MODES

Obtaining the image of surface topography scanning simultaneously with elastic modulus mapping

Resolution of scanning is typical for SPM working in the open air and is about 10 nm in XY and better 1 nm in Z axis. The image of elastic modulus map is obtained during one pass with topography scanning. Examples of surface topography images and elastic modulus maps are presented on Fig.

Scratch hardness test

Scratch hardness test (or sclerometry test) with NanoScan consists in producing the scratches on the sample surface with subsequent imaging of the resulting scratch traces. Before the measurements, the indentor shape is calibrated on a reference sample using the series of scratches at several defined loads. The material hardness value is calculated in comparison to the reference hardness as a proportion between the loads and widths of scratches on the tested and reference materials.


Scratch hardness test

The comparative tests show good correlation for this technique with Vickers hardness (Table 1).
Scanning and deformation of the surface is made by the same tip. It makes possible to avoid difficulties with searching the produced scratches and indents and reduces the time required for measurement procedure.

Table 1. Comparative hardness tests

Material	Vickers hardness, GPa	σ	NanoScan scratch hardness, GPa	σ
Quartz	11	± 1	11	± 1
Topaz	17	± 1	19	± 1
Garnet	19	± 1	19	± 1
Sapphire	23	± 1	23	± 1
Cubic ZrO₂	24	± 2	27	± 1
Cubic BN	-	-	60	± 3
Diamond IIa (100)	-	-	137*	± 6
Diamond IIa (111)	-	-	137*	± 5

* the value obtained using the indentor made of ultrahard fullerite С₆₀.

Hardness and elastic modulus measurements by instrumented nanoindentation

The method of dynamic nanoindentation has been implemented in NanoScan devices. The algorithm is based on measuring and analysis of indentation load-displacement data. This technique underlies the international standard of hardness testing ISO 14577.


The common view of load-displacement diagram. The hardness and elastic modulus calculation parameters are shown on the figure.

The typical experimental graph of load (P) versus depth (h) is shown on Fig. It contains loading and unloading P(h) diagrams. In this method hardness of a sample is calculated as:

where Ас – is indent projection area at maximal indentation load Pmax.

Reduced elastic modulus value is calculated as:

where constant ß depends on indenter geometry, and contact stiffness S is determined by the angle of slope of the tangent to the unloading curve in the point Pmax.

Contact area at maximal load Ас is determined by intenter geometry and contact depth hc and it is described by the tip geometry function Ас = f (hc)

Nanoindentaiton on multiphase materials


Aluminum alloy D16. a) before indentation, b) after indentation

Elastic modulus measurements by force spectroscopy

NanoScan is capable of measuring the quantitative value of elastic modulus by the force spectroscopy technique. This method consists in the oscillating the probe sensor simultaneously with loading. The oscillation amplitude is less 10 nm, frequency is around 10 kHz. When the diamond indentor is in contact with the surface, the frequency increases with increasing load.
According to the analytical description based on Hertz model, the slope of the frequency dependence versus probe displacement (approach curve) is proportional to the elastic modulus of the material in the area of contact.
Before the test, the device is calibrated on reference materials with known elastic modulus values. The resulting elastic modulus value is evaluated as a proportion between approach curves slopes and reference elastic modulus.


The slope of ∆f curve characterizes the elastic modulus of the material.	Approach curve measurement schema.

This method is nondestructive and allows correct elastic modulus measurements in the range up to 1000 GPa. The material layer involved in the test can be as small as 100 nm. This makes possible to measure the elastic modulus of thin films without substrate influence.

The comparative measurements on different materials showed correct elastic modulus values in the wide range.

Mechanical properties of MEMS


Schematics for measuring membrane properties.	Loading/unloading curve: membrane stiffness and flexure (a), membrane touching the substrate (b).

Mechanical properties of thin films

Measuring hardness, elastic modulus, strength, fracture toughness, adhesion and thickness of thin films.


DLC film on silicon substrate.

Microindentation. Pile-up analysis

Utility for automated contact area estimation. Accounting for the surface profile around the imprint.


Titanium (99%).

Mechanical nanolithography

Controlled production of defined nano-profile by mechanical manipulation with diamond indentor.


Fused silica.