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Optical absorption in very thin (< 100Å) dielectric films and its origin
Classified Abstracts 1113--1120
484
temperature reached so far is 2.3 × 10-5°K, and energy containment times are of the order of 10tL sec. The apparatus is in course of modification with a hope of improving its performance.
(Great Britain). w. J. s. N. K. Allen et al., Nature, 199 (4889), 13 July 1963, 123-126.
19.
Radiation
19 : 30 1113. Silicon surface barrier radiation detectors : some designs and applications. (Great Britain) P. G. Salmon and F. L. Allsworth, U.K.A.E.A. Rep. A.E.R.E-R4122, April 1963. 19:30 1114. Optical absorption in very thin ( < 100A.) dielectric films and its origin. (France) It is well known that the optical behaviour of rather thick transparent dielectric films in metal surfaces can be accurately described by a two-homogenous layer model in which the metal has a characteristic complex index and the dielectric film has a real index close to the bulk value. This type of model, however, breaks down for films less than about 100A thick. From experiments carried out with barium stearate films of this order of thickness, the author concludes that the index of refraction and thickness per molecular monolayer is constant and independent of the number of molecular layers on the metal surface, but that the layers nearest the metal are absorbing while those far away are transparent. This behaviour is due to the space charge of the electric double layer caused by the contact of two dissimilar phases. (U.S.A.) (Author, modified) R. C. Plumb, Colloque sur l'optique des conches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19:49 1115. On the properties and production of thin films with a graded refractive index. (France) The interest in inhomogeneous dielectric thin films arises in connexion with optical coating and filtering problems. The inhomogeneity consists of a gradient of the refractive index in a direction perpendicular to the film surface and may be produced by varying the ratio of the evaporating rates of two sources containing different substances and operated simultaneously. The author has studied the theoretical and experimental possibilities of making the inhomogeneity in a reproducible and wellcontrolled way. Expressions are obtained for the refractive index on the following assumptions : that the evaporative rate varies linearly with time, the volume of the two components is equal to the sum of the individual volumes, and that the refractive index n can be expressed in the form n 2 - 1 = A N I + B N 2 , where A and B constants for a given wave length and N1 and N2 are the number of atoms per unit volume of the mixture. Defining W'I(O) and W'I(T) as the rate of deposition of component (1) at the beginning and end of deposition, with a corresponding notation for component (2), the author defines a parameter c~= W'2(O)/W'I(T)for the special Case W'I(O) : O and W'~(T) = O. Roughly speaking, the height of the reflectance maxima increases with increasing wave number for ~<½ and decreases with increasing wave number for ~ > ½. (Sweden)
rotated so that the reflected light is observed at various angles. The film thickness d is given by d = ANA/2#(cos r2 - cos rl), where A = wavelength of filtered light ; /~ = refractive index ; and AN = number of fringes observed between angles of refraction r~ and ra. The technique is especially suited for films thicker than one micron. An accuracy of 12 per cent is claimed. (U.S.A.) (Authors, modified) W. A. Pliskin and E. E. Conrad, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19 • 33 1117. An immersion spectrophotometric determination of the opticalconstants of interference of films. (France) Immersion either increases or decreases the degree of interference, depending on the relative magnitudes of the component wavevectors. Interference peak heights were measured on a spectrophotometer with the specimen immersed in various pure liquids. Extrapolation to zero interference gives the condition of no refractive change in crossing-the medium/film interface. Immersion effects associated with an absorbing film are discussed by the author in terms of a complex refractive index. (U.S.A.) (Author, modified) W. P. Ellis, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press).
1118. Ellipsometric
investigations
of oxide
films
19 : 30 : 41 on GaAs.
(France) The real part of the complex index of GaAs has been determined by ellipsometric methods. This value together with the extinction co-efficient k, were then used in the exact solution of the fundamental equation of allipsometry by computer technique. Samples of GaAs with different orientations were subjected to various surface treatments and the influence of these variable on the optical properties investigated. The resulting samples were subsequently oxidised and again examined by ellipsometry. The results obtained were correlated with those of multiple beam interferometry and infrared total internal reflection. (U.S.A.) (Authors, modified) K. H. Zaininger and A. C. Revesz, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19 : 30 : 41 1119. Relation between the optical absorption spectrum of silver film and its film structure. (France) Anomalies in the optical properties of thin metallic films arise from inhomogeneous structures such as uneveness, cracks or isolated particles and can be explained by means of a model in which all the films have two-dimensional colloid structure composed of ellipsoids of rotation. In the present paper the author refines this model by introducing dipole interaction between polarized ellipsoids. By assuring a Poisson distribution of axial ratio of ellipsoids, the shape of the anomalous absorption band of silver films can he explained. (Authors, modified) S. Yamaguchi, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press).
W . J. S.
R. Jacobson, Colloque sur l'optiques des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19 : 30 1116. A simple non-destructive technique for thickness and refractive index measurement of transparent films on refleetive substrates. (France) The technique involves the use of a microscope equipped with a monochromatic filter on the objective and a stage that can be
19 : 30 : 41 1120. Optical properties of thin palladium film. (France) The author lists the optical constants of Pd films of various thicknesses for wavelengths ranging from 2000 to 25,000A~. Electrical resistance data as well as value for the Hall constant are also given. (France) (Author, modified) P. Lostis, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, 3". Physique (in press).
