The NSOM, an NRELdesigned and built instrument,

is used for nanoscale

characterization and for

investigating submicron

spatial variations in optical

properties of materials.

(Warren Gretz,

NREL/PIX04542.)

BR-530-22212 • March 2000

Printed with a renewable-source ink on paper containing at least 

50% wastepaper, including 20% postconsumer waste.

National Renewable Energy Laboratory

1617 Cole Blvd., Golden, CO 80401

NREL is a national laboratory of the U.S. Department of Energy,

operated by Midwest Research Institute, the Battelle Memorial

Institute, and Bechtel

Measurements and Characterization is a division of the 

National Center for Photovoltaics at NREL

Web site: http://www.nrel.gov/measurements

Phone: (303) 384-6675

Fax: (303) 384-6604

the tip follows the surface contour. Used for analyzing rough surfaces, it produces high-resolution

images that can be manipulated.

• Error mode. A technique that is performed more

quickly than topography mode, by disabling the

fast response of the feedback loop. This mode

requires flat or polished specimens.

• Friction mode. A contact technique in which

AFM records the friction between the material

and the probe tip as the tip is scanned across

the surface.

• Electrostatic force mode. A voltage applied

between the sample and the tip induces an extra

electrostatic force, which is linked to the surface

potential and surface charge on the sample.

• Cross-section mode. Uses conventional contact

or non-contact mode to analyze samples in crosssection. The cross-section is prepared by cleaving

or breaking the original sample.

• Ultra-high vacuum of 10-11 torr range (vacuum AFM).

Minimizes contamination of sample and deters the

growth of an oxide layer. This enables more sensitive

measurements. 

• Vibration isolation. Isolating the instrument from vibration

is one of the characteristics that enables the AFM to

perform extremely sensitive measurements.

• Image manipulation. Allows the three-dimensional

exploration of a sample from all angles and

allows various kinds of manipulation

that enhance analysis.

• Field of view — from

atoms to about 100 μm.

This type of range enables

the AFM to address largerscale problems, making it

a complementary technique to scanning electron microscopy and

transmission electron

microscopy (see Analytical

Microscopy insert).

• Lateral resolution to 30 Å.

Along with the sensitive vertical resolution, this feature allows topographic

imaging and three-dimensional profiling on the

nanoscale.

Near-Field Optical MicroscopySpectroscopy (NSOM)

This custom-designed analytical instrument is unique

to the Measurements and Characterization Division.

It uses a probe with a very narrow, extruded optical

fiber tip coated with aluminum. Laser light is sent

through the optical fiber, into the tip, and onto the surface of the material being analyzed. The tip, held just a

few nanometers above the material, is scanned across

the surface. As it is scanned, the laser light interacts

with the surface, while a microscope monitors the

interaction. Because it uses a tip that has such a narrow aperture that is scanned so closely to the surface,

the spatial resolution obtained by the NSOM far

exceeds that achievable with normal optical microscopes, which is fundamentally limited to half a wavelength (1/2 λ).

Applications

• Fundamental material studies. Used for investigating

submicron spatial variations in optical properties of

materials or devices.

• Nanoscale studies. Used to examine the optical absorption of individual defects and impurities, and thus,

study their role in semiconductor materials. Also used

for analyzing the PV effect on the nanoscale.

• Optical and spectroscopic studies. Valuable tool for

exploring fundamental optical and spectroscopic

properties of semiconductors.

Special Features

• Lateral resolution better than 1/10 λ. 

• Continuous-wavelength laser source.

• Near-field optical-beam-induced current (NOBIC). Used

for investigating the PV effect on the nanoscale and for

examining the influence that individual defects or impurities may have on the PV effect.

• Nanoscale photoluminescence (PL).
Electron

Microscopy

The defining feature of

electron microscopy is

that each analytical

technique employs an

electron beam as a

source for bombarding

the sample under

investigation. Through

its interaction with

matter, the electron

beam produces a variety

of signals that may be used

for imaging and that, with

additional analytical attachments, are used to study a

material's topographical, crystallographic, and structural

properties — all of which can

be correlated with the material's

chemical, electrical, optical,

and luminescence properties.

