ENGRI_111_hw6_2007solutions - ENGRI 111 Solutions -...

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Solutions - Homework # 6, 2007 1 1. Compare and contrast the STM with the AFM. Include a) operating principle, b) type of materials appropriate for analysis, and c) ambient conditions required for analysis 0 a) AFM – measures atomic interaction forces (van der Waals) using a cantilever probe and a laser to measure deflections 1 http://nanoindentation.cornell.edu/Machine/Nanoindentation-Machine.htm STM – measures the tunneling current between a conducting tip and sample http://www.sljus.lu.se/stm/NonTech.html 2 b) AFM – insulators and conductors, including metals, polymers, ceramics and biological samples STM – conductors c) AFM – normal room atmosphere (although vacuum or dry environment is necessary for true atomic resolution due to 1 interference from the natural water layer that forms on surfaces in an uncontrolled atmosphere). Measurements where the sample and the tip are completely immersed in liquid are also possible. STM – vacuum is necessary to prevent impurities or water from disrupting the
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ENGRI_111_hw6_2007solutions - ENGRI 111 Solutions -...

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