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Atomic Force Microscopy (AFM) is a high-resolution imaging technique used to study surfaces at the atomic and molecular levels. AFM can observe surfaces that are too small to be seen with traditional microscopy, such as individual atoms or molecules, and has become a vital tool in the field of nanotechnology. The AFM probe consists of a sharp tip attached to a cantilever. The tip is brought close to the sample surface, and the cantilever is deflected by the forces acting on the tip as it scans over the surface in a raster pattern. The deflection of the cantilever is measured using a laser beam, and this information is used to construct an image of the surface topography. The sensitivity of the cantilever to atomic-scale forces allows AFM to image surfaces with sub-nanometer resolution.
Background of Thin Films Deposition using Physical Vapor Deposition techniques
Physical vapor deposition (PVD) considers various vacuum deposition techniques to grow pristine thin films and coatings for miscellaneous applications. In general, the entire working principle of PVD tools captures the vapor phase of source materials and condensed phase of deposited thin films. The most common PVD processes are sputtering and evaporation. PVD tools are well known in industry to develop devices for mechanical, optical, chemical, or electronic functions. Currently, our Thin Films Lab has three different PVD tools namely, Phoenix™ sputtering system, Explorer™ evaporator, and Veeco™ dual chamber molecular beam epitaxy (MBE) system.
For all the three techniques, uniform films of high purity can be achieved through cleaning the excess atmospheric particles under high vacuum deposition pressure. In a sputtering tool, atoms are ejected into the vapor phase in the presence of an inert process gas plasma, which is commonly Argon due to its inactive reaction nature with other molecules and tend to deposit on all surfaces in the vacuum chamber. Finally, a substrate placed in the chamber will be coated with a thin film.
In an evaporation tool, the basic working principle follows two phenomena. Firstly, the evaporation of hot source materials and secondly the condensation as thin films on the substrate. Like other PVD tools, evaporation happens under vacuum, hence, any other residuals are generally removed during the process using roughing as well as cryo pumps. Molecular Beam Epitaxy (MBE) is a significant deposition technique to grow epitaxial, layered structures under ultrahigh vacuum conditions on different substrate materials. In general, chemical reaction occurs through molecular beam impinging on the surface; this chemical reaction is the material transition from the gas phase in the molecular beam to the solid state on top of the substrate.