484
temperature reached so far is 2.3 × 10-5°K, and energy containment times are of the order of 10tL sec. The apparatus is in course of modification with a hope of improving its performance.
(Great Britain). w. J. s. N. K. Allen et al., Nature, 199 (4889), 13 July 1963, 123-126.
19.
Radiation
19 : 30 1113. Silicon surface barrier radiation detectors : some designs and applications. (Great Britain) P. G. Salmon and F. L. Allsworth, U.K.A.E.A. Rep. A.E.R.E-R4122, April 1963. 19:30 1114. Optical absorption in very thin ( < 100A.) dielectric films and its origin. (France) It is well known that the optical behaviour of rather thick transparent dielectric films in metal surfaces can be accurately described by a two-homogenous layer model in which the metal has a characteristic complex index and the dielectric film has a real index close to the bulk value. This type of model, however, breaks down for films less than about 100A thick. From experiments carried out with barium stearate films of this order of thickness, the author concludes that the index of refraction and thickness per molecular monolayer is constant and independent of the number of molecular layers on the metal surface, but that the layers nearest the metal are absorbing while those far away are transparent. This behaviour is due to the space charge of the electric double layer caused by the contact of two dissimilar phases. (U.S.A.) (Author, modified) R. C. Plumb, Colloque sur l'optique des conches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19:49 1115. On the properties and production of thin films with a graded refractive index. (France) The interest in inhomogeneous dielectric thin films arises in connexion with optical coating and filtering problems. The inhomogeneity consists of a gradient of the refractive index in a direction perpendicular to the film surface and may be produced by varying the ratio of the evaporating rates of two sources containing different substances and operated simultaneously. The author has studied the theoretical and experimental possibilities of making the inhomogeneity in a reproducible and wellcontrolled way. Expressions are obtained for the refractive index on the following assumptions : that the evaporative rate varies linearly with time, the volume of the two components is equal to the sum of the individual volumes, and that the refractive index n can be expressed in the form n 2 - 1 = A N I + B N 2 , where A and B constants for a given wave length and N1 and N2 are the number of atoms per unit volume of the mixture. Defining W'I(O) and W'I(T) as the rate of deposition of component (1) at the beginning and end of deposition, with a corresponding notation for component (2), the author defines a parameter c~= W'2(O)/W'I(T)for the special Case W'I(O) : O and W'~(T) = O. Roughly speaking, the height of the reflectance maxima increases with increasing wave number for ~<½ and decreases with increasing wave number for ~ > ½. (Sweden)
rotated so that the reflected light is observed at various angles. The film thickness d is given by d = ANA/2#(cos r2 - cos rl), where A = wavelength of filtered light ; /~ = refractive index ; and AN = number of fringes observed between angles of refraction r~ and ra. The technique is especially suited for films thicker than one micron. An accuracy of 12 per cent is claimed. (U.S.A.) (Authors, modified) W. A. Pliskin and E. E. Conrad, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19 • 33 1117. An immersion spectrophotometric determination of the opticalconstants of interference of films. (France) Immersion either increases or decreases the degree of interference, depending on the relative magnitudes of the component wavevectors. Interference peak heights were measured on a spectrophotometer with the specimen immersed in various pure liquids. Extrapolation to zero interference gives the condition of no refractive change in crossing-the medium/film interface. Immersion effects associated with an absorbing film are discussed by the author in terms of a complex refractive index. (U.S.A.) (Author, modified) W. P. Ellis, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press).
1118. Ellipsometric
investigations
of oxide
films
19 : 30 : 41 on GaAs.
(France) The real part of the complex index of GaAs has been determined by ellipsometric methods. This value together with the extinction co-efficient k, were then used in the exact solution of the fundamental equation of allipsometry by computer technique. Samples of GaAs with different orientations were subjected to various surface treatments and the influence of these variable on the optical properties investigated. The resulting samples were subsequently oxidised and again examined by ellipsometry. The results obtained were correlated with those of multiple beam interferometry and infrared total internal reflection. (U.S.A.) (Authors, modified) K. H. Zaininger and A. C. Revesz, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19 : 30 : 41 1119. Relation between the optical absorption spectrum of silver film and its film structure. (France) Anomalies in the optical properties of thin metallic films arise from inhomogeneous structures such as uneveness, cracks or isolated particles and can be explained by means of a model in which all the films have two-dimensional colloid structure composed of ellipsoids of rotation. In the present paper the author refines this model by introducing dipole interaction between polarized ellipsoids. By assuring a Poisson distribution of axial ratio of ellipsoids, the shape of the anomalous absorption band of silver films can he explained. (Authors, modified) S. Yamaguchi, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press).
W . J. S.
R. Jacobson, Colloque sur l'optiques des couches minces solides, Marseille, 8-15 Sept. 1963, J. Physique (in press). 19 : 30 1116. A simple non-destructive technique for thickness and refractive index measurement of transparent films on refleetive substrates. (France) The technique involves the use of a microscope equipped with a monochromatic filter on the objective and a stage that can be
19 : 30 : 41 1120. Optical properties of thin palladium film. (France) The author lists the optical constants of Pd films of various thicknesses for wavelengths ranging from 2000 to 25,000A~. Electrical resistance data as well as value for the Hall constant are also given. (France) (Author, modified) P. Lostis, Colloque sur l'optique des couches minces solides, Marseille, 8-15 Sept. 1963, 3". Physique (in press).