Miniature Knudsen Cell - Molecular Effusion Source
This miniature K-cell from SciCam provides a stable high temperature furnace for the controlled deposition of a wide range of materials. This is the ideal tool for reproducibly depositing small areas of thin films of material with coverages from monolayers to continuous film. For maximum versatility the furnace is fitted with easily removable crucibles (liners) made of PBN or Alumina to suit the deposition material. The liners are are fitted with removable apertures which define and limit the output beam. The modular 'cartridge' design means that all parts are easily replaceable so that a new furnace or liner may be inserted to accommodate a change of materials or for routine maintenance.
Features of the miniature K-Cell
Operating Principle of the K-Cell
The SciCam Knudsen cell utilizes the principle of molecular effusion ( demonstrated by Knudsen in 1909). . The material to be deposited is heated to provide a suitable vapor pressure in an isothermal enclosure. Molecular effusion from an aperture in the end of the cell gives rise to a cosine intensity distribution. The deposition rate is extremely stable being determined by the temperature of the furnace which is accurately controlled with a PID controller.
The graphite furnace of the cell is designed as a removable cartridge which contains the crucible, heater element and heat shields. The heater filament is a tantalum foil element which is isolated with PBN shields. The temperature of the furnace is monitored by a thermocouple which is carefully placed in the graphite in order to accurately reflect the internal temperature of the furnace. The crucible can be changed by the user and is available in PBN and alumina.
Power Supply and Temperature Control
The power supply/controller is three term PID controller which takes account of the need to regulate the power to the heater depending on the filament temperature. The set temperature is displayed on an LCD panel.
Specifications of K-Cell and Controller
Topac Inc 231 CJC Highway, Cohasset MA 02025 USA
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