Electron Charging Effects Research Articles

Mechanical properties and photomechanical effect in GaP single crystals

Abstract Mechanical properdes of GaP single crystals have been investigated from 100° to 300°C by observing dislocation rosette patterns on indented specimen surfaces. It has been found that GaP has mechanical properties which are common to those of other III–V compounds or elemental semiconductors in several points: the {111} surface polarity dependence of microhardness, the mobility difference between α- and β-dislocations, and the conduction type dependence of dislocation mobility. The growth of dislocation rosettes is suppressed by baking specimens in air. Contrary to the case of II–VI compounds, illumination of visible light during indentation enhances the mobility of dislocations. These experimental results are discussed in terms of an effect of electronic charge of dislocation on its mobility.

Molecular orbital calculations on transition metal complexes. Part II. Hexa-aquometal(II) and hexa-aquometal(III) ions

CNDO Molecular orbital calculations are reported for hexa-aquometal(II) complexes (TiII—CuII) and hexa-aquometal(III) complexes (TiIII—CoIII). The mechanism for spin delocalisation in these complex ions is discussed and the CNDO results suggest that an approximately tetrahedral geometrical configuration around the oxygen atoms is evident. In general it is found that equilibrium bond lengths are not well predicted; however the ions CuII(H2O)6, CrII(H2O)6, and MnIII(H2O)6, which have orbitally degenerate ground states, are predicted to undergo a distortion of the Jahn–Teller type. Electronic configurations, covalency, and charge effects are also discussed.

Theory of Formation of Very Thin Oxide Films on Metals

The growth of oxide on initially oxide-free evaporated aluminum films at room temperature and atmospheric pressure has been studied in parallel experiments, using elliptically polarized light to measure the film thickness and vibrating capacitor measurements to measure changes in the Volta potential. The film thickness reaches 21 Å in 106 sec and varies essentially logarithmically with time in the time range from 102 to 106 sec. The Volta potential is almost constant during the initial stages of growth and then varies approximately logarithmically with time. The observed change of Volta potential, interpreted as resulting from changes in the Galvani potential, is approximately 350 mV in 106 sec of oxidation. A logical extension of the Mott theory is presented which includes (1) the effect of electronic space charge resulting from equilibration of electrons between the metal and oxide and (2) the electric field in the oxide, both in its role as a barrier to electron penetration of the oxide and in its control over the migration of interstitial aluminum ions. The extended theory predicts a linear relation between V½X (V is Galvani potential difference across the oxide and X is oxide thickness) and ln (oxidation time) whose slope is 3ℏ/(32me)½, m and e being the mass and charge of the electron and ℏ being Planck's constant divided by 2π. The experimentally determined slope has the value 1.32×10−8 V½·cm as compared to the theoretical slope of 1.46×10−8 V½·cm.

The Influence of the Cathode Material on Measured Breakdown Strengths of Solid and Liquid Dielectrics

An outline is given of a general method of accounting for the effect of electronic and ionic space charge in the breakdown of solid and liquid dielectrics. Detailed calculations are performed for a special model of both a liquid and a solid dielectric, and the results are compared with recent experimental work. Ex(tct calculation is not possible, but it is shown that for some substances an effect due to cathode material may well be measurable, and the factors influencing such an effect are examined.