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The optical absorption line is 1s₁- 2p₀ at the absorption spectrum of arsenic doped silicon has been studied for various arsenic concentrations at four temperatures. The concentrations are .9 x 10¹⁵ cm⁻³, 1.7 x 10¹⁵ cm⁻³, 4.0 x 10¹⁵ cm⁻³ and 1.5 x 10¹⁶ cm⁻³, the temperatures are 4.2°K, 53°K, 77°K, and 90°K. Spectrometer broadening was accounted for in the observed line-widths. There was observed two temperature independent broadening mechanisms, concentration and strain broadening. Two temperature dependent broadening mechanisms were observed, phonon broadening and the statistical Stark effect. The five, broadening mechanisms are believed to account for the total line-width through the use of the Voigt analysis half-breadth method. A shift of the peak position with temperature was noted and a possible explanation presented. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In this thesis a theoretical study is made of the resonance spectra of the B¹¹ nuclei in a single crystal of Kernite (Na₂B₄0₇.4H₂0) whose, quadrupole moments interact with the electric field gradient at the nuclear sites in the crystal in the presence of an external magnetic field when the magnetic and quadrupole interaction energies are comparable. Using the results of the high field work of Waterman and Volkoff, energy levels and transition frequencies have been calculated numerically using the University of British Columbia ALWAC-III-E digital computer over a range of magnetic fields in the region intermediate between the limiting cases of pure quadrupole energy levels slightly perturbed by magnetic interactions and Zeeman energy levels slightly perturbed by quadrupole interactions. The magnetic field was taken to be oriented in the plane perpendicular to the two-fold symmetry axis of the crystal and the calculations were carried out for different orientations of the external magnetic field in steps of 30°. A general theory has been developed for the calculation of signal intensities in the case of crossed coil spectrometer (induction method) and has been applied to the present case. The signal intensities for absorption type spectrometers are proportional to the transition probabilities, and results are given for the case of Kernite which enables one to compare the expected signal intensities of absorption spectrometers with those of induction spectrometers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An investigation has been made into the possibility of observing optical transitions (in the 100-micron region) between the ground state of a donor impurity In silicon and the remaining five states of the {1s} set introduced by Kohn and Luttinger. While such transitions are forbidden in the usual effective mass approximation, it is found that application of corrections to the effective-mass wave functions leads to an enhanced transition probability. Under- the assumption of a simple cubic lattice of impurities, the calculated absorption coefficient is of the order of 10 cm[power -1] at an impurity concentration of 1 x 10[power 18] cm[power -3], and falls off exponentially with decreasing impurity concentration. An upper limit is placed on the region in which the transition should be observable by the broadening of the 2s-2p impurity band. It is estimated that for concentrations greater than 5 x 10[power 18] cm[power -3] the transition of interest will be obscured. The calculated values of the absorption coefficient are probably only accurate to within, one, or even two, orders of magnitude, because of the approximations involved. However, there would appear to be no firm theoretical reason why the 1s[superscript (0)] → 1s[superscript (5)] transition should not be observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis describes the experimental investigation of the complete resonance absorption spectrum of B¹¹ nuclei in a single crystal of kernite (Na₂B₄O₇.4H₂O) placed in a uniform external magnetic field, and its interpretation in terms of the perturbation of the nuclear Zeeman energy, levels by the interaction of the nuclear electric quadrupole moment with the crystalline electrostatic field gradient. Some observations on the Na²³ spectrum in kernite are also included. The present experiment is one of a series carried out in this laboratory on the study of such nuclear electric quadrupole interactions. In the two previous cases studied, those of Li⁷ and Al²⁷ in LiAl(SiO₃)₂ (spodumene), the atomic positions and symmetry of the crystal are such that there is only one kind of site for each of the two nuclear species studied as far as the electric field gradient is concerned. For both these cases the simplest possible spectrum of 2I lines was observed for any orientation of the crystal with respect .to the erternal magnetic field. In the Li⁷ case first order perturbation theory was adequate to explain the observed spectrum while second order theory was required for the Al²⁷ spectrum. In order to study in detail one case of a complex spectrum due to nuclei of the same species in different non-equivalent positions in the unit cell, the methods of radio frequency spectroscopy used for the previous experiments were applied to the study of the complete B¹¹ [formula omitted] spectrum in kernite (Na₂B₄O₇.4H₂O) in a magnetic field of 7060 gauss. The B¹¹ resonance absorption spectrum was observed in detail as the crystal was rotated about three mutually perpendicular axes. Eleven lines due to B¹¹ were observed when the symmetry axis of the crystal was perpendicular or parallel to the magnetic field, and twenty-one lines were observed in all other orientations of the crystal. In addition to some of these lines were slightly split in some orientations of the crystal. This observed number of lines was interpreted by assuming four essentially non-equivalent boron sites in the crystal with four others obtained from them by a 180° rotation about the b axis of the monoclinic kernite crystal. This interpretation drawn directly from the experimental data is in agreement with the previously proposed symmetry of the crystal on the basis of X-ray data. The complete set of properties of the quadrupole coupling tensor [formula omitted] was determined at each of the non-equivalent B¹¹ sites. The values of the quadrupole coupling constants [formula omitted] at the four essentially non-equivalent sites are .645±.003, .588±003, 2.563±007, 2.567±.010 Mc/s, and the corresponding asymmetry parameters are .54±.01, .60±.02, .163±.010, .116±.010. The orientation of the electric field gradient tensors at the four nuclear sites are given in the thesis. The preliminary investigation of the Na²³ spectrum in kernite leads to a direct contradiction of the positions for these atoms proposed on the basis of earlier X-ray data. Whereas the previously proposed structure postulates three non-equivalent sodium positions, two of which are on axes of symmetry, the Na²³resonance spectrum shows definitely that there are essentially two non-equivalent sodium sites neither of which is on an axis of symmetry. