Pub Date : 1967-11-01DOI: 10.1088/0508-3443/18/11/305
J. Male
A Hall effect measurement technique is described which overcomes some of the difficulties presented by materials combining a small Hall angle with a large temperature coefficient of conductivity. The major problem of `offset' voltage suppression is dealt with by using a direct primary current in conjunction with an alternating magnetic field and narrow-bandwidth phase-conscious signal detection. The method has been used to study the temperature dependence of the Hall mobility in some chalcogenide glasses and liquids in the systems As-Se-Te and As-Se-Te-Tl between 20 and 500°c. The mobilities are generally about 10-1 cm2 v-1 sec-1 and show only weak temperature dependence. The Hall coefficients are always negative for the amorphous materials while the thermoelectric powers are always positive. The implications of these results are briefly discussed.
{"title":"Hall effect measurement in semiconducting chalcogenide glasses and liquids","authors":"J. Male","doi":"10.1088/0508-3443/18/11/305","DOIUrl":"https://doi.org/10.1088/0508-3443/18/11/305","url":null,"abstract":"A Hall effect measurement technique is described which overcomes some of the difficulties presented by materials combining a small Hall angle with a large temperature coefficient of conductivity. The major problem of `offset' voltage suppression is dealt with by using a direct primary current in conjunction with an alternating magnetic field and narrow-bandwidth phase-conscious signal detection. The method has been used to study the temperature dependence of the Hall mobility in some chalcogenide glasses and liquids in the systems As-Se-Te and As-Se-Te-Tl between 20 and 500°c. The mobilities are generally about 10-1 cm2 v-1 sec-1 and show only weak temperature dependence. The Hall coefficients are always negative for the amorphous materials while the thermoelectric powers are always positive. The implications of these results are briefly discussed.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"12 1","pages":"1543-1549"},"PeriodicalIF":0.0,"publicationDate":"1967-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91430202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-11-01DOI: 10.1088/0508-3443/18/11/301
M. Lancefield, P. Schofield
A variational principle devised originally for the isotropic Milne problem without capture has been developed for anisotropic scattering. The theory is described for linear anisotropy but the extension to higher-order anisotropy is, in principle, straightforward. The flux in the energy-dependent problem is expressed in terms of the corresponding one-velocity solution which is already well known; as a result some new one-velocity half-space Green functions are introduced. Then a variational principle for the extrapolation length may be written down and the angular distribution of emergent neutrons determined by iterating the trial function. Results are presented for both isotropic and anisotropic scattering models. Using linearly anisotropic scattering, there is excellent agreement with experiment, except at grazing incidence, for the spectrum emerging from a water surface.
{"title":"The thermal-neutron Milne problem","authors":"M. Lancefield, P. Schofield","doi":"10.1088/0508-3443/18/11/301","DOIUrl":"https://doi.org/10.1088/0508-3443/18/11/301","url":null,"abstract":"A variational principle devised originally for the isotropic Milne problem without capture has been developed for anisotropic scattering. The theory is described for linear anisotropy but the extension to higher-order anisotropy is, in principle, straightforward. The flux in the energy-dependent problem is expressed in terms of the corresponding one-velocity solution which is already well known; as a result some new one-velocity half-space Green functions are introduced. Then a variational principle for the extrapolation length may be written down and the angular distribution of emergent neutrons determined by iterating the trial function. Results are presented for both isotropic and anisotropic scattering models. Using linearly anisotropic scattering, there is excellent agreement with experiment, except at grazing incidence, for the spectrum emerging from a water surface.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"21 1","pages":"1497-1515"},"PeriodicalIF":0.0,"publicationDate":"1967-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86615612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-11-01DOI: 10.1088/0508-3443/18/11/311
C. Bowlt
The energy distribution of cathode rays transmitted through thin dielectric films changes during bombardment. This has been measured and is accounted for by the accumulation of space charge.
{"title":"The effect of space charge on the transmission of cathode rays through thin insulating films","authors":"C. Bowlt","doi":"10.1088/0508-3443/18/11/311","DOIUrl":"https://doi.org/10.1088/0508-3443/18/11/311","url":null,"abstract":"The energy distribution of cathode rays transmitted through thin dielectric films changes during bombardment. This has been measured and is accounted for by the accumulation of space charge.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"7 1","pages":"1585-1588"},"PeriodicalIF":0.0,"publicationDate":"1967-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82687983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-11-01DOI: 10.1088/0508-3443/18/11/302
G. Wexler, C. Taylor
A detailed solution of Laplace's equation is obtained with boundary conditions appropriate for the study of classical transport through cylindrical constrictions. The potential, which is expressed in the spheroidal harmonic representation, can be used to describe the electrical and thermal spreading resistance problems and similar problems occurring in gaseous diffusion, magnetism, hydrodynamics and scalar diffraction theory (e.g. for acoustics) in the long-wavelength limit. The argument is based on standard variational and eigenfunction methods. A summary is given of the procedure required for adapting it to obtain solutions for the same configuration with different boundary conditions and also for the wave equation replacing Laplace's equation.
