TF-LFA Laser Flash for thin films
Thermal Conductivity / Diffusivity measurements for thin films
Information of the thermo physical properties of materials and heat transfer optimization of final products is becoming more and more vital for industrial applications.
Over the past few decades, the flash method has been developed into the most commonly used technique for the measurement of the thermal diffusivity and thermal conductivity of various kinds of solids, powders and liquids.
Thermophysical properties from thin-films are becoming more and more important in industries for products such as, phase-change optical disk media, thermoelectric materials, light emitting diodes (LEDs), phase change memories, flat panel displays and of curse all kinds of semiconductors.
In all these cases, a thin film gets deposit on a substrate in order to give a device a particular function. Since the physical properties of these films differ from bulk material, these data are required for accurate thermal management predictions.
Based on the well established Laser Flash technique, the Linseis Laserflash for thin films (TF-LFA) now offers a whole range of new possibilities to analyze thermophysical properties of thin films from 80nm up to 20 μm thickness.
1. High Speed Laserflash Method (Rear heating Front detection (RF)):
As thermal properties of thin layers and films differ considerably from the properties of the corresponding bulk material a technique overcoming the limitations of the classical Laserflash method is required: the “High Speed Laserflash Method”.
The measurement geometry is the same as for the standard Laserflash technique: detector and laser are on opposide sides of the samples. Because IR-detectors are to slow for measurement of thin layers, detection is done by the so called thermoreflectance method. The idea behind this technique is that once a material is heated up, the change in the reflectance of the surface can be utilized to derive the thermal properties. The reflectivity is measured with respect to time, and the data received can be matched to a model which contains coefficients that correspond to thermal properties.
2. Time Domain Thermoreflectance Method (Front heating Front detection (FF)):
The Time-Domain Thermoreflectance technique is a method by which the thermal properties (thermal conductivity, thermal diffusivity) of thin layers or films. The measurement geometry is called “front heating front detection (FF)” because detector and laser are on the same side of the sample. This method can be applied to thin layers on non-transparent substrates for which the RF technique is not suitable.
3. Combined High Speed Laserflash (RF) and Time Domain Thermoreflectance Method (FF):
Of curse both methods can also be implemented in a single system to combine the advantages of both.
RT up to 500°C
-100°C up to 500°C
|Heating and cooling rates:||0.01 up to 20°C/min|
|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|
All thermo analytical devices of LINSEIS are PC controlled, the individual software modules exclusively run under Microsoft® Windows® operating systems. The complete software consists of 3 modules: temperature control, data acquisition and data evaluation. The Linseis 32 – bit software encounters all essential features for measurement preparation, execution and evaluation, just like with other thermo analytical experiments.
- Fully compatible MS® Windows™ 32 – bit software
- Data security in case of power failure
- Thermocouple break protection
- Evaluation of current measurement
- Curve comparison
- Storage and export of evaluations
- Export and import of data ASCII
- Data export to MS Excel
- Automatic or manual input of related measurement data: (density), Cp (Specific Heat)
- Model wizard for selection of the appropriate model
- Determination of contact resistance
- Easy and user-friendly data input for temperature segments, gases etc.
- Software automatically displays corrected measurements after the energy pulse
- Fully automated measurement
The Software has been developed in collaboration with Prof. David G Cahill (University of Illinois Urbana-Champaign, The Grainger College of Engineering – Materials Science & Engineering)
Application Example: SiO2
Comperison of measured and calculated curves (2-layer model)
Mo thin layer on SiO2; Temperature-time-curve of samples of different thickness
Temperature-time-curve of ZnO-samples of different thickness
Measured thermal conductvity and thermal contact resistance of ZnO thin films
Enhanced Light-Induced Transverse Thermoelectric Effect in Tilted BiCuSeO Film via the Ultra-thin AuNPs Layer (published Nanoscale Research Letters)
Inkjet Printed Large-Area Flexible Few-Layer Graphene Thermoelectrics (published Advanced Functional Materials)