This chapter describes the thin films’ characteristics including their thickness, composition, surface morphology, and adhesion. The thin-film thickness measurement is vital for ensuring the desired application performance. Techniques such as gravimetric methods, optical methods, and direct measurement methods. The composition of thin films significantly influences their properties and functionalities. Techniques like energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy are utilized to analyze the elemental composition and detect impurities. The surface morphology of thin films, including roughness and microstructure, plays a critical role in determining their optical and mechanical properties. Enhancing adhesion between thin films and substrates is essential for the durability and effectiveness of coatings. Understanding the mechanism of adhesion at the molecular level can lead to the development of more robust thin-film applications. Proper cleaning of substrates is crucial for achieving high-quality thin films. In summary, the study of thin-film characteristics encompasses a range of measurements and analysis techniques.