SOLID STATE DIVISION ANNUAL PROGRESS REPORT FOR PERIOD ENDING AUGUST 31, 1959

Abstract

; 5 8 : 5 : 8 : : 9 < 6 8 9 6 8 6 5 ; 8 6 : 4 9 > < D ; lattice atom was investigated in detail. The results are of general interest since the method used is limited only by the validity of the interatomic potential assummed. Cross sections for the displacement of lattice atoms by gamma rays up to 5 Mev were calculated. A theoretical study was made of the slowing down process for a primary displaced atom in a solid. The small amplitude motion of dislocation loops was investigated in detail, taking into account the whole elastic field interaction between different parts of the loop. The extension and interval correlations in a radiation-induced displacement cascade were investigated. The numerical data apply to copper. A special model for annealing of defects in solids is discussed. Dislocation Interactions: Studies were made of the variations of internal friction and elastic modulus during irradiation of pure copper crystals at a number of temperatures in the range 90 to 300 deg K. Using neutron irradiation as a tool, it is shown that there are at least two dislocation contributions to the Young's modulus and internal friction of Cu at low temperatures. An apparatus was developed which makes possible the continuous observation of the Young's modulus and internal friction of a metal sample. Low-temperature Irradiation Studies: Activation energies for the annealing of copper and aluminum following reactor bombardment near 4 deg K were measured. Isochronal annealing studies of Cu, Ag, Au, Pt, and Zn were made after neutron bombardment of these materials at 4 deg K. It was confirmed that the residual resistivity of high purity copper can be greatly reduced by annealing in an oxidizing atmosphere. A redetermination of the stored-energy release in reactorirradiated Cu between 30 and 50 deg K was made. The design of a new facility for irradiation damage experiments at very low temperatures is described. A helium-cooled facility was installed in the pool of the ORR, which allows samples to be irradiated at about 50 deg C in an inert atmosphere. Electron Microscope Studies: Fission fragment tracks in thin films of UO/sub 2/ were studied and found to be essentially a surface effect in which material at the surface is displaced as a result of the passage of the fission fragments. An improved replication technique for copper is described. Chemical Properties of Metal Surfaces: The kinetics of the dissolution of copper crystals in aqueous solutions were investigated. The diffusion of deuterium in deuteron-irradiated Cu was studied in the temperature range -50 < T < 50 deg C by monitoring neutrons from the D(d,n)He/sup 3/ reaction. Alloy Studies: Experiments were conducted on the effect of irradiation on atomic rearrangements in Cu-Al, Ni-Be, Ni-Cu, Au-Cd, and Fe-C. Semiconductor Studies: A model for the potential well surrounding disordered regions in neutron-irradiated Ge and Si is discussed. The different effects of Co/sup 60/gammaray and fast-neutron bombardment on the electrical behavior of Ge are discussed in terms of the distribution of lattice defects. Thermal neutron capture in Si and Ge is considered. The effect of neutron and gamma irradiation upon minority carrier lifetime in Ge was studied. The effect of 14-Mev neutron irradiation upon the electrical properties of Ge was studied. A preliminary study was made of the change in thermoelectric power of n-type germanium as a result of neutron irradiation. Annealing of radiation-induced conductivity changes in n-type Ge was found to take place in the range between 77 and 273 deg K. The charge-center concentration as a function of temperature of high-purity, n-type Ge under fast- neutron irradiation is compared to similar data obtained for Co/sup 60/ gamma-ray irradiations. The difiusivity, solid solubility, and acceptor behavior of Cu in Ge was investigated. The effect of neutron spectrum on conluctivity changes in n- type Ge was investigated. Hall coefficient and Hall mobility were