SCHOFIELD1	Calculation of band bending effects in STM measurements of semiconductor nanostructures
Type	Experimental/modelling
#students	1
Orientation	Why is the scientific problem of interest at all? . The scanning tunnelling microscope (STM) provides the ability not only to image surfaces at the atomic-scale, but also to manipulate the atoms on the surface to create atomic-scale nanostructures. The fabrication of such structures on semiconductor surfaces holds the potential for the development of the next generation electronic devices. Examples being explored in our group at the LCN include atom manipulation of chemical passivation layers for the creation of functional defect states, the positioning of individual dopant atoms for the creation of atomic-scale devices, and molecular functionalization of semiconductor surfaces through the adsorption of organic molecules.
How	How is the research going to shed light on the given problem?. In order to properly interpret the results of STM measurements on semiconductor surfaces it is necessary to properly describe the electrostatic influence that the STM tip has on the surface. This is especially important for atomic-scale nanostructures where changes in charge state of the nanostructure induced by the STM tip can dramatically alter their appearance, with consequences for the interpretation of the data.
What	What is the specific thing that the student will do, and how does it fit inside the overall project? In this project, the student will calculate tip-induced band bending for real measurement situations, including effects such as the finite size of the STM tip, the doping density profile of the substrate, the presence of surface states within the bulk band gap and localized point charges at atomic-sized surface nanostructures. The project will involve working closely with ongoing STM measurements of atomic-scale nanostructures being fabricated and measured at the LCN.
Special Knowlegde
Supervisor	Dr Steven Schofield s.schofield@ucl.ac.uk