TF-LFA Laser Flash for thin films

Thermal Conductivity / Diffusivity measurements for thin films

Description

On point

In industrial applications, understanding the thermophysical properties of materials and optimizing heat transfer in final products has become increasingly crucial.

In recent decades, the flash method has evolved as the primary technique for measuring thermal diffusivity and thermal conductivity in a wide range of materials, including solids, powders, and liquids.

Thin-film thermophysical properties have gained significant importance in various industries, impacting products like phase-change optical disk media, thermoelectric materials, light-emitting diodes (LEDs), phase-change memories, flat panel displays, and a variety of semiconductors. Thin films are deposited onto substrates to impart specific functions to devices. Given that the properties of these films differ from bulk materials, accurate thermal management predictions necessitate precise data.

Building upon the established Laser Flash technique, the Linseis Laserflash for thin films (TF-LFA) now provides an extensive array of capabilities for analyzing thermophysical properties in thin films ranging from 80nm to 20 μm in thickness.

Methods

1. High-Speed Laserflash Method (Rear Heating Front Detection – RF):

When dealing with the thermal properties of thin layers and films, it becomes evident that these properties significantly differ from those of the bulk material. To address this, a technique that overcomes the limitations of the traditional Laserflash method is necessary, known as the “High-Speed Laserflash Method.

The measurement geometry closely resembles the standard Laserflash technique, with the detector and laser positioned on opposite sides of the samples. However, due to the inadequacy of IR detectors for measuring thin layers, detection is accomplished using the thermoreflectance method. This technique capitalizes on the concept that changes in surface reflectance can be utilized to deduce thermal properties once the material is heated. Reflectivity is monitored over time, and the resulting data can be correlated with a model containing coefficients that correspond to thermal properties.

2. Time Domain Thermoreflectance Method (Front Heating Front Detection – FF):

The Time-Domain Thermoreflectance technique is employed to determine the thermal properties, including thermal conductivity and thermal diffusivity, of thin layers or films. In this measurement geometry, known as “front heating front detection (FF),” both the detector and the laser are positioned on the same side of the sample. This approach is particularly useful for assessing thin layers on non-transparent substrates, where the RF technique is not applicable.

3. Combining High-Speed Laserflash (RF) and Time Domain Thermoreflectance Method (FF):

Certainly, it’s possible to integrate both methods into a single system, thus harnessing the benefits of each approach.

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Specifications

TF-LFA*
Temperature range:	RT RT up to 500°C -100°C up to 500°C
Heating and cooling rates:	0.01 up to 20°C/min
Pump-Laser:	Nd:YAG Laser
Maximum Impulse current:	90mJ/Impuls (software controlled)
Pulsewidth:	5 ns (optional 1 ns)
Probe-Laser:	CW DPSS-Laser (473 nm), max. 50 mW
Photoreceiver:	Si-PIN-Photodiode, active diameter: 0.8 mm, bandwidth DC … 400MHz, risetime: 1ns
Thermal diffusivity measuring range:	0,01 mm²/s to 1000 mm²/s
Sample diameter:	round samples ∅ 10…20 mm
Sample thickness:	80 nm up to 20 µm
Atmospheres:	inert, oxidizing, reducing
Vacuum:	up to 10E^-4mbar
Electronics:	Integrated
Interface:	USB

*Specs depend on configurations

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Software

All of LINSEIS’ thermo-analytical instruments are operated through PC control, with their individual software modules designed exclusively for Microsoft® Windows® operating systems. The complete software comprises three modules: temperature control, data acquisition, and data evaluation. The Linseis 32-bit software incorporates all the necessary features for preparing, executing, and evaluating measurements, similar to other thermo-analytical experiments.

General Features:

The software is fully compatible with MS® Windows™ 32-bit.
It ensures data security in case of power failures.
Provides thermocouple break protection.
Enables the evaluation of current measurements.
Supports curve comparison.
Allows for storage and export of evaluations.
Facilitates the export and import of data in ASCII format.
Permits data export to MS Excel.

Evaluation Software:

Offers the option for automatic or manual input of related measurement data such as density and Cp (Specific Heat).
Features a model wizard to assist in selecting the appropriate model.
Allows for the determination of contact resistance.

Measurement Software:

Provides an easy and user-friendly interface for inputting data related to temperature segments, gases, and more.
Automatically displays corrected measurements after the energy pulse.
Supports fully automated measurements.

It’s worth noting that this software was developed in collaboration with Prof. David G. Cahill from the University of Illinois Urbana-Champaign, The Grainger College of Engineering – Materials Science & Engineering, ensuring a high level of expertise and quality in its design.