Among the techniques we use

are scanning electron

microscopy, electron probe

microanalysis, and transmission/scanning transmission electron microscopy. These microscopy

techniques are augmented by X-ray diffraction.

Scanning Electron Microscopy (SEM)

Because of its versatility and the wide range of information it can provide,

the scanning electron microscope is often the preferred starting tool

for analytical microscopy. With SEM, a focused beam of high-energy

electrons is scanned over the surface of a material. The electron beam

interacts with the material, causing a variety of signals — secondary

electrons, backscattered electrons, X-rays, photons, etc. — each of

which may be used to characterize a material with respect to specific

properties. The signals are used to modulate the brightness on a display CRT, thereby providing a high-resolution map of the selected

material property. The Division has two state-of-the-art SEMs, providing

With analytical attachments, SEM

becomes an extremely versatile

technique. Here, SEM uses a superimposed EBIC line scan to indicate

the location of a shallow buried

junction (about 3000 Å from the

transparent conducting oxide interface)

in a copper indium diselenide

thin-film device.

System

JEOL

JXA-8900L

JEOL 

JSM-5800

JEOL 6320F

Philips 

CM-30

Scintag 

MAJOR INSTRUMENTATION FOR ELECTRON MICROSCOPY

Analytical Technique

Electron probe microanalysis

Scanning electron microscopy 

Field-emission scanning electron

microscopy

Transmission and scanning

transmission electron

microscopy

X-ray diffraction

Typical Applications

Quantitative compositional analysis for

elements heavier than boron

Topographical, compositional, electrical, structural,

and luminescence analyses

Topographical, compositional, and electrical

analyses

Microstructural, crystallographic, lattice imaging;

compositional analysis of thin films, semiconductors, metals, ceramics, and particulates

Compositional and phase identification;

texture, stress, and thin-film analyses

Signal Source

Beam of high-energy

electrons

Narrow beam of 

electrons

Narrow beam of 

electrons

Highly focused

monoenergetic beam

of electrons

Monochromatic beam

of X-rays

Accelerating

Voltage

0.2 to 40 kV

0.3 to 30 kV

0.5 to 30 kV

50 to 300 kV

—

Signal

Detected

X-rays, photons,

electrons

X-rays, photons,

electrons

X-rays, photons,

electrons

Transmitted

electrons and

X-rays 

X-ray diffraction

patterns

Elements

Detected

B to U

—

—

F to U (STEM)

All; but not

element-specific

1 μm

By using different analytical capabilities with SEM, one can correlate properties of

a material. Here, a topographical image of CdTe (upper micrograph) is correlated

with a cathodoluminescence image (lower micrograph), to indicate those areas

that are active (brighter areas) and those that represent recombination centers

(darker areas). 
Under ultra-high vacuum, the STM produced

this atomic image of an Si (111) surface,

showing a 7 x 7 reconstruction.

Proximal

Probe

Techniques

Proximal probe techniques employ probes

that scan extremely

close to the material

being analyzed —

just a few

angstroms away

from the surface or

even in contact with

the material. The signal

used to map and analyze

the surface may be generated

in a number of ways —

electric current,

attractive/repulsive forces

(including magnetic

forces), or even friction.

The techniques we use

include scanning tunneling

microscopy and atomic

force microscopy. With lateral resolutions to 1 Å and vertical resolutions to 0.1 Å, these are

extremely sensitive techniques that enable us to perform topographical

imaging and three-dimensional profiling on the atomic and

nanoscales. We have also designed and built a customized proximal

probe instrument for near-field optical microscopy, which gives us

the unusual capability to investigate submicron spatial variations

and electron relaxation states.

