An ion beam is a stream of charged particles, known as ions, that are accelerated and directed towards a target. These ions can be positive or negative and are produced by ion sources, which can include devices like mass spectrometers or ion implanters. Ion beams are used in various applications, including materials science, semiconductor manufacturing, and medical therapies. When an ion beam strikes a material, it can alter the material's properties, such as its structure or composition. This process is utilized in techniques like ion implantation, where ions are embedded into a substrate to modify its electrical or physical characteristics. Ion beams are also important in nuclear physics and particle accelerators for research purposes.