Date of Award
2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Physics
Department
Physics
First Advisor
David Heskett
Abstract
I have used a k-resolved inverse photoemission spectrometer to measure the spectral line intensity attenuation with increasing temperature observed on the unoccupied electronic structure of Ni(110) along the azimuth. By employing the Debye-Waller model to the results of a transition into the sp-derived bulk state, I estimate the effective surface Debye temperature of Ni(110) to be 240 ± 20 K. A phonon-slab calculation based on density functional perturbation theory yields a Debye temperature of a bi-layer Ni(100) slab is 343 K. The experimental underestimate can be explained by the fact that the valence electrons involved in inverse photoemission do not necessarily mimic the thermal vibrations of surface atoms. A measurement of the temperature-dependent intensity of a transition into a crystal-derived surface state reveals a strong temperature dependence, whose value decreases as the position of the state approaches the projected bulk band boundary of the surface band structure. We attribute this to the surface state gaining bulk-like character near the boundary.
We have investigated the spectral peak intensity of this surface state recovery through isothermal annealing conducted on an ion-sputtered Ni(110) surface. From this we have determined an activation energy for surface self-diffusion of ~0.26 eV.
I have characterized the electronic components of the pulse-detecting circuit connected to a Geiger-Müller detector in this in-house built inverse photoemission spectrometer. The plot of probability distribution for the time gap between two consecutive pulses can be used to identify spurious counts from continuous Geiger discharge when the quenching mechanism is insufficient. After configuring the electronic readouts, the dead time of the detector was estimated to be 0.95 ± 0.05 ms. I have determined the full width at half maximum of the total energy resolution function of this spectrometer to be 0.42 ± 0.02 eV by collecting a spectrum of polycrystalline tantalum at the Fermi edge.
Creative Commons License
This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 License.
Recommended Citation
Lathpandura, Lakshitha Dinusha, "THERMAL AND ELECTRONIC PROPERTIES OF NI(110) SURFACE USING INVERSE PHOTOEMISSION SPECTROSCOPY" (2024). Open Access Dissertations. Paper 1695.
https://digitalcommons.uri.edu/oa_diss/1695