Scanning Tunneling Microscopy (STM)

The scanning tunneling microscope uses an atomically sharpened

tungsten or platinum-iridium tip that is scanned within a few

angstroms of a sample surface. A bias voltage is applied between the

sample and the tip, producing a quantum-mechanical tunneling current across the gap. The magnitude of the tunneling current depends

on the distance between the tip and the surface and on the local density of states. A piezoelectric transducer scans the tip across the sample

surface. In topographic mode, a feedback loop operated with the

scanner maintains a constant distance between the tip and the surface. A monitor measures the precise position of the scanner that,

together with the sensitivity of the tunneling current, enables the STM

to produce real, three-dimensional images of the surface topography.

In current mode, the fast response of the feedback loop is disabled and

the variation in the current with surface topography is measured, also

producing a three-dimensional image. In both modes, the STM has the

ability to resolve single atoms. Because the tunneling current also

depends on the local density of states, the STM can be used for

nanoscale spectroscopic studies. For instance, the STM can generate

current-versus-voltage curves, and their derivatives, for different points

of the surface.

Applications

• Surface Imaging. Scans the surface of materials to produce topographic images with atomic lateral resolutions.

• Three-dimensional profiling. Can profile samples in real, threedimensional space with vertical resolutions to 0.1 Å. Through storage

of digital information, the three-dimensional image may be manipulated

— rotated, enhanced with color, filtered, enlarged, and displayed

from any altitude or azimuth.

• Materials. Used for investigating a wide range of materials, including

semiconductors, conducting samples, and features of microelectronic

devices.

• Spectroscopic studies. By measuring variations in current, voltage,

tip/surface separation, and their derivatives, the electronic properties

of the surface can be studied.

Special Features

• Ultra-high vacuum of

10-11 torr range. Minimizes

sample contamination and

deters growth of an oxide

layer, to enable more

sensitive measurements.

• Vibration isolation.

Isolating the instrument

from vibration is one of

the characteristics that

enables the STM to perSystem

Customized NSOM

ThermoMicroscopes

AutoProbe VP

ThermoMicroscopes

AutoProbe CP

RHK 100 STM

MAJOR INSTRUMENTATION FOR PROXIMAL PROBE TECHNIQUES

Analytical Technique

Near-field optical microscopy

Vacuum atomic force microscopy and

scanning tunneling microscopy

Air-ambient atomic force microscopy

and scanning tunneling microscopy

Vacuum scanning tunneling

microscopy

Typical Applications

Submicron spatial variations in 

optical properties

Nanoscale and atomic characterization of

conducting and non-conducting surfaces

Nanoscale and atomic characterization of

conducting and non-conducting surfaces

Nanoscale and atomic level imaging of

conductive samples

Signal Source

Continuous-wavelength laser

Atomic forces between probe

and surface/bias voltage

Atomic forces between probe

and surface/bias voltage

Bias voltage

Signal Detected

Light

Tip deflection (voltage)/

tunneling current

Tip deflection (voltage)/

tunneling current

Tunneling current

Scanning tunneling microscopy is used

for imaging, three-dimensional profiling,

and spectroscopic studies of material

surfaces on the nanoscale and atomic

levels. (Jim Yost Photography/PIX02031.)
Special Features

• EDS. For simultaneous

display of most of the

chemical spectrum

(from boron to uranium) and for quick surveys of the area of

interest before performing a more accurate quantitative analysis with WDS.

• WDS. Four spectrometers

with ten diffracting crystals.

The use of a single-channel

analyzer allows much better

peak resolution and, therefore, helps to resolve peak

overlap problems that are

common in PV materials.

• Extensively computerized.

Computer system controls the

electron beam, spectrometers,

specimen stage, and data processing.

Transmission and Scanning Transmission

Electron Microscopy (TEM/STEM)

With transmission electron microscopy (TEM), a thin (<200 nm) sample is

bombarded by a highly focused beam of single-energy electrons. The beam

has enough energy for the electrons to be transmitted through the sample.

The transmitted electron signal is greatly magnified by a series of electromagnetic lenses. The magnified transmitted signal may be observed in two

ways, through electron diffraction or direct electron imaging. Electron diffraction patterns are used to determine the crystallographic structure of the

material. Direct electron images yield information about the microstructure

of the material and about its defects. With scanning transmission electron

microscopy (STEM), the electron beam is raster-scanned across the material.