{"title":"The potential and wave equations for a finite cylinder attached to one or two semi-infinite slabs","authors":"G. Wexler, C. Taylor","doi":"10.1088/0508-3443/18/11/302","DOIUrl":"https://doi.org/10.1088/0508-3443/18/11/302","url":null,"abstract":"A detailed solution of Laplace's equation is obtained with boundary conditions appropriate for the study of classical transport through cylindrical constrictions. The potential, which is expressed in the spheroidal harmonic representation, can be used to describe the electrical and thermal spreading resistance problems and similar problems occurring in gaseous diffusion, magnetism, hydrodynamics and scalar diffraction theory (e.g. for acoustics) in the long-wavelength limit. The argument is based on standard variational and eigenfunction methods. A summary is given of the procedure required for adapting it to obtain solutions for the same configuration with different boundary conditions and also for the wave equation replacing Laplace's equation.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"146 1","pages":"1517-1526"},"PeriodicalIF":0.0,"publicationDate":"1967-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80539637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-10-01DOI: 10.1088/0508-3443/18/10/308
D. Morley, D. G. Schofield, L. Allen, D. G. Jones
A formula is derived which allows the degree of coherence across the beam of a multi-mode laser to be calculated. Good experimental agreement is obtained for the case of TEM00 and TEM10 modes in simultaneous oscillation.
{"title":"Spatial coherence and mode structure in the He-Ne laser","authors":"D. Morley, D. G. Schofield, L. Allen, D. G. Jones","doi":"10.1088/0508-3443/18/10/308","DOIUrl":"https://doi.org/10.1088/0508-3443/18/10/308","url":null,"abstract":"A formula is derived which allows the degree of coherence across the beam of a multi-mode laser to be calculated. Good experimental agreement is obtained for the case of TEM00 and TEM10 modes in simultaneous oscillation.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"4 1","pages":"1419-1422"},"PeriodicalIF":0.0,"publicationDate":"1967-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84784479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-10-01DOI: 10.1088/0508-3443/18/10/310
D. Bhawalkar, A. M. Goncharenko, R. Smith
The form of the Gaussian beam in an anisotropic medium has been found by solution of Maxwell's equations. For mathematical convenience a cylindrical beam (two-dimensional) is considered, with the field constant in one cross-sectional dimension and varying as the Gaussian function in the other. For uniaxial crystals, and for biaxial crystals where the propagation is in one of the principal planes, two solutions are obtained, corresponding to the ordinary and extraordinary waves. The Gaussian beam for the ordinary wave is identical to that for an isotropic medium. The extraordinary Gaussian beam is modified by double refraction and by an increase in the beam spread of 11/33. The properties of the extraordinary Gaussian beam are derived and applied to the problem of an optical resonator filled with an anisotropic medium. The low- and high-loss regions are found for the resonator together with its resonant frequencies. Two kinds of anisotropic cavity are distinguished: those where the optic axis of the medium is at 0? or 90? to the optical axis of the cavity and those where the optic axis is at 45? to the cavity axis. The three-dimensional Gaussian beam is treated by assuming that it can be represented by two orthogonal two-dimensional beams. The effect of anisotropy on the extraordinary beam gives rise to nonspherical wavefronts and elliptical cross sections. Some applications of the theory to laser problems are outlined.
{"title":"Propagation of Gaussian beams in anisotropic media","authors":"D. Bhawalkar, A. M. Goncharenko, R. Smith","doi":"10.1088/0508-3443/18/10/310","DOIUrl":"https://doi.org/10.1088/0508-3443/18/10/310","url":null,"abstract":"The form of the Gaussian beam in an anisotropic medium has been found by solution of Maxwell's equations. For mathematical convenience a cylindrical beam (two-dimensional) is considered, with the field constant in one cross-sectional dimension and varying as the Gaussian function in the other. For uniaxial crystals, and for biaxial crystals where the propagation is in one of the principal planes, two solutions are obtained, corresponding to the ordinary and extraordinary waves. The Gaussian beam for the ordinary wave is identical to that for an isotropic medium. The extraordinary Gaussian beam is modified by double refraction and by an increase in the beam spread of 11/33. The properties of the extraordinary Gaussian beam are derived and applied to the problem of an optical resonator filled with an anisotropic medium. The low- and high-loss regions are found for the resonator together with its resonant frequencies. Two kinds of anisotropic cavity are distinguished: those where the optic axis of the medium is at 0? or 90? to the optical axis of the cavity and those where the optic axis is at 45? to the cavity axis. The three-dimensional Gaussian beam is treated by assuming that it can be represented by two orthogonal two-dimensional beams. The effect of anisotropy on the extraordinary beam gives rise to nonspherical wavefronts and elliptical cross sections. Some applications of the theory to laser problems are outlined.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"87 1 1","pages":"1431-1441"},"PeriodicalIF":0.0,"publicationDate":"1967-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84025365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-10-01DOI: 10.1088/0508-3443/18/10/316
A. K. Aggarwal, P. Kaw
The earlier theories of optical measurement of atmospheric refractive index gradient are modified in such a way as to remove certain assumptions which seemed to be neither well justified nor necessary. Further, two simple methods for the measurement of this quantity, which are especially suitable for large and small gradients respectively, are proposed.
