Jonathan I. Gittleman

Radio‐Frequency‐Sputtered Films of β‐Tungsten Structure Compounds

Radio‐frequency sputtering has been used to deposit films of intermetallic binary systems (AxBy) in which the composition varies continuously from about 10 at.% to 80 at.% for the B constituent. Within this composition range the following β‐tungsten structured compounds were obtained: V3Si, Nb3Sn, Nb3Pt, Nb3Au, Nb3Al, Nb3Ge, and Ta3Ge. For films with thickness ranging from 3000 to 10 000 A values of Tc were observed which were within 1°K of previously reported best bulk values. In the case of Ta3Ge a new β‐W superconductor has been found with a Tc of about 8°K.

Electrical properties of carbon-polymer composites

Both the experimental and theoretical aspects of the transport of electric charge in carbon black-polymer composites are reviewed. The morphology of these composites is discussed emphasizing its influence on the transport which is dominated by tunneling of electrons between adjacent carbon clusters and through the polymer film which separates them. The tunneling, which is enhanced by thermal fluctuations, leads to a resistivity ρ(T) ∞ exp[T1/7 (T+T0)] at low electric fields and to nonlinear effects at high electric fields which are also a function of Tl/(T+T0). This tunneling mechanism is compared with the mechanisms dominant in cermets and amorphous semiconductors.

Are pyrolyzed polyimides conducting polymers

We present the optical properties and the temperature dependence of the resistivity of the pyrolyzed polyimide Pyraliin® which is electrically conducting. Our results indicate that the pyrolyzed material can be described as consisting of carbonized islands in an insulating matrix.

Characteristics of the electrochromic materials Au-Wo3 and Pt-Wo3

The electrochromic cermet Au-WO3 is composed of grains of Au, approximately 20-120å in diameter, embedded in a matrix of amorphous WO3. As prepared, the cermet is blue and when electrochemically colored it is red or pink. The matrix must be amorphous in order for the red color to develop. In polycrystalline Au-WO3 films, the colored state is dark blue. We find that the properties of the amorphous WO3 matrix in the presence of Au are different from pure amorphous WO3. In particular, the presence of the Au grains suppresses the high electrical conductivity characteristic of colored WO3. Pt-WO3 cermets are compared and contrasted with Au-WO3. We discuss the optical and electrical properties of the Au-W03 cermets and their possible use in display devices.

Optical properties of granular magnesium films

Abstract We studied the optical properties of magnesium cermets formed by co- sputtering magnesium metal and MgF 2 . An absorption peak was observed at about 2500 A, in good agreement with the predictions of the Maxwell-Garnett theory. The weakness and large width of the absorption is indicative of very small metal grains.

Laser‐induced surface diffusion

A Brownian motion model for laser‐induced surface diffusion is proposed to account for the kinetics of surface transport of the evaporated molecules from a thin discontinuous film under a focused laser beam. The model is solved exactly where the evaporation rate of the molecules is assumed to be proportional to the temperature rise above the ambient of the absorber layer. The surface diffusion constant and molecular velocity are obtained by comparing the results of calculations with transmission electron micrographs of recorded pits in Te trilayer opticial discs. These values are in good agreement with Einstein’s relation.