Elastic and inelastic helium beam scattering from Cu(100) surfaces and vibrational modes in incommensurate systems

Structural and vibrational properties of clean and oxygen covered, single crystal Cu(100) surfaces were studied, using the technique of high resolution helium beam scattering. To carry out these investigations it was necessary to first design and build a high performance neutral atom scattering experimental setup, consisting of: (1) a high intensity, supersonic neutral atom beam source; (2) a UHV scattering chamber with sample manipulation and diagnostic facilities; (3) a novel, metastable atom detector system. Experimental results pertaining to the following are presented: (1) new information on quasi-elastic electron helium atom scattering observed in the metastable atom detector: (2) elastic He atom scattering from clean and oxygen covered Cu(100) surfaces; and (3) inelastic He atom scattering from clean Cu(100) surfaces. These experiments were performed with the detector moving in and out of the scattering plane, the latter being a novel feature of this setup. The analysis of these data gives the inherent vibrational modes of the surface. Finally, a computational investigation of the structural and dynamic properties of a model incommensurate system, the one-dimensional, finite Frenkel-Kontorova chain, is reported