Journal of Physics D: Applied Physics

McKee, J S C; Randell, C P; Wilk, S F J

doi: 10.1088/0022-3727/9/13/001pmid: N/A

20 to 50 MeV protons are used to induce K X-ray fluorescence in heavy elements. Relative cross-sections, Kbeta : Kalpha and Kalpha 2: Kalpha 1 ratios are presented, and it is suggested that protons in this energy range may be used as a precise tool in trace element analysis.

Nayyar, V P; Verma, N K

doi: 10.1088/0022-3727/9/13/002pmid: N/A

Presents a theoretical study of the effects of non-uniform illumination on the two-point resolution of a semi-transparent and pi -phase annular aperture microscope. It has been observed that the limiting separation exhibits an oscillatory character around the incoherent limit. The best resolution is obtained in a good contrast image when the illumination is of the type (1- rho 2)-12/, rho being the radial coordinate in the lens aperture.

Bochner, N; Pipman, J

doi: 10.1088/0022-3727/9/13/003pmid: N/A

A method is developed for measuring diffusion constants in transparent mixtures by means of double-exposure holographic interferometry. The diffusion constant is deduced by a simple and direct measurement of the interferograms. The method was checked with sugar solution and water and gives reasonable agreement with other methods.

Kinloch, K A R; Fraser, S M

doi: 10.1088/0022-3727/9/13/004pmid: N/A

The production and location of background fringes was analysed for spherical and plane waves for two methods of practical application in holographic interferometry. The result of the analysis was used to predict the fringe separation for a practical system and gave good agreement.

Hong, N S; Jones, A R

doi: 10.1088/0022-3727/9/13/005pmid: N/A

It is demonstrated that the visibility, or modulation depth, of the AC signal produced in the light scattered by a particle crossing an interference pattern can be used to obtain particle size. A method is described for direct determination of size distribution which is not strongly dependent upon refractive index.

Misell, D L

doi: 10.1088/0022-3727/9/13/006pmid: N/A

The application of approximate methods such as the weak-phase and the weak-phase/weak-amplitude approximations, to the analysis of conventional transmission electron microscope images is examined. The specimen thickness must be respectively less than 5 and 15 nm for stained and unstained biological specimens for the valid application of the weak-phase approximation. These thickness limits can be extended to 10 and 25 nm respectively using the weak-phase/weak-amplitude approximation. The effect of specimen thickness is to place severe restrictions on the interpretation of an image in terms of the specimen structure. The thickness effect becomes increasingly severe as the image resolution improves. Suggestions are made for minimizing experimentally both the effects of specimen thickness and defocus error.

Halder, S K; Sen, Suchitra; Gupta, S P Sen

doi: 10.1088/0022-3727/9/13/007pmid: N/A

A detailed study of copper films was made in the thickness range 80-330 nm for the 111, 200, 220, 311 and 222 reflections. Only high concentrations of growth-twin stacking faults have been observed. The line-shift analysis has shown the existence of small lattice parameter changes and appreciable residual stresses, tensile in nature, for the films deposited from an oblique vapour beam. The line-broadening analyses considering multiple-order and single-order ('linlog') reflections have shown the presence of small coherent domain sizes lying in the range 45-175 AA and an appreciable amount of total RMS strain resulting in a density of dislocations rho approximately 1011 cm-3. The effective coherent domain size De and RMS strain values obtained from the 'linlog' method show considerable anisotropy and the average ratio (De)111/(De)100 approximately 2.0 signifies a fairly large contribution of stacking faults to the domain size broadening. For all the films more than 100 nm thick the 'apparent' orientation factor R approximately=3.0-4.0 indicates a preferential orientation of (111) planes parallel to the film surface.

Serpi, A

doi: 10.1088/0022-3727/9/13/008pmid: N/A

Photoconductivity, quenching, thermally stimulated current and decay characteristics are studied in ZnIn2S4 single crystals. Evidence is obtained for the presence of three impurity levels taking part in the photoconductivity process. Optical quenching is attributed to a sensitization centre, which acts as a competitive recombination level. An exponential distribution of electron traps is revealed both by pulsed photoconductivity and by thermocurrent analysis. The two experimental techniques accordingly provide the value of 70 meV/decade for the trap distribution. Some aspects of the nature of the impurity centres are examined.

Mathur, P C; Dhall, A K; Lomash, S K; Goyal, M L

doi: 10.1088/0022-3727/9/13/009pmid: N/A

The parametric interaction between the second harmonic and the fundamental frequency of X-band GaAs Gunn devices has been studied with the help of a coaxial resonator. An increase in microwave voltage output of the fundamental has been observed by loading the device properly at the second harmonic. The reduced rise time of the switching transients has also been observed in the presence of second harmonic. These studies have been accomplished by measuring the device negative conductance as a function of RF voltage in the presence of the second harmonic.

Sakaki, Y; Anayama, T

doi: 10.1088/0022-3727/9/13/010pmid: N/A

Describes a method to estimate the number of domain walls during flux reversal in 50% Ni-Fe tape-wound cores on the assumption that the induced voltage of the magnetic core under the application of an MMF is a function of the number of walls participating in flux reversal. The study shows that the abrupt change of total flux reversal time in the intermediate-field region, where the applied field intensity is several times larger than the coercive force, is attributable to the increase in the number of domain walls with increasing applied field. The flux reversal time calculated on the basis of the estimated number of domain walls and the equation of wall motion agrees well with the observed one.