An x-ray line shift analysis in vacuum-evaporated silver filmsSen, Suchitra; Halder, S K; Gupta, S P Sen
doi: 10.1088/0022-3727/6/17/304pmid: N/A
Thin films of silver of thickness 58-212 nm (580-2125 ) were prepared by evaporation on glass substrates at a residual air pressure of similar 105 Torr, and x-ray diffraction line profiles were chart-recorded on a Geiger counter x-ray diffractometer at room temperature using Cu K radiation. The peak positions of 111, 200, 220 and 311 reflections were measured, and from the peak shifts of adjacent pairs of reflections the lattice parameter changes, residual stresses and stacking fault concentrations in the films were determined as a function of film thickness. In relatively thin films (<100 nm), an appreciable decrease in the lattice parameter from the bulk value and a predominance of extrinsic stacking faults were observed. The residual stresses in the plane of the films were found to be compressive in nature, varying from similar 017 to similar 0011010 N m2 (similar 24 to similar 1104 psi) with the increase in thickness. The results have been analysed and discussed in the light of existing work on thin metallic films.
Structure cristalline des couches minces de sulfure de zinc prpares par pulvrisation cathodique ractive en fonction des conditions de prparationBugnet, P; Deforges, J; Durand, S
doi: 10.1088/0022-3727/6/17/305pmid: N/A
The crystalline structure of thin films of ZnS, prepared by reactive cathodic sputtering, has been studied in relation to the parameters of the synthesis: anode-cathode voltage, H2S ratio in the gaseous mixture, anode and cathode temperatures.The principal structure types of ZnS are cubic zinc-blende, which is normally obtained at temperatures lower than 1000C, and hexagonal wurtzite, obtained at higher temperatures. With reactive cathodic sputtering one can obtain either blende, or wurtzite, at low temperatures by modification of one parameter.It is shown that sputtered ZnS films have the wurtzite structure when the values of the parameters are such that an excess of zinc is condensed for instance in the case of a high voltage, or at a low H2S ratio. They have the blende structure in the opposite case. The blende structure shows preferential orientation, with the [111] axis perpendicular to the substrate, when the H2S ratio is very high.
A simple rotating jet-thinning apparatus for producing taper sections and electron microscope specimens from silicon and compound semiconductorsBicknell, R W
doi: 10.1088/0022-3727/6/17/306pmid: N/A
Descriptions are given of a jet-thinning apparatus which rotates the specimen in the jet stream, and a method of producing continuously chlorinated methanol via a double concentric emulsifier jet. The system has been successfully used to produce uniform electron microscope specimens from a variety of semiconductor materials, and by double-sided thinning, buried heterojunction dislocation networks have been examined.Examples are also given of the use of the apparatus for preparing shallow angle taper sections for examination by chemical staining methods. With the use of the internal interference fringes, the depth of of staining at p-n junctions etc has been measured to better than 500 . The advantages of chemically prepared taper sections over conventional mechanically lapped specimens are discussed.
Stress relaxation in regenerated celluloseHaughton, P M; Sellen, D B
doi: 10.1088/0022-3727/6/17/307pmid: N/A
Stress relaxation measurements on single fibres of regenerated cellulose (viscose), which had a low degree of anisotropy, are described. These were made in the temperature range +20 to 185C for the time interval 003 to 1000 s using tensile strains of the order of 03%.The results are discussed in relation to existing reaction rate theories, and it is concluded that they cannot be explained in terms of such theories if only a single relaxation process is considered. A distribution of activation energies can be derived from the data if the system is regarded as approximately linear. A modified Ferry transform is used for this purpose, the theory of which is discussed. The distribution so derived is bimodal and corresponds approximately to fully bonded glucose rings moving singly and in pairs. Measurements on other hydrogen-bonded systems may help to establish the validity of this result.
The elastic moduli of particle-filled materialsVeldkamp, J D B
doi: 10.1088/0022-3727/6/17/308pmid: N/A
The effective elastic moduli of a particle-filled material are analytically derived from a consideration of the deviations of the particle and matrix materials from either parallel or series connection. In the analysis an equivalent cell is defined based upon the operation of a force or deformation in an elementary cell representative of the composite; in addition, so-called particle and matrix stresses and strains are introduced. These parameters enable an expression for the respective energies of the constituents to be derived from both the parallel and series connection approach. The equation of both expressions gives the elastic modulus of the composite. This holds for six of the nine moduli. The other three are derived from separate considerations. The expressions obtained involve the way in which the particles are arranged, their shape and volume fraction, and the relevant elastic moduli of both materials. The numerical results are in good agreement with experimental values.
The elastic constants of calcium tungstate, 42-300 KGluyas, M; Hughes, F D; James, B W
doi: 10.1088/0022-3727/6/17/309pmid: N/A
The temperature dependences from 42 to 300 K of the seven adiabatic elastic constants of CaWO4 have been determined by measurements of ultrasound wave velocities using the `sing-around' and pulse superposition methods. The adiabatic elastic constants have been calculated from the measured ultrasound wave velocities by a perturbation method using just seven of the eleven measured velocities and by an iterative method using all the measured velocities; agreement has been found between the two sets of values. The complementary data on the thermal expansion and heat capacity at constant pressure of CaWO4 have been used with the present results to find the isothermal elastic constants, the heat capacity at constant volume, the Grneisen parameters, and the Debye characteristic temperature at 0 K. The Debye characteristic temperature has been found from the heat capacity at constant volume from 10 to 300 K after subtraction of the Einstein heat capacity terms from the total heat capacity.
The effect of interfacial radial and shear stress on fibre pull-out in composite materialsTakaku, A; Arridge, R G C
doi: 10.1088/0022-3727/6/17/310pmid: N/A
The extraction of a stainless steel wire embedded in an epoxy resin has been studied as a function of the embedded length. The models developed to elucidate the dependence of the debonding stress and the pull-out stress on the embedded length are applied successfully to the experimental results. The nonlinear variation of the debonding stress with the embedded length is caused by the distribution of shear stress along the wire. The variation of pull-out stress with embedded length is caused by the decrease of the frictional stress due to the Poisson contraction of the wire under tensile stress. The effect of wire contraction on the friction process was confirmed by using different initial wire tensions. The residual compressive stress at the interface due to resin shrinkage and the coefficient of friction were determined from the analysis of the pull-out process.