摘要:

Impurity ions in insulating crystals can be regarded as isolated electronic systems. Their paramagnetic resonance is determined by their ground state characteristics, which can be derived from application of Hund's rules, together with simple applications of ligand‐field theory and consideration of spin‐orbit interaction. The paramagnetic resonance is characteristic of the ion and its coordination in the crystal, and furnishes a powerful diagnostic tool.Fcenters can be regarded as special cases of ions, of particularly simple nature.Vcenters also can be understood in this way, often in terms of molecular ions. Distortions from the full symmetry of the host crystal site, due to the Jahn‐Teller effect, are frequent and predictable. Optical absorption, arising from transitions to higher levels, is closely related to the above properties, and is briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.1777129

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The sharp lines of the optical spectrum of trivalent chromium in oxides can be used to determine the position and splitting of the2Estate. They can be calibrated by stress experiments on an ion which is initially in a purely cubic field, and can then be used to study the surroundings of ions in noncubic fields. Further information can be obtained from ground‐state splittings, which depend in a different way on the symmetry of the surroundings. The method is used to investigate deformed cubic sites in magnesium oxide and aluminum oxide. In aluminum oxide, chromium lines as narrow as 0.10 cm−1have been observed at low temperatures, and show a fine structure attributed to the chromium isotopes. Some progress has been made in understanding the chromium pair spectra observed at higher concentrations.

ISSN:0021-8979    

DOI:10.1063/1.1777130

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The relationships between equilibrium hydrogen pressure, hydrogen content, and temperature have been derived for nonstoichiometric transition metal hydrides from both statistical mechanical and thermodynamic considerations. By comparing the derived equations with experimental pressure‐composition isotherms, the type of lattice defect causing deviations from stoichiometry as well as the energies of defect formation and interaction can be calculated. This was done for uranium hydride and palladium hydride. The energies obtained were 69 kcal/mole for the vacancy formation energy, and 4.4 kcal/mole for the attractive vacancy interaction energy in uranium hydride. The corresponding energies in palladium hydride were 58.0 kcal/mole and 0.35 kcal/mole. The derived relationships are of general applicability to any nonstoichiometric binary compound which is deficient in the volatile component.

ISSN:0021-8979    

DOI:10.1063/1.1777131

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

This paper describes several mechanisms for the equilibration of lattice defects in a number of crystalline solids in which the state of equilibrium has been disturbed by changes of temperature, diffusion processes, and phase changes, including precipitation from solid solution and internal chemical reactions.

ISSN:0021-8979    

DOI:10.1063/1.1777132

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Existing knowledge of point defects and their interactions in uncolored alkali halide crystals is briefly reviewed. Attention is drawn to recent experimental and theoretical work which indicates that vacancy pairs arenothighly mobile defects. This has important implications for some hypotheses on the kinetics of color center reactions at low temperatures.This knowledge of defects in uncolored crystals is then applied to a discussion of the reactions which may take place betweenFcenters and impurity ions in additively‐colored doped crystals and the theoretical possibilities are compared with experimental information onZcenters. Consideration of the thermodynamic equilibria in these reactions seems to eliminate theZ1andZ2centers of Pick as possible causes of either of theZ1andZ2absorption bands in KCl. (TheZ2model of Pick is identical with theZ1model of Seitz and is a divalent impurity cation which has trapped an electron.) Two possible centers for theZ2band presen tthemselves; (a) an associate of anFcenter with a divalent cation and (b) an associate of anFcenter with an impurity‐vacancy pair (theZ2model of Seitz). The structure of theZ1center is not resolved by these considerations. Attention is drawn to some paradoxical experimental results onZ1andZ2centers and further experiments to resolve outstanding questions are suggested.

ISSN:0021-8979    

DOI:10.1063/1.1777133

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An apparently quite general model for an essentially‐ordered semiconductor compound containing impurity traces consists: (1) of atomic point defects randomly distributed over appropriate, equivalent sites and contributing to the internal energy of the crystal by terms linear in the concentration of each type of atomic point defect, and (2) an electronic energy band structure in which the concentration and type of ``impurity'' levels is determined by the concentration and type of atomic point defects. The assignment of donor or acceptor character to the native interstitials and vacancies is predicted in a specific case by analogy with the alkali halides. Otherwise the nature of the binding is irrelevant, provided the un‐ionized impurity level associated with each substitutional atomic point defect bears the same charge as that on the substituted atom. From the appropriate quasi‐grand partition function, one obtains the usual Fermi‐Dirac distribution for electrons as well as distribution functions for the atomic point defects. In addition, one obtains expressions for the chemical potentials of the thermodynamic components. The latter are utilized in a discussion of those aspects of the M&sngbnd;N phase diagram pertinent to the semiconductor compound MN and in a discussion of amphoteric impurities.

ISSN:0021-8979    

DOI:10.1063/1.1777134

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

It is a well‐known result of semiconductor physics, that the conductivity of a semiconducting oxide can be shifted in the direction of increasedpconductivity or decreasednconductivity by addition of small proportions of oxides of lower cation valency and that the reverse is true in the case of higher valency of the added cation. This effect is understood on the basis of the corpuscular semiconductor theory of Wagner and Schottky and is even used for establishing the nature of the conduction mechanism in certain materials. It is generally supposed that the only necessary condition for this doping effect is solubility in the solid state and that this is granted by a similarity of the cation radii. No importance has been attributed to the chemical nature of the dope, and for this reason we have tried to dopep‐conducting nickel oxide with other oxides, differing not only in valence but also in their chemical nature.

ISSN:0021-8979    

DOI:10.1063/1.1777135

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The structures of praseodymium oxide phases of composition PrO1.83, PrO1.81, PrO1.78, PrO1.71, and PrO1.69are discussed in terms of the structures of PrO2.00and PrO1.50(CandAtypes). The way in which the existence of these several stable structures are mirrored in the physical and chemical properties is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1777136

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The problem of point‐defect equilibria in compound semiconductors is considered. It is shown that the expected donor or acceptor properties of a defect in a compouud are entirely independent of the type of binding (ionic or covalent) in the compound. From general thermodynamic arguments it is shown that the number of degrees of freedom of a compound in internal equilibrium is one more than the number of chemical constituents of the compound independent of the number and nature of the defects it contains. The consequences of this are discussed and it is shown how mass action laws result, describing internal reactions among the defects. An example from the literature is presented to illustrate the methods of setting up and solving these mass action laws and how the solutions might be compared with experimental results. Finally, association between oppositely charged defects in solids is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1777137

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Germanium solutions supersaturated with respect to both oxygen and copper have been investigated in the range 300–500°C by means of conductivity and Hall effect measurements. Kinetics results indicate that the initial rates of disappearance of holes is second order in both the Cu and the O concentrations. The failure of the hole mobility to increase with degree of reaction suggests the formation of an ion cluster. Determinations of ionization energy during reaction show changes in the level scheme of Cu to occur and confirm previous work on the ionization properties of donors produced by oxygen. A tentative model is proposed consisting of an initial cluster of two Cu and four O atoms on which further oxygen reactions take place. The diffusion of oxygen is found to be accelerated by the presence of Cu.

ISSN:0021-8979    

DOI:10.1063/1.1777138

出版商:AIP    

年代:1962

数据来源: AIP