Lee Kammerdiner

Dielectric properties of Mg-doped Ba0.96Ca0.04Ti0.84Zr0.16O3 thin films fabricated by metalorganic decomposition method

Mg-doped Ba0.96Ca0.04Ti0.84Zr0.16O3 (BCTZ) thin films have been proposed as a promising material for microelectronic device applications based on high dielectric materials. Perovskite polycrystalline Mg-doped BCTZ thin films were fabricated on a Pt/Ti/SiO2/Si substrate by metalorganic decomposition method. Dielectric properties were improved after a Pt/Mg-doped BCTZ thin film/Pt capacitor was post-annealed at 700 °C in O2 atmosphere for 30 min. A high dielectric constant of 460 at 1 MHz, a low dissipation factor less than 4.5%, and a low leakage current density of 4×10−7 A/cm2 at 3 V were obtained. Improved dielectric properties were discussed in conjunction with reduction of oxygen vacancies and electrons due to the post-annealing and Mg dopants.

Low temperature deposited Ba0.96Ca0.04Ti0.84Zr0.16O3 thin films on Pt electrodes by radio frequency magnetron sputtering

Ba0.96Ca0.04Ti0.84Zr0.16O3 films acceptor doped with Sc were deposited on Pt/TiO2/SiO2/Si substrates using radio frequency magnetron sputtering. Substrate temperatures throughout the fabrication process remained at or below 450 °C, which allows this process to be compatible with many materials commonly used in integrated circuit manufacturing. In addition, this process made no use of oxygen in the sputter gas or in annealing atmospheres and thus it remains compatible with easily oxidized materials. A relative dielectric constant of 166 was achieved along with a loss tangent of 1.9% at 100 kHz. Leakage current densities of 1.6×10−8 A/cm2 were observed at 300 K with 300 kV/cm of applied electric field.

Critical currents and scaling laws in sputtered copper molybdenum sulfide

We have measured critical current densities Jc, of superconducting copper molybdenum sulfide prepared by sputtering onto heated sapphire substrates. In addition, we have examined the samples with SEM, TEM, electron microprobe, and x-ray diffraction techniques. Critical currents were measured as a function of external magnetic field and as a function of temperature and sample preparation conditions. We find that a scaling law P = CBc2nf(b) describes our results, where P is the pinning force per unit volume, Bc2 is the upper critical field, b is the reduced field b ≡ B/Bc2, f(b) is a function of b only, and C is a constant of proportionality. Our results fit the flux shearing model of Kramer from relatively low b (≃0.5) to b = 1. Furthermore, applying this model to PbMo6S8, we estimate the critical current density as a function of magnetic field. For example, we predict Jc108 A/m2 at 26 T. From analysis of all experimental data on our samples, we conclude that flux pinning is mainly on excess Mo metal. The Mo is present as a second phase in the predominantly Chevrel-phase CuxMo6S8, while all the Cu metal is included in the Chevrel phase.

Critical currents in sputtered copper molybdenum sulphide

Critical currents in a sputtered Chevrel‐phase copper molybdenum sulphide have been measured at 4.2 K as a function of applied magnetic field. Self‐field critical‐current values up to 109 A/m2 were found, decreasing to 108 A/m2 at 3 T. Graphs of pinning forces versus field were found to be independent of field direction, and the pinning mechanism is sample independent. Critical‐current densities for sputtered lead molybdenum sulphide are estimated to be ≳108 A/m2 at 26 T based on a scaling law for pinning.

Structural and dielectric properties of Ba0.7Sr0.3TiO3 thin films grown on thin Bi layer-coated Pt(111)/Ti/SiO2/Si substrates

Abstract In this work, the growth and study of dielectric properties of Ba0.7Sr0.3TiO3 (BST) thin films grown on thin Bi layer coated Pt(111)/Ti/SiO2/Si substrates, depending on thin Bi layer thickness is reported. The BST thin film (thickness 180 nm) grown on 10-nm-thick Bi layer exhibited more improved structural and dielectric properties than that grown on bare Pt(111)/Ti/SiO2/Si substrate. The 10-nm-thick Bi layer in optimum configuration was effective for the grain growth of BST phase and suppressed the formation of the oxygen-deficient layer at the interface between the BST thin film and bottom electrode, which resulted in an increase in dielectric constant and a decrease in leakage current density of the Pt/BST thin film/Pt capacitor.

Critical currents in sputtered PbMo6S8

Critical currents in sputtered Chevrel‐phase lead molybdenum sulphide have been measured at several temperatures as a function of applied magnetic field up to 19 T. We find a critical current density of ∼5×107 A/m2 at 15 T and 1.8 K, and the effective upper critical field was estimated to be 30 T. The pinning force at low fields was found to be dependent on the amount of free lead.

Dielectric properties and tunability of Mg-doped Ba0.96Ca0.04Ti0.84Zr0.16O3 thin films on Pt/MgO fabricated by metal organic decomposition method

Mg-doped Ba0.96Ca0.04Ti0.84Zr0.16O3 (BCTZ) thin films were fabricated on Pt/MgO substrate by metallorganic decomposition (MOD) method. The structures of these films were analyzed by X-ray diffraction. The electrical measurements were performed on metal–ferroelectric-metal capacitors with platinum as the top and bottom electrode. The dielectric properties were improved after the capacitors were post annealed at 700 °C in oxygen atmosphere for 30 min. A high dielectric constant of 504 and a dissipation factor of less than 4% were obtained at 1 MHz. The Pt/BCTZ/Pt/MgO capacitors exhibited high tunability of 55% at an applied field of 55 kV/cm.

Low-pressure sputtering of high-T c Nb3Ge

A modified technique for the sputtering of high-Tc Nb3Ge using low Ar pressure is reported. The experimental arrangement involved only conventional equipment and ordinary vacuum conditions. Nb3Si with the A-15 structure was also prepared in a similar manner.

Analyses of sputtered films of Nb3Ge

The analyses of Nb‐Ge films prepared by sputtering with a modified rf arrangement are reported. The results indicate the importance of thermalization of sputtered particles for the formation of the high‐transition‐temperature compound Nb3Ge.

Low temperature sputter deposition of Ba0.96Ca0.04Ti0.84Zr0.16O3 thin films on Ni electrodes

The integration of high-K materials, such as ferroelectrics in the paraelectric state, in integrated circuits presents several challenges. If high-K materials are deposited on-chip after or between Al metalization steps, then these challenges include limits on processing gas composition, deposition temperature and electrode material. Specifically, the atmosphere present during deposition and annealing must be oxygen-free; the deposition and annealing temperatures must not exceed 450°C; and the electrode material must be etchable with chemical techniques. We studied rf magnetron sputtered Ba 0.96 Ca 0.04 Ti 0.84 Zr 0.16 O 3 (BCTZ) with Ni electrodes because this system meets all the above requirements. The BCTZ deposition process uses pure Ar as the sputter gas and a substrate temperature of 450°C. Subsequent anneals may be performed in a reducing (forming gas) atmosphere with little effect on either the dielectric constant or leakage current. The Ni electrodes provide a good substrate for BCTZ films and are much easier to integrate than Pt films. Observed values for the relative dielectric constant K, exceeding 100, were not as high as for BCTZ films on Pt electrodes, however these values are sufficient to provide a clear advantage over other, non-ferroelectric materials. Overall, the device characteristics observed prove that the Ni/BCTZ/Ni capacitor is a valuable technology for on-chip capacitor applications.