1. Department of Physics, Faculty of Science, Thaksin University, Phatthalung, Thailand
2. Functional Materials and Nanotechnology Center of Excellence, Walailak University, Nakhon Si Thammarat, Thailand
3. Division of Physics, School of Science, Walailak University, Nakhon Si Thammarat, Thailand
4. School of Engineering and Technology, Walailak University, Nakhon Si Thammarat, Thailand