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E-Thesis 89 views 21 downloads

Development of a desktop STM using ballistic electron emission microscopy and spectroscopy to study Ni-SiC Schottky contacts. / Omar A Al-Hartomy

Swansea University Author: Omar A Al-Hartomy

Abstract

Ballistic electron emission microscopy and spectroscopy (BEEM/BEES) have been employed by developing a basic desktop STM in air in order to study Ni-SiC samples. The electronic properties of Ni contacts to SiC are highly dependent on their manufacturing process and this study generated suitably thin...

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Published: 2005
Institution: Swansea University
Degree level: Master of Philosophy
Degree name: M.Phil
URI: https://cronfa.swan.ac.uk/Record/cronfa42875
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Abstract: Ballistic electron emission microscopy and spectroscopy (BEEM/BEES) have been employed by developing a basic desktop STM in air in order to study Ni-SiC samples. The electronic properties of Ni contacts to SiC are highly dependent on their manufacturing process and this study generated suitably thin contacts for BEEM measurements that were Schottky in nature and made under UHV evaporation conditions. The sample also required an Ohmic contact to allow the detection of the BEEM current and these were formed using an Edwards evaporator. BEEM is a three terminal measurement based upon the generation of pico amp currents and as a result amplifier circuits with I/V conversion were used to amplify the BEEM current to give a voltage in the range of ±10V for input into an auxiliary channel of the basic STM control unit. Also, a sample holder (110 mm x 210 mm) was modified which allowed a 3rd contact to the sample within the usual STM set-up.During this work, simultaneous STM and BEEM images have been recorded at various tunnelling currents and bias voltages. These images show distinct differences and the interface behaviour appears modified by varying electrical properties between the Ni and SiC which are resolved spatially on the nanoscale within the BEEM image. Furthermore, measurements were made to determine the Schottky barrier height values using BEES in different locations by observing the ballistic current as a function of voltage. It was found that the Schottky barrier varied between 1.48 eV to 2.35 eVdepending on the region or features analysed. The interaction at room temperature between Ni and SiC is discussed in light of these measurements and compared to current literature to resolve the origin of the observed Schottky barrier height variations.
Keywords: Microscopy, spectroscopy
College: College of Science