preparation of indium tin oxide films at room temperature by pulsed laser deposition

The electrical and optical properties of room temperature laser deposited indium tin oxide films were studied. It was found that the resistivity of the film was quite sensitive to the deposition conditions. At the optimized conditions, film with a bulk resistivity value of 2.8 × 10 −4Ω cm and optical transmission of greater than 90% could be obtained. By using an in situ resistance measurement, it was shown that the initial growth mode was via island formation. Additionally, a classic transition from two- to three-dimensional behavior for the resistance was observed. The mean free path obtained was 550 Å.

AI-12.5 wt % Si ribbons prepared by melt spinning

Aluminium-silicon alloy with composition 12.5 wt% Si was rapidly quenched from the melt at a cooling rate of about 106 Ks−1 using the melt-spinning technique. The resulting ribbons were investigated by resistivity measurements and X-ray diffraction. The resistivity of the 20 μm thick ribbons was 26.6 μΩcm. This is 4.4 times its bulk resistivity value. The activation energy calculated from isothermal ageing was 1.14 ± 0.1 eV. The limit of primary solid solubility is extended almost to the eutectic composition and the large supersaturation is relieved by thermal annealing.

Indium Tin Oxide Films Formation by Laser Ablation

AbstractThe electrical and optical properties of room temperature laser deposited indium tin oxide films were studied. It was found that the resistivity of the film was quite sensitive to the deposition conditions. At the optimized conditions, films with a bulk resistivity value of 2.8×10−4 Ω-cm and optical transmission of greater than 90% could be obtained. By using an in situ resistance measurement, it was shown that the initial growth mode was via island formation. Additionally, a classic transition from two- to three-dimensional behavior for the resistance was observed.

Characterization of electron-beam deposited tungsten films on sapphire and silicon

In this work, the electrical and structural properties of e-beam deposited tungsten films on sapphire are described. Tungsten thin films (200–400 nm) were evaporated on sapphire substrates at different substrate temperature Ts. Film resistivity varied from 95 μΩ cm deposited at room temperature to 5.5 μΩ cm deposited at Ts between 440 and 500 °C. The resistivity value of 5.5 μΩ cm is comparable to the bulk resistivity value of 5.50–5.65 μΩ cm. The crystalline structure of these films was characterized by x-ray diffraction and scanning transmission electron microscopy (STEM) (Kikuchi lines). The films show a distinct increase in the degree of crystal orientation as Ts approaches 400 °C. The films deposited at 400 °C and above shows (100) epitaxial growth on the (11̄02) plane or r plane of sapphire, which has a distorted fourfold symmetry. Film stresses which vary from tensile (7.3×109 dyn/cm2) to compressive (−4.4×109 dyn/cm2) between 100 and 500 °C were measured by the interference fringe technique. The intrinsic stress was determined to vary from 8.3×109 dyn/cm2 at Ts=100 °C to 2.4×109 dyn/cm2 at Ts=500 °C. The observed intrinsic stresses (tensile) in epitaxial films are regarded as produced by the lattice misfit at the film–substrate interface. The minimum total film stress was obtained between Ts=350 and 400 °C, where tensile intrinsic stress was compensated by the compressive thermal stress. The properties of tungsten films on silicon, silicon oxide, and polysilicon substrates are also discussed.

Thermally induced changes of CuxS films and effect on CdS-CuxS solar-cell response

Changes in the electrical sheet resistance and optical density of copper-sulfide (CuxS) films have been measured as functions of thermal aging in air. It was found that sheet resistance (or bulk resistivity) and optical density (or absorption coefficient) both initially increase with aging, and subsequently decrease. Maximum bulk resistivity and absorption coefficient values, corresponding to the chalcocite phase of CuxS, were found to be about 0.1Ω cm and 5×104 cm−1 (at 1.8 eV photon energy), respectively. CdS/CuxS solar-cell short-circuit current and efficiency were monitored as functions of thermal aging time, degradation being directly related to CuxS sheet resistance. The dependence of sheet resistance on CuxS stoichiometry is discussed. Several possible mechanisms are proposed to account for the observed behavior.

Technique for Measuring Position Dependent Electrical Resistivity

An eddy current method is given for determining electrical resistivity as a function of distance beneath the surface of a cylindrical metal core within a coil. The method is also useful for studying surface phenomena such as the anomalous skin effect, and provides a relative measure of bulk resistivity values on short, thick samples with an accuracy of at least 0.05%. Bulk resistivity values for copper, obtained by this method, agree with known values. An example is presented in which the resistivity data shows that working the surface layers of a high purity copper sample led to an imperfection density 25 times higher at the surface than it was 160 μ beneath the surface.