Study of semiconductor and metal surfaces using a novel scanning Kelvin probe.

This thesis reports design and construction of a novel Scanning Kelvin probe (SKP) compatible with the Ultra-High-Vacuum (UHV) environment - the first automatic, high resolution, UHV-SKP in the UK. The Kelvin Probe is a capacitor device used to measure the work function phi between a vibrating reference electrode (the tip) and the surface under investigation. It utilises a non-contact, non-destructive measurement mode allowing work function measurements at temperatures in the range from (300 - 1100) K. The work function is a multi-parameter variable highly sensitive to changes in surface and interface chemical composition, adsorbate induced surface dipole and surface atomic geometry. We have also followed the variable temperature oxidation kinetics of Si(111) in the range (100 - 600) K and show that magnitude of the Delta phi peak during the initial adsorption curve decreases in a linear fashion with increasing substrate temperature. Moreover, the transient work function measurements on the O2/Si(111) surface at 300 K show that the lifetime of the precursor states depend strongly on oxygen exposure. We examined high (Rhenium Re, Tungsten W, Molybdenum Mo and Platinum Pt) and low (Calcium Ca, Lanthanum Hexaborid LaB6, Gadolinium Gd) work function materials as target surfaces for Hyperthermal Surface Ionisation (HSI) used in a new mass spectroscopy ionisation technique. We particularly investigated the high work function materials with respect to their oxidation behaviour as it substantially increases their phi’s. We present and discuss the following experimental evidence: a) the magnitude and sign of phi changes in terms of adsorbate induced dipoles, b) the effect of molecular hydrogen exposure on the clean surface, and c) the effect of subsequent oxygen exposure. The oxidised Rhenium exhibited the highest work function with phi = (7.15 ± 0.1) eV at a temperature of ~900 K. LaB6, indicated the lowest work function with phi = (2.45 ±0.1) eV, while Ca gave the best results for HSI.

Author dc:creator

• Petermann, Uwe

Advisor dc:contributor.advisor

• I. Baikie

• Scanning Kelvin probe (SKP)
• Ultra-high vacuum (UHV) instrumentation
• Surface work function measurement
• Oxidation kinetics
• Surface adsorption phenomena
• Hyperthermal surface ionisation

Language dc:language

en

Identifier

oai:rgu-repository.worktribe.com:2807523
https://doi.org/10.48526/rgu-wt-2807523

OAI identifier oai:identifier

oai:rgu-repository.worktribe.com:2807523