Vapor delivery systems and methods that control the heating and flow of vapors from solid feed material, especially material that comprises cluster molecules for semiconductor manufacture. The systems and methods safely and effectively conduct the vapor to a point of utilization, especially to an ion source for ion implantation. Ion beam implantation is shown employing ions from the cluster materials. The vapor delivery system includes reactive gas cleaning of the ion source, control systems and protocols, wide dynamic range flow-control systems and vaporizer selections that are efficient and safe. Borane, decarborane, carboranes, carbon clusters and other large molecules are vaporized for ion implantation. Such systems are shown cooperating with novel vaporizers, ion sources, and reactive cleaning systems.