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A systematic study has been done on the absorption and luminescence spectra of transition metal complexes with low-spin electronic configuration d⁶, in order to clarify the spectroscopic behavior of these complexes. The spectra have been measured in solutions and crystals at temperatures between 4 K and room temperature. The lifetimes of the luminescence were measured, too, as an aid to the assignments of the bands. Suitable equipment has been designed and assembled for these measurements. The series of transition metal complexes with different metal atoms and ligands was chosen in order to cover a large range of ligand field strengths and bonding characteristics. Some complexes of Co(lll), Ru(ll), Rh(lll), Os(ll), Ir(lll) and Pt(lV) have been found to luminesce. Other complexes have been investigated and even the absence of luminescence was important for the general understanding of the phenomenon. The results of this investigation show that for the complexes here studied the luminescence originates from the electronic transition ³T₁g, ↦ ¹A₁g , i.e. a transition of d-d type. Also, a luminescence of charge-transfer type has been reported in the literature for some d⁶ complexes. From our data and from the information already-available, some empirical rules were formulated for the luminescence of d⁶ low-spin complexes. A priori use of these rules enables us to prognosticate the presence and the characteristics of the luminescence of other d⁶, low-spin complexes. / Science, Faculty of / Chemistry, Department of / Graduate

The theory of the phonon broadening of optical absorption lines in impurity doped semiconductors is discussed starting with Kubo's formulation of the adiabatic dielectric susceptibility. The absorption constant is related to a two particle temperature Green's function using Matsubara's method. The interaction of the electrons (or holes) with the lattice vibrations is assumed to be small so that it can be treated as a perturbation to the independent electron and lattice vibration systems. Using this approximation, Dyson equations are obtained, using the technique of Feynman diagrams, for the one particle electron and phonon Green's functions and for the two particle Green's function and these are solved within the framework of the approximation. The line shape function is calculated explicitly and it is found that the line consists of a sharp peak whose width depends on temperature and is due to the finite lifetime of the bound carrier states, and of a continuous background due to multi-phonon processes which accompany the optical absorption. The technique used here is compared with previous work on this problem employing temperature dependent double-time advanced and retarded Green's functions. The results obtained are compared with those obtained by previous authors. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In uncompensated phosphorus or arsenic-doped silicon, observation of the shallow, donor absorption line spectrum for donor concentrations from 10(12) to 2 x 10(18)/cc, yields information about the bound states of the donor electrons and the behavior of the conduction band edge. With increasing concentration, the photon induced IS(A) → 2P(o) and IS(A) → y 2P(±) transition lines are observed to broaden in energy, and shift to slightly lower energies; the lineshapes, Lorentzian at low donor concentrations, become asymmetric with the formation of a tail to the low energy side. A superposed absorption background is observed for donor concentrations greater than 2 x 10(16)/cc. Above 2 x 10(17)/cc an absorption edge in the 10-to-30 meV region with an exponential energy dependence is observed. The change in the absorption line spectrum is due primarily to the final states. The halfwidths of the transitions are well explained by a donor-pair model (or effective hydrogen molecule (Macek, 1971)), with the donor distribution assumed random. The difference in broadening of the 2P(±) level compared to the 2P(o) level is due to the anisotropic effective mass of the donor electron. The transition lineshapes are quantitatively explained in terms of the convoluted Fano function (Bhatia, 1970; Fano, 1962). The Fano parameters Q and T, are interpreted in terms of the evidence for the conduction band tailing and the possible configuration interaction. The integrated absorption coefficient of the line spectrum and the decrease of the absorption cross section above the conduction band threshold with increasing concentration are also accounted for in terms of band tailing. The experimental results are in agreement with the infrared absorption data for antimony-doped germanium (Nisida and Horii, 1969). / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The presence of configuration interaction, between the "internal" acceptor states of group III impurities in silicon and P₃⁄₂ band Bloch states, has been observed. The effect of impurity-impurity interaction on the line shape of the boron, gallium and indium internal acceptor lines has been studied. The observed characteristic asymmetric line shape is explained by introducing the interaction of the internal state with the degenerate P₃⁄₂ valence band Bloch states, and the inhomogeneous impurity-impurity interaction. The ionization energy of the substitutional impurity in the host lattice is found to be a deciding factor in this interaction. The internal and external absorption spectra of silicon doubly-doped with boron and indium acceptors is studied. The observed broadening of the boron external absorption lines in Si(B,In) is explained by neutral impurity scattering. The presence of indium in Si(B,In) crystal lattice, modifies the P₃⁄₂ valence band Bloch states and hence the configuration interaction. This modification is found responsible for the observed features of the boron 2p′ internal line in Si(B,In). The coupling between the lattice and the impurity bound carrier for deep monovalent acceptors in silicon, such as gallium and indium, is found to be stronger than for the shallow boron impurity. This suggests the possible existence of phonon-assisted transitions associated with these deep impurities. Such transitions are observed in the absorption spectrum of indium doped silicon. The phonon-assisted transitions are superimposed on the photoionization continuum transitions of the indium acceptors. Interference effects between the phonon-assisted transition and the transitions to the continuum states modify the position and line shape of the transitions. Using the phonon dispersion curves for silicon, interpretation of the results is presented. As a supplementary study, the temperature dependence of the indium external line 2, is investigated. The temperature dependence of halfwidth of indium line 2 in Si(In) supports the stronger electron-phonon coupling in Si(In). / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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