Anomalous electrical resistive behaviour of Al-O-Pb sputtered alloys

Application of the sputtering technique to (Al-O) _x Pb_100-x alloys containing an immiscible lead element has been found to result in the formation of a duplex material consisting of f cc lead particles dispersed in an amorphous Al _x O _y oxide matrix. The particle size and interparticle distance of the lead phase were about 10 to 50 nm and 10 to 40 nm, respectively. The Al-O-Pb alloys have been found to exhibit an extremely high electrical resistivity (), e.g., 4.06 x 10⁶ cm for (Al-O)_87.5 Pb_12.5 at 273 K, as well as a large positive temperature-dependent resistivity reaching 92% Of 273. The peculiar resistivity behaviour was interpreted by assuming the mechanism that only the lead phase embedded in Al_xO_y matrix contributes to electrical conductivity and the mobility of lead electrons is greatly reduced in the intervening oxide region among lead phases. It has thus been demonstrated that the composite material exhibiting peculiar characteristics, which cannot be achieved in metallic composite materials, is obtained by simultaneously sputtering oxide and an insoluble metallic element.     

Segregation in sputtered Co-Cr films

The segregation growth process in sputtered Co-Cr films is investigated by examining the effect of substrate temperature on the segregated microstructure and magnetic properties. In sputtered Co-25at%Cr films, segregation occurs below 560°C, and both the saturation magnetization and the perpendicular anisotropy constant show a maximum around a substrate temperature of 300°C, where a specific microstructure, called a CP (chrysanthemum-like pattern) structure, is observed. The results suggest that the CP structure becomes observable in the highly segregated state and generates high perpendicular anisotropy. A new segregation growth model is derived from the results of the CP structure observations. Using this model, it is possible to explain the continuous transition of the magnetization mode between the continuous and the particulate modes.     

Magnetization reversal in sputtered Co-Cr films

The magnetic characteristics of a set of r.f. sputtered Co-Cr films of various composition and thickness are examined in order to evaluate their performance for perpendicular recording. The mechanism of the magnetization reversal is discussed on the bases of: i) the shape of the rotational hysteresis loss as a function of the internal rotating field, ii) the value of the rotational hysteresis integral, iii) the dependence of the coercivity Hc, and the remanence coercivity Hr, on the angle between the easy direction and the field direction. In particular the measurements of rotational hysteresis were performed by monitoring the rate of change of the angular velocity of a top containing the specimen spinning in a magnetic field perpendicular to its axis. The deviation of the experimental behaviour from the ideal models are related to the amount of anomalies in the columnar structure of the film.     

Electromigration in sputtered Al-Cu thin films

Lifetime predictions for aluminum metallization vary considerably depending on many factors. These include the deposition scheme and resulting microstructure of the film, linewidth and geometric variations, alloying elements and testing procedure. Many experimental techniques have been used to study metallization lifetimes. Most involve mass transport measurements in both bulk and thin film samples. A method has been developed for lifetime predictions using a continuous resistance monitoring technique. This allows for lifetime measurements that are more sensitive and, consequently, more accurate than present techniques.     

Thermomagnetic writing in Gd-Co sputtered films

A model for thermomagnetic writing in Gd-Co sputtered films at its compensation temperature is described. In the vicinity of the compensation temperature, the films have rectangular hysteresis loops with large values of coercive force. Spots are thermomagnetically written and erased by using a He-Ne laser in conjunction with an external magnetic field, and a diameter approximately of1.5 sim 2 mum is achieved. Photographs of spots written thermomagnetically are shown. The written domains are circular and clear in shape, and are stable. Temperature dependences of coercive force in Gd-Co sputtered films, and characters of spot diameter as a function of applied magnetic field and writing laser power are reported.     

Electromigration in sputtered copper films on polyimide

Electromigration damage (EMD) is one of the major causes for the failures of interconnects. In this study, the electromigration of Cu on polyimide is investigated. An empirical formula is used to evaluate the EMD of Cu film. The activation energy (Q) obtained is significantly less than those of lattice and grain boundary diffusion. This suggests that the electromigration in copper proceeds via an interfacial diffusion path. The geometry of the metallization also affects the activation energy. Any abrupt change in the interconnect direction and metal width causes current crowding and should be avoided. The current exponents (n), calculated from EMD data, are 3.58 and 3.35 for straight and zig-zag Cu films, respectively.     

Plasma polymer films from sputtered polyimide

Deposition of plasma polymer films by r.f. magnetron sputtering of polyimide in an atmosphere of argon, nitrogen and in a self-sputtering mode is studied. In situ analytical techniques are applied to monitor the composition of both plasma and growing film during the deposition. A co-evaporation regime is observed at higher applied powers. Such a regime is characterized by a significant increase in deposition rate of plasma polymer films. In addition CO-based groups appear in the plasma volume and in the resulting films. The films deposited in a pulsed mode are similar in composition to those deposited in the continuous regime at equivalent power. The plasma polymer films are found to be stable to short-term oxidation in air.     