This produces a variety of electron and X-ray signals that may be used for

compositional analysis.

Applications

• Structural analysis. Yields information on the microstructure and defects of

materials.

• Compositional analysis. Using EDS, provides small-spot (30 nm) qualitative

or quantitative compositional analysis of materials, detecting elements from

fluorine to uranium.

• High-resolution imaging. Can produce images of atomic lattices with

2.3 Å point-to-point resolution.

• Cross-sectional analysis. Used for investigating the structure and imperfections of multilayer films.

• Wide range of materials. Analyzes the structure and composition of thinfilm or bulk organic and inorganic materials, including electronic materials,

ceramics, metals, biological samples, and particulates.

Special Features

• STEM. Images are formed by raster-scanning the electron beam

across the sample and collecting the transmitted or scattered electrons. Many signals may be collected, including bright- and darkfield images, and X-rays for EDS.

• EDS. Performs qualitative or quantitative compositional analysis for

elements from fluorine to uranium. 

• 300 kV acceleration potential. Produces a highly focused beam

containing coherent monoenergetic electrons with a small wavelength (about 0.002 nm). This promotes high point-to-point

resolution and high electron mean free path for greater

penetration depth.

• 2.3 Å point-to-point resolution. Enables in-depth information on

atomic structure of samples using lattice imaging. 

• Complete processing lab. For producing both negatives and positives

of images and diffraction patterns. 

Using electron diffraction and electron

imaging, the TEM/STEM analyzes the

crystallographic structure, microstructure, and composition of a wide

range of organic and inorganic materials.

(Jim Yost Photography/PIX02016.)

Two HRTEM (high-resolution TEM)

images. The left image reveals a

buried hexagonal phase in cubic

CdTe. The right image shows the

atomic structure of planar defects

in thin-film silicon: a twin defect

(in which the upper layers are

rotated 180° from the lower layers),

an intrinsic stacking fault (ISF —

in which adjacent layers are shifted

slightly), and an extrinsic stacking

fault (ESF — in which there is an

intervening layer between two layers

slightly shifted from each other).
Special Features

• EDS. For simultaneous

display of most of the

chemical spectrum

(from boron to uranium) and for quick surveys of the area of

interest before performing a more accurate quantitative analysis with WDS.

• WDS. Four spectrometers

with ten diffracting crystals.

The use of a single-channel

analyzer allows much better

peak resolution and, therefore, helps to resolve peak

overlap problems that are

common in PV materials.

• Extensively computerized.

Computer system controls the

electron beam, spectrometers,

specimen stage, and data processing.

Transmission and Scanning Transmission

Electron Microscopy (TEM/STEM)

With transmission electron microscopy (TEM), a thin (<200 nm) sample is

bombarded by a highly focused beam of single-energy electrons. The beam

has enough energy for the electrons to be transmitted through the sample.

The transmitted electron signal is greatly magnified by a series of electromagnetic lenses. The magnified transmitted signal may be observed in two

ways, through electron diffraction or direct electron imaging. Electron diffraction patterns are used to determine the crystallographic structure of the

material. Direct electron images yield information about the microstructure

of the material and about its defects. With scanning transmission electron

microscopy (STEM), the electron beam is raster-scanned across the material.

This produces a variety of electron and X-ray signals that may be used for

compositional analysis.

Applications

• Structural analysis. Yields information on the microstructure and defects of

materials.

• Compositional analysis. Using EDS, provides small-spot (30 nm) qualitative

or quantitative compositional analysis of materials, detecting elements from

fluorine to uranium.

• High-resolution imaging. Can produce images of atomic lattices with

2.3 Å point-to-point resolution.

• Cross-sectional analysis. Used for investigating the structure and imperfections of multilayer films.

• Wide range of materials. Analyzes the structure and composition of thinfilm or bulk organic and inorganic materials, including electronic materials,

ceramics, metals, biological samples, and particulates.

Special Features

• STEM. Images are formed by raster-scanning the electron beam

across the sample and collecting the transmitted or scattered electrons. Many signals may be collected, including bright- and darkfield images, and X-rays for EDS.