{"title":"Optical measurement of the atmospheric refractive index gradient","authors":"A. K. Aggarwal, P. Kaw","doi":"10.1088/0508-3443/18/10/316","DOIUrl":"https://doi.org/10.1088/0508-3443/18/10/316","url":null,"abstract":"The earlier theories of optical measurement of atmospheric refractive index gradient are modified in such a way as to remove certain assumptions which seemed to be neither well justified nor necessary. Further, two simple methods for the measurement of this quantity, which are especially suitable for large and small gradients respectively, are proposed.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"23 1","pages":"1485-1489"},"PeriodicalIF":0.0,"publicationDate":"1967-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83281657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-10-01DOI: 10.1088/0508-3443/18/10/312
R. Khan
Cerenkov radiation within a cylindrical waveguide with elliptic cross section due to a particle moving along a line parallel to the axis of the cylinder through one focus is considered. As is usual in waveguide problems, modes of frequencies are obtained; moreover the energy due to radiation concentrates on a line parallel to the axis through the other focus.
{"title":"Cerenkov radiation in a cylindrical waveguide with elliptic cross section","authors":"R. Khan","doi":"10.1088/0508-3443/18/10/312","DOIUrl":"https://doi.org/10.1088/0508-3443/18/10/312","url":null,"abstract":"Cerenkov radiation within a cylindrical waveguide with elliptic cross section due to a particle moving along a line parallel to the axis of the cylinder through one focus is considered. As is usual in waveguide problems, modes of frequencies are obtained; moreover the energy due to radiation concentrates on a line parallel to the axis through the other focus.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"17 1","pages":"1453-1457"},"PeriodicalIF":0.0,"publicationDate":"1967-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74659263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-10-01DOI: 10.1088/0508-3443/18/10/303
P. B. Hart, P. Etter, B. Jervis, J. Flanders
Single-crystal films of silicon have been deposited on the (1l02) plane of α-alumina by the pyrolysis of silane. Carrier concentration and mobility have been studied in the films as functions of growth temperature and substrate preparation. The effects of initial and overall growth rate have also been examined. Undoped layers are p-type with carrier concentrations from 1015 to 1017 holes/cm3 depending on growth temperature. Hole mobilities up to 174 cm2 v-1 sec-1 have been obtained. Diodes, MOST's and low-gain bipolar transistors have been formed in the material and minority carrier lifetime in the nanosecond range has been estimated from device characteristics.
{"title":"Electrical properties of epitaxial silicon films on α-alumina","authors":"P. B. Hart, P. Etter, B. Jervis, J. Flanders","doi":"10.1088/0508-3443/18/10/303","DOIUrl":"https://doi.org/10.1088/0508-3443/18/10/303","url":null,"abstract":"Single-crystal films of silicon have been deposited on the (1l02) plane of α-alumina by the pyrolysis of silane. Carrier concentration and mobility have been studied in the films as functions of growth temperature and substrate preparation. The effects of initial and overall growth rate have also been examined. Undoped layers are p-type with carrier concentrations from 1015 to 1017 holes/cm3 depending on growth temperature. Hole mobilities up to 174 cm2 v-1 sec-1 have been obtained. Diodes, MOST's and low-gain bipolar transistors have been formed in the material and minority carrier lifetime in the nanosecond range has been estimated from device characteristics.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"8 1","pages":"1389-1496"},"PeriodicalIF":0.0,"publicationDate":"1967-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90333345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1967-10-01DOI: 10.1088/0508-3443/18/10/304
D. Lovett, D. Ballentyne
Cadmium arsenide has a large concentration of high-mobility carriers (electrons) and possesses a small lattice thermal conductivity. It should therefore exhibit a large Righi-Leduc effect. This effect has been measured in the temperature range 300-64°K in magnetic fields of 500-12 × 103 Oe and results shown to agree with predicted values for a degenerate semiconductor. Values of the Righi-Leduc co-efficient of 066 × 104 cm2 v-1 sec-1 at room temperature and 14 × 104 cm2 v-1 sec-1 at 85°K have been obtained in low magnetic fields.
{"title":"The Righi - Leduc effect in cadmium arsenide","authors":"D. Lovett, D. Ballentyne","doi":"10.1088/0508-3443/18/10/304","DOIUrl":"https://doi.org/10.1088/0508-3443/18/10/304","url":null,"abstract":"Cadmium arsenide has a large concentration of high-mobility carriers (electrons) and possesses a small lattice thermal conductivity. It should therefore exhibit a large Righi-Leduc effect. This effect has been measured in the temperature range 300-64°K in magnetic fields of 500-12 × 103 Oe and results shown to agree with predicted values for a degenerate semiconductor. Values of the Righi-Leduc co-efficient of 066 × 104 cm2 v-1 sec-1 at room temperature and 14 × 104 cm2 v-1 sec-1 at 85°K have been obtained in low magnetic fields.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"19 1","pages":"1399-1402"},"PeriodicalIF":0.0,"publicationDate":"1967-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80054987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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