ENGRI111_HW5_2004_Key - ENGRI 111 Solutions - Homework # 5...

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ENGRI 111 Solutions - Homework # 5 – Option I 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 a) AFM – measures atomic interaction forces (van der Waals) using a cantilever probe and a laser to measure deflections 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 b) AFM – insulators and conductors, including metals, polymers, ceramics and biological samples STM – conductors (typically, although some groups are working to extend STM to semiconductors and insulators i.e. Prof. Umbach) c) AFM – normal room atmosphere (although vacuum or dry environment is necessary for true atomic resolution due to interference from the natural water layer that forms on surfaces in an uncontrolled atmosphere) STM – ultra high vacuum (UHV) is necessary to prevent impurities or water from disrupting the flow of tunneling current
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This homework help was uploaded on 02/03/2008 for the course ENGRI 1110 taught by Professor Giannelis during the Fall '07 term at Cornell University (Engineering School).

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ENGRI111_HW5_2004_Key - ENGRI 111 Solutions - Homework # 5...

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