Selective-black absorbers using sputtered cermet films

Selective-black absorbers have high solar absorptivity and low infrared emissivity. We have prepared excellent selective-black absorbers by using r.f. sputtering to deposit MgO-Au and Cr₂O₃-Cr cermet films, which are highly absorbing in the solar spectrum and highly transparent in the infrared, on metal substrates. Both types of films are found to consist of individual crystallites less than 200 Å in size. Absorbers with solar adsorptivity of over 0.9 and infrared emissivity of less than 0.1 have been prepared by depositing films of 75 vol.% MgO-25 vol.% Au on molybdenum-coated stainless steel. These absorbers are stable in air up to 400°C. Absorbers with similar optical properties have been obtained by depositing films of 71 vol.% Cr₂O₃-29 vol.% Cr on nickel-coated stainless steel, provided that these films are covered with a Cr₂O₃ antireflection coating. These absorbers are stable in air up to 300°C. Computer calculations indicate that even better selective properties can be obtained by using Cr₂O₃-Cr films with a graded composition profile rather than a discrete Cr₂O₃ coating.     

Aging processes in thin radio-frequency sputtered zinc films

Thin zinc films with thicknesses ranging between 200 and 1100 Å were radio- frequency sputtered onto Vycor substrates at 293 K. Thermal aging induces a decrease in resistivity between 300 and 385 K. A kinetic analysis of the isothermal resistance recovery showed that the resistance decay is a first-order process and that two distinct temperature regions with different activation energies appear. At “low” temperatures the activation energy is 0.17 eV, suggesting a surface reordering. At “high” temperatures the activation energy increases from 0.4 to 0.64 eV with increasing thickness; the resistance recovery is attributed to a grain boundary diffusion process. These interpretations are in good agreement with the occurrence of Mayadas-Shatzkes conduction in these polycrystalline films with a constant average grain size.     

Magnetic properties and microstructure of sputtered Co-Cr films

Microscopic structural parameters of sputter-deposited Co-Cr films, such as the effective crystallite size along the thickness direction Deff(=coherent length), the strain < ε²>^1/2, and the lattice spacing d00.2have been systematically studied by means of X-ray analysis and transmission electron microscopy (TEM) in conjunction with the magnetic properties. Cross-sectional observations by TEM revealed that a number of slip bands exist in the poorly oriented films. Slip and deformation bands interrupt the coherency along the c-axis in films, giving a spread to the orientation of the c-axis across the band boundaries. The effective crystallite size Defffor such poorly oriented films was found to be less than 200 Å, which is consistent with the period of contrast observed by TEM. When a film was annealed, Deffwas found to increase and the saturation magnetization Ms decreased, implying that Cr segregation as well as slip bands decreased throughout the thickness.     

Magnetic properties and microstructure of sputtered Co-Cr films

The magnetic properties of sputter-deposited Co-Cr films are discussed in relation to the microstructure observed using high resolution transmission electron microscopy. When the dispersion angle ΔΘ₅₀ of the c axis from the film normal decreases, a columnar structure becomes less clear. Detailed observation of a column in a poorly oriented film revealed the existence of a great number of slip bands associated with stacking faults. These faults are considered to be the cause of the decrease in the degree of the c axis orientation. Further, the column boundary was found to be sharp, implying that no significant precipitation of chromium occured thereabouts.     

Polycrystalline growth and recrystallization processes in sputtered ITO thin films

Indium tin oxide (ITO) thin films with various thicknesses from 170 to 700 nm have been grown onto unheated glass substrates by sputtering from ceramic target, and subsequently annealed in vacuum at temperatures ranging from 250 to 350 °C. The structure, morphology and electro-optical characteristics of the ITO samples have been analyzed by X-ray diffraction, atomic force microscopy, four-point electrical measurements and spectrophotometry. Polycrystalline ITO growth has been found varying with film thickness. The thickness also determined the recrystallization achievable by annealing and the electro-optical thin film properties.     

Structure of sputtered Ni2P films

Crystalline and amorphous nickel phosphide (Ni₂P) films are grown by d.c. magnetron sputtering onto various substrate materials, including silicon, III-V compound semiconductors, glass and metals (copper and aluminum). X-ray diffraction and transmission electron microscopy studies showed that the film structure changes most sensitively with the thermal conductivity of the substrates.     

Photoluminescence from RF sputtered SiCBN thin films

Silicon carbon boron nitride (SiCBN) thin films were synthesized by reactive co-sputtering of silicon carbide (SiC) and boron nitride (BN) targets. As-deposited samples show distinct photoluminescence (PL) peaks at 465, 483 and 497 nm. The films were annealed in dry oxygen ambient at different temperatures to investigate the effect of annealing on film properties. Subsequent measurements on the annealed samples show diminished PL peak intensities. X-ray diffraction analysis shows that the as-deposited films are amorphous in nature and there is no change in the microstructure even after high temperature annealing. Surface characterization of the films by X-ray photoelectron spectroscopy reveals change in chemical composition at different annealing temperatures. Carbon concentrations in the films are sensitive to annealing temperatures and could cause the change in photoluminescence properties.