• EDS. Performs qualitative or quantitative compositional analysis for

elements from fluorine to uranium. 

• 300 kV acceleration potential. Produces a highly focused beam

containing coherent monoenergetic electrons with a small wavelength (about 0.002 nm). This promotes high point-to-point

resolution and high electron mean free path for greater

penetration depth.

• 2.3 Å point-to-point resolution. Enables in-depth information on

atomic structure of samples using lattice imaging. 

• Complete processing lab. For producing both negatives and positives

of images and diffraction patterns. 

Using electron diffraction and electron

imaging, the TEM/STEM analyzes the

crystallographic structure, microstructure, and composition of a wide

range of organic and inorganic materials.

(Jim Yost Photography/PIX02016.)

Two HRTEM (high-resolution TEM)

images. The left image reveals a

buried hexagonal phase in cubic

CdTe. The right image shows the

atomic structure of planar defects

in thin-film silicon: a twin defect

(in which the upper layers are

rotated 180° from the lower layers),

an intrinsic stacking fault (ISF —

in which adjacent layers are shifted

slightly), and an extrinsic stacking

fault (ESF — in which there is an

intervening layer between two layers

slightly shifted from each other).
Under ultra-high vacuum, the STM produced

this atomic image of an Si (111) surface,

showing a 7 x 7 reconstruction.

Proximal

Probe

Techniques

Proximal probe techniques employ probes

that scan extremely

close to the material

being analyzed —

just a few

angstroms away

from the surface or

even in contact with

the material. The signal

used to map and analyze

the surface may be generated

in a number of ways —

electric current,

attractive/repulsive forces

(including magnetic

forces), or even friction.

The techniques we use

include scanning tunneling

microscopy and atomic

force microscopy. With lateral resolutions to 1 Å and vertical resolutions to 0.1 Å, these are

extremely sensitive techniques that enable us to perform topographical

imaging and three-dimensional profiling on the atomic and

nanoscales. We have also designed and built a customized proximal

probe instrument for near-field optical microscopy, which gives us

the unusual capability to investigate submicron spatial variations

and electron relaxation states.

Scanning Tunneling Microscopy (STM)

The scanning tunneling microscope uses an atomically sharpened

tungsten or platinum-iridium tip that is scanned within a few

angstroms of a sample surface. A bias voltage is applied between the

sample and the tip, producing a quantum-mechanical tunneling current across the gap. The magnitude of the tunneling current depends

on the distance between the tip and the surface and on the local density of states. A piezoelectric transducer scans the tip across the sample

surface. In topographic mode, a feedback loop operated with the

scanner maintains a constant distance between the tip and the surface. A monitor measures the precise position of the scanner that,

together with the sensitivity of the tunneling current, enables the STM

to produce real, three-dimensional images of the surface topography.

In current mode, the fast response of the feedback loop is disabled and

the variation in the current with surface topography is measured, also

producing a three-dimensional image. In both modes, the STM has the

ability to resolve single atoms. Because the tunneling current also

depends on the local density of states, the STM can be used for

nanoscale spectroscopic studies. For instance, the STM can generate

current-versus-voltage curves, and their derivatives, for different points

of the surface.

Applications

• Surface Imaging. Scans the surface of materials to produce topographic images with atomic lateral resolutions.

• Three-dimensional profiling. Can profile samples in real, threedimensional space with vertical resolutions to 0.1 Å. Through storage

of digital information, the three-dimensional image may be manipulated

— rotated, enhanced with color, filtered, enlarged, and displayed

from any altitude or azimuth.

• Materials. Used for investigating a wide range of materials, including

semiconductors, conducting samples, and features of microelectronic

devices.

• Spectroscopic studies. By measuring variations in current, voltage,

tip/surface separation, and their derivatives, the electronic properties

of the surface can be studied.

Special Features

• Ultra-high vacuum of

10-11 torr range. Minimizes

sample contamination and

deters growth of an oxide

layer, to enable more

sensitive measurements.

• Vibration isolation.

