Xinwei Wang, Director of the Micro/Nanoscale Thermal Science Laboratory

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Facilities and Equipment (selected)

1. Advanced techniques for measuring the thermal conductivity and thermal diffusivity of micro/nanoscale wires, films, coatings, bulk solids, and liquids

Over the years, we have developed many advanced techniques for measuring thermophysical properties of materials, including thermal conductivity, thermal diffusivity, and specific heat. The below techniques are either first developed in our laboratory or further developed based on current technologies. Theyconsist of complete equipment setup, computer-controlled data acquisition system, data processing program, and uncertainty analysis program.

Photo-based Techniques

(1) Optical Heating and Electrical Thermal Sensing (OHETS) technique (a frequency domain technique): for measuring micro/nanoscale wires and free-standing films

(2) Transient Photo-Electro-Thermal (TPET) Technique (a time domain technique): for measuring micro/nanoscale wires and free-standing films

(3) Pulsed Laser-assisted Thermal Relaxation (PLTR) technique (a time domain technique with impulse excitation): for measuring micro/nanoscale wires and free-standing film. A second generation-PLTR2 has been developed to measure the thermal conductivity/diffusivity of films in both in-plane and cross-plane directions.

(4) Photothermal-radiation (PTR) technique (a frequency domain technique): for measuring coatings and free-standing thin films in the thickness direction.

Electro-thermal Techniques

(1) Transient Electro-Thermal (TET) Technique (a time domain technique): for measuring micro/nanoscale wires and free-standing films

(2) Steady-state Electro-Raman Thermal (SERT) technique (a steady-state technique): for measuring micro/nanoscale wires.

(3) Three-omega technique (a frequency-domain technique): for measuring micro/nanoscale wires


The TET technique is the best and has proved to work extremely well for measuring the thermal conductivity, thermal diffusivity, and volumetric specific heat, as well as surface emissivity of various micro/nanoscale wires and free-standing films. It is routinely used in our lab for studying thermal transport in various one-dimensional fibers and films.

PLTR2 is extremely powerful in characterizing the anisotropic thermal conductivity/diffusivity of microscale films down to 10 K.

2. Techniques for Raman-based Micro/Nanoscale Thermal Probing and Characterization
Four Raman systems have been designed and developed for probing of interface energy coupling and thermal transport with sub-nm resolution. Combined with our 3D nanopositioning system, systematic work has been conducted to study the optical, thermal, and stress fields induced by near-field laser focusing. A resolution down to 20 nm has been achieved.

In addition to steady-state Raman, four novel and advanced Raman techniques have been first developed in our lab to achieve unprecedented measurement capacity and accuracy of 2D materials. They are also capable of distinguishing phonon transport and charge carrier transport.

(1) Time-domain differential Raman (TD-Raman)

(2) Frequency-resolved Raman (FR-Raman)

(3) Energy transport state-resolved Raman (ET-Raman)

(4) Frequency domain ET-Raman (FET-Raman)

Here the ET-Raman probably represents the most advanced Raman technique in characterizing the phonon transport, interface energy transport, and charge carrier diffusion in 2D materials. It takes a completely different way from the widely used pump-probe technique while still can probe the transient physics behavior from microsecond scale down to picosecond scale.

3. Scanning Probing Microscope (SPM)

A multi-functional SPM: D3000 Scanning Probe Microscope is being routinely used in our lab for surface structure and morphology characterization. This system has been integrated with our free Raman system to study the sub-10 nm thermal field and heat conduction induced by near-field focusing by the SPM tip upon laser irradiation.

4. Cryogenic Station

A cryogenic station that uses He refrigeration cooling and liquid N2-assisted vacuum pumping. It provides a important platform for material properties measurement down to 10 K and to study the material phonon diffusion domain size. Our TET and PLTR2 technologies have been integrated with this system to provide pioneering study of thermal transport in various 1D and 2D materials, and evaluating the structure domain size in a unprecedented way.

Also an optical cryogenic station (77 K-890 K) is established and integrated with our Raman system to provide wide temperature study of materials’ physical properties using our Raman techniques.

Thermal Characterization Services

A service center has been established in our lab to provide thermal characterization service to public. The cost of sample measurement depends on the sample preparation process, measurement time, and data processing. You are encouraged to contact us to estimate the cost based on your specific sample and measurement need. More details of the measurement capacity are listed as below:

Keywords: thermal conductivity measurement, thermal conductivity of coatings, thermal conductivity of films, thermal conductivity of fibers and wires, thermal conductivity of bulk materials (very large size), interface thermal resistance

Contact (Prof. X. Wang) for more measurement capacity and quote.

1. Coatings

Our techniques can measure coatings of metallic, dielectric, and semiconductive materials. The required coating’s thickness varies from mm down to 100 nanometer

Properties that can be measured include thermal conductivity, density, thermal diffusivity, thermal contact resistance, and thickness of coatings. This depends on what properties are given in sample preparation.

2. Fibers, wires, and free-standing films

Our techniques provide unique capabilities of measuring the thermal conductivity, thermal diffusivity, and volumetric specific heat of fibers, wires, and free-standing films of any material type. The required sample length can be cm down to less than 1mm. The required sample thickness (or diameter) is mm down to nanometers

Properties that can be measured: thermal conductivity, thermal diffusivity, volumetric specific heat, and surface emissivity. For free-standing films, the thermal conductivities in the in-plane and out-of-plane directions can be measured to reveal the material’s anisotropic nature.

3. Bulk materials (no size limit and almost none sample preparation)

This very unique measurement takes advantage of our recent advances in technology development. The sample has no size limit and no specific surface treatment is needed.