5 kV  = 0.5 nm

Atomic resolution TEM image

EBPG (Electron beam pattern generator) 100 kV  = 0.12 nm

SNOM To locate single molecules: Optical microscopy: -fluorescence (labeling) -particle tagging (-electron microscopy)

Piezoelectric (Voltage – Displacement) Precise tip control is achieved with Piezoelectrics Displacement accurate to ±.05 Å PZT = (Pb,Zr)TiO 3

Basic Principles of STM Electrons tunnel between the tip and sample, a small current I is generated (10 pA to 1 nA). I proportional to e -2κd, I decreases by a factor of 10 when d is increased by 1 Å. d ~ 6 Å Bias voltage: mV – V range

Copper Surface Silicon

Silicium-oppervlak met stappen (Bron: Sandia Nat.Labs.) Si(100)

Two Modes of Scanning Constant Height Mode Constant Current Mode Usually, constant current mode is superior.

Instrumental Design Continued Tips Cut platinum – iridium wires Tungsten wire electrochemically etched Tungsten sharpened with ion milling Best tips have a point a few hundred nm wide Vibration Control Coiled spring suspension with magnetic damping Stacked metal plates with dampers between them

Interpreting STM Images Hydrogen on Gadolinium “Topography” model good for large scale images, but not for the atomic level. Electron charge density model more accurate for atomic level images. Best model requires complex quantum mechanical considerations

Atomic Force microscope (Scanning Force Microscope) Piezo Electric positioner Feedback electronics Laser diode Deflection detector Flexible cantilever Probe tip display

AFM Tip

yy zz l L l ~ 100  m L ~ 3 cm  z ~ 1000  y !!! Detection: beam deflection Optical lever amplification

Scanning modes Constant heightConstant force Contact modeTapping mode High frictionNo friction forces

Resolution: scanning probe microscope objecttip geometry image Tip convolution is not linear: results DO NOT add up Resolution is depends on tip AND sample

Imaging and manipulation of Carbon nanotubes

Millipede 1024 tips