Connected to the class 1000 clean room, the furnace stacks have a total of six locations capable of accepting furnace tubes up to four inches in diameter. Each tube location has a three zone heated area which is five feet long. The furnaces have been upgraded and retrofitted with modern digital controllers, and are capable of processing materials up to 1350oC. The furnaces are used for a variety of processing, including diffusion, oxidation, annealing, purification, and crystal growth. Each furnace tube is dedicated to a particular process to prevent cross contamination. The bulk of the furnaces extend outside the S.M.A.R.T. Laboratory class 1000 clean Room to conserve space and reduce particulate contamination in the clean area. From inside the S.M.A.R.T. Laboratory clean room (pictured below), the furnaces have covered exhaust ports to remove annealing gases and vaporized materials from the clean room area.