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Investigating local Scanning Tunneling Spectroscopy workfunction measurements as an alternative to Ultraviolet Photoelectron Spectroscopy workfunction measurements

Davenschot, Jan Henk (2019) Investigating local Scanning Tunneling Spectroscopy workfunction measurements as an alternative to Ultraviolet Photoelectron Spectroscopy workfunction measurements.

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Abstract:To be able to design multi layered semiconductor devices from 2D-materials the value of a material property known as the work function plays an important role. The work function is the amount of energy needed to remove an electron from the surface of a material. A difference in work functions in heterojunctions leads to a situation that results in a built-in voltage in the device or the threshold voltage in transistors. Most reliable values of the work function are determined by the measurement method photon electron spectroscopy which uses the photoelectric effect to determine the work function. This technique has as disadvantage that the measured value of the work function is the average of the measured surface. This approach is sufficient for most applications however when one wants to know the local work function of a material surface there is another method using a scanning tunneling microscope to perform scanning tunneling spectroscopy. In this method the current is measured as a function of distance to the surface of the material. By fitting the obtained result to an exponential model it is possible to obtain the work function from the decay coefficient. This assignment aimed to investigate if it is possible to obtain reliable local values of the work function using scanning tunneling spectroscopy on TMDs. Before doing so the used model was tested on bulk materials. Due to unexpectedly low values obtained using this approach it was deemed unreliable.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:51 materials science, 53 electrotechnology
Programme:Electrical Engineering BSc (56953)
Link to this item:http://purl.utwente.nl/essays/80163
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