Isolating the instrument

from vibration is one of

the characteristics that

enables the STM to perSystem

Customized NSOM

ThermoMicroscopes

AutoProbe VP

ThermoMicroscopes

AutoProbe CP

RHK 100 STM

MAJOR INSTRUMENTATION FOR PROXIMAL PROBE TECHNIQUES

Analytical Technique

Near-field optical microscopy

Vacuum atomic force microscopy and

scanning tunneling microscopy

Air-ambient atomic force microscopy

and scanning tunneling microscopy

Vacuum scanning tunneling

microscopy

Typical Applications

Submicron spatial variations in 

optical properties

Nanoscale and atomic characterization of

conducting and non-conducting surfaces

Nanoscale and atomic characterization of

conducting and non-conducting surfaces

Nanoscale and atomic level imaging of

conductive samples

Signal Source

Continuous-wavelength laser

Atomic forces between probe

and surface/bias voltage

Atomic forces between probe

and surface/bias voltage

Bias voltage

Signal Detected

Light

Tip deflection (voltage)/

tunneling current

Tip deflection (voltage)/

tunneling current

Tunneling current

Scanning tunneling microscopy is used

for imaging, three-dimensional profiling,

and spectroscopic studies of material

surfaces on the nanoscale and atomic

levels. (Jim Yost Photography/PIX02031.)
Electron

Microscopy

The defining feature of

electron microscopy is

that each analytical

technique employs an

electron beam as a

source for bombarding

the sample under

investigation. Through

its interaction with

matter, the electron

beam produces a variety

of signals that may be used

for imaging and that, with

additional analytical attachments, are used to study a

material's topographical, crystallographic, and structural

properties — all of which can

be correlated with the material's

chemical, electrical, optical,

and luminescence properties.

Among the techniques we use

are scanning electron

microscopy, electron probe

microanalysis, and transmission/scanning transmission electron microscopy. These microscopy

techniques are augmented by X-ray diffraction.

Scanning Electron Microscopy (SEM)

Because of its versatility and the wide range of information it can provide,

the scanning electron microscope is often the preferred starting tool

for analytical microscopy. With SEM, a focused beam of high-energy

electrons is scanned over the surface of a material. The electron beam

interacts with the material, causing a variety of signals — secondary

electrons, backscattered electrons, X-rays, photons, etc. — each of

which may be used to characterize a material with respect to specific

properties. The signals are used to modulate the brightness on a display CRT, thereby providing a high-resolution map of the selected

material property. The Division has two state-of-the-art SEMs, providing

With analytical attachments, SEM

becomes an extremely versatile

technique. Here, SEM uses a superimposed EBIC line scan to indicate

the location of a shallow buried

junction (about 3000 Å from the

transparent conducting oxide interface)

in a copper indium diselenide

thin-film device.

System

JEOL

JXA-8900L

JEOL 

JSM-5800

JEOL 6320F

Philips 

CM-30

Scintag 

MAJOR INSTRUMENTATION FOR ELECTRON MICROSCOPY

Analytical Technique

Electron probe microanalysis

Scanning electron microscopy 

Field-emission scanning electron

microscopy

Transmission and scanning

transmission electron

microscopy

X-ray diffraction

Typical Applications

Quantitative compositional analysis for

elements heavier than boron

Topographical, compositional, electrical, structural,

and luminescence analyses

Topographical, compositional, and electrical

analyses

Microstructural, crystallographic, lattice imaging;

compositional analysis of thin films, semiconductors, metals, ceramics, and particulates

Compositional and phase identification;

texture, stress, and thin-film analyses

Signal Source

Beam of high-energy

electrons

Narrow beam of 

electrons

Narrow beam of 

electrons

Highly focused

monoenergetic beam

of electrons

Monochromatic beam

of X-rays

Accelerating

Voltage

0.2 to 40 kV

0.3 to 30 kV

0.5 to 30 kV

50 to 300 kV

—

Signal

Detected

X-rays, photons,

electrons

X-rays, photons,

electrons

X-rays, photons,

electrons

Transmitted

electrons and

X-rays 

X-ray diffraction

patterns

Elements

Detected

B to U

—

—

F to U (STEM)

All; but not

element-specific

1 μm

By using different analytical capabilities with SEM, one can correlate properties of

a material. Here, a topographical image of CdTe (upper micrograph) is correlated

with a cathodoluminescence image (lower micrograph), to indicate those areas

that are active (brighter areas) and those that represent recombination centers

(darker areas). 
The NSOM, an NRELdesigned and built instrument,

is used for nanoscale

characterization and for

investigating submicron

spatial variations in optical

properties of materials.

