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Basic Principles of Advanced AFM

Modes & ApplicationsModes & Applications

Dr. Stanislav Leesment, NT-MDT,16th June 2014

Webinar Overview

• AFM Operation: main principles• Topography in Contact and Noncontact modes• Phase Imaging• High Resolution• Choice of cantilever• Spreading resistance imaging (conductive AFM/Current mapping)• Kelvin Probe Microscopy (KPM)• Piezoresponce Force Microscopy (PFM)

M ti F Mi (MFM)• Magnetic Force Microscopy (MFM)• Nanolithography• Force Spectroscopy• HybriD™ Mode• HybriD™ Mode• Questions and Answers

AFM Operation: Main Principles

AFM: Scanning by Sample

SAMPLE SCANNING

AFM: Scanning by Tip

TIP SCANNING

Topography ImagingTopography Imaging. Contact and Noncontact Modes.

Contact Mode

According the Hook’s lawAccording the Hook’s law, Force interaction between tip and the sample isand the sample is proportional to tip bending and the cantilever stiffness. Stiffness for contact mode cantilevers can vary from 0 01 to several N/m0,01 to several N/m

Contact-Mode Based Modes

Noncontact (Semicontact, Tapping, AM-AFM) ModeAFM b 50 kH k 0 5 N/AFM probe, w=50 kHz, k = 0.5 N/m, Q = 80, Rt =10 nm, A0 = 5 nm

S. Belikov et al Fall 2012 MRS Proceedings, 2013

Phase Imaging

Phase Imaging. Scan Examples.

Name: Water on MicaEnvironment: AirTip: NSG10Size: 10x10 umSample and Image Courtesy:Sample and Image Courtesy:Reinier Oropesa-Nuñez, CEAC, Cienfuegos, Cuba

High-Resolution Imaging in AM-AFM in Air

C18H38Phase

C36H74PTFEPhaseHeight

CnH2n+2

C18H38C22H46

2.8 nm3.0 nm

18

22 46C36H74C60H122C122H246C242H486

4.5 nm7.5 nm15.0 nm29.0 nm

18 nm 50 nm 90 nm

Height Height HeightHeightC122H246 C242H486 C390H782 C122H246

C390H782

242 48649.0 nm

135 nm

Image Courtesy: Dr. S. Magonov, NT-MDT

4 of 35750 nm 750 nm550 nm

Magonov, NT MDT Development Co.

Tip Sharpness Limitation

ZAFM line profile

X2

5 10Probe tip

R 10 R=10 nm

R = 1 R 1 nm X axis direction

Real object (e g DNA molecule)Real object (e.g. DNA molecule)

Probes for High Resolution

Left: high-resolution AFM phase image of poly(dG)–poly(dG)–poly(dC) triplex DNA. The top graph shows a cross-section of the image along the white line (at the bottom part of the image). Right: histogram of distances between adjacent peaks on cross-sections taken on many molecules (overall >200 values); the average distance is 3.4 nm (SD = 0.9 nm)

D. Klinov, B. Dwir, E. Kapon, N. Borovok, T. Molotsky and A. Kotlyar. High-resolution atomic force microscopy of duplex and triplex DNA molecules. Nanotechnology 18 (2007), 225102.

Cantilever Choice

Cantilever Choice

NT‐MDT AFM probes

Semicontact / noncontact Contact

HA NC HA HR HA FMHA_C

Semicontact / noncontact(tapping)

Contact

HA_NC, HA_HR, HA_FM

NSG01, NSG10, NSG30, NSG03CSG01, CSG10, 

CSG30

Pt TiN A W MFM LM

Conductive Magnetic

Pt TiN Au W MFM01, MFM10

MFM_LM

MFM_HC

Electromagnetic Properties

Spreading Resistance Imaging (SRI)

Spreading Resistance imaging

MDMO‐PPV and PCBM Blend

Top left topography obtained in SSRM mode (-5V), top right – current mapping, bottom right current cross-section profilecross section profile.

