# Measure the out-of-plane k of suspended thin film

• leehoom
In summary, the conversation discusses the possibility of measuring the out-of-plane thermal conductivity of a suspended thin film. The conventional method involves depositing the film on a thick substrate, but the participants are interested in finding a way to measure it while the film is suspended. One suggestion is using the time-domain thermoreflectance method, but the article on it is vague and the method may not be fully developed. The use of 3 omega method for suspended thin films is also brought up.

#### leehoom

Hi there,

Does anyone know if there is any method to measure the out-of-plane thermal conductivity of a suspended thin film? As the conventional way of measuring the out-of-plane thermal conductivity is to deposit the thin film on a thick substrate, but we want it suspended.

Bystander said:
http://en.wikipedia.org/wiki/Time-domain_thermoreflectance
The article is very vague, and I suspect the method is less than fully developed. In principle, it should work. In practice it might be a "learning experience."

As most of TDTR method used previously was thin film on a substrate, I'm not sure whether it can be applied to suspended film condition. Also, I'm curious if 3 omega method can be applied to suspended thin film structure.

## 1. What is the purpose of measuring the out-of-plane k of suspended thin film?

The out-of-plane k measurement is used to determine the in-plane stress and strain of a suspended thin film, which is important for understanding its mechanical properties and performance.

## 2. How is the out-of-plane k of a thin film measured?

The out-of-plane k is typically measured using techniques such as X-ray diffraction or scanning electron microscopy coupled with focused ion beam milling. These methods allow for precise measurement of the film's thickness and strain in the out-of-plane direction.

## 3. What factors can affect the accuracy of out-of-plane k measurements?

The accuracy of out-of-plane k measurements can be affected by factors such as sample preparation, equipment calibration, and the presence of defects or impurities in the film. It is important to carefully control these factors to ensure accurate results.

## 4. Can the out-of-plane k of a thin film change over time?

Yes, the out-of-plane k of a thin film can change over time due to factors such as thermal expansion, stress relaxation, or exposure to external forces. It is important to monitor these changes to ensure the stability and reliability of the film.

## 5. How is the out-of-plane k related to other mechanical properties of a thin film?

The out-of-plane k is directly related to the in-plane stress and strain of a thin film, which in turn affect its mechanical properties such as stiffness, strength, and ductility. By accurately measuring the out-of-plane k, scientists can better understand and predict the mechanical behavior of thin films.