Infrared Thermal Microscopy for Understanding Transport in Heterogeneous Materials

Event Date: September 17, 2014
Authors: A. Marconnet
Journal: Indo-US Workshop on Nanomaterials for Energy
Indo-US Workshop on Nanomaterials for Energy , West Lafayette, IN, 2014.

With the recent advances in nanoscale and microscale devices and materials, improved metrology techniques are needed to provide insight thermal properties and device performance. High resolution infrared (IR) microscopy allows non-contact, high-resolution (~1.7 μm/pixel), two-dimensional, transient temperature mapping for applications ranging from identifying hot spots in novel devices to improved methods for Seebeck coefficient and thermal conductivity for new materials. This seminar will discuss several thermal measurement techniques we developed to take advantage of the temperature mapping capabilities and allow measurement of microstructure materials. For example, measuring the thermal properties of thin films is often challenging due to the high surface to volume ratio and unintended heat loss pathways. We developed an improved technique for measuring the thermal diffusivity of thin films using a modified Ångström method. As opposed to conventional techniques, using the IR microscope allows non-contact temperature sensing eliminating heat loss pathways that would be present if thermocouples were used. Additionally, non-uniformities in the material are often reflected in variations in the thermal gradients. Beyond thermal diffusivity, a miniaturized 1-D reference bar method allows characterization of thermal conductivity and has proven useful for characterization of a range of materials from carbon aerogels to liquid metals. Finally, combining the temperature mapping capabilities of the IR microscope with electrical measurements allows characterization of thermoelectric properties. The precise measurement of the spatial temperature gradients yields high accuracy characterization of Seebeck coefficient ensuring that the temperature is known at the locations of the voltage measurements. The new and improved measurement techniques provide robust characterization techniques useful for a range of materials.