MDMO‐PPV and PCBM Blend

Current maps with various bias voltage,

10 V 5 V 1 V-10 V -5 V -1 V

+1 V +5 V +10 V

Conductivity Map of OTS Sample

CurrentTopography

Current contrast of “Flowers” about 2 pA

Sample Courtesy: Prof. Jacob Sagiv, Weizmann Institute of Science, Israel

Probes for Spreading Resistance

Probes for Spreading Resistance should normally have relatively small

20 nm

should normally have relatively small spring constant 0,05 – 1 N/m contact probes and good conductive coating p g g(PtIr, TiN, Au)

Kelvin Probe Force Microscopy (KPFM)

Two-Pass KPFM

KPFM on Carbon Nanotubes

3 3

2 2

1 1

It should be noticed that SKM image reveals three kinds of nanotubes : 1) Nanotubes with electric potential about 1 V, these nanotubes have smallest diameter (about 1.5 nm)

Topography SKM image

) p , ( )2) Nanotubes with electric potential about 0.5 V which have diameter about 2-3 nm 3) Thickest nanotubes which give smallest contrast in SKM and have biggest diameter (4 nm)

Charge Lithography on GaAs

Raster lithography on the GaAs substrate made with a diamond coated probe. Topography (left) and Kelvin mode (right) images. p g p y ( ) ( g ) gLithography is made by surface charging under the layer of GaAs oxide. Topography image shows nothing, when the right image made in SKM mode demonstrates areas charged positively and negatively on the neutral background. 

Single-Pass Electric Studies: EFM, KFM, dC/dZ, dC/dV

Working frequencies: mech ≈ 70 kHz;elec = 3-5 kHz; 2nd Eigen mode (2E) ≈ 450kHz;

KFM-AMnon-res dC/dZ-AMnon-resKFM-AMres dC/dZ-AMres – 2E, 3EKFM-PM dC/dZ-PM

3rd Eigen (3E), etcKFM PMnon-res dC/dZ PMnon-res

Multi-Frequency Study of Electrical Properties

Single-Pass and Double-Pass KFM of Fluoroalkanes on Mica

C i f Si l P d D bl P KFM M dComparison of Single-Pass and Double-Pass KFM Modes

F14H20 onF14H20 on mica

Probes for KPFM

FMG01/PtResonance frequency 60 kHz

20 nm

Resonance frequency ~60 kHz

Piezoresponce Force Microscopy (PFM)

Piezoresponse Force Microscopy

TopographyPFM studies of TGS sample.

• Cantilevers (40 N/m) with Pt coating were used for measurements

20 µm

• AC-sample mode with 10V@100kHz applied was used for PFM measurements.

VPFM Amplitude VPFM Phase

20 µm 20 µm20 µm 20 µm

Piezoresponse Force Microscopy

Block scheme of PFM

Hi h T M l l F l i C l f Dii l i B id (DIPAB)

PFM: Non-Orthogonal Domains

Topography Amplitude, VPFM Phase, VPFMHigh-Temperature Molecular Ferroelectric Crystal of Diisopropylammonium Bromide (DIPAB)

PFM: 60V@100kH@

z

Amplitude, LPFM Phase, LPFM4 m 4 m 4 m

DIPAB

DIPAB P f T U h (UC S

426Kb

cDIPAB – courtesy Prof. T. Usher (UC San Bernardino)

4 m 4 m

35

Probes for PFM

Probes for PFM should normally have high spring constants 1 100 N/m and

20 nm

high spring constants 1 – 100 N/m and coating with high conductivity (PtIr, TiN)

Magnetic Force Microscopy (MFM)

MFM Principle

Different magnetic domain structures ofnonhomogenious Yttriumnonhomogenious YttriumIron Garnet (YIG) films. YIG film has substantialvariation of anisotropyvariation of anisotropyfield along the filmthickness

Temperature Dependency

Temperature control: -28 +300°CTemperature control: 28...+300 C

MFM images of the cobalt monocrystal with uniaxialanisotropy. Phase transition occurs when temperature increases. Images obtained from the same area, 14x40 μm. Sample courtesy of Prof. A.G. Pastushenkov, Tver University, Russia.

