10-29-07 - 10-29-07 scanning probe microscopy Features...

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10-29-07 scanning probe microscopy Features common between stm and afm o Scan range:200x200 micron lateral, 10 micron vertical o Some vibration isolation required o Scan rates: 10 nm/sec to 1000 Typical 512x512 pixels at 512 pixels/sec Scanning tunneling microscopy (stm) o Conductive samples (sustain ~50 pA at ~1 V) o Lateral resolution (tip dependent) as small as ~0.1 nm o Vertical resolution: ~0.1 nm o Image in air or vacuum (preferred since impurities in air will obscure the image) Atomic Force microscopy (afm) o Insulating, conductive, magnetic samples o Lateral rsolution (tip dependent): typically ~10 nm o Vertical resolution: typically 0.03 nm o Image in air, vacuum, fluids Image on scanning probe microscopy on slide 2 o In a material, to move in angstroms, use a tube scanner (in real life aprox a few inches long, and something called a piezoelectric tube—has electrodes outside, and when apply diff voltages, it will move/change shape) Piezoelectric (picture on slide 3) o A few materials that sows the piezoelectric effect o One of them is called ferroelectric: in the crystalline structure, there is an electric dipole. For example in bariam titanate—the shape of the crystal structure isn’t symmetrical, therefore there is an electric dipole—it is instantaneously occurring— dipole will respond to a magnetic field when applied. o Some materials without an electric dipole, but there are materials where you can make it have one when pressure is applied. Some materials respond to pressure by
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making a net dipole. Ad then when you put an electric upon it, it will cause the material to shift, and cause it to expand or to contract.
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10-29-07 - 10-29-07 scanning probe microscopy Features...

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