Scanning Probe Microscopy

SPM 250 EVTState-of-the-Art AFM and STM Technology for Advanced SPM Research

� Extreme Stability � Highest Productivity � Variable Sample Temperature Range

<20 K to 450 K � Low LHe Consumption Flow Cryostat � Video Speed STM � KolibriSensor™ for nc-AFM � SPC 260 or Nanonis™ Control System

Customized Systems and Solutions

Surface Analysis and Preparation Components

Nanostructures and Thin Film Deposition

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Components for Surface Analysis

SPM 250 EVT

Introduction

With scanning probe microscopy (SPM) being a powerful

tool for nanotechnology on the atomic scale, SPECS li-

censed the STM (scanning tunneling microscopy) system

from University of Aarhus. Up until then, commercial

SPM systems were approaching the needs of scientists

with a wide variety of SPM techniques, yet neglecting

fundamental problems arising from the lack of mechani-

cal stability and from time-consuming operational re-

quirements from its users. The STM 150 Aarhus, entered

the market showing ultimate stability and ease of use at

the very same time. In doing so SPECS managed to of-

fer STM systems that operate productively and stable on

a daily basis, thereby allowing scientists to spend more

time thinking about possible experiments rather than

investing valuable time operating the instrument itself.

Mechanical Loop

One of the key features of the Aarhus SPM family mem-

bers is the smallest possible mechanical loop between

sensor and surface using the miniaturized approach

mechanism. With most other instruments not having

such a feature, the Aarhus SPM gains its fundamental

stability from this miniaturized mechanical loop.

Tip Replacement

Another key feature for all Aarhus SPM family members

is not having to replace probing sensors, e.g. a tunneling

tip. The lack of instrumental stability, i.e. from sensor

damaging contact with the surface (‘tip crashes’) along

with the lack of cleaning possibilities, i.e. removing con-

taminants and sensor sharpening, made ‘in-situ’ tip re-

placement necessary for most other instruments. Within

the Aarhus SPM family a different approach is used. By

using a protection shield all sensors are left within the

instrument and are bombarded with a parallel ion beam.

The sensors are not just cleaned but also sharpened in a

very reproducible and time-efficient manner.

Extended Variable Sample Temperatures < 20 K

The SPM 250 Aarhus EVT transfers the extreme produc-

tivity and stability of the Aarhus STM familiy into an Ex-

tended Variable Temperature (EVT) range using a special

designed high-end liquid helium (LHe) based cooling

device. Its extremely low accoustic noise enables guar-

anteed best „Aarhus-stability“. For this the flow cooler

is decoupled from the sample stage by a series of spring

suspended masses followed by a double stage suspen-

sion of the stage. Those decoupling masses of 2 kg each

perfectly suppress possible “bubble” noise originating

from the flow cryostat.

Highest temperature accuracy during LHe cooling to low-

est temperatures is mandatory to reach extremely low

drift. For this an ultra-precise measurement of true sam-

ple temperature is realized.

SPM 250 Aarhus EVT with shielding open (left) and closed (right)

Innovation in Surface Spectroscopy and Microscopy Systems

A tight mechanical and thermal contact of sample hold-

er and SPM stage is realized by a locking mechanism.

Together with the shielded stage a

fast cool down of samples to mini-

mum temperatures can be realized.

A typical time span of 20 min from

insertion of a sample at room tem-

perature to “ready for SPM” at

below 20 K and has been shown.

Furthermore the shielding by a

cooled copper encapsulation

avoids fast contamination of

the cold sample. For tem-

perature ramps counter

heating of the sample is

possible even to elevat-

ed temperatures up to

450 K.

A comparably low LHe con-

sumption can be realized in

operation as well as during

the fast cool down of the

cryostat from

room tem-

perature.

Only about 10 l of

LHe is consumed

while in between

3 h the SPM stage

is completely

cooled down to

minimum tem-

perature <20 K.

The typical LHe

consumption

during opera-

tion at 20 K is

about 2 litres

per hour.

Cross sectional view of SPM 250 Aarhus EVT

Close-up of sample stage

Results

The adsorption of physisorbed argon on the Au(111) sur-

face has been studied by STM at a sample temperature

of 14 K. Even locally the sample temperature does not

change strongly by the close-to-room temperature tip

in front of the sample indicating the temperature stabil-

ity of the sample stage. In other cases the argon layer

would have vanished during scanning. From Fig. 4 it is

obviously, that the Ar adlayer does not affect the Her-

ringbone structure of the underlying Au substrate.

Physisorbed Argon on Au(111): T = 14 K (I = 0.2 nA; U = 1.2 V)

The next result shows local defects in the Ar adlayer indi-

cating true atomic resolution. The excellent stability and

resolution of the instrument is demonstrated by imaging

the corrugation of only about 0.02nm.

Physisorbed Argon on Au(111): T = 14 K (I = 0.5 nA; U = 0.63 V)

SPM 250 EVT

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KolibriSensor and Nanonis Control System

Using Nanonis’ state-of-the-art control in atomic force

microscopy (AFM), the Aarhus SPM family allows imag-

ing of non-conductive samples in non-contact AFM (nc-

AFM) mode. In combination with SPECS’ development

of the KolibriSensor, a quartz oscillator-based sensor,

atomically resolved imaging is possible. Furthermore,

considering the significantly more demanding AFM tech-

nology, this Aarhus SPM family member makes atomi-

cally resolved imaging of conductive and non-conduc-

tive samples possible on a daily basis. By separating the

tungsten tip from the resonator, force and tunneling

signals can be recorded simultaneously and completely

independently of one another. The SPM 250 Aarhus EVT

represents a new generation of UHV systems to examine

every possible surface at the atomic scale even at sample

temperatures below 20 K.

Technical Data

SPM 250 EVT

Mounting Flange DN 250CF

Temperature Range 20 K - 450 K

Temperature Stability Better 0.2 K

LHe-consumption at 20 K Approx. 2 litres per hour

In Situ Access Specular and evaporation

Scan Range 1.500 nm x 1.500 nm

Sensitive Z Range ±175 nm

Approach Speed ≤1 mm/min

Drift-rate T <= 50 K < 0,1 nm/min (vert), < 0,5 nm/min (lat)

Stability < 10 pm

SPM 250 EVT

Compact SPM 250 Aarhus EVT System with vibration isolaton

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Technical alterations reserved. The information in this document is provided with greatest care but SPECS does not assume any liability arising from the application or use of the information or product described here. SPECS, Kolibri and Tyto as well as the corresponding logos are registered trademarks of SPECS Surface Nano Analysis GmbH in Germany and other

countries worldwide. Nanonis is a registered trademark of SPECS Zurich GmbH in Switzerland and other countries worldwide. Other product and company names mentioned herein are trademarks or trade names of their respective companies.Printed in March 2011

Innovation in Surface Spectroscopy and Microscopy Systems