Domain Structure Transformation in External Magnetic Field

Changes of the domain structure of Au/Co/Au ...Co/Au sandwich t t

Out-of-Plain External Magnet

structure.H = 500 OeH = 0 Oe

H = 1000 Oe H = 1500 Oe

In-Plain External Magnet

MFM Probes

Fig 1 Topography (left) and

MFM_LM – low moment tips

Fig. 1. Topography (left) and Magnetic MFM (right) images of Self-Assembled particle array after Co/Pd thin film depositionafter Co/Pd thin film deposition. Scan size 3x3 um. Sample Courtesy - Prof. Manfred Albrecht, Chemnitz University ofAlbrecht, Chemnitz University of Technology, Institute of Physics

MFM_HC – high correcitivity tips

Nanolithography

Types of Nanolithography

Vector lithographyon OTS layer

Modes: Methods: Regimes:- Force- Voltage- Current

Methods:- Vector- Raster

g- Constant- Gradient- Pulse

3×2 ×4 = 24 Types! Current Pulse

- Pulse Gradient

Force Lithography

Voltage and Current Lithography

Local Anodic Oxidation of Titanium film ilm

Channel width ~20 nm

Precise Closed-Loop Control

Closed-loop OFF Closed-loop ON

Voltage Raster Nanolithography

2 µm1 µm

Nanomanipulation

Carbon nanotubes on silicon substrate. Manipulation of nanotubes in pthe specified direction (before (left), after nanomanipulations (right)).Scan size: 2.6x2.6 µm

Probes for Nanolithography

Diamond Coated Conductive Probes (DCP Series)- DCP01DCP01- DCP10- DCP20

Probes with W2C, TiO, TiN and Pt coatings were also reported to be successfully used in nanolithoapplicationsapplications

Scanning Force Spectroscopy (SFM)

Atomic Force Spectroscopy Principle

Mechanical Properties of the Sample

Force Curves on Different Materials

PDMS60PDMS8 PDMS8

Standard Models for AFM

Rubbery materials: PDMS8, PDMS60 and PDMS 130

PDMS130Models: Hertz, Sneddon, JKR, DMT

Polymer Material

Elastic Modulus Macro

Elastic Modulus AFM

Work of Adhesion Macro

Work of Adhesion AFM

PDMS-8 13.4MPa 13.9MPa 49 J/m2 32 J/m2

PDMS-60 1.61MPa 1.74MPa 58 J/m2 52.2 J/m2

PDMS-130 0.74MPa 0.66MPa 47–58 J/m2 42.1 J/m2

D DForce Curves measured on PS/PBD

PBD

PS

Z Z

Force Curves on Melanoma Life Cell

Images were obtained with use of colloidal probe CPC_SiO2-A

HybriD Mode™

HybriD Mode™ mode: One Curve – Multiple Data

In Hybrid Mode™ the tip-sample distance is modulated according to the quasi-y p p g qharmonic law. Thus tip enters a force interaction with the sample thousands of times persecond. Force-distance curve analysis enables maps of topographical, mechanical andelectrical properties of the sample to be extracted with high spatial resolution.C l H b id d i t h dh i d l ti it i i tCommonly Hybrid mode gives topography, adhesion and elasticity mapping pictures

PS-LDPE BlendT h Adh i E M d lTopography Adhesion E Modulus

Scan Size:Polyethylene blobs on 

l t hScan Size: 3×3 µm

polystyrene spheres

E Modulus overlaid over topography

HybriD Mode + Conductivity Mapping

+

Hybrid mode™ was coupled with spreading resistance imaging: a constant y p p g g gDC voltage was applied between the sample and conductive tip. Thus while getting a topography, adhesion and elasticity properties of the sample current going through the circle was recorded.

Complex Study of CNT

Topograpy Current Stiffness

Scan size: 1×1 µm

Image Courtesy: Sergey ZayatsSample Courtesy: Dr. Irma Kuljanishvili, Saint Louis University, Department of Physics

Living Stem Cells

Topography Modulus Map

Post-Processing Capabilities

Revolution Cartridge

Revolution CartridgeInnovative Revolution Head

MFMStiff

SKMSoft

- safe and easy Cartridge replacement - Change methods with the same probes- no system tweaking required (Plug & Play)- high throughput operation

g p~ 40 x less probe replacements

Revolution Cartridge

Find more information at: http://ntmdt com/titaniumFind more information at: http://ntmdt.com/titanium

Thank you for your attention!

All the animations used in presentation can be downloaded at:h // d / i i lhttp://www.ntmdt.com/spm-principles