Thermoelectric fields transverse to an applied temperature gradient have been observed in artificially created tilted multilayer structures. Copper-constantan multilayer structures were prepared by sintering of a compressed stack of copper/constantan/copper foils and by cutting the stack obliquely to its axis. Tilted multilayer structures represent a new class of thermoelectric devices, and applications for detection of light are demonstrated.

No abstract

The anisotropy ∆S of the thermopower in thin films of the high-Tc superconductor Bi2Sr2CaCu2O8 is investigated using off-c-axis epitaxial film growth and the off-diagonal Seebeck effect. The measurements represent a new method for the investigation of anisotropic transport properties in solids, taking advantage of the availability of oriented grown crystalline thin films instead of using bulk crystals. First results for the temperature dependence ∆S(T ) in Bi2Sr2CaCu2O8 thin films are presented and described within a two-band model. Subjecting the films to heat treatments in different gases at relatively low temperatures, ∆S could reversibly be changed in a wide range.

No abstract

The anisotropy of the oxygen diffusion in the high-Tc-superconductor Bi2Sr2CaCu2O 8+δ was investigated using off-c-axis prepared thin films. High-quality oriented films with thickness 1000 Å and c-axis inclined by a tilt angle α with respect to the normal of the film surface were grown up to α = 15 • . Oxygen diffusion following a small change of the ambient oxygen partial pressure in the temperature range 200-400 • C was monitored by in situ resistance measurements. Diffusion times according to an activated process τ −1 = τ −1 0 exp[−E/kBT ] were found, with E = 0.6 eV and τ0 = τ0(α) becoming smaller with increasing tilt angle. A comparison of the experimental τ0(α) with a calculation of τ0 for an ideal monocrystalline film suggests that as-grown films consist of crystalline grains with lateral dimensions ∼ 1 µm.