(Warren Gretz,

NREL/PIX04542.)

BR-530-22212 • March 2000

Printed with a renewable-source ink on paper containing at least 

50% wastepaper, including 20% postconsumer waste.

National Renewable Energy Laboratory

1617 Cole Blvd., Golden, CO 80401

NREL is a national laboratory of the U.S. Department of Energy,

operated by Midwest Research Institute, the Battelle Memorial

Institute, and Bechtel

Measurements and Characterization is a division of the 

National Center for Photovoltaics at NREL

Web site: http://www.nrel.gov/measurements

Phone: (303) 384-6675

Fax: (303) 384-6604

the tip follows the surface contour. Used for analyzing rough surfaces, it produces high-resolution

images that can be manipulated.

• Error mode. A technique that is performed more

quickly than topography mode, by disabling the

fast response of the feedback loop. This mode

requires flat or polished specimens.

• Friction mode. A contact technique in which

AFM records the friction between the material

and the probe tip as the tip is scanned across

the surface.

• Electrostatic force mode. A voltage applied

between the sample and the tip induces an extra

electrostatic force, which is linked to the surface

potential and surface charge on the sample.

• Cross-section mode. Uses conventional contact

or non-contact mode to analyze samples in crosssection. The cross-section is prepared by cleaving

or breaking the original sample.

• Ultra-high vacuum of 10-11 torr range (vacuum AFM).

Minimizes contamination of sample and deters the

growth of an oxide layer. This enables more sensitive

measurements. 

• Vibration isolation. Isolating the instrument from vibration

is one of the characteristics that enables the AFM to

perform extremely sensitive measurements.

• Image manipulation. Allows the three-dimensional

exploration of a sample from all angles and

allows various kinds of manipulation

that enhance analysis.

• Field of view — from

atoms to about 100 μm.

This type of range enables

the AFM to address largerscale problems, making it

a complementary technique to scanning electron microscopy and

transmission electron

microscopy.

• Lateral resolution to 30 Å.

Along with the sensitive vertical resolution, this feature allows topographic

imaging and three-dimensional profiling on the

nanoscale.

Near-Field Optical MicroscopySpectroscopy (NSOM)

This custom-designed analytical instrument is unique

to the Measurements and Characterization Division.

It uses a probe with a very narrow, extruded optical

fiber tip coated with aluminum. Laser light is sent

through the optical fiber, into the tip, and onto the surface of the material being analyzed. The tip, held just a

few nanometers above the material, is scanned across

the surface. As it is scanned, the laser light interacts

with the surface, while a microscope monitors the

interaction. Because it uses a tip that has such a narrow aperture that is scanned so closely to the surface,

the spatial resolution obtained by the NSOM far

exceeds that achievable with normal optical microscopes, which is fundamentally limited to half a wavelength (1/2 λ).

Applications

• Fundamental material studies. Used for investigating

submicron spatial variations in optical properties of

materials or devices.

• Nanoscale studies. Used to examine the optical absorption of individual defects and impurities, and thus,

study their role in semiconductor materials. Also used

for analyzing the PV effect on the nanoscale.

• Optical and spectroscopic studies. Valuable tool for

exploring fundamental optical and spectroscopic

properties of semiconductors.

Special Features

• Lateral resolution better than 1/10 λ. 

• Continuous-wavelength laser source.

• Near-field optical-beam-induced current (NOBIC). Used

for investigating the PV effect on the nanoscale and for

examining the influence that individual defects or impurities may have on the PV effect.

• Nanoscale photoluminescence (PL).