KLA Instruments

Application Note

How to Select a Nano Indenter® Tip

Introduction

It is important to select the correct tip for your nanoindentation

application. KLA Instruments™ offers high precision indenter

tips that enable the finest quality data for your research. Our

indenter tips are designed to meet all of your demanding

applications. This application note can be used as a guide in the

selection process to determine the best tip for your needs.

There are five main types of indenter tips, each with a different

geomtery for a variety of applications:

 Berkovich

 Vickers

 Cube-Corner

 Cone

 Sphere

Berkovich

The Berkovich indenter tip is the most frequently used indenter

tip for instrumented indentation testing (IIT) to measure

mechanical properties on the nanoscale. The Berkovich

indenter tip, shown in Figure 1, is a three-sided pyramid that

can be ground to a point, thus maintaining self-similar

geometry at very small scales. This geometry is often preferred

to the Vickers indenter tip, which is a four-sided pyramid.

Figure 1. The Berkovich indenter tip is defined as a three-sided

pyramid with an included angle of 142.3°.

The Berkovich indenter tip is ideal for most testing purposes. It

is not easily damaged and can be readily manufactured. It

induces plasticity at very small loads, which produces a

meaningful measure of hardness. The Berkovich indenter tip

has an included angle of 142.3°, which minimizes the influence

of friction.

Berkovich Recommended Applications

There are many applications suitable for the Berkovich

indenter tips. Some examples include:

 Bulk materials

 Thin films

 Polymers (E’ > 1GPa)

 Scratch testing

 Wear testing

 Micro-electromechanical systems (MEMS)

 In-situ imaging

Vickers

The Vickers indenter tip is also used in IIT to measure

mechanical properties on the nanoscale, and is defined by a

four-sided pyramid, as shown in Figure 2.

Figure 2. The Vickers indenter tip is defined as a four-sided pyramid.

Application Note

Vickers Recommended Applications

There are many applications suitable for the Berkovich

indenter tips. Some examples include:

 Bulk materials

 Films and foils

 Scratch testing

 Wear testing

Cube-Corner

The Cube-Corner indenter tip is a three-sided pyramid with

mutually perpendicular faces arranged as the corner of a cube,

as shown in Figure 3. The centerline-to-face angle for this

indenter is 34.3°, whereas for the Berkovich indenter it is 65.3°.

The sharpness of the cube corner produces much higher

stresses and strains in the area of the contact, which is useful in

producing very small, well-defined cracks around hardness

impressions in brittle materials. These cracks can be used to

estimate fracture toughness at very small scales.

Figure 3. The Cube-Corner indenter tip is defined as a three-sided

pyramid, with a centerline-to-face angle of 34.3°.

Cube-Corner Recommended Applications

There are many applications suitable for the Cube-Corner

indenter tips. Some examples include:

 Thin films

 Scratch testing

 Fracture toughness

 Wear testing

 MEMS

 In-situ imaging

Cone

The cone indenter tip, shown in Figure 4, has a sharp self-similar geometry, and the simplicity of its conical symmetry

makes it attractive from a modeling standpoint. Many models

used to support IIT are based on conical indentation contact.

The cone is also attractive because the complications

associated with the stress concentrations at the sharp edges of

the indenter are absent. However, very little IIT testing has

been conducted with cones. The primary reason is that it is

difficult to manufacture conical diamonds with sharp tips,

making them of little use in the small-scale work around which

most of IIT has developed. This problem does not apply at

larger scales, where much could be learned by using conical

indenters in IIT experimentation.

Figure 4. The Cone indenter tip.

Cone Recommended Applications

There are many applications suitable for the Cone indenter

tips. Some examples include:

 Scratch testing

 Wear testing

 Micro-electromechanical systems (MEMS)

 In-situ imaging

Sphere

Stresses develop differently during indentation when using a

spherical indenter tip (shown in Figure 5) compared to either a

Berkovich or Vickers tip. For spherical indenters, the contact

stresses are initially small and produce only elastic

deformation. As the spherical indenter is driven into the

surface, a transition from elastic to plastic deformation occurs,

which can theoretically be used to examine yielding and work

Application Note

hardening, and to recreate the entire uniaxial stress-strain

curve from data obtained in a single test. IIT with spheres has

been most successfully employed with larger-diameter

indenters. At the micron scale, the use of spherical indenters

has been impeded by difficulties in obtaining high-quality

spheres made from hard, rigid materials. This is one reason the

Berkovich indenter has been the indenter of choice for most

small-scale testing, even though it cannot be used to

investigate the elastic-plastic transition.

Sphere Recommended Applications

The Sphere indenter tip is typically used for scratch testing.

Custom Shape

At times, standard geometry indenters may not achieve the

desired results. KLA Instruments Applications Engineers work

with the customer to choose a custom-designed indenter

geometry to best suit their application.

Figure 5. The sphere indenter tip.

Shape 3-sided pyramid

Bulk materials, thin

films, polymers,

scratch, wear,

MEMS, imaging

65.3°

24.56d2

8.1873d3

0.908

70.32°

-

Vickers

Cube-Corner

3-sided pyramid w/

perpendicular faces

Thin films, scratch,

fracture toughness,

wear, MEMS,

imaging

35.2644°

2.5981d2

0.8657d3

0.5774

42.28°

-

Cone (angle ψ)

Conical

Modeling,

scratch, wear,

imaging, MEMS

-

πa2

-

-

-

d·tanψ

Sphere (radius R)

Spherical

4-sided pyramid

Bulk materials,

films and foils,

scratch, wear

68°

24.504d2

8.1681d3

0.927

70.2996°

-

Applications

Scratch

Centerline-to-face angle, α

Area (projected), A(d)

Volume-depth relation, V(d)

Projected area/face area, A/Af

Equivalent cone angle, ψ

Contact radius, a

-

πa2

-

-

-

(2Rd-d2)1/2

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