The SPM device in our laboratory

The SPM device in our laboratory

Example C-AFM

1 µm gold grid

MFM: magnetic force microscope

AFM with magnetic probe

e.g. hard disc, tape

magnetic tip

laserphotodiode

piezo-element

Magnetic Force Microscopy (MFM)

NC-mode, information about topography and magnetic properties; tip close to the surface: topography is dominating

tip-to-surface distance increases: magnet effects dominate

∆T

multilayers homogeneous amorphous phase crystalline phase

Thin films:

crystallisation occurs at theinterface

Thick films:

∆T

crystalline phasemultilayers

∆T∆T

The thin film project in my group

Te deposited onto a 5 Å thick Cr layer Te deposited onto 100-Si Tdep = 300 K

AFM

Example NC-AFM mode

Te onto 100-Si at 300 K

Te on a (100)-Si surface deposited at about 390 K

Example NC-AFM mode

AFM picture

line scan across the film

Roughness of a 80 Å thick Te layer deposited at 300 K onto 100-Si

line scan across the film

Roughness of a 80 Å thick Te layer deposited at 100 K onto 100-Si

Cr-Se multilayers as deposited and annealed

Phase change materials

Große Inseln fressen kleine

Ag-Inseln auf der Metalloberfläche Ag(111) (K. Morgenstern, Berlin)

187 Aufnahmen im Abstand von 200s bei Raumtemperatur

Bilder von bewegten Atomen

Perspective view of the STM image of a reconstructed Au(110)-1××××2 surface

Missing row type;distance between rows: 8.16 Å

Corrugation in [001] direction

STM image of an Al(111) surface

Steps: monoatomic, diatomic and triatomic

STM image of a hexagonal (111)Al surface showing atomic resolution

AFM image of a ferroelectric crystal

STM image of a GaSb film deposited onto a GaAs surface

False coloured, lattice mismatch between GaAs and GaSb of 7%, dislocations in the GaSb film, lowers the performance as infrared light detector

Properties of transition metal dichalcogenides

Procedures in Scanning Probe Microscopies, ed. Colton et al., Wiley, 1998

Structure of transition metal dichalcogenides

natural MoS2

SnS1.2Se0.8

Procedures in Scanning Probe Microscopies, ed. Colton et al., Wiley, 1998

CC-STM, many defects,

impurities or occlusions

CH-STM, bright atoms Se,

less bright atoms S

Ni3 cluster on MoS2

Sample bias: A) 2 V, B) +1.4 V, C) -2 V

J.G.Kushmerick et al., J. Phys. Chem. B, 104, 2980, 2000.

Electrons tunnel from tip into empty states of the sample

Electrons tunnel from sample into empty states of the tip

The Ni3 cluster perturbates the MoS2 surface electronic structure

Carbon Nanotube Tips• Well defined shape and composition.• High aspect ratio and small radius of curvature (“perfect” tip would be a delta

function tip).• Mechanically robust.• Chemical functionalization at tip.

DNA

CNT Tips

Images taken from Nanodevices, Inc. (www.nanodevices.com)

and Wooley, et al., Nature Biotech. 18, 760

• Dip Pen Lithography.

SPM Lithography

Mirkin, et al. from Northwestern University

• Electrochemistry: carbon nanotube used as a conducting AFM tip for local oxidation of Si.

SPM Lithography

Dai, et al. from Stanford

Million Cantilever Wafer

Millipede Memory

Millipede Memory

Millipede Memory

Cantilever Gas Sensors (Noses)

Cantilever Gas Sensors (Noses)

Chemical Force Microscopy

Idea : Use tips with defined surface chemistry

Chemical Force

Microscopy

Tip Modification by* Thiol chemistry* Silane chemistry* Avidin-Streptavidine

Combination Pulsed Force Mode and CFM :CH3-Tip , Letters : CH3 ; Background OH (image by G. Papastavrou, S. Akari )

• Force Modulation Microscopy FMM - mechanical properties

• Phase Detection Microscopy PDM - elasticity, adhesion, friction

• Electrostatic Force Microscopy EFM - detection of static charges

• Scanning Capacitance Microscopy SCM - spatial variations in capacitance

• Thermal scanning Microscopy TSM - thermal conductivity of surface

• Nanolithography

Many more related techniques

Potential and Limitations

• Parameters measured: surface topography (AFM, STM); local electronic structure (STM)• Destructive: No• Vertical resolution: STM: 0.01 Å ; AFM: 0.1 Å• Lateral resolution: STM: atomic; AFM: atomic to 1 nm• Accuracy: better than 10% in distance• Imaging/mapping: Yes• Field of view: from atoms to > 250 µm• Sample requirements: STM: solid conductors and semiconductors, conductive

coating required for insulatorsAFM: solid conductors, semiconductors, insulators

• Main uses: real-space 3D imaging in air, vacuum, or solution with unsurpassed resolution;high-resolution profilometry; imaging of nonconductors (AFM)

• Instrument cost: about $65,000 (ambient) to > $200,000 (ultrahigh vacuum)