A scanning tunneling microscope control system with potentiometric capability

dc.contributor.advisorTapson, Jonen_ZA
dc.contributor.authorBredekamp, Adriaan Hen_ZA
dc.date.accessioned2014-08-15T14:02:06Z
dc.date.available2014-08-15T14:02:06Z
dc.date.issued2003en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractThis report starts by describing the background research and work that had already been done on the UCT scanning tunneling microscope (STM). This system is being developed in the Department of Electrical Engineering at UCT. It goes on to describe the continuation of the research work that was done for this dissertation on the STM at UCT. The work was originally started by Dr. Tapson for his PhD (1994). and continued by the author for his MTech degree in ) 997 and 1998. The work was temporary discontinued from May 2000 till August 2002 to enable the author to work as a contract engineer at the Institute of Physics in Basel, Switzerland to learn more about the construction of probe microscopes. The new work evolved around the need to implement scanning tunneling potentiometry (STP) capability in the new STM. This capability should give the end-user the capability of looking at the sub-surface structure of any material on a sub-micron scale. The basic STP function must be implemented in two dimensions in the plane of the specimen. The STM tip is then used as a highly localized voltmeter to sense what the potential distribution is at that point on the surface. The potential information that is obtained is then used to plot two images of the potential distribution over the surface in the X and Y directions. The topographic information is obtained in the usual way from the STM scan. This method gives three collocated imagesas the result and a better understanding of the surface structure is obtained in this way. The penetration depth of the potential scan can be varied by adjusting the frequency of the applied AC signal in the X and Y directions. This use of the skin effect should allow the end user to obtain slices of the surface at various penetration levels of the specimen. These slices will give a picture of what happens from the surface up to a certain penetration depth. The interpretation of these images could be very difficult because the skin effect does not stop at a defined penetration depth. Only the 3 dB point is defined, which means that sub surface structures below the 3 dB point will also have an influence on the obtained image. During the course of the research new hardware and scanning software was implemented to enable the error-free acquisition of new data. This entailed splitting the existing XY controller into three separate parts namely a Communications interface, and two STP measurement boards. This was suggested as one of the conclusions of the MTech thesis results. The PC software stayed the same but for a change in the array size, that holds theacquired data. This was again changed after the work experience in Basel and is explained in chapter 6.en_ZA
dc.identifier.apacitationBredekamp, A. H. (2003). <i>A scanning tunneling microscope control system with potentiometric capability</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Electrical Engineering. Retrieved from http://hdl.handle.net/11427/6555en_ZA
dc.identifier.chicagocitationBredekamp, Adriaan H. <i>"A scanning tunneling microscope control system with potentiometric capability."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Electrical Engineering, 2003. http://hdl.handle.net/11427/6555en_ZA
dc.identifier.citationBredekamp, A. 2003. A scanning tunneling microscope control system with potentiometric capability. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Bredekamp, Adriaan H AB - This report starts by describing the background research and work that had already been done on the UCT scanning tunneling microscope (STM). This system is being developed in the Department of Electrical Engineering at UCT. It goes on to describe the continuation of the research work that was done for this dissertation on the STM at UCT. The work was originally started by Dr. Tapson for his PhD (1994). and continued by the author for his MTech degree in ) 997 and 1998. The work was temporary discontinued from May 2000 till August 2002 to enable the author to work as a contract engineer at the Institute of Physics in Basel, Switzerland to learn more about the construction of probe microscopes. The new work evolved around the need to implement scanning tunneling potentiometry (STP) capability in the new STM. This capability should give the end-user the capability of looking at the sub-surface structure of any material on a sub-micron scale. The basic STP function must be implemented in two dimensions in the plane of the specimen. The STM tip is then used as a highly localized voltmeter to sense what the potential distribution is at that point on the surface. The potential information that is obtained is then used to plot two images of the potential distribution over the surface in the X and Y directions. The topographic information is obtained in the usual way from the STM scan. This method gives three collocated imagesas the result and a better understanding of the surface structure is obtained in this way. The penetration depth of the potential scan can be varied by adjusting the frequency of the applied AC signal in the X and Y directions. This use of the skin effect should allow the end user to obtain slices of the surface at various penetration levels of the specimen. These slices will give a picture of what happens from the surface up to a certain penetration depth. The interpretation of these images could be very difficult because the skin effect does not stop at a defined penetration depth. Only the 3 dB point is defined, which means that sub surface structures below the 3 dB point will also have an influence on the obtained image. During the course of the research new hardware and scanning software was implemented to enable the error-free acquisition of new data. This entailed splitting the existing XY controller into three separate parts namely a Communications interface, and two STP measurement boards. This was suggested as one of the conclusions of the MTech thesis results. The PC software stayed the same but for a change in the array size, that holds theacquired data. This was again changed after the work experience in Basel and is explained in chapter 6. DA - 2003 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2003 T1 - A scanning tunneling microscope control system with potentiometric capability TI - A scanning tunneling microscope control system with potentiometric capability UR - http://hdl.handle.net/11427/6555 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/6555
dc.identifier.vancouvercitationBredekamp AH. A scanning tunneling microscope control system with potentiometric capability. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Electrical Engineering, 2003 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/6555en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Electrical Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherAppl Scen_ZA
dc.titleA scanning tunneling microscope control system with potentiometric capabilityen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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