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Title: Investigation of nickel-silicon carbide formation
Author: Blackwood, I. P.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2005
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The topological and electronic properties of nickel (Ni) contacts to 4H-SiC have been investigated on the nano-meter scale, using scanning tunnelling microscopy (STM), atomic force microscopy (AFM) and scanning tunnelling spectroscopy (STS). The main aim of this work is to understand and control the contact formation mechanisms which occur in Ni-SiC junctions as a function of temperature. The fundamental system consisting of a sub-monolayer coverage of Ni on atomically clean 4H-SiC was studied with STM, from room temperature to 1000°C. After deposition of Ni localised I-V measurements were performed on Ni clusters using variable tip-sample separation STS (VTSS-STS), a surface barrier height of 1.85eV was observed along with the formation of metal induced gap states (MIGS). The apparent band-gap increased by 0.3eV at 500°C, corresponding with the production of Ni-silicide. Alternatively, after annealing between 700 and 900°C a gradual reduction of 1.15eV was observed. Graphite surfaces with fully diffused clusters were seen with STM after annealing at 1000°C. The properties of these clusters varied with their diffusion depth. Clusters relatively close to the surface displayed dominating physical properties whilst others deeper exhibited both physical and electronic properties. A separate combined AFM and STM study further supported these results. A Si interlayer was used to control the reactions which occurred in the fundamental Ni-SiC system. The Si interlayer sample displayed Ohmic characteristics immediately after Ni deposition, without a post metal deposition anneal and an average contact resistance of 1.3xl0-5Ωcm2 was observed. The electrical properties of this surface were studied with circular transmission line measurements (CTLM), whilst the electronic and chemical properties were investigated using x-ray photoelectron spectroscopy (XPS). The nature of the contact remained Ohmic even after annealing